Träfflista för sökning "AMNE:(ENGINEERING AND TECHNOLOGY Mechanical Engineering Tribology) srt2:(2020-2024)"

Sökning: AMNE:(ENGINEERING AND TECHNOLOGY Mechanical Engineering Tribology) > (2020-2024)

Resultat 1-50 av 459

Sortera/gruppera träfflistan

Sortering: Träffar per sida:

Numrering	Referens	Omslagsbild	Hitta
1.	Vilardell, A. M., et al. (författare) B2-structured Fe3Al alloy manufactured by laser powder bed fusion : Processing, microstructure and mechanical performance 2023 Ingår i: Intermetallics (Barking). - : Elsevier. - 0966-9795 .- 1879-0216. ; 156 Tidskriftsartikel (refereegranskat)abstract Prealloyed Fe3Al was successfully manufactured by laser powder bed fusion. The best set of process parameters led to parts with a relative density of 99.5 %, a surface roughness, Sa, of 31.5 ± 5.6 μm and a hardness of 319 ± 14 HV0.1. Its microstructure as well as its mechanical properties at room and high temperatures were analyzed. The results of the chemical composition showed minor variations in aluminum content oscillating between 21 and 28 at.% along the melt pool. Additionally, elongated grains were observed to grow parallel to the building direction, as well as the development of a weak 001 texture along the building direction. The mechanical properties were influenced by the temperature. Compression tests showed a loss in strength with the increase in temperature, from a yield strength of 621 ± 40 MPa at room temperature to 89 ± 20 MPa at 650 °C. Reciprocating sliding wear tests showed that fragmentation of the intermetallic at room temperature occurs, whereas plastic deformation dominated at higher temperatures. For all temperatures, tribochemical wear was also present due to the oxidation of wear debris.
2.	Li, Xiaojian, 1991, et al. (författare) A new method for performance map prediction of automotive turbocharger compressors with both vaneless and vaned diffusers 2021 Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 235:6, s. 1734-1747 Tidskriftsartikel (refereegranskat)abstract A new approach to predict the performance maps of automotive turbocharger compressors is presented. Firstly, a polynomial equation is applied to fit the experimental data of flow coefficient ratios for the centrifugal compressors with both vaneless and vaned diffusers. Based on this equation, the choke and surge flow coefficients under different machine Mach numbers can be quickly predicted. Secondly, a physically based piecewise elliptic equation is used to define compressors’ characteristic curves in terms of efficiency ratio. By introducing the flow coefficient ratio into the efficiency correlation, the empirical coefficients in the piecewise elliptic equation are uniquely calibrated by the experimental data, forming a unified algebraic equation to match the efficiency maps of the compressors with both vaneless and vaned diffusers. Then, a new universal equation, which connects the work coefficient, the impeller outlet flow coefficient and the non-dimensional equivalent impeller outlet width, is derived by using classical aerothermodynamic method. The off-design pressure ratio is predicted based on the equivalent impeller outlet width with less knowledge of the compressor geometry and no empirical coefficients. Finally, three state-of-the-art turbocharger compressors (one with vaneless diffuser, two with vaned diffusers) are chosen to validate the proposed method, and the results show a satisfactory accuracy for the performance map prediction. This method can be used for the preliminary design of turbocharger compressors with both vaneless and vaned diffusers, or to assess the design feasibility and challenges of the given design specifications.
3.	Bayani, Mohsen, 1981 (författare) Squeak and Rattle Prediction for Robust Product Development in the automotive industry 2021 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Squeak and rattle are nonstationary, irregular, and impulsive sounds that are audible inside the car cabin. For decades, customer complaints about squeak and rattle have been, and still are, among the top quality issues in the automotive industry. These annoying sounds are perceived as quality defect indications and burden warranty costs to the car manufacturers. Today, the quality improvements regarding the persistent type of sounds in the car, as well as the increasing popularity of electric engines, as green and quiet propulsion solutions, stress the necessity for attenuating annoying sounds like squeak and rattle more than in the past. The economical and robust solutions to this problem are to be sought in the pre-design-freeze phases of the product development and by employing design-concept-related practices. To achieve this goal, prediction and evaluation tools and methods are required to deal with the squeak and rattle quality issues upfront in the product development process. The available tools and methods for the prediction of squeak and rattle sounds in the pre-design-freeze phases of a car development process are not yet sufficiently mature. The complexity of the squeak and rattle events, the existing knowledge gap about the mechanisms behind the squeak and rattle sounds, the lack of accurate simulation and post-processing methods, as well as the computational cost of complex simulations are some of the significant hurdles in this immaturity. This research addresses this problem by identifying a framework for the prediction of squeak and rattle sounds based on a cause-and-effect diagram. The main domains and the elements and the sub-contributors to the problem in each domain within this framework are determined through literature studies, field explorations and descriptive studies conducted on the subject. Further, improvement suggestions for the squeak and rattle evaluation and prediction methods are proposed through prescriptive studies. The applications of some of the proposed methods in the automotive industry are demonstrated and examined in industrial problems. The outcome of this study enhances the understanding of some of the parameters engaged in the squeak and rattle generation. Simulation methods are proposed to actively involve the contributing factors studied in this work for squeak and rattle risk evaluation. To enhance the efficiency and accuracy of the risk evaluation process, methods were investigated and proposed for the system excitation efficiency, modelling accuracy and efficiency and quantification of the response in the time and frequency domains. The demonstrated simulation methods besides the improved understanding of the mechanisms behind the phenomenon can facilitate a more accurate and robust prediction of squeak and rattle risk during the pre-design-freeze stages of the car development.
4.	Persson, Erik, et al. (författare) Clamp Force Accuracy in Threaded Fastener Joints Using Different Torque Control Tightening Strategies 2021 Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2021 Tidskriftsartikel (refereegranskat)abstract The assembly of threaded fasteners may seem straightforward. However, there are many factors to consider to achieve quality tightened joints, including the joint material, threaded fastener, and coatings. Additionally, there are many assembly tool types and torque application strategies to choose from. This investigation studies the tightening speed dynamics when using torque as a control method. The clamp force obtained in the joint changes when tightening at high speed or when the speed varies greatly during tightening. This type of tightening is called highly dynamic. Highly dynamic torque control tightening strategies are studied, such as impact, pulse, and inertia-controlled methods, and compared with the continuous drive strategy, which is a standard dynamic torque tightening method. The clamp force and its scatter caused by the torque accuracy in the assembly tool type are investigated for the abovementioned torque application strategies. The study also focuses on the different results obtained from the International Organization for Standardization’s (ISO) 16047:2005 (Fasteners-Torque/clamp force testing) standard compared to a production-like setup.
5.	Munavirov, Bulat, 1986- (författare) Ionic lubricants : Molecular features and surface protection mechanisms 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In this thesis ionic liquids (ILs) are investigated as prospective candidates for lubrication. Three custom synthesized phosphonium orthoborate type ILs were extensively studied from the prospective of molecular structuring both in bulk and at the interface and from the prospective of their lubricating performance as neat lubricants and as additives in oils. A wide selection of contact geometries and surface finishes has been utilized to broaden the applicability of the achieved results. Tribological performance of orthoborate ILs when used as additives in oils was additionally benchmarked against two commercial ILs - phosphonium phosphate, phosphonium phosphinate.Studies on the bulk molecular mobility in the orthoborate ILs performed by means of Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) clearly showed that the distinct molecular organisation in these systems depends on the chemical structure of orthoborate anion. These results demonstrated a clear correlation with tests of the tribological performance of neat orthoborate ILs, where friction reduction, wear protection and particularities of surface interactions were shown to be clearly defined by anion chemistry. Moreover, this finding was further proven to be relevant when using ILs as additives in oils. A comparison of tribological performance of orthoborate ILs with phosphinate and phosphate ILs showed that a change in anion structure could basically revert the tribological performance of oil solution: from lower to higher friction and wear when compared to the neat oil lubricity.One of the orthoborate ILs - trihexyltetradecylphosphonium bis(mandelato)borate (PBMB) – was selected for a thorough study when used as a sacrificial oil additive. A joint PFG NMR and Quartz Crystall Microbalance (QCM) study demonstrated the build-up of a PBMB rich film on a electrically charged surface. This provided an experimental prove for the possibility of electrostatically driven physisorption of ILs. Tribological tests performed on the same oil composition demonstrated that PBMB when reaching the surface triggered tribochemical reactions and formation of a surface protective tribofilm. Phosphonium orthoborate ILs demonstrated an outstanding performance (decreasing wear by up to 92% and friction by up to 50%) in lubricated mechanical contacts, both when used as neat lubricants and when used as additives. These results are based on an extensive study employing a wide variation in contact geometries, surface finish and motion type. The details of such performance are investigated through an extensive surface analysis and further linked to the chemical structure of the anion.
6.	Larsson, Joakim, 1989-, et al. (författare) The effect of bearing length on the surface quality of drawn wires 2020 Ingår i: Wire Journal International. - 0277-4275. ; 53:2, s. 50-55 Tidskriftsartikel (refereegranskat)
7.	Karlsson, Stefan, 1984-, et al. (författare) Non-destructive strength testing of microindented float glass by a nonlinear acoustic method 2023 Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 391 Tidskriftsartikel (refereegranskat)abstract The present paper describes a method for non-destructive testing of the glass strength. Square 10 × 10 cm2 samples of annealed float glass was inflicted with a controlled defect in the centre of the atmospheric side using Vickers microindentation-induced cracking with a force of 2 N, 5 N and 10 N and compared to an un-indented reference. The samples were non-destructively tested using a nonlinear acoustic wave method resulting in defect values. The average of the defect values was found to linearly correlate to the indentation force in a log–log relationship. The samples were subsequently tested in a ring-on-ring setup that allows for an equibiaxial stress state. The indentation-induced cracking gave practically realistic strength values in the range of 45 to 110 MPa. The individual sample values for failure stress as a function of normalized defect value show linear trends with approximately half of the data within 95% confidence limit. In summary, this study provides an initial proof-of-concept for a non-destructive testing of the strength of glass.
8.	Krishna, Visakh V, et al. (författare) Long term rail surface damage considering maintenance interventions 2020 Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 460 Tidskriftsartikel (refereegranskat)abstract A new methodology to estimate costs for wear and Rolling Contact Fatigue (RCF) on rails that cause a major portion of track maintenance costs is presented. It is demonstrated for a standard UIC-Y25 bogie and the FR8RAIL bogie, a softer and cross-braced iteration of the former, based on running conditions for the Swedish iron-ore line. Various non-linearities in the vehicle and track models have been considered. The rail profile evolution and the surface-initiated fatigue on the rail surface for different track radii with progressive tonnage are calculated using iterative multibody simulations. Additionally, the impact of maintenance measures on the long-term rail profile evolution has been considered with optimal preventive rail grinding actions implemented at fixed tonnage intervals based on the recommendations from EN13231-5. The rail profile attributes after 100 Mega Gross Tonnes passage are presented and discussed for both running gears. In doing so, the methodology addresses the long-term ‘track-friendliness’ of running gears considering wear, RCF and the intermediate track maintenance strategies.
9.	Kumar, Mayank, 1991- (författare) Friction in threaded fasteners : Influence of materials and tooling 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Threaded fasteners represent the most common type of machine element, with a unique function that facilitates ease of assembly and disassembly. This ease of disassembly allows machine parts to be reused, refurbished, and recycled. Easy as these components are to assemble, several factors must be considered to achieve the desired clamp force and to utilize the fastener to its full load capacity. The research presented in the thesis compares different tightening strategies and assembly tools to show that the clamp force and it´s scatter are influenced by the variation in the coefficient of friction (CoF) to a much larger extent than by the accuracy of an assembly tool. The research therefore focus on understanding the frictional response in a threaded fastener joint during tightening.A range of design and assembly factors are considered to identify how to increase reliability of the threaded fastener joints. These factors include tightening speed, coating, surface topography, fastener storage conditions, cutting fluid residue and joint material. A torque-controlled, two-step tightening method was mainly used in the studies as it is widely practiced across the production floor of the motor vehicle and general industries to tighten threaded fastener joints. A state-of-the-art friction test rig (FTR) was built to quantify variations in the CoF in the thread and under-head contacts during tightening. Coatings and contact surfaces are also characterized using SEM, FIB, indenters, and optical microscopes to gain an insight to find the likely reasons behind CoF variation. Fasteners with different Zn-based coatings were tightened on plates with surface topographies similar to those found in the motor vehicle industry. The samples were not cleaned before the testing but used "as-received" from the supplier. The degree of damage to the joint surface and fastener thread from the tightening depends on the hardness of the coating. The hardest coating (Zn-Ni) remained relatively unchanged but gave twice as high CoF in the under-head contact compared to the softest coating (Zn-flake). The under-head friction often dominates the tightening process and may be significantly affected by the joint surface topography and the level of cleanliness. In the automotive industry, many parts to be assembled are not thoroughly cleaned, increasing the risk of cutting fluid residue on the joint surface. Different types of cutting fluids were compared in a study with fasteners tightened against “as-received" and cleaned plates. It was shown that CoF might drastically decrease depending on the coating and cutting fluid types. An ester-based fluid performed best, providing the lowest CoF in the under-head contact due to its higher viscosity and polarity. A water-based fluid showed a significantly larger scatter. Water can also influence friction due differences in humidity and temperature. Sometimes fasteners are stored outside a factory which could lead to water diffusion in the coating in hot-humid climate or condensation of water on the fastener surface when it is brought from the outside storage at sub-zero temperatures into the production hall. Water on the coating and inside of it could lead to low CoF, with overtightening and fastener failure as a result. Four Zn-based coatings were compared and showed different response depending on the coating structure and topcoat. Another way to reduce CoF is to use variable speed tightening. It will also increase productivity, as it is faster. It will also improve operator ergonomics, as it gives much lower reaction torque. Much higher CoF was found for EPZ coating when tightened at a constant and very low speed, 5 rpm, due to cohesion that resulted in material transfer, compared to CoF during high, variable speed tightening. At the same time, speed had negligible influence on the CoF when using soft Zn-flake coating as the coating easily sheared off, acting as a solid lubricant.A soft coating is also practical when used in contact with parts made using additive manufacturing (AM). The AM parts are often rough, but a soft coating can mitigate an increase in the under-head CoF. An interesting finding was that the cheapest solution of using an uncoated fastener works very well. An anti-corrosion oil on the plain fastener helped in achieving low CoF. When the AM plate was machined, the CoF and surface damage significantly increased due to the lay of the surface topography created by machining. The findings presented in the thesis increase understanding of how various design and assembly factors govern friction in the thread and under-head contacts. The under-head contact dominates friction response. A proper selection and adjustment of these factors will help design engineers to optimize joint designs and achieve high fastener strength utilization.
10.	Ganvir, Ashish, 1991-, et al. (författare) Tribological performance assessment of Al2O3-YSZ composite coatings deposited by hybrid powder-suspension plasma spraying 2021 Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 409 Tidskriftsartikel (refereegranskat)abstract The advent of high-throughput plasma spray systems that allow axial feeding encourages the study of using liquid feedstock for various next-generation functional applications. The current study explores the benefit of such a plasma spray system to deposit hybrid powder-suspension Al2O3-YSZ ceramic matrix composite (CMC) coatings for tribological applications. The tribological performance of the hybrid processed CMC coatings was assessed using scratch, ball-on-plate wear and erosion tests and compared with that of monolithic powder-derived Al2O3 coatings. As-deposited and tribo-tested coatings were characterized using Scanning Electron Microscopy, X-ray Diffraction and Energy Dispersive Spectroscopy to analyse their microstructure and phase constitution. The results showed that the tribological performance of the hybrid powder-suspension Al2O3-YSZ CMC coating was significantly improved by enhancing the wear resistance under scratch, dry sliding ball-on-plate and erosion tests as compared to the conventional APS deposited monolithic Al2O3 coating. About 36% decrease in the dry sliding ball-on-plate specific wear rate and up to 50% decrease in the erosion wear rate was noted in the hybrid powder-suspension Al2O3-YSZ CMC coating as compared to the conventional APS deposited monolithic Al2O3 coating. The study concludes that the hybrid powder-suspension route can create CMC coatings with unique multi-length scale microstructures which can be attractive for combining different tribological attributes in the same coating system.
11.	Moghaddam, Pouria Valizadeh (författare) On the role of microstructure in wear of nanostructured carbide-free bainitic steels 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The significance of steel production for the development of sustainable society and economy is immense. Today’s fast growing global economy poses an increasing demand for improving the properties of steel. The development of nanostructured carbide-free bainitic steel with an excellent combination of strength and toughness is an attempt to satisfy this global demand. During austempering, the precipitation of cementite can be suppressed by addition of approximately 1.5 wt% silicon and a duplex microstructure comprising of extremely fine aggregates of retained austenite and bainitic ferrite can be obtained. Owing to their excellent mechanical properties, these novel steels exhibit considerable potential to replace quenched and tempered bearing steel or pearlitic rail steel. In these applications, wear play a crucial role in determining the performance of the components. However, the majority of studies have been limited to mechanical properties of these steels but not much attention has been paid to their tribological behaviour. Notably, the role of retained austenite and bainitic ferrite on wear performance has not yet fully understood. Furthermore, machining process is an inevitable step in the manufacturing of metal products. During the machining, contact temperature can rise to several hundred degrees. However, high temperature tribological behaviour of these steels in conjunction with coated cutting tool has not yet been addressed. Therefore, the aim of the present research work is to gain a deeper understanding of the correlation between microstructure and tribological performance of carbide-free bainitic steels in various conditions.To achieve this aim, tribological behaviour of nanostructured carbide-free bainitic steels has been investigated under dry rolling/sliding, sliding and two-body abrasive wear conditions. A number of steel grades were austempered under a wide range of temperatures and durations to obtain different carbide-free bainitic microstructures. The results have been compared with that of quenched and tempered bearing steel. Moreover, high temperature tribological behaviour of carbide-free bainitic and 316L stainless steels during interaction with TiAlN PVD coating has also been studied under dry reciprocating sliding condition.The results show that a relatively higher retained austenite content and its stability enhance wear resistance under rolling/sliding condition. Moreover, wear performance of carbide-free bainitic steel has been found to be superior to that of the quenched and tempered bearing steel. However, under sliding condition, the effect of retained austenite on wear heavily depends on sliding speed. At low sliding speed and under adhesive-dominated wear condition, higher retained austenite content results in improved wear performance due to the higher work hardenability. In contrast, at high sliding speed where oxidative wear is dominant, a microstructure with the lowest content of retained austenite exhibits the highest wear resistance. The higher amount of bainitic ferrite provides a hard underlying substrate for a thin and mechanically stable compositional mixed layer and thereby enhances the wear resistance. The formation and microcracking of a brittle white etching layer of quenched and tempered steel is responsible for its inferior wear resistance. Under two-body abrasive wear conditions, higher retained austenite content leads to improved wear resistance. A microstructure providing an optimum combination of hardness and toughness shows the best abrasive wear resistance. During reciprocating sliding, the tribological response of carbide-free bainitic steel is altered with increasing temperature. Higher temperature results in severe material transfer from carbide-free bainitic steel to TiAlN coated cemented carbide. Furthermore, at elevatedtemperature, a porous oxide layer grows on the transferred materials and reduce friction coefficient.In summary, there is no simple and general relationship between microstructure and wear resistance. Depending upon the dominant wear mechanisms and operating conditions, retained austenite and bainitic ferrite affect the wear behaviour in radically different manners.
12.	Hakeem, Abbas Saeed, et al. (författare) Synthesis and characterization of alkaline earth and rare earth doped sialon Ceramics by spark plasma sintering 2021 Ingår i: International journal of refractory metals & hard materials. - : Elsevier. - 0263-4368. ; 97 Tidskriftsartikel (refereegranskat)abstract Several sialon ceramics compositions were synthesized by selecting metal oxides (MOs) in the nanosize range as additives in the oxynitride network. Nanosized precursors, including Si3N4, SiO2, AlN, Al2O3, and MO (MO =MgO, CaO, SrO, BaO, Y2O3, La2O3, CeO2, Nd2O3, Eu2O3, Dy2O3, Er2O3 and Yb2O3,) were used in the present study. Probe sonication and spark plasma sintering techniques were used for mixing the powder precursors and subsequent synthesis of sialon ceramics at a relatively low temperature of 1500 ◦C. Formation of α-sialon(general formula represented by Mm/vSi12-(m+n)Alm+nOnN16-n) was investigated for m and n values of 1.1 and 0.6, respectively and their structural, morphological, thermal, and mechanical properties were evaluated. The synthesized samples were characterized using X-ray diffractometry and field emission scanning electron microscopy to study the effect of the MOs on the microstructure and resulting densification, hardness, fracture toughness, thermal expansion, and thermal conductivity. The sialon samples synthesized using the selected MOs exhibited similar relative densities in the range of 96 to 99% among all the samples and Vickers hardness (HV10) values, in the range of 15 to 20.8 GPa, depending on the type of MO. However, RE MOs exhibited a higher HV than AE MOs.Fracture toughness (KIc) was ~4 MPa⋅m1/2 for most of the samples, but the sample doped with Yb2O3 had the highest KIc of 6.3 MPa⋅m1/2. The thermal conductivity decreased as the atomic number (atomic radii) of the AE increases and in the case of RE exhibited a random tendency. On the other hand, the thermal expansion coefficient increased with increasing atomic radii of the AE, and a mixed trend, with values in the range of 2.63 to2.83 ppm⋅K-1, was observed for RE doped sialon ceramics. These behaviors are attributed to the resulting morphology and structure of alpha sialon comprised of both equiaxed and elongated grains. The properties of these sialon ceramics could be tailored by the proper selection of suitable precursors and synthesis parameters.
13.	Ansin, Caroline, 1996, et al. (författare) Simulation and Field Measurements of the Long-term Rail Surface Damage due to Plasticity, Wear and Surface Rolling Contact Fatigue Cracks in a Curve 2022 Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 591-601 Konferensbidrag (refereegranskat)abstract A methodology that simulates the long-term rail surface damage in a cross-section of a curve for a given traffic scenario is presented. The numerical model considers plastic deformation, wear, and initiation of rolling contact fatigue (RCF) surface cracks. The models and simulations are calibrated and validated, respectively, against field profile measurement data.
14.	Skrypnyk, Rostyslav, 1991 (författare) Long-term rail damage evolution in railway crossings 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract To accommodate the passage of wheels in intersecting traffic routes, fixed railway crossings have discontinuous rails leading to an intense load environment due to repeated wheel-rail impacts. This gives rise to high costs associated with repair and maintenance of the rails in the crossing. For given traffic conditions, several approaches to crossing design can be undertaken to mitigate the material degradation and hence reduce the life cycle cost. In the present thesis, the option of selecting a more suitable crossing material is explored. To obtain a guideline for material selection, the in-track performance of different materials during the life of a crossing needs to be predicted. In this work, an existing simulation methodology is extended by improving its robustness and computational efficiency. The methodology is able to account for the dynamic vehicle-track interaction, resolve the elasto-plastic wheel-rail contact, and consider the main damage mechanisms related to the running surface of a crossing rail. In this thesis, the methodology is updated by including a metamodel of plastic wheel-rail normal contact, which is introduced to meet the computational challenge of performing a large number of finite element simulations. The metamodel is based on the contact theory of Hertz. It is shown that the metamodel yields accurate results while accounting for the inelastic material behaviour. The simulation methodology is applied to several test cases. In the first study, it is employed to compare the short-term performance of two rail steel grades that are commonly used in crossings: the fine-pearlitic steel R350HT and the austenitic manganese steel Mn13. A representative load sequence generated by means of Latin hypercube sampling, taking into account variations in worn wheel profile, vehicle speed and wheel-rail friction coefficient, is considered. After 0.8 million gross tonnes (MGT) of traffic, it is predicted that the use of rolled Mn13 will result in approximately two times larger ratchetting strain as compared to the R350HT. In the second study, the methodology is used to simulate approximately 12 MGT of traffic in a crossing. The results of the simulations are compared with data measured in the field. It is shown that the simulations are in good qualitative agreement with the measurements. Finally, the methodology is used to quantify the difference in long-term damage between crossings with different crossing angles. As expected, the crossing with the largest crossing angle is subjected to the highest impact loads and exhibits the most damage after 52 MGT of simulated traffic.
15.	Vilhelmson, Henrik, 1997, et al. (författare) Dynamic vehicle–track interaction and structural loading in a crossing panel–calibration and assessment of a model with a 3D representation of the crossing rail 2024 Ingår i: Vehicle System Dynamics. - 1744-5159 .- 0042-3114. ; In Press Tidskriftsartikel (refereegranskat)abstract A three-dimensional (3D) finite element model of a railway crossing panel for use in multibody simulation (MBS) of dynamic vehicle–track interaction is presented. It is a two-layer track model with stock rails and sleepers represented by beam elements and a crossing rail represented by 3D solid elements. The track model uses linear bushings for the rail fastenings and bi-linear bushings for the ballast to allow for potentially voided sleepers. Based on the output from the MBS, the structural loading of the crossing in terms of strains, stresses and sleeper-ballast contact pressures is extracted in a post-processing step. The model is calibrated and validated to measurement data from a comprehensively instrumented switch & crossing (S&C) demonstrator installed in the Austrian railway network as a part of the European research programme Shift2Rail. The applied procedure for the calibration and critical assessment of the crossing model is described in detail. It is based on a model parameterisation with eight parameters relating to the rail fastening and foundation stiffnesses and to a distribution of the ballast voids. The calibration method uses Latin hypercube samples to explore the parameter space in a sensitivity analysis before a parameter optimisation is performed using a gradient-based method on a response surface built from a polyharmonic spline. In a comparative study it is shown that the 3D model and a more conventional beam model of the crossing rail show similar calibration results and good agreement with the measured data. The 3D model allows for the extraction of stress concentrations in the crossing rail but has an increased computational time of about 30% compared to the beam model.
16.	Al-Maqdasi, Zainab, 1986-, et al. (författare) Synergistic Effect of Multiscale Reinforcement on Wear of Wood Polymer Composites 2022 Ingår i: PolyTrib 2022. ; , s. 34-35 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
17.	Mallipeddi, Dinesh, 1987, et al. (författare) Investigation of the surface integrity of mechano-chemically finished powder metallurgy gears 2022 Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 115, s. 142-147 Konferensbidrag (refereegranskat)abstract Automotive gears are facing stringent requirements regarding weight and functional surfaces, especially in view of the electric powertrain. To achieve these demands, powder metallurgy gears need to be finished using grinding, and in certain cases, mechano-chemical treatments. With regards to the latter, five different triboconditioning strategies based on vibratory tub finishing and/or centrifugal barrel finishing were considered and their effects on the surface integrity and friction behavior were investigated. Triboconditioning improved the surface roughness after grinding and resulted in higher compressive residual stresses. Additionally, microscopic observations of the surface topography were carried out. The lowest friction coefficients were observed for triboconditioning with a doped material (tribofilm) on the finished surface.
18.	Niebles Atencio, Bercelay, 1979, et al. (författare) Experiments and Lattice-Boltzmann Simulation of Flow in a Vertically Aligned Gearbox 2023 Ingår i: Journal of Tribology. - 0742-4787 .- 1528-8897. ; 145:11 Tidskriftsartikel (refereegranskat)abstract This paper presents a study of the oil flow in a vertically arranged FZG gearbox. The splash and churning losses are experimentally evaluated using measurements of the resistance torque. Using high speed imaging, the instantaneous oil splashing inside the gearbox is also presented and compared with Computational Fluid Dynamics (CFD) results from the Lattice-Boltzmann method (LBM), instead of the traditional grid-based finite volume method. Four different configurations, including a spur gear based on the standard FZG geometry and a disc pair wheel-pinion with the same tip diameters of the standard geometries are used. The experiments cover a range from 500 to 3000 rpm and three oil levels are studied. For the CFD simulations, the same oil levels and rotational speeds are used. The experimental results indicate torque differences depending on the oil level and the configuration. The splashing pattern is also different from the standard horizontal FZG case, which is typically studied in the literature. On the other hand, the CFD simulations and flow visualization experiments are in relative agreement with one another. The similarities and differences in the torque values for the different configurations and the splashing pattern for both experiments and CFD simulations are analyzed and discussed.
19.	Sadeghi Kati, Maliheh, 1979, et al. (författare) Gain-scheduled H Controller Synthesis for Actively-steered Longer and Heavier Commercial Vehicles 2020 Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 234:7, s. 2045-2065 Tidskriftsartikel (refereegranskat)abstract This paper proposes a gain-scheduled controller synthesis for improving the lateral performance and stability of articulated heavy vehicles by active steering of the selected towed vehicle units. The longitudinal velocity is on-line measurable, and it is thus treated as a scheduling parameter in the gain-scheduled controller synthesis. The lateral performance of four articulated heavy vehicles, including existing Nordic heavy vehicles and prospective longer articulated heavy vehicles, are investigated with and without active steering and compared with a commonly used conventional tractor–semitrailer. The control problem is formulated as an ℋ∞H∞ static output feedback, which uses only information from articulation angles between the steered vehicle unit and the vehicle unit in front of it. The solution of the problem is obtained within the linear matrix inequality framework, while guaranteeing ℋ∞H∞ performance objectives. Effectiveness of the designed controller is verified through numerical simulations performed on high-fidelity vehicle models. The results confirm a significant reduction in yaw rate rearward amplification, lateral acceleration rearward amplification, and high-speed transient off-tracking, thereby improving the lateral stability and performance of all studied heavy vehicles at high speeds.
20.	Mahade, Satyapal, 1987-, et al. (författare) Investigating Load-dependent Wear Behavior and Degradation Mechanisms in Cr3C2-NiCr coatings deposited by HVAF and HVOF 2021 Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 4595-4609 Tidskriftsartikel (refereegranskat)abstract Wear resistant coatings that comply with non-toxic environment goals are highly desirable. Cr3C2-NiCr is a promising alternative to the toxic, ‘Co’- containing WC-Co coatings to mitigate wear. The purpose of this study was to examine the suitability of Cr3C2-NiCr coatings for automotive brake disc application by systematically investigating their dry sliding wear behavior at different test conditions. Therefore, High Velocity Air Fuel (HVAF) and High Velocity Oxy Fuel (HVOF) were employed to deposit Cr3C2-NiCr coatings. The powder feedstock and as-deposited Cr3C2-NiCr coatings were characterized for their microstructure and phase composition using SEM and XRD. Mechanical properties (hardness, fracture toughness), porosity and surface topography of the as-deposited coatings were evaluated. The coatings were subjected to sliding wear tests at different normal loads (5 N, 10 N and 15 N) using alumina ball as the counter surface. Coefficient of friction (CoF) evolution of HVAF and HVOF deposited coatings, along with their wear performance, was obtained for different normal load conditions. The wear performance ranking of HVAF and HVOF processed coatings was influenced by the test conditions, with HVAF coatings demonstrating better wear resistance than HVOF coatings at harsh test conditions and the HVOF coatings performing better under mild wear test conditions. Detailed post-wear analysis of worn coatings, the alumina ball counter-body and the resulting debris was performed to reveal the degradation mechanisms at different test conditions. Findings from this work provide new insights into the desirable microstructural features to mitigate wear, which can be further exploited to deposit wear-resistant coatings.
21.	Reddy, Akepati Bhaskar, 1990- (författare) Sustainable Lubrication and Tribotronics enabled by Ionic Materials 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Developments in machine design play a crucial role in the global endeavor towards sustainability. The potential for energy conservation and emission reduction has pushed lubrication research to the forefront, with the lubricant considered to be a vital machine component. As a result of the need for high machine efficiency and longevity, as well as that of greener lubricants, ionic liquids (ILs) are gaining attention for lubrication applications, especially in combination with biodegradable oils. ILs also present a unique opportunity for developing active lubrication, tribotronic systems. To make them an industrially viable option, however, an in-depth understanding of IL lubrication behavior is required. In this doctoral work, investigations of the tribologically relevant ionic boundary films formed by non-halogenated ILs dispersed in a carrier medium (polar solvent or bio-oil) were conducted using a variety of tribological techniques and neutron reflectance. The effect of external actuation by electric potential on the extent, ionic composition, and tribological relevance of the interfacial boundary films was also studied. The results revealed that the ionic architecture and the condition of IL in the oil play an important role in defining the lubricity of the adsorbed boundary films. Clear electroresponsivity was also observed across methods, with the relative concentration of cations and anions in the interfacial film and the lubricating film thickness changing with the electric potential bias. It was established that the anions, playing an anchor role on the surface, are crucial for the formation of robust load-carrying boundary films. A methodology using electrochemical impedance spectroscopy was developed for measuring and characterizing the electric conductivity of complex lubricating greases with ionic and non-ionic additives. According to these measurements, the electrical characteristics of greases depend on the interactions of IL with the grease matrix. Overall, this work contributes towards the development of sustainable lubrication and tribotronic systems using ILs.
22.	Shoja, Siamak, 1980 (författare) Microstructure and plastic deformation of textured CVD alumina coatings 2020 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract It is known that the wear performance of α-alumina coatings produced by chemical vapor deposition (CVD) is significantly influenced by the type and degree of texture. However, the main reasons behind this behavior are not fully understood. This thesis contains studies of two related topics for increasing the understanding of α-alumina coatings. The first topic concerns the microstructure and texture development of CVD α-Al2O3 coatings, and the second topic concerns calculations and analysis of the Schmid factors ( m ) for coatings with different textures. By combining different analysis methods (such as XRD, SEM, FIB/SEM, TKD, TEM, STEM, XEDS), and theoretical and experimental Schmid factor analysis by MATLAB and EBSD, the microstructure and plastic deformation of α-alumina coatings were investigated. The microstructures of three different CVD α-Al2O3 layers deposited onto a Ti(C,N,O) bonding layer were studied. Grain boundary diffusion of heavy elements from the substrate to the bonding layer/α-Al2O3 interface was observed. This may be the cause of a disturbance in the early growth of α-Al2O3. Additionally, it was found that the number of interfacial pores at the bonding layer/α-Al2O3 interface increased by introducing the H2S gas. The H2S gas also promoted an earlier development of the (0001) texture. The orientation of the grains was developed to the desired texture both as a gradual change over several grains and as an abrupt transformation from one grain to another. The probability of plastic deformation in different wear zones on the rake face of a cutting tool was investigated theoretically and experimentally by analyzing Schmid factors for textured α-Al2O3 coatings. Schmid factor diagrams were constructed using MATLAB/MTEX and used to extract frequency distributions for different slip systems and textures. The results were compared with lateral distribution maps of Schmid factors obtained from experimental coatings. It was observed that basal slip is most easily activated in the transition zone, followed by prismatic slip systems 1 and 2 in coatings with an (0001)-texture. The homogeneous plastic deformation behavior observed in this coating is also connected to mostly high Schmid factors in the m -value distribution. The differences between the m -value distributions for the three slip systems are not that pronounced in the (01-12) and (11-20) textures, and the distributions are relatively wide. The low wear rate and more homogeneous deformation of the coating with (0001) texture compared to the other coating textures may be the result of the high plasticity, offered by the easy activation of basal slip and prismatic 1 slip, and the low spread of Schmid factor values at the transition zone. In conclusion, the results presented in this thesis form a knowledge platform that can be used to understand the microstructure and wear mechanisms of textured CVD α-alumina coatings.
23.	Moghaddam, Pouria Valizadeh, et al. (författare) High temperature tribology of TiAlN PVD coating sliding against 316L stainless steel and carbide-free bainitic steel 2021 Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 159 Tidskriftsartikel (refereegranskat)abstract Reciprocating sliding wear tests were performed on TiAlN coating against 316L stainless steel and carbide-free bainitic steel at temperatures of 40, 400 and 800 oC. The results indicate that material transfer is more pronounced for the softer stainless steel at lower temperatures but at 800 oC, carbide-free bainite exhibits relatively more material transfer. Friction coefficient of stainless steel increases when temperature increases. However, for carbide-free bainite, there is a reduction in friction coefficient at elevated temperatures. This can be attributed to formation of an easily sheared iron oxide layer at elevated temperatures. In case of stainless steel, generation of a thin tribofilm containing aluminium oxide and oxidised transferred material can protect the TiAlN coating against wear at 800 oC.
24.	Hoier, Philipp, 1988, et al. (författare) Tool wear by dissolution during machining of alloy 718 and Waspaloy: a comparative study using diffusion couples 2020 Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 106:3-4, s. 1431-1440 Tidskriftsartikel (refereegranskat)abstract The wear of metal cutting tools is known to take place by the combined and simultaneous effects of several wear mechanisms. Knowledge of the relative contribution of the individual wear mechanisms is required to understand and predict the tool wear during cutting different workpiece materials and alloys. It has been shown previously that machining two heat resistant superalloys, alloy 718 and Waspaloy, leads to distinctively different tool wears. Even though the subject has been addressed in various studies, there are still open questions regarding the underlying reasons for the differing tool wear rates. In particular, the relative contributions of diffusion/dissolution when machining the two alloys have not been addressed so far. Therefore, a qualitative comparison of the chemical interaction between the tool material and the two superalloys was made by using diffusion couple tests. The aim was to mimic the high temperatures and intimate contact between workpiece and tool material at the tool rake and flank faces during cutting under controlled and static conditions. The obtained results suggest that it is unlikely that differences in flank wear rate when machining the two superalloys are caused by significantly varying magnitudes of tool atoms dissolving into the respective workpiece. Analysis of the tool/superalloy interfaces in the diffusion couples revealed diffusion-affected zones of similar size for both tested superalloys. Increasing test temperature led to enhanced interdiffusion which suggests an increase in tool wear by diffusion/dissolution for higher cutting temperature. For alloy 718, the higher test temperature also led to depletion of carbon together with formation of tungsten within the tool in close vicinity to the interface with the superalloy.
25.	Bayani, Mohsen, 1981, et al. (författare) Empirical characterisation of friction parameters for non-linear stick-slip simulation to predict the severity of squeak sounds 2021 Ingår i: SAE International Journal of Vehicle Dynamics, Stability, and NVH. - : SAE International. - 2380-2162 .- 2380-2170. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Squeak and rattle (S&R) are nonstationary annoying sounds inside the car cabin that impose high warranty costs on car manufacturers. The need for taking S&R preventing measures and the maturity level and cost considerations of the physical prototypes during the pre-design-freeze stages justifies the use of virtual simulation methods. Squeak is a friction-induced high-frequency sound that is attributed to the stick-slip friction phenomenon. The importance of the friction parameters in the squeak severity prognosis is analytically and experimentally mentioned in the literature. However, studying the variation of these parameters respecting the changes in loading and driving conditions with the aim of application in virtual simulations has remained limited or too simplistic. In this work, the rate weakening effect of the friction coefficient curve was involved in the nonlinear finite element simulation of stick-slip events by an exponential decay formulation. The approximated squeak severity by the virtual simulations for selected material pairs agreed with the empirical results from a flexural stick-slip test bench. From the empirical stick-slip data, the dependence of the squeak severity on the friction decay coefficient and the difference of static and kinetic friction coefficients at low and high normal loads were observed, respectively. The relativity of friction parameters on the test conditions demands a dynamic updating of the friction model that can be achieved by polynomial or exponential approximations. Also, the observed polynomial relationship between the squeak severity and the operational conditions can be used to estimate the squeak severity from the linear dynamic simulation results. The outcome of this work can help to better understand the influence of the friction modelling parameters and their variation respecting the operational conditions. This can facilitate a more accurate prediction of squeak risk by employing virtual simulation tools in the pre-design-freeze stages of car development.
26.	Ruggiero, A., et al. (författare) Accurate Measurement of Reciprocating Kinetic Friction Coefficient through Automatic Detection of the Running-In 2020 Ingår i: IEEE Transactions on Instrumentation and Measurement. - : Institute of Electrical and Electronics Engineers Inc.. - 0018-9456 .- 1557-9662. ; 69:5, s. 2398-2407 Tidskriftsartikel (refereegranskat)abstract Tribological tests are adopted to estimate the kinetic friction coefficient (COF) of the material of interest according to the American Society for Testing and Materials (ASTM) standard. Typically, for the measurement process, several replicas, as well as a postprocessing data treatment, are necessary to take into account the observed casual variability of the measurand. This article describes a statistical approach aiming to highlight the running-in phase and the most significant time intervals during the steady-state for each test replica. A two-steps procedure based on the adoption of the bootstrap method allows the automatic detection of the running-in time interval and the outlier filtering of the steady-state. Experimental activity has been carried out by performing multiple tests through the ball-on-flat tribometer in order to verify the improvement allowed by the authors' proposal about the dry friction COF measurement in terms of both accuracy and repeatability. © 1963-2012 IEEE.
27.	Sharifzadeh, Seyed Mojtaba, 1988, et al. (författare) An effective tyre to road friction estimation applied to heavy vehicles 2023 Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : Sage Publications. - 0954-4070 .- 2041-2991. ; 237:14, s. 3547-3558 Tidskriftsartikel (refereegranskat)abstract Knowledge about the tyre to road friction is central to many vehicle functions as well as the overall performance of the vehicle. In this paper, a new real-time algorithm is presented for estimating the coefficient of friction using available on-board sensor information. A computationally efficient algorithm is presented, that reduces resources usage compared to previously published approaches. Issues connected to heavy vehicles and friction estimation is addressed, such as wind up of hub assembly and vehicle speed sensing. The performance of the algorithm is illustrated on data sets acquired from the test track recordings in winter conditions.
28.	Six, K., et al. (författare) A whole system model framework to predict damage in turnouts 2023 Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 61:3, s. 871-891 Tidskriftsartikel (refereegranskat)abstract This paper presents a whole system model framework that enables a holistic prediction of accumulated track damage in railway turnouts. A modular approach allows for insight into the interaction of different damage mechanisms such as rail profile change due to the plastic deformation and wear as well as track settlement. The methodology focuses on the two most critical areas of the turnout in terms of damage: switch and crossing panels. It is shown that at the beginning of the service life of the turnout the running surface of the rails in these areas change significantly due to plastic deformation, which in turn increases the dynamic impact forces from passing vehicles. These impact forces cause vertical track settlement that is most pronounced in the crossing area. Track settlement introduces additional dynamics into the system leading to self-reinforcing behaviour. It is shown that the proposed methodology can predict accumulated track damage accounting for the coupling between different damage modes such as track settlement, rail profiles plastic deformation and wear. It can therefore be used for holistic assessment of turnouts e.g. in design optimisation studies.
29.	Öhman, Sebastian, 1991-, et al. (författare) Selective kinetic growth and role of local coordination in forming Al2TiO5-based coatings at lower temperatures 2021 Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 2:17, s. 5737-5751 Tidskriftsartikel (refereegranskat)abstract Negative thermal expansion is an elusive property found among certain materials, whose potential applications have remained limited due to the many challenges faced in their synthesis. Herein, we report the successful formation of aluminium titanate-based coatings (Al2TiO5), a material renowned for its low-to-negative thermal expansion, by the co-deposition of aluminium-isopropoxide and titanium-isopropoxide in a hot-wall chemical vapour deposition instrument. While coatings grown at 450 °C were amorphous as-deposited, a short-range order into the Al2TiO5-phase was found and analysed by using Raman spectroscopy. Upon subsequent annealing at 700 °C for 3 hours, crystalline coatings were achieved without forming any binary phases. The selective synthesis of the Al2TiO5 phase is ascribed to the precursors’ inherent chemical similarities, resulting in a kinetic targeting of this phase and a short-range homogeneity, entailing its preferred crystallisation. The role of local coordination is expressed by demonstrating the formation of intergrowth phases ascribed to lower coordinating interstices in the compound. Both the formation and crystallisation temperatures reported herein, as well as the timescales needed for the synthesises, are considerably lower than any conventional adopted solid-state techniques used so far to attain the Al2TiO5 phase.
30.	Khan, Saad Ahmed, 1987-, et al. (författare) Wheel-rail squeal sound reduction using top of rail friction modifier: a case study 2020 Ingår i: International Journal of COMADEM. - : COMADEM International. - 1363-7681. ; 23:1, s. 69-76 Tidskriftsartikel (refereegranskat)
31.	Nielsen, Jens, 1963, et al. (författare) Wheel–Rail Impact Loads, Noise and Vibration: A Review of Excitation Mechanisms, Prediction Methods and Mitigation Measures 2021 Ingår i: Notes on Numerical Fluid Mechanics and Multidisciplinary Design. - Cham : Springer International Publishing. - 1612-2909 .- 1860-0824. ; 150, s. 3-40, s. 3-40 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract Railway noise and ground-borne vibration induced by wheel–rail impact loads are generated by discrete wheel/rail surface irregularities or local deviations in the nominal wheel–rail contact geometry. On the running surface of a rail, a discrete irregularity can be inherent to the railway design, for example at crossings or insulated joints. On the wheel or rail, the irregularity could also be the result of surface damage due to rolling contact fatigue cracking or a consequence of wheel sliding without rolling. This review describes the mechanisms of wheel–rail impact generated by wheel flats, rail joints and crossings. These can be a source of locally increased noise and vibration levels and increased annoyance, as well as of damage to vehicle and track components. The wheel–rail excitation at such irregularities, as indicated by the vertical wheel centre trajectory, leads to an abrupt change of momentum, potentially causing a momentary loss of wheel–rail contact followed by an impact on the rail. The resulting loading is a transient and often periodically repeated event exciting vibration in a wide frequency range with most of the energy concentrated below about 1 kHz. For the numerical prediction of high-magnitude transient loading and situations potentially leading to loss of contact, a non-linear wheel–rail contact model is required, implying that the simulation of contact force is carried out in the time domain. To avoid the need for large, computationally expensive models, a hybrid approach has been developed in which the time history of the contact force is transformed into an equivalent roughness spectrum; this is used as input to frequency-domain models for the prediction of noise and vibration. Since the excitation mechanism is similar to that for rolling noise, the same types of measures to mitigate wheel and track vibration can be applied. However, the main priority should be to control the irregularity by design and regular maintenance.
32.	Ekberg, Anders, 1967, et al. (författare) RAIL AND WHEEL HEALTH MANAGEMENT 2022 Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 179-188 Konferensbidrag (refereegranskat)abstract Rail and wheel health management is investigated with focus on deterioration phenomena in the wheel/rail contact interface – plastic deformation, wear, and rolling contact fatigue (RCF). How operational conditions affect deterioration, and how they can be included in track health predictions is discussed together with a more in-depth description of deterioration mechanisms. Here means of measuring, quantifying, and predicting deterioration is in focus. This provides the basis for the outline of a rail and wheel health management framework. As discussed in the paper, the proposed framework is well in line with the requirements in the ISO 55000 standard for asset management.
33.	Ekberg, Anders, 1967, et al. (författare) Rail and wheel health management 2023 Ingår i: Wear. - 0043-1648. ; 526-527 Tidskriftsartikel (refereegranskat)abstract Rail and wheel health management is investigated with focus on deterioration phenomena in the wheel/rail contact interface – plastic deformation, wear, and rolling contact fatigue (RCF). How operational conditions affect deterioration, and how they can be included in wheel/rail health predictions is linked to a more in-depth description of deterioration mechanisms. Here means of measuring, quantifying, and predicting deterioration is in focus. This discussion provides the basis for the outline of a rail and wheel health management framework. As discussed in the paper, the proposed framework is well in line with the requirements in the ISO 55000 standard for asset management.
34.	Kumar, Rahul, et al. (författare) Bioinspired and Multifunctional Tribological Materials for Sliding, Erosive, Machining, and Energy-Absorbing Conditions: A Review 2024 Ingår i: Biomimetics. - 2313-7673. ; 9:4 Forskningsöversikt (refereegranskat)abstract Friction, wear, and the consequent energy dissipation pose significant challenges in systems with moving components, spanning various domains, including nanoelectromechanical systems (NEMS/MEMS) and bio-MEMS (microrobots), hip prostheses (biomaterials), offshore wind and hydro turbines, space vehicles, solar mirrors for photovoltaics, triboelectric generators, etc. Nature-inspired bionic surfaces offer valuable examples of effective texturing strategies, encompassing various geometric and topological approaches tailored to mitigate frictional effects and related functionalities in various scenarios. By employing biomimetic surface modifications, for example, roughness tailoring, multifunctionality of the system can be generated to efficiently reduce friction and wear, enhance load-bearing capacity, improve self-adaptiveness in different environments, improve chemical interactions, facilitate biological interactions, etc. However, the full potential of bioinspired texturing remains untapped due to the limited mechanistic understanding of functional aspects in tribological/biotribological settings. The current review extends to surface engineering and provides a comprehensive and critical assessment of bioinspired texturing that exhibits sustainable synergy between tribology and biology. The successful evolving examples from nature for surface/tribological solutions that can efficiently solve complex tribological problems in both dry and lubricated contact situations are comprehensively discussed. The review encompasses four major wear conditions: sliding, solid-particle erosion, machining or cutting, and impact (energy absorbing). Furthermore, it explores how topographies and their design parameters can provide tailored responses (multifunctionality) under specified tribological conditions. Additionally, an interdisciplinary perspective on the future potential of bioinspired materials and structures with enhanced wear resistance is presented.
35.	Mussa, Abdulbaset, et al. (författare) Wear mechanisms and wear resistance of austempered ductile iron in reciprocal sliding contact 2022 Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 498-499 Tidskriftsartikel (refereegranskat)abstract Austempered ductile irons (ADIs) are used in applications commonly exposed to severe contact conditions, and as a consequence wear damage frequently followed by failure of components. Hence, wear resistance of the material governs the final life time of a component. In the present work, the sliding wear resistance of two ausferritic spheroidal graphite ductile irons ADI1 and ADI2 used commonly in mining and construction equipment was investigated. ADI1 and ADI2 were heat treated to a similar strength, the volume fraction of the carbon-rich austenite in ADI1 and ADI2 was around 30% and 16%, respectively, and they both contained 10 – 13% nodular graphite. The wear tests were performed using a slider-on-flat-surface (SOFS) tribometer. Case-hardened steel plates made of a high strength steel, 22NiCrMo12–F, were used as the counterface. The wear tests were conducted under lubricated sliding contact at normal loads of 50, 100, 200 and 300 N, and at each load level sliding at 100, 200 and 300 m. The friction force between contacting surfaces was continuously monitored during sliding. The lubrication used in the present investigation was a mineral-oil-based paste commonly used in applications where high frictional heating is generated. Wear mechanisms of the tested specimens were investigated by means of optical and scanning electron microscopy and X-ray diffraction, and the wear damage was quantified using a 3D-profile optical interferometer. The main wear mechanisms, severe plastic deformation and surface delamination, were discussed concerning test conditions and material properties. The ADI1 grade with the higher volume of carbon-rich austenite displayed better resistance to sliding wear at high normal loads. The higher normal loads promoted larger deformation at and beneath the contact surface and initiated austenite transformation into hard martensite. Thus, it was concluded that the increase of wear resistance in ADI1 was due to the formation of marteniste. On the other hand, the ADI2 grade with higher silicon content showed lower wear resistance at high normal loads. This was associated with cracking of the proeutectoid ferrite presented in ADI2.
36.	Sarkar, Saptarshi, 1992, et al. (författare) Mitigation of transient torque reversals in indirect drive wind turbine drivetrains 2023 Ingår i: Wind Energy. - 1099-1824 .- 1095-4244. ; 26, s. 803-825 Tidskriftsartikel (refereegranskat)abstract Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well-known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their rolling contact fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well-known that these premature failures are attributed to surface damages such as white surface flaking (WSF), white etching cracks (WECs) and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied to demonstrate their TTR mitigation capabilities. Then, a novel idea of open-loop high-speed shaft mechanical brake control is proposed. The results presented here show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high-speed shaft and reducing the risk of bearing slip by actuating the high-speed shaft brake at the onset of the transient event. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time applied to it. This novel approach allows the wind turbines to protect the gearbox bearings from TTRs using the existing hardware on the turbine.
37.	Al-Maqdasi, Zainab, 1986-, et al. (författare) Tribological Study on Wood and Graphene Reinforced High Density Polyethylene 2022 Ingår i: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials. - Lausanne : EPFL Lausanne, Composite Construction Laboratory. - 9782970161400 ; , s. 585-592 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Wear rate (WR) and coefficient of friction (COF) for high-density polyethylene (HDPE)and its composites of wood flour (WF) and/or graphene nanoplatelets (GNPs) are studied. Theinvestigation is performed by pin-on-disc test configuration on samples with different moisturecontents (dry, and samples saturated at RH of 33% and 79% in room temperature). The effect ofthe different scales of reinforcement (GNPs and WF) on these properties is discussed. Themorphological/microstructural changes in the materials induced by the motion in contact and/ormoisture content are investigated by differential scanning calorimetry (DSC). Results show thatreinforcing the polymer with WF or GNPs reduces the WR significantly, compared to neat HDPE.The hybrid reinforcements contribute to maximum improvement in wear resistance (>98%) andin the reduction of COF (>11%). The improvement in the tribological behavior of bio-basedmaterials has a significant impact on sustainable development through the improved design,durability, and environmental impact.
38.	Meyer, Knut Andreas, 1990, et al. (författare) Anisotropic yield surfaces after large shear deformations in pearlitic steel 2020 Ingår i: European Journal of Mechanics, A/Solids. - : Elsevier BV. - 0997-7538. ; 82 Tidskriftsartikel (refereegranskat)abstract Rolling contact fatigue often initiates in the highly deformed surface layer of railway rails. However, the behavior of pearlitic rail steels, subjected to such large shear strains, is not well known. Due to buckling, it is not possible to obtain the large shear deformation with tubular test bars. We have, therefore, developed a novel experimental methodology. Large shear strains (up to 1.13) were obtained by twisting cylindrical solid test bars under a compressive axial load. After that, these bars were re-machined into thin-walled tubular test bars. The remachined bars were then used to characterize the behavior of the deformed material. Changes in both the elastic and plastic responses are observed, quantified, and discussed. We evaluate the ability of different yield criteria to model the experimentally measured yield surfaces. Three anisotropic yield criteria are considered: Hill (1948), Barlat's yld2004-18p, and Karafillis and Boyce (1993). The accuracies of these criteria are evaluated and compared to the estimated experimental uncertainty. Furthermore, cross-validation is used to investigate the predictive abilities of the yield criteria. It turns out that the Hill yield criterion fits and predicts the experimental data very well. Finally, the evolution of yield surfaces is found to be strongly dependent on the amount of plastic deformation defining the yield limit.
39.	Calderon Salmeron, Gabriel, 1990- (författare) Reduced friction by ionic technology : Grease lubrication of bearings for e-motors 2024 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Reducing the environmental impact of machinery relies on all machinery components operating more efficiently. Rolling element bearings are an indispensable part of all modern machinery, enabling and facilitating machine operation. Greases, an often overlooked machine component, are an essential part of rolling bearings and have the greatest scope for improving the bearing efficiency. Thus, studying the mechanisms of friction generation and energy loss originating from the grease and all of its components in a grease-lubricated bearing is fundamental for further improving their efficiency. This is a challenging task since only fully formulated commercial greases are often available, making it difficult to study in isolation the contribution of each individual component to the friction process. The complexity of studying grease lubrication increases further due to the intricacy of measuring friction within the bearing. Robust methodologies and standards for measuring grease efficiency within a rolling element bearing are scarce and must be developed.This doctoral thesis investigated the effect of different grease components, such as different grease thickeners and a non-halogenated ionic liquid grease additive, on the frictional performance of rolling bearings operating under conditions typical of those encountered in electric motors. This required that a new and robust experimental set-up was designed with the purpose of continuously measuring friction torques from a rolling element for prolonged periods. An evaluation of the role of each of the grease components in the process of friction generation thus became possible. First, the effect of the running-in procedure on the grease ageing was studied. Imposing an increasing speed profile appeared to induce a mild ageing on the greases. In the second and third studies, the effect of different thickeners on the lubrication performance during the bleeding phase was studied under steady-state conditions. Compared to lithium-complex grease, polypropylene grease reduced the energy consumption of the grease-lubricated bearing. A modified polypropylene grease, with recycled polypropylene in the thickener, was also tested. The experiments with the recycled polypropylene grease finished successfully with no traces of bearing damage and friction torque values lying between the lithium complex and polypropylene greases. This represented a milestone in the development of greases with recycled materials. In a fourth study, the effects of three different grease thickeners (lithium complex, polyurea (diurea) and polypropylene) were evaluated on lubrication performance and energy-saving potential during prolonged conditions of transient and variable speeds, typical for electric motors of battery electric vehicles. From the analysis of the resulting friction torques, it was concluded that the thickener influences the friction torque through the process of dynamic bleeding and that friction torques under both steady-state and transient speed conditions were predominantly controlled by rolling friction. In the fifth study, the addition of a non-halogenated ionic liquid to a LiX grease resulted in a drastic 45% reduction of energy dissipation. The feasibility and potential of using this novel grease under e-motor conditions were discussed. Finally, the overall environmental footprint (kg CO2-eq) of a grease-lubricated bearing system was estimated (production of grease and bearing together with energy consumption over a typical service life). Reducing friction torques and their corresponding energy losses through a better design of individual grease formulations appears to ensure that the greatest impact on CO2-eq released can be obtained.
40.	Dhakal, Nayan, et al. (författare) Impact of processing defects on microstructure, surface quality, and tribological performance in 3D printed polymers 2023 Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 23, s. 1252-1272 Tidskriftsartikel (refereegranskat)abstract Additive manufacturing (AM), also known as three-dimensional (3D) printing, of polymer-based materials is growing as a time-efficient, economical, and environmentally sustainable technique for prototype development in load-bearing applications. This work investigates the defects arising from the processing in material extrusion-based AM of polymers and their impact on the part performance. The influence of raster angle orientation and printing speed on tribological characteristics, microstructure, and surface finish of acrylonitrile butadiene styrene (ABS) fabricated in a heated build chamber was studied. Comprehensive analysis with fractography and tomography revealed the formation, distribution, and locations of internal voids, while surface defects were studied with the topography analysis of as-printed surfaces. Surface roughness and tribological results show that printing speed can be optimally increased with a minimal impact on interlayer bonding and part performance. Increased printing speed allowed up to 58% effective reduction in printing time obtaining comparable mechanical properties at varying process parameters. 3D printed ABS exhibited dry sliding friction coefficients in the range of 0.18–0.23, whilst the maximum specific wear rate was 6.2 × 10−5 mm3/Nm. Higher surface roughness and increased printing speed exhibited delayed running-in during dry sliding, while insignificant influence was observed for steady-state friction and wear behaviors. The findings indicate that improved surface finish and reduced internal defects can be achieved with a controlled build environment allowing for higher printing speed. The observations in this study are evidence that 3D printing can be adapted for the sustainable manufacturing of polymeric components for tribological applications.
41.	Kumar R, Avinash, et al. (författare) The hydraulic and thermal performances of rectangular and square microchannel with different hydraulic diameters cooled by graphene–platinum hybrid nanofluid 2022 Ingår i: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. - : SAGE Publications. - 2041-2983 .- 0954-4062. ; 236:13, s. 7473-7483 Tidskriftsartikel (refereegranskat)abstract The objective of this paper is to analyze the effect of hydraulic diameter and channel shape on the thermal and hydrodynamic characteristics of a microchannel cooled by Graphene–Platinum/water hybrid nanofluid for electronic cooling applications. The study was performed numerically using mathematical software called Maple 19.0. Microchannels having square and rectangular cross-sections, and hydraulic diameters ranging from 200 µm to 1,000 µm were taken into consideration. Thermal resistance, heat transfer coefficient, pressure drop, and friction factor were evaluated for different conditions and their corresponding graphs are presented and discussed. It was evident from the results that low thermal resistance and high heat transfer coefficient was achieved upon decreasing the hydraulic diameter, which is favorable for the cooling of electronic chips and devices. Based on the Reynolds number, the heat transfer coefficient increased by 2–4 times for both rectangular and square microchannels, on decreasing the hydraulic diameter from highest value (1,000 µm) to lowest value (200 µm). However, friction factor and pressure drop increased for channels with lower hydraulic diameters. In addition, rectangular microchannels exhibited better heat transfer performance, while square microchannels had lower friction factor and pressure drop. Rectangular microchannels presented a maximum enhancement of 30% in heat transfer coefficient and a reduction of 18% in thermal resistance, when compared to square microchannels. The results also suggested that the performance of microchannels with 500 µm hydraulic diameter is balanced, considering both heat transfer performance and pressure drop constraints.
42.	Landström Voortman, Eric, 1993, et al. (författare) Improved Finite Element Modelling of Tread Braked Wheel Performance Verified by Brake Rig Tests 2023 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract The objective of the present study is to validate a finite element material model for railway wheel steel against brake rig test results. The material model for pearlitic ER7 wheel steel has been calibrated for thermomechanical loading based upon the regulatory requirements for brake rig tests using specimen test results. The material model has shown better adherence to thermomechanical results compared to previous material models, but ultimately full-scale validation is required. To verify and further develop the model, a combined experimental and numerical campaign was launched. Using a custom-built brake rig at Chalmers University, two different designs of European freight wheels are tested at power levels of 30 and 50 kW for durations of up to 45 min with maximum temperatures exceeding 600 °C. Wheel rim displacements are measured during experiments and residual stresses are measured before and after each test using an instrument employing the elastoacoustic effect. Temperatures are measured using thermocouples on the wheel web, sliding thermocouples on the tread and a high-speed thermographic camera. The experimental results are then compared to finite element simulations at the same brake power levels using the aforementioned material model. The results show possible correspondence between the experimental and finite element results, indicating that the numerical model may be accurate enough for preliminary predictions of braking damage, while also highlighting challenges of thermal model assumptions.
43.	Larsson, Sylvia (författare) Effect of process parameters and biomass composition on flat-die pellet production from underexploited forest and agricultural biomass 2021 Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 302 Tidskriftsartikel (refereegranskat)abstract This study investigates the impact of biomass moisture content, press-channel length, energy input, and die temperature on pellet quality in pilot-scale flat-die pellet production. In addition, observed correlations between pellet quality and the chemical composition of the pelletized biomass assortments are presented. Ten different feedstock assortments: Scots pine bark, Scots pine forest residues, willow, poplar stemwood with bark, beech stemwood with bark, wheat straw, reed canary grass, corn cobs, sunflower shells, and grape seed cakes were pelletized in a flat-die pilot-scale pelletizer with a die-channel diameter of 6 mm. The die-channel length varied within a range of 18–60 mm and biomass moisture content from 10% to 23%. In all, 72 pelletizing experiments were performed.Biomass moisture content was the most important parameter for mechanical durability. The feedstock moisture content required to obtain maximum pellet durability depended on the feedstock and showed correlations with its extractives and galactose content. For all feedstocks, bulk density correlated negatively with moisture content. The mechanical durability and bulk density of pellets increased with energy consumption. Energy consumption increased with press-channel length and was correlated with acetyl-group content.
44.	Mahade, Satyapal, 1987-, et al. (författare) Novel suspension route to incorporate graphene nano-platelets in HVAF-sprayed Cr3C2-NiCr coatings for superior wear performance 2021 Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 13, s. 498-512 Tidskriftsartikel (refereegranskat)abstract Graphene nano platelets (GNP) have several attractive properties, including excellent lubricity that can be used to develop wear-resistant coatings. Thermally sprayed chromium carbide-nickel chromium (Cr3C2-NiCr) coatings are widely employed to impart wear resistance to engineering components. This work attempts to improve the wear resistance of high velocity air fuel (HVAF) sprayed Cr3C2-NiCr coatings by incorporating GNP using a hybrid approach in which Cr3C2-NiCr (powder) and GNP (suspension) are co-axially injected. Two different powder-to-suspension delivery ratios were employed in this study that utilizes a liquid feedstock in tandem with a HVAF system. Furthermore, for comparison, a pure (without graphene) Cr3C2-NiCr reference coating was deposited by the HVAF process using identical spray parameters. The as-sprayed coatings were characterized for their microstructure and phase constitution by SEM/EDS and X-Ray Diffraction. Mechanical properties such as hardness and fracture toughness were evaluated using micro-indentation technique. The hybrid coatings were subjected to dry sliding wear tests and wear performance was compared with reference Cr3C2-NiCr. The GNP incorporated hybrid coatings exhibited lower CoF and lower wear rates than the reference Cr3C2-NiCr coating. Post wear SEM/EDS analysis revealed different wear mechanisms predominant in the investigated coatings. Utilizing the above as a case study, this work provides key insights into a new approach to produce GNP incorporated coatings for mitigating wear.
45.	Pujante, Jaume, et al. (författare) Wear Mechanisms in Press Hardening: An Analysis through Comparison of Tribological Tests and Industrial Tools 2023 Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 11:5 Tidskriftsartikel (refereegranskat)abstract Press hardened components have become widespread in the automotive industry in structural and crash-resistant applications, thanks to the combination of the complex shapes and high mechanical properties obtained. However, the press hardening of coated boron steel results in severe adhesive-based wear, with tool maintenance being required in as few as 3000 cycles. The current industrial implementation of press hardening is defined to work around this phenomenon. While this aspect has been studied by different authors, most of the literature deals with laboratory-scale tribosimulators, leaving an open question into how this knowledge transfers to macroscopic effects on the industrial process. In this work, wear in press hardening is studied by comparing the results obtained in laboratory conditions with a pilot-scale line, and finally, with wear mechanisms observed on industrial tools. The aim of this study is to consolidate the current knowledge about the micro-mechanisms involved, and to understand to what extent the existing tests reproduce the actual mechanisms observed in the press floor. The results show how material transfer mainly happens as an accumulation of dust compacted into initial defects on the tool surface. Moreover, this mechanism is effectively reproduced in laboratory tribosimulators and pilot environments, showing a similar morphology to wear on industrial tools. The work sheds light on the underlying causes of wear, and its potential mitigation strategies.
46.	Pålsson, Björn, 1981 (författare) A Parameterized Turnout Model for Simulation of Dynamic Vehicle-Turnout Interaction with an Application to Crossing Geometry Assessment 2020 Ingår i: Lecture Notes in Mechanical Engineering. - Cham : Springer International Publishing. - 2195-4356 .- 2195-4364. ; , s. 351-358 Konferensbidrag (refereegranskat)abstract This paper presents a parameterized structural track model for the simulation of dynamic vehicle-turnout interaction in a multi body simulation environment. The model is demonstrated by performing simulations for different vehicle speeds, crossing geometries and fixations between crossing rail and sleepers with different stiffness. Results are presented for dynamic wheel-rail contact forces, bending moments in crossing rail and sleepers and sleeper-ballast contact pressure. The main conclusions are that (a) the peak dynamic bending moment in the sleeper under the crossing transition is significantly higher with a stiff direct fixing compared to a softer indirect fixing and (b) the structural loading in terms of bending moment in the crossing rail, bending moment in the underlaying sleeper and sleeper-ballast contact pressure increases proportionally and significantly with increased impact angle and vehicle speed for wheels passing over the crossing transition.
47.	Ricciardi, Vincenzo, et al. (författare) A Novel Semi-empirical Dynamic Brake Model for Automotive Applications 2020 Ingår i: Tribology International. - : Elsevier BV. - 0301-679X. ; 146 Tidskriftsartikel (refereegranskat)abstract In this work, the authors propose a semi-empirical dynamic brake model with the intent of improving the simulation fidelity of Model-, Software-, and Hardware-in-the-Loop environment in vehicle dynamics studies. This model has been parametrized and validated for three passenger cars’ brake systems composed of ECE linings and cast iron discs. The proposed model outperforms the State-of-the-Art by accounting for changes in the interfacial properties and thermal state at the brake pad-disc contact. This work is the result of a joint collaboration between Technische Universität Ilmenau (Ilmenau, Germany) and Volvo Cars (Gothenburg, Sweden). The results show that the braking time, disc temperature and local contact pressure play a fundamental role on the contact area dynamics and, hence, on the friction coefficient.
48.	Skrypnyk, Rostyslav, 1991, et al. (författare) Long-term rail profile damage in a railway crossing: Field measurements and numerical simulations 2021 Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 472-473 Tidskriftsartikel (refereegranskat)abstract Railway crossings are subjected to a severe load environment leading to a degradation of rail profiles due to wear and accumulated plastic deformation. This damage is the result of the high magnitudes of contact pressure and traction generated in the wheel–rail contact during each wheel transition between wing rail and crossing nose. An extensive measurement campaign has been carried out at a test site in Austria in a particularly severely loaded crossing manufactured from an explosion depth hardened (EDH) manganese steel grade. For an accumulated traffic load of 65 Mega-Gross-Tonnes (MGT), the evolution of profile degradation for 16 cross-sections along the crossing rail has been recorded on multiple occasions. The results from the measurement campaign are used to validate a previously presented multidisciplinary and iterative simulation methodology for the prediction of long-term rail damage. It is shown that the predicted rail profile degradation exceeds the measured degradation for some of the cross-sections but generally a good qualitative agreement is observed. Possible reasons for the higher predicted damage are the uncertain distribution of traffic at the test site and differences in material properties between the crossing in the field and the test specimens used for calibration of the cyclic plasticity model. The influence of the frequency of updating the rail profiles in the iterative simulation methodology, and the compromise between computational cost and the number of load cases accounted for in the applied load sequence, are addressed.
49.	Skrypnyk, Rostyslav, 1991, et al. (författare) On the influence of crossing angle on long-term rail damage evolution in railway crossings 2021 Ingår i: International Journal of Rail Transportation. - : Informa UK Limited. - 2324-8386 .- 2324-8378. ; 9:6, s. 503-519 Tidskriftsartikel (refereegranskat)abstract The rails in railway crossings are subjected to severe load environment leading to degradation of running surface due to wear and accumulated plastic deformation. To compare long-term degradation of three fixed crossings with different crossing angles, nominally designated 1:12, 1:15, and 1:18.5, a multidisciplinary simulation methodology is applied to predict damage of the crossing rail. For a given traffic scenario, including up to 65 MGT of facing move passenger traffic in through route, the results show that damage increases with increasing crossing angle. The ratio between the maximum damage for the crossings with the largest and smallest crossing angles is found to be about three in terms of wear and about two for plastic deformation. Initially high rate of plastic deformation reduces significantly after the first 2–5 MGT, and after 10–30 MGT it approaches a nearly constant value that is significantly lower than the wear rate.
50.	Somhorst, Joop, et al. (författare) Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine 2021 Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:3, s. 890-910 Tidskriftsartikel (refereegranskat)abstract The effect of two thermal barrier coatings and their surface roughness on heat transfer, combustion, and emissions has been investigated in a single-cylinder light-duty diesel engine. The evaluated thermal barrier coating materials were plasma-sprayed yttria-stabilized zirconia and hard anodized aluminum, which were applied on the piston top surface. The main tool for the investigation was cylinder pressure analysis of the high-pressure cycle, from which the apparent rate of heat release, indicated efficiency, and heat losses were derived. For verification of the calculated wall heat transfer, the heat flow to the piston cooling oil was measured as well. Application of thermal barrier coatings can influence engine operating conditions like charge temperature and ignition delay. Therefore, extra attention was paid to choosing stable and repeatable engine operating points. The experimental data were modeled using multiple linear regression to isolate the effects of the coatings and of the surface roughness. The results from this study show that high surface roughness leads to increased wall heat losses and a delayed combustion. However, these effects are less pronounced at lower engine loads and in the presence of soot deposits. Both thermal barrier coatings show a reduction of cycle-averaged wall heat losses, but no improvement in indicated efficiency. The surface roughness and thermal barrier coatings had a significant impact on the hydrocarbon emissions, especially for low-load engine operation, while their effect on the other exhaust emissions was relatively small.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Resultat 1-50 av 459

Avgränsa träffmängd

Typ av publikation: tidskriftsartikel (352); konferensbidrag (42); doktorsavhandling (36); forskningsöversikt (13); bokkapitel (5); rapport (3); visa fler...; annan publikation (3); licentiatavhandling (3); bok (1); patent (1); visa färre...

Typ av innehåll: refereegranskat (398); övrigt vetenskapligt/konstnärligt (60); populärvet., debatt m.m. (1)

Författare/redaktör: Shi, Yijun (53); Larsson, Roland (44); Almqvist, Andreas (38); Björling, Marcus, 19 ... (29); Emami, Nazanin (26); Olofsson, Ulf, 1962- (26); visa fler...; Hardell, Jens (24); Marklund, Pär (23); Prakash, Braham (19); Pelcastre, Leonardo (18); Wahlström, Jens (16); Glavatskih, Sergei (15); Mu, Liwen (12); Leckner, Johan (12); Rutland, Mark W., Pr ... (11); Kalliorinne, Kalle (11); Zhao, Jun (11); Jacobson, Staffan, P ... (10); Lyu, Yezhe, 1987- (9); Berglund, Kim, 1982- (8); Krajnik, Peter, 1977 (8); Heinrichs, Jannica (8); Pålsson, Björn, 1981 (7); Klement, Uta, 1962 (7); Johansson, Pontus (7); Westbroek, René (7); Zhang, Renyun (6); Larsson, Elin (6); Vuorinen, Esa, assoc ... (6); Wiklund, Urban (5); Claesson, Per M. (5); Nielsen, Jens, 1963 (5); Ekberg, Anders, 1967 (5); Zhang, Fan (5); Kabo, Elena, 1972 (5); Andersson, Henrik, D ... (5); Wallqvist, Viveca (5); Nyborg, Lars, 1958 (5); Lu, Xiaohua (5); Hummelgård, Magnus, ... (5); Kassman Rudolphi, Ås ... (5); Örtegren, Jonas, 197 ... (5); Minami, Ichiro (5); Kalin, Mitjan (5); Glavatskih, Sergei, ... (5); Hua, Jing (5); Luo, Zhenyang (5); Choudhry, Jamal (5); Wojas, Natalia (5); Decrozant-Triquenaux ... (5); visa färre...

Lärosäte: Luleå tekniska universitet (216); Kungliga Tekniska Högskolan (99); Chalmers tekniska högskola (88); Lunds universitet (44); Uppsala universitet (22); RISE (17); visa fler...; Högskolan i Halmstad (8); Mittuniversitetet (7); Högskolan Väst (5); Karlstads universitet (5); Blekinge Tekniska Högskola (5); Högskolan Dalarna (4); VTI - Statens väg- och transportforskningsinstitut (4); Linköpings universitet (3); Sveriges Lantbruksuniversitet (3); Göteborgs universitet (2); Jönköping University (2); Högskolan i Skövde (2); Linnéuniversitetet (2); Stockholms universitet (1); Örebro universitet (1); Södertörns högskola (1); visa färre...

Språk: Engelska (457); Svenska (1); Tyska (1)

Forskningsämne (UKÄ/SCB): Teknik (459); Naturvetenskap (37); Medicin och hälsovetenskap (9)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

LIBRIS.kb.se

Stäng

Kopiera och spara länken för att återkomma till aktuell vy