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1.
  • Azizoğlu, Yağız, 1986-, et al. (författare)
  • Finite Element Analysis of cold pilgering using elastic roll dies
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 207, s. 2370-2375
  • Tidskriftsartikel (refereegranskat)abstract
    • A finite element model of cold pilgering with elastic roll dies have been developed and used to investigate the influence of roll die deformation on the material flow, contact region, roll separating force and tube dimensions. Full scale experiments were performed to validate the contact surface and tube dimensions. The results show that the influence of roll die flattening is not significant on the contact length. However, elastic deformation of roll die has strong influence on both the wall thickness reduction and roll separating force. Thus it is recommended to consider elasticity of roll dies when forces and tube dimensions are estimated.
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2.
  • Abadikhah, Hossein, 1987, et al. (författare)
  • A systematic approach to derive dynamic equations for homogeneous and functionally graded micropolar plates
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 199, s. 1429-1434
  • Konferensbidrag (refereegranskat)abstract
    • This work considers a systematic derivation process to obtain hierarchies of dynamical equations for micropolar plates being either homogeneous or with a functionally graded (FG) material variation over the thickness. Based on the three dimensional micropolar continuum theory, a power series expansion technique of the displacement and micro-rotation fields in the thickness coordinate of the plate is adopted. The construction of the sets of plate equations is systematized by the introduction of recursion relations which relates higher order powers of displacement and micro-rotation terms with the lower order terms. This results in variationally consistent partial differential plate equations of motion and pertinent boundary conditions. Such plate equations can be constructed in a systematic fashion to any desired truncation order, where each equation order is hyperbolic and asymptotically correct. The resulting lowest order flexural plate equation is seen to be of a generalized Mindlin type. The numerical results illustrate that the present approach may render accurate solutions of benchmark type for both homogeneous and functionally graded micropolar plates provided higher order truncations are used. Moreover, low order truncations render new sets of plate equations that can act as engineering plate equations, e.g. of a generalized Mindlin type.
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3.
  • Ainegren, Mats, 1963-, et al. (författare)
  • A portable roller ski rolling resistance measurement system
  • 2013
  • Ingår i: The Impact of Technology on Sport V. - : Elsevier. ; , s. 79-83
  • Konferensbidrag (refereegranskat)abstract
    • Roller skis are used by cross-country skiers, biathletes and ski-orienteers for their snow-free training and in roller ski competitions. Additionally, much of the current sports research into the physiology and biomechanics of crosscountry skiing is conducted indoors on treadmills using roller skis. For elite athletes, the differences in performance are quite small, thus emphasising the importance of knowing the roller skis' rolling resistance coefficient, especially in connection to research and roller ski competitions. The purpose of this study was to develop a roller ski rolling resistance measurement system (P-RRMS) that is portable and therefore useful in different contexts and locations. The P-RRMS was designed as a small treadmill, equipped with roller ski stabilizing lateral supports and a screwed bar for applying different vertical loads on the roller ski. The design uses only one force sensor, with possible measurements of three directions of force and torque around three axes. The weight of the P-RRMS is 100 kg and it is equipped with wheels to facilitate transportation.
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4.
  • Alavian Ghavanini, Farzan, 1978, et al. (författare)
  • Growth characterization of vertically aligned carbon nanofibers on top of TiN buffer layer for nanoelectromechanical devices
  • 2010
  • Ingår i: Procedia Engineering, 24th Eurosensor 24th Conference Linz, AUSTRIA, SEP 05-08, 2010. - : Elsevier BV. - 1877-7058. ; 5, s. 1115-1118
  • Konferensbidrag (refereegranskat)abstract
    • Initial growth of vertically aligned carbon nanofibers (VACNFs) from Ni catalyst seeds in the range of 40 to 100 nm as fabricated using hole-mask colloidal lithography on top of reactively sputtered TiN is studied. We observe that the initial growth conditions could cause a growth mode transition from base-type to tip-type. We attribute this transition to a change in the crystallographic orientation of the Ni catalyst seeds induced by initial growth conditions. A convenient method to deposit stoichiometric TiN films is also presented.
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5.
  • Amin, Muhammad, 1979, et al. (författare)
  • Carbon nanotubes as base material for fabrication of gap waveguide components
  • 2014
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 87, s. 931-934
  • Konferensbidrag (refereegranskat)abstract
    • Carbon nanotubes are being used here as a base material for rapid prototyping of a high frequency device. It has beenimplemented on a ridge gap resonator for 220-325 GHz which has previously been fabricated in Si. Microfabrication with Si has its benefits but it is time consuming when etching high ratio structures. CNT based structures offer a rapid and low cost turnover for prototyping. Measurements comparing the CNT-based structure to a previously made Si structure and simulations are presented. The unloaded Q-values and the loss/mm are presented from simulations, Si-based resonator measurements and CNT-based resonator measurements.
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6.
  • Andersen, Lars Vabbersgaard, et al. (författare)
  • Variation in models for simple dynamic structure–soil–structure interaction problems
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 199, s. 2306-2311
  • Konferensbidrag (refereegranskat)abstract
    • To account for dynamic cross-coupling of structures via the soil, a computational model must be accurate enough to provide the correct overall behaviour of the scattered wave field. However, simplicity is also important when a model should be used for design purposes, especially in the early design stages and feasibility studies. The paper addresses the accuracy of simple models in which an array of structures is simplified into blocks placed on the ground surface or embedded within the soil. Comparisons are made between models that account or do not account, in a proper manner, for the inertia and embedment of the structures. Especially, the limitations of simplified models are discussed regarding their capability to quantify the insertion loss accurately.
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7.
  • Andersson, Mike, et al. (författare)
  • SiC-FET sensors for selective and quantitative detection of VOCs down to ppb level
  • 2016
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 168, s. 216-220
  • Tidskriftsartikel (refereegranskat)abstract
    • With the increased interest in development of cheap, simple means for indoor air quality monitoring, and specifically in relation to certain well-known pollutant substances with adverse health effects even at very low concentrations, such as different Volatile Organic Compounds (VOCs), this contribution aims at providing an overview of the development status of the silicon carbide field effect transistor (SiC FET) based sensor platform for ppb level detection of VOCs. Optimizing the transducer design, the gas-sensitive material(s) composition, structure and processing, its mode of operation - applying temperature cycled operation in conjunction with multivariate data evaluation - and long-term performance it has been possible to demonstrate promising resultsregarding the sensor technology’s ability to achieve both single-digit ppb sensitivity towards e.g. naphthalene as well as selective detection of individual substances in a mixture of different VOCs.
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8.
  • Andersson, Niclas, et al. (författare)
  • The Interface between industrialized and project based construction
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 196, s. 220-227
  • Tidskriftsartikel (refereegranskat)abstract
    • Today, digitalization is the single most significant change factor for the construction sector as well as for society in general, which will bring new opportunities for intelligent and sustainable cities, efficient management of available resources and a general reduction of carbon emissions. Digitalization will enable continuous and integrated information exchange between all actors of the construction process. The development of an integrated digital information infrastructure for the construction sector will reach beyond the traditional project process and e.g. include the urban planning processes, where geographical information systems (GIS) are currently used, and the manufacturing processes of industrialized construction where e.g. product data management (PDM) systems constitute the product information platform. This study provides a survey of the interface between industrialized and project based construction from an information and business relation perspective. The purpose and main objectives of the study are to review and map the current information exchange between industrialized and project based construction in order to identify existing and potential areas of digitalization and standardization for improved information flow. The survey finds that industrial suppliers still frequently use company specific product standards, that PDF-, Word- or Excel-files constitute the normally used file format and that recurrent restructuring and re-entering of information from one system to another characterize the information exchange. Further, contractors approach industrialized construction in three distinctive ways, and express a generally growing interest for industrialized construction, which include closer and more long-term business relations with industrial suppliers. Despite the identified problems of information exchange and lack of common standards, the survey concludes that improved business relations provides the most urgent area of development in order to better integrate the industrialized and project based construction.
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9.
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10.
  • Aziz, Maryam, et al. (författare)
  • Mobility impact on the end-to-end delay performance for VoIP over LTE
  • 2012
  • Ingår i: Procedia Engineering. - Coimbatore : Elsevier. - 1877-7058. ; , s. 491-498
  • Konferensbidrag (refereegranskat)abstract
    • Long Term Evolution (LTE) is the last step towards the 4th generation of cellular networks. This revolution is necessitated by the unceasing increase in demand for high speed connection on LTE networks. This paper focuses on the performance evaluation of End-to-End delay under variable mobility speed for VoIP (Voice over IP) in the LTE network. In the course of E2E performance evaluation, realizing simulation approach three scenarios have been modeled using OPNET 16.0. The first one is the baseline network while among other two, one consists of VoIP traffic solely and the other consists of FTP along with VoIP. E2E delay has been measured for both scenarios in various cases under the varying mobility speed of the node. Simulation results have been studied and presented in terms of comparative performance analysis of the three network scenarios. In light of the result analysis, the performance quality of a VoIP network (with and without the presence of additional network traffic) in LTE has been determined and discussed. The simulation results for baseline VoIP network (non-congested) congested VoIP network and congested VoIP with FTP network show that as the speed of node is gradually increased, E2E delay slightly increases.
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11.
  • Banks, J., et al. (författare)
  • Assessing Human-Fluid-Structure Interaction for the International Moth
  • 2016
  • Ingår i: Procedia Engineering. - : Elsevier Ltd. - 1877-7058. ; , s. 311-316
  • Konferensbidrag (refereegranskat)abstract
    • The International Moth is an ultra-lightweight foiling dinghy class. Foil deflections and dynamic sailor-induced motions are identified as two key areas relating to foiling moth performance that are currently ignored in Velocity Prediction Programs (VPP). The impact of foil deflections is assessed by measuring the tip deflection and twist deformation of a T-foil from an International Moth. The full field deformation due to an applied load is measured using Digital Image Correlation (DIC). The foil's structural properties can then be determined based on the measured structural response. The deformations are then calculated for an estimated steady sailing force distribution on the T-foil and their impact on performance is evaluated. To investigate the impact of dynamic sailor motions a system is developed that allows a sailor's dynamic pose to be captured when out on the water by determining the orientations of key body segments using inertial sensors. It is validated against measured hiking moments and is demonstrated to work out on the water whilst sailing. Both these studies pave the way towards developing a Dynamic VPP for the international Moth, which can include unsteady human and foil interactions.
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12.
  • Barsoum, Zuheir, et al. (författare)
  • Computational Weld Mechanics - Towards a Simplified and Cost Effective Approach for Large Welded Structures
  • 2015
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; , s. 62-69
  • Konferensbidrag (refereegranskat)abstract
    • The current paper presents the development of a finite element analysis framework for computational weld mechanics, in order to carry out cost-effective predictions of welding induced residual stresses with good accuracy. Different approaches for describing the welding heat sources were investigated. The paper also investigates the influence of thermo-mechanical material properties of frequently used steel grades (S355-S960) on welding residual stresses and angular distortion. The predicted residual stresses were validated experimentally on several different small scale specimens with X-ray diffraction techniques. Finally, the developed simulation framework is demonstrated on complex welded structures in a construction equipment vehicle.
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13.
  • Barsoum, Zuheir, et al. (författare)
  • Managing Welding Induced Distortion - Comparison of Different Computational Approaches
  • 2015
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; , s. 70-77
  • Konferensbidrag (refereegranskat)abstract
    • This study aims to assess and compare three different approaches of inherent strain method for prediction of welding induced distortion; inherent strain, inherent deformation and shrinkage force approaches. The FEA was performed on T-fillet welded structures. The results are compared with elastic-plastic FEA and experiments and shows a qualitative good agreement. It is found that the inherent strain and inherent deformation approaches are suitable to predict transverse shrinkage and transverse bending whereas to predict the longitudinal shrinkage and longitudinal bending the shrinkage force approach is more suitable.
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14.
  • Bernard, Thomas, et al. (författare)
  • SAFEWATER - Innovative tools for the detection and mitigation of CBRN related contamination events of drinking water
  • 2015
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 119, s. 352-359
  • Tidskriftsartikel (refereegranskat)abstract
    • The safety and or security of drinking water can be threatened by natural disasters, accidents or malevolent attacks. The European FP7 project SAFEWATER aims at developing a comprehensive event detection and event management solution for drinking water security management and mitigation against major deliberate, accidental or natural CBRN related contaminations. New cost-effective C, B, and RN sensors will be developed. An innovative concept with a broad network of low-cost sensors - "domestic sensors" (complementary to a set of sensors in strategic locations) will be developed. A technology platform will be provide which is able to capture and analyze the data collected by the sensors and from other information systems and give a full overview of the crisis to the responders by means of online look-ahead simulations to efficiently manage potential crises. For testing the SAFEWATER solution it will be integrated with on utility-partners' information systems.
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15.
  • Biel, Anders, et al. (författare)
  • Damage and plasticity of adhesive layers : an experimental study
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 10, s. 2280-2285
  • Tidskriftsartikel (refereegranskat)abstract
    • Time independent inelasticity is often modelled as due to plasticity and/or damage. The difference is manifested at reversed loading; plasticity reveals itself by a remaining strain in the unloaded state while damage is revealed by a decrease in the elastic stiffness during unloading. With thin adhesive layers, the deformation is inhomogeneously distributed along the layer. Large deformations occur at the ends of the layer. In the more central parts, the layer is virtually undeformed. This makes a direct measurement of the unloading properties virtually impossible. In the present paper, novel experiments are performed in order to evaluate the inelastic properties of epoxy adhesives. The load is first increased to a level corresponding to 50, 60, 70 or 80% of the fracture energy. The load is then reversed. The first step creates a zone of inelastically deformed adhesive at the start of the layer. During a final loading phase, the properties of this zone are analysed. Major differences due to the loading direction are observed. Some comparisons with simulation models are performed.
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16.
  • Biermann, Dirk, et al. (författare)
  • Experimental and computational investigation of machining processes for functionally graded materials
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 19, s. 22-27
  • Tidskriftsartikel (refereegranskat)abstract
    • Experiments on dry face turning offunctionallygraded heat treatable steel are conducted. The workpieces have a hardened zone of approx. 60 HRC and a non-hardened zone of approx. 30 HRC. PCBN tools are used with different feeds, cutting speeds and depths of cut. Measurements of residual stresses in the surface layer reveal compressive stresses in the hardened zone and tensile stresses in the non-hardened zone. These experimental observations are compared with the results of representative simulations of the cutting process. A large-deformation thermo-elasto-viscoplastic material model is used and the geometry of the cutting tool is precisely reflected by the finite element discretisation. To predict the overall response, an adaptive remeshing scheme and full thermo-mechanical coupling is accounted for. Moreover, measured residual stresses are incorporated as initial conditions within the simulation.
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17.
  • Brolin, Karin, 1974, et al. (författare)
  • Explicit finite element methods for equestrian applications
  • 2016
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 147, s. 275-280
  • Konferensbidrag (refereegranskat)abstract
    • A virtual human body model (HBM), developed for vehicle crash simulations, was used to conduct a pilot study of dangerous accidents that occur in equestrian sports. It was performed to illustrate the potential that the explicit finite element (FE) HBMs have to improve rider safety and to assess the protective capacity of the safety vest. Four different questions were addressed: 1. When a rider is trampled by a horse, how does the risk of injury vary with chest impact location? 2. Does a safety-vest provide protection if the rider is kicked by a horse and does the protection vary with the violence of the hoof impact? 3. Can a safety-vest provide any benefit when the rider is hit by the horse after a rotational fall? 4. How does the risk for thoracic injuries vary when the rider falls off the back of a horse at different angles? The HBM was the Total Human Model for Safety AM50 version 3.0 (Toyota Motor Corporation, Japan), improved for thorax injury predictability in a previous automotive project. The FE code was LS-DYNA (Livermore Software Technology Corporation, USA). Models of a generic safety vest, a horse impactor and a hoof were developed as part of this project. The risk of thorax injury was evaluated with stresses and strains measured for each rib, and the chest deformation criteria Dmax and DcTHOR. 1. The risk of injury was higher for hoof impacts close to the sternum compared to more lateral locations that had up to 25% less risk. Hence, this knowledge could be used to optimize novel safety-vest designs with HBM simulations. 2. Yes, the safety-vest provided protection against horse kicks, and it varied with the violence of the kick. Therefore, if the range of impact energy that occurs in real-world accidents is known, HBM simulations can be used to optimize the vest material properties. 3. No, the safety-vest did not provide any benefit when the horse lands on top of the rider. This conclusion suggests that safety measures should focus on preventing this type of accident, rather than designing personal protection for the rider. 4. When the rider falls with the head first, the number of predicted rib fractures increases compared to flat falls. However, the model predicts rib fractures for all of the falls simulated from a height of 1.5 meters for a rider without a safety vest. To conclude, FE HBMs have the potential to improve equestrian safety and further studies on equestrian safety-vests designs are warranted. (C) 2016 The Authors. Published by Elsevier Ltd.
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18.
  • Bur, Christian, et al. (författare)
  • Discrimination and Quantification of Volatile Organic Compounds in the ppb-Range with Gas Sensitive SiC-Field Effect Transistors
  • 2014
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058.
  • Konferensbidrag (refereegranskat)abstract
    • Gas sensitive FETs based on SiC have been studied for the discrimination and quantification of hazardous volatile organiccompounds (VOCs) in the low ppb range. The sensor performance was increased by temperature cycled operation (TCO) anddata evaluation based on multivariate statistics, here Linear Discriminant Analysis (LDA). Discrimination of formaldehyde,naphthalene and benzene with varying concentrations in the ppb range is demonstrated. In addition, it is shown that naphthalenecan be quantified in the relevant concentration range independent of the relative humidity and against a high ethanol background.Hence, gas sensitive SiC-FETs are suitable sensors for determining indoor air quality.
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19.
  • Bushlya, Volodymyr, et al. (författare)
  • Characterization of White Layer Generated when Turning Aged Inconel 718
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 19, s. 60-66
  • Konferensbidrag (refereegranskat)abstract
    • Abstract in UndeterminedWhite layer formation is considered as a part of minimum array of parameters characterizing surface integrity of the machined product. The paper is aimed on identification and characterization of white layer generated when finish turning aged Inconel 718 with Al2O3-SiCw ceramic tools under different cutting conditions, tool wear and coolant application. As expected intensity of white layer formation was proportional to cutting speed and tool wear. High resolution transmission electron microscopy (HRTEM) performed on white layer revealed formation of nanostructured material with grain size of 50-150 nm. Long-term ultrasonic-assisted etching of white layer allowed to uncover its morphology, where subsequent AFM measurements confirmed HRTEM findings. Observations by high resolution SEM provided evidence that gamma' Ni-3(Al,Ti) phase remained intact. (C) 2012 Published by Elsevier Ltd. Selection and peer-review under responsibility of Prof. E. Brinksmeier
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20.
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21.
  • Chai, Guocai, et al. (författare)
  • Creep and LCF Behaviors of Newly Developed Advanced Heat Resistant Austenitic Stainless Steel for A-USC
  • 2013
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 55, s. 232-239
  • Tidskriftsartikel (refereegranskat)abstract
    • Austenitic stainless steel grade UNS S31035 (Sandvik Sanicro® 25) has been developed for use in super-heaters and reheaters in the next generation of A-USC power plants. This new grade shows very good resistances to steam oxidation and hot corrosion, and higher creep rupture strength than other austenitic stainless steels available today. This makes it an interesting alternative for super-heaters and reheaters in future high-efficient coal fired boilers. This paper will mainly focus on the study of the creep and LCF behavior of the material at temperatures from 600 °C to 750 °C by using TEM and ECCI. The mechanisms at different temperatures and loading conditions have been identified. The interactions between dislocations and precipitates and their contribution to the creep rupture strength have been discussed. In this paper, different models have been used to evaluate the long-term creep behavior of the grade. A creep rupture strength near 100 MPa at 700 °C for 100 000 h has been predicted.
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22.
  • Chai, Guocai, et al. (författare)
  • Low and High Cycle Fatigue Behavior of Nickel-base Alloy att High Temperatures
  • 2013
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058.
  • Konferensbidrag (refereegranskat)abstract
    • Low and high cycle fatigue behaviors of Alloy 690 have been investigated at temperatures up to 330 °C and number of cycles up to 2 × 109. Two interesting phenomena were observed. At high temperature, the alloy shows a secondary strain hardening in the cyclic stress-strain response. Formation of nano-twins and interactions between moving dislocations and stacking faults or interstitial atoms could contribute to this secondary strain hardening. For very high cycle fatigue, subsurface fatigue crack initiation at grain boundaries has been observed. EBSD investigation shows that strain accumulation is much localized. The fatigue damage is a localised plasticity exhaustion process.
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23.
  • Chai, Guocai, et al. (författare)
  • Secondary Hardening Behavior in Super Duplex Stainless Steels during LCF in Dynamic Strain Ageing Regime
  • 2013
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 55, s. 123-127
  • Tidskriftsartikel (refereegranskat)abstract
    • Cyclic deformation behaviors in five modified duplex stainless steel S32705 grades have been studied at 20 °C, 200 °C, 250° and 350 °C. The influence of temperature and nitrogen concentration on the occurrence of the second hardening phenomenon, in the stress response curve was focused. An increase in nitrogen concentration can have a positive effect on dynamic strain ageing by increasing the first hardening and also the second hardening behavior during cyclic deformation. Furthermore, an increase in nitrogen concentration in the super duplex stainless steel increases the fatigue life in the strain ageing temperature range. The occurrence of strain ageing in duplex stainless steel has greatly changed dislocation structures. The formation of irreversible dislocation structures and stacking faults can contribute to the formation of second hardening in the stress response curve.
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24.
  • Chen, Lan, et al. (författare)
  • The Influence of Building Packing Densities on Flow Adjustment and City Breathability in Urban-like Geometries
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier Ltd. - 1877-7058. ; 198, s. 758-769
  • Tidskriftsartikel (refereegranskat)abstract
    • City breathability refers to the air exchange process between the flows above and within urban canopy layers (UCL) and that of in-canopy flow, measuring the potential of wind to remove and dilute pollutants, heat and other scalars in a city. Bulk flow parameters such as in-canopy velocity (Uc) and exchange velocity (UE) have been applied to evaluate the city breathability. Both wind tunnel experiments and computational fluid dynamics (CFD) simulations were used to study the flow adjustment and the variation of city breathability through urban-like models with different building packing densities. We experimentally studied some 25-row and 15-column aligned cubic building arrays (the building width B=72 mm and building heights H=B) in a closed-circuit boundary layer wind tunnel. Effect of building packing densities (λp=λf=0.11, 0.25, 0.44) on flow adjustment and drag force of each buildings were measured. Wind tunnel data show that wind speed decreases quickly through building arrays due to strong building drag. The first upstream building induces the strongest flow resistance. The flow adjustment length varies slightly with building packing densities. Larger building packing density produces lower drag force by individual buildings and attains smaller velocity in urban canopy layers, which causes weaker city breathability capacity. In CFD simulations, we performed seven test cases with various building packing densities of λp=λf=0.0625, 0.11, 0.25, 0.36, 0.44 and 0.56. In the cases of λp=λf=0.11, 0.25, 0.44, the simulated profiles of velocity and drag force agree with experiment data well. We computed Uc and UE, which represent horizontal and vertical ventilation capacity respectively. The inlet velocity at 2.5 times building height in the upstream free flow is defined as the reference velocity Uref. Results show that UE/Uref changes slightly (1.1% to 0.7%) but Uc/Uref significantly decreases from 0.4 to 0.1 as building packing densities rise from 0.0625 to 0.56. Although UE is induced by both mean flows and turbulent momentum flux across the top surface of urban canopy, vertical turbulent diffusion is found to contribute mostly to UE.
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25.
  • Cronholm, Kent, 1973 (författare)
  • Design of experiment based on VMEA (Variation Mode and Effect Analysis)
  • 2013
  • Ingår i: Procedia Engineering (5th International Conference on Fatigue Design, Fatigue Design 2013). - : Elsevier BV. - 1877-7058. ; 66, s. 369-382
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents a method where the Variation Mode and Effect Analysis is used to convert subjective knowledge about variation and importance of parameters for a certain characteristic among practicing engineers into numerically comparable values. In a case study, with fuel consumption of an articulated hauler as the target function, the method is used to quantify and arrange external parameters in order to design an experiment. A suggestion of a test plan describing a fractional factorial test at two levels intended to investigate the influence of the external parameters is presented. Performance and analysis of the experiment are discussed together with assumptions and uncertainties. © 2013 The Authors. Published by Elsevier Ltd.
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26.
  • Cvetkovski, Krste, 1983, et al. (författare)
  • Thermal softening of fine pearlitic steel and its effect on the fatigue behaviour
  • 2010
  • Ingår i: Procedia Engineering: 10th International Fatigue Congress, FATIGUE 2010; Prague; Czech Republic; 6 June 2010 through 11 June 2010. - : Elsevier BV. - 1877-7058. ; 2:1, s. 541-545
  • Konferensbidrag (refereegranskat)abstract
    • Associated with the durability of railway wheelsets, thermal damage was studied for two different steels in the temperature range 500 °C to 725 °C. Softening caused by cementite spheroidisation in the pearlitic materials leads to changes in the mechanical behaviour. It was found that higher contents of silicon and manganese leads to better resistance to softening. Correspondingly, softening leads to loss in fatigue life times at given stress amplitudes as read out from Wöhler curves. However the higher alloyed steel looses much less in fatigue life time than the less alloyed steel.
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27.
  • Dalaei, Kamellia, 1975, et al. (författare)
  • Stability of Residual stresses Created by Shot Peening of Pearlitic Steel and Their Influence on Fatigue Behaviour
  • 2010
  • Ingår i: 10th International Fatigue Congress, FATIGUE 2010; Prague; Czech Republic; 6 June 2010 through 11 June 2010. - : Elsevier BV. - 1877-7058. ; 2:2, s. 613-622
  • Konferensbidrag (refereegranskat)abstract
    • In this study the effect of shot peening on the fatigue lifetime of a near pearlitic microalloyed steel was investigated. The fatigue tests were run in strain control with parallel recording of stress relaxation and recovery of the work hardened surface zone at different total strain amplitudes exerted to the test specimens. These relaxation processes were followed versus cycle number up to half of the fatigue life time (N=Nf/2). Provided that the global plastic strain amplitude is lower than about 0.08 % a noticeable increase in life time is seen. Lower plastic strain amplitude increases the life time. At small plastic strain amplitudes it was found that the fatigue life time could be increased more than tenfold by the shot peening process.
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28.
  • Duanmu, Lin, et al. (författare)
  • Relationship between Human Thermal Comfort and Indoor Thermal Environment Parameters in Various Climatic Regions of China
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 205, s. 2871-2878
  • Konferensbidrag (refereegranskat)abstract
    • Architectural design is based on the reliability and rationality of construction standards. The thermal comfort standard is a very important part of construction standards. In this study, Chinese researches about the field survey of various areas were summarized. The distribution range of thermal comfo rt temperature and neutral temperature were obtained by using the PMV evaluation index. The neutral temperature of different types of buildings in different seasons was summarized. Its relationship with indoor parameters was analyzed in detail. These findings provide a basis for the formulation of building specifications and architectural design in future.
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29.
  • Emadi, A., et al. (författare)
  • An UV linear variable optical filter-based micro-spectrometer
  • 2010
  • Ingår i: Procedia Engineering, Proc. Eurosensors XXIV, September 5-8, 2010, Linz, Austria. - : Elsevier BV. - 1877-7058. ; 5, s. 416-419
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents the design, fabrication and spectral measurements of an Ultra-Violet (UV) Linear Variable Optical Filter (LVOF)-based micro-spectrometer operating in the 300 nm - 400 nm wavelength range. The UV LVOF has been fabricated in an IC-Compatible process using resist reflow. Characterization by passing monochromatic light through the LVOF, shows high linearity of the profile. It is expected that using signal processing, spectral resolution better than 0.5 nm can be achieved with this UV LVOF. The filter provides the possibility to have a robust high-resolution micro-spectrometer in the UV on a CMOS chip.
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30.
  • Eriksson, Mats, 1963-, et al. (författare)
  • Drinking water monitoring with voltammetric sensors
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 25, s. 1165-1168
  • Tidskriftsartikel (refereegranskat)abstract
    • Pulsed voltammetry has been applied to drinking water monitoring. This non-selective technique facilitates detection of several different threats to the drinking water. A multivariate algorithm shows that anomaly detection is possible with a minimum of false alarms. Multivariate analysis can also be used to classify different types of substances added to the drinking water. Low concentrations of sewage water contaminating the drinking water can be detected. A network of such sensors is envisaged to facilitate real-time and on-line monitoring of drinking water distribution networks.
  •  
31.
  • Eriksson, Robert, et al. (författare)
  • Fractographic Study of Adhesion Tested Thermal Barrier Coatings Subjected to Isothermal and Cyclic Heat Treatments
  • 2011
  • Ingår i: Procedia Engineering. - Elsevier : Elsevier BV. - 1877-7058. ; 10, s. 195-200
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermal barrier coatings (TBC) are used in gas turbines to protect metallic components from high temperature. In the present study adhesion tests have been conducted on APS TBC coated specimens subjected to different heat treatments. Isothermal and cyclic heat treatments have been conducted at temperatures around 1100 °C and the adhesion have been tested using the method described in ASTM C633. The fracture surfaces resulting from the adhesion test have been investigated and the fracture behavior has been characterized. A difference in fracture mechanism between the three heat treatments has been found. The two cyclic heat treatments give fracture in the top coat/bond coat interface while isothermal heat treatment gives fracture in the top coat.
  •  
32.
  • Frier, Cristian, et al. (författare)
  • Flooring-systems and their interaction with furniture and humans
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 199, s. 146-151
  • Tidskriftsartikel (refereegranskat)abstract
    • Flooring-system designs may be sensitive in terms of their vibrational performance due the risk that serviceability-limit-state problems may be encountered. For evaluating the vibrational performance of a flooring system at the design stage, decisions must be made by the engineer in charge of computations. Passive humans and/or furniture are often present on a floor. Typically, these masses and their way of interacting with the floor mass are ignored in predictions of vibrational behaviour of the flooring system. Utilizing a shell finite-element model, the paper explores and quantifies how non-structural mass can influence central parameters describing the dynamic behaviour of the flooring system with focus on elevated non-structural mass.
  •  
33.
  • Galstyan, V., et al. (författare)
  • Fabrication of TiO 2 and TiO 2 nanotubular arrays and their gas sensing properties
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 25, s. 757-760
  • Tidskriftsartikel (refereegranskat)abstract
    • Pure TiO 2 and TiO 2 nanotubular arrays were successfully sensitized. Nanotubular arrays were prepared by electrochemical anodization of thin films of Ti and of Ti-Nb deposited on alumina substrates with two different roughness. Morphological characterization and functional properties are presented. The gas sensing properties of TiO 2 and TiO 2 nanotubes with different gases have been tested in a wide range of operating temperatures. © 2011 Published by Elsevier Ltd.
  •  
34.
  •  
35.
  • Gibanica, Mladen, 1988, et al. (författare)
  • A reduced interface component mode synthesis method using coarse meshes
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 199, s. 348-353
  • Konferensbidrag (refereegranskat)abstract
    • Component mode synthesis is a technique to simplify the analysis of complicated finite element models. A structure is split into substructures from which reduced order models can be generated and subsequently assembled. A model reduction performance gain can be limited if the component interfaces contain many degrees of freedom, which is often the case for high resolution models. In this paper a substructuring framework with interface reduction is presented. The method first splits a detailed model into substructures. The substructures’ fine mesh is then coarsened on the internal region, while keeping the boundary mesh intact. Thereafter a Guyan reduction is performed on each coarse mesh substructure. The Guyan computations are cheap due to the reduced size of the linear equation system necessary to solve for the coarse mesh system. After synthesis of the statically reduced systems, a reduction basis for the interface degrees of freedom is computed. Thereafter a Craig-Bampton reduction is performed on each fine mesh substructure using projections with the reduced interface degrees of freedom and fixed interface modes. The method is verified on a dense mesh plate model consisting of two substructures.
  •  
36.
  • Girhammar, Ulf Arne, et al. (författare)
  • Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods - Introducing a Handbook Part 1 : Design Principles for Horizontal Stabilisation
  • 2016
  • Ingår i: WORLD MULTIDISCIPLINARY CIVIL ENGINEERING-ARCHITECTURE-URBAN PLANNING SYMPOSIUM 2016, WMCAUS 2016. - : Elsevier. ; 161, s. 618-627
  • Konferensbidrag (refereegranskat)abstract
    • The authors have developed a plastic design method for sheathed timber frame shear walls. It has been presented and discussed for inclusion in Eurocode 5 and a Swedish handbook has been presented. In the plastic method, you can choose to transfer the anchoring force via the leading stud to the substrate, corresponding to a fully anchored shear wall (no uplift of studs), but you can also choose to utilize the sheathings to transfer the tensile force via the sheathing-to-framing joints to the substrate by anchoring the bottom rail, corresponding to a partially anchored shear wall (studs experience uplift). By the plastic method several alternatives for anchoring the wall are possible and they can also be combined in such a way that each of them take a portion of the uplifting force, e.g. through a simple tying down device, through the sheathing-to-framing joints and through anchoring of the shear wall to the transverse wall. The method also makes it possible to include the load-bearing capacity of wall segments including openings. The handbook treats primarily shear walls, but for the sake of completeness some aspects of the roof and floor diaphragms are also discussed. The interior force distribution in sheathed timber frame walls weak in shear is discussed, as are the fundamental difference between the effect of vertical loads on the stabilisation of walls which are rigid or weak in shear, and how the plastic design method is applied to multi-storey timber buildings. (C) 2016 The Authors. Published by Elsevier Ltd.
  •  
37.
  • Girhammar, Ulf Arne, et al. (författare)
  • Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods - Introducing a Handbook Part 2 : Design of Joints and Anchoring Devices
  • 2016
  • Ingår i: WORLD MULTIDISCIPLINARY CIVIL ENGINEERING-ARCHITECTURE-URBAN PLANNING SYMPOSIUM 2016, WMCAUS 2016. - : Elsevier. ; 161, s. 628-635
  • Konferensbidrag (refereegranskat)abstract
    • In this part 2, the practical design and strength of a number of different joints is described: (1) Sheathing-to-framing joints the plastic design method is based on the premise that the load-displacement relationship of the sheathing-to-framing joints has sufficiently large plastic deformation capacity; the sheathing-to-framing joints have great influence on the load-carrying capacity of the wall; (2) Stud-to-rail joints by utilizing the shear capacity of the stud-to-rail joints, the plastic design method can be simplified and the load-carrying capacity can be increased; (3) Hold down devices for the (leading) stud - the capacity of the tying down force of the hold down determines whether the shear wall will act as fully or partially anchored; tying down the shear walls by connecting them to the transverse walls leads to a 3-dimensioonal behaviour that is a very favourable for the load-carrying capacity and the stiffness of the shear wall; through transverse walls the anchoring of the leading stud can be reduced or eliminated (those types of transverse wall connections are not discussed in detail in this paper); and (4) Anchoring devices for the bottom rail in - partially anchored shear walls it is necessary that the bottom rail is anchored to the substrate against uplift. Characteristic values for the different types of joints are given. Also, joints between the panels in the walls, roofs and floors are described briefly. (C) 2016 The Authors. Published by Elsevier Ltd.
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38.
  • Golling, Stefan, et al. (författare)
  • Modelling of Plastic Deformation and Fracture in Hot Stamped Steel with Multi-Phase Microstructure
  • 2017
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 207, s. 687-692
  • Tidskriftsartikel (refereegranskat)abstract
    • Hot stamping is an industrialized technique with the aim of improving material properties by heat treatment and forming of a component in a single production step. Within the field of hot stamping the method of tailored material properties evolved. Components with tailored material properties possess different mechanical properties in designated areas. The mechanical properties in a blank are modified by the formation of different microstructures. Martensite is a microstructure with high strength but low ductility, ferrite has lower strength but higher ductility. Using special tooling tough martensite and soft ferrite can be placed in adjacent sections in a blank. Between those sections a transition zone consisting of a mixed microstructure exists with mechanical properties between martensite and ferrite. Transition zones possess intermediate cooling rates, hence formation of bainite and composites of bainite and another phase can from.This paper presents an approach of modelling the complete process from austenitized blank to fracture. The method presented relies on the prediction of phases formed during cooling using an austenite decomposition model. In the course of ferrite formation the carbon content in the remaining austenite increases, the carbon content in austenite influences formation of additional daughter phases. The estimated phase composition is used in a homogenization scheme to predict the hardening of the material during plastic deformation. Fracture in the different microstructural phases is predicted using the strain decomposition provided by the homogenization and a fracture criteria. The homogenization scheme and the fracture criteria use measured data from single phase microstructures, i.e. ferrite, bainite and martensite.A heat treatment process for tensile test specimens is used to produce samples with different volume fractions of the microstructures ferrite, bainite and martensite. The pre-cut specimens are austenitized, ferrite is formed in a second furnace with lower temperature, bainite and martensite are formed by the use of a temperature controlled plane tool.Prediction of the phase content in mixed microstructures showed good agreement with microstructural characterization and therefore results can be used as input value for the homogenization. Comparing experimental and numerical results for a variety of different mixed microstructures good agreement in the prediction of hardening and fracture is found.It is concluded that the use of a homogenization method combined with a fracture model can be used to predict the mechanical response of mixed microstructures. The method described in the present work can be applied in the development of hot stamped components.
  •  
39.
  • Grahn, Sten, et al. (författare)
  • Exploring a Model for Production System Design to Utilize Large Robots in Human-Robot Collaborative Assembly Cells
  • 2018
  • Ingår i: Procedia Manufacturing. - : Elsevier B.V.. - 2351-9789. ; 25, s. 612-619
  • Konferensbidrag (refereegranskat)abstract
    • It has been shown that large robots can be safely installed for human-robot collaborative assembly cells in experimental setups. It has also been found that these installations require demanding considerations of a significant number of layout and safety parameters. This indicates that successful commercial implementations will require a resource efficient model for production system design that anticipates utilization of large robots in collaborative settings. Experiences from experimental setups have been used to explore a basic model for such production system design, to stimulate a discussion regarding what model characteristics should be tested and validated in future research. 
  •  
40.
  • Gustafsson, Andreas, et al. (författare)
  • Experimental and Numerical Investigation of Ratcheting in Pressurized Equipment
  • 2015
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 130, s. 1233-1245
  • Tidskriftsartikel (refereegranskat)abstract
    • As part of a project within the Swedish nuclear industry with the objective to investigate the performance of different constitutive models in ratchet simulation, an extensive experimental program has been conducted on pressurized tube specimens. In total 30 test specimens made of two different materials, 316L and P235, have been manufactured and tested. In order to determine material properties, monotonic tensile load and internal pressure experiments have been performed. The remaining test specimens have been used for ratcheting experiments. The experimental results show ratcheting in the hoop direction when the tube is subjected to certain combinations of internal pressure and cyclic axial strains. The higher the pressure is and the larger the strain ranges are, the higher the ratcheting response becomes. Measured ratcheting strains are compared to numerical simulations using different constitutive models. In this paper the interrelated models of Prager, Armstrong-Frederick and Chaboche are investigated. In addition to these, the Besseling model is investigated. Based on the result from this investigation, recommendations on how to conduct ratcheting simulation of pressurized equipment subjected to cyclic secondary loading are presented.
  •  
41.
  • Gustafsson, David, et al. (författare)
  • Fatigue Crack Growth behaviour of Inconel 718 - the Concept of a Damaged Zone Caused by High Temperature Hold Times
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 10, s. 2821-2826
  • Tidskriftsartikel (refereegranskat)abstract
    • Fatigue crack growth testing of Inconel 718 has been carried out at the temperatures 550 °C and 650 °C. The tests were conducted using a mix of hold times and pure cyclic loading, referred to as block tests. From the test results, the existence of an embrittled volume or damaged zone in the vicinity of the crack tip has been revealed. It has been found that the evolution of this damaged zone can be sufficiently well described using a power law function with an exponent n = 0.25.
  •  
42.
  • Gustafsson, David, 1983, et al. (författare)
  • Fatigue crack growth behaviour of Inconel 718 with high temperature hold times
  • 2010
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 2:1, s. 1095-1104
  • Konferensbidrag (refereegranskat)abstract
    • In this work, fatigue crack growth measurements have been made on center-cracked tension specimens of Inconel 718, where the focus has been to observe the effect of high temperature hold times on the fatigue crack growth behaviour of the material. The material testing has been done at three different temperatures, namely 450 °C, 550 °C and 650 °C. All testing were done in an isothermal LCF context with a standard test method for measuring the fatigue crack growth rates. © 2010 Published by Elsevier Ltd.
  •  
43.
  • Habermann, Mateus, 1981, et al. (författare)
  • Land use Regression as Method to Model Air Pollution. Previous Results for Gothenburg/Sweden
  • 2015
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 115, s. 21-28
  • Konferensbidrag (refereegranskat)abstract
    • In the past 20 years, considerable progress has been made to improve urban air quality in the EU. However, road traffic still contributesconsiderably to the deterioration of urban air quality to below standards, which requires a method to measure properly and model pollutionlevels resulting from road traffic. In order to visualize the geographical distribution of pollution concentration realistically, we applied the LandUse Regression (LUR) model to the urban area of Gothenburg.The NO2 concentration was already obtained by 25 samplers through the urban area during 7-20 May, 2001. Predictive variables such asaltitude, density, roads types, traffic and land use were estimated by geographic information system in buffers ranging 50 to 500 m-radii. Linearregression (α=5%) between NO2 and every predictive variable was calculated, and the most robust variables and without collinearity variableswere selected to the multivariate regression model. The final formula was applied using Kriging in a grid map to estimate NO2 levels.The average of measurements was 23.5 μg/m³ (± 6.8 μg/m³) and 180 predictive variables were obtained. The final model explained 59.4% ofthe variance of NO2 concentration with presence of altitude and sum of traffic within 150 m around the sampler sites as predictor variables. Thecorrelation measured versus predicted levels of NO2 was r = 0.77 (p
  •  
44.
  • Hagentoft, Carl-Eric, 1958, et al. (författare)
  • Drying potential of cold attic using natural and controlled ventilation in different Swedish climates
  • 2016
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 146, s. 2-7
  • Konferensbidrag (refereegranskat)abstract
    • Problems with high humidity levels and mold growth in cold attics have been increasing over the last few years. The high humiditylevels are to a large extent a consequence of the increasing demand on energy efficiency. Houses are frequently retrofitted withadditional attic insulation, which leads to a colder attic space and hence a higher humidity. Replacing furnace heating by heatpumps or district heat may also lead to problem. Also newly built attics have problems. The quite novel technical solution withcontrolled mechanical ventilation of the attic is generally estimated to be risk free in Swedish climate. With controlled mechanicalventilation the attic is intentionally ventilated only when the inflowing air is drying out the attic, otherwise it is shut off. The dryingpotential of controlled ventilation is analyzed for different climate zone in order to map the relative efficiency compared withtraditional natural ventilated attics.
  •  
45.
  • Haller, Martin, et al. (författare)
  • Increasing the Accuracy of a Prefab Building Design Process Simulation Using Simulated Annealing
  • 2014
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 85, s. 214-221
  • Tidskriftsartikel (refereegranskat)abstract
    • Monte-Carlo simulation analysis has been discussed in project management literature as tool for proactive scheduling and to gain better insights into projects which are characterized by a high level of complexity and uncertainty, such as the design phase of prefab building projects. The application of simulation as proactive scheduling tool in construction projects is hampered by limited accessibility of proper input data, though, because of long project duration, the often temporary organization and multidisciplinary nature of such projects. In this study we use simulated annealing to adjust parameters of a simulation model for which the simulation outcome is sensitive to data perturbation by making use of data from related parameters which is easier to estimate. The applicability of the approach was demonstrated on a real life project, the construction of a 1100 m2 residential building in Sweden. More precisely, we used Design Structure Matrix simulation, i.e. an activity network based Monte-Carlo simulation technique with which stochastic project evolution (deviations from the planned activity sequence due to unexpected iteration of sub-processes) can be simulated, to model the workflow of the design process of the observed project. Then, by means of the simulated annealing approach, we adjusted the rework probabilities (model parameter) such that the frequencies of executed activities in simulated activity sequences fitted the frequencies as observed in the real project. Adjusting input data by using prior knowledge of the dependencies of the project activities and cross analysis with related data that is easy to estimate would help to increase the accuracy of simulations when access to statistical data of the input variable in question is limited. The suggested approach is interesting for practitioners who work with standardized design processes (e.g. as part of standardized building systems) and continuous improvement
  •  
46.
  • Hannes, Dave, et al. (författare)
  • Experimental study of weld fatigue strength reduction for a stainless steel piping component
  • 2018
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; , s. 383-391
  • Konferensbidrag (refereegranskat)abstract
    • An experimental mean curve and a design fatigue curve corresponding to 95% survival probability were derived from realistic fatigue experiments on a non-welded water pressurized piping component with primarily focus on high cycle fatigue. The components were subjected to a synthetic variable amplitude bending deformation. Comparison with the results obtained for a similar piping component with a circumferential butt weld allowed the determination of an experimental fatigue strength reduction factor. Comparison with the fatigue procedure and design curve in ASME BPVC Section III allowed to quantify its conservatism with regards to accounting for the presence of a weldment and more generally transferability. © 2017 The Authors.
  •  
47.
  • Huotari, Joni, et al. (författare)
  • Nanostructured Mixed Phase Vanadium Oxide Thin Films as Highly Sensitive Ammonia Sensing Material
  • 2014
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 87, s. 1035-1038
  • Tidskriftsartikel (refereegranskat)abstract
    • Pulsed laser deposition was used to produce vanadium oxide thin films on oxidized silicon substrates. Structural characterization concluded that the films consisted of two phases, orthorombic V2O5 and triclinc V7O16. Thin films performance as conductometric gas sensors was tested and they were found to be sensitive to ammonia gas already at ppb-level concentrations. Also selectivity of NH3 to NO was high. The cross-sensitivity measurements between ammonia and NO showed that the responses to these gases can be discriminated from each other even at 20 ppm concentrations. This is promising result from selective catalytic reduction point of view.
  •  
48.
  • Hörnqvist Colliander, Magnus, 1979, et al. (författare)
  • Dynamic strain ageing and dynamic precipitation in AA7030 during cyclic deformation
  • 2010
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058 .- 1877-7058. ; 2:1, s. 265-273
  • Konferensbidrag (refereegranskat)abstract
    • The effects of dynamic strain ageing (DSA) and dynamic precipitation (DP) on the stress-strain response during low-cycle fatigue of naturally aged (NA) and peak-aged (PA) AA7030 alloy at different temperatures was investigated. The results show that the PA temper is largely unaffected by DSA/DP, and the cyclic deformation behavior is controlled by the accumulation of dislocations and strain localization due to repeated shearing of precipitates. In the NA temper, on the other hand, the effect of temperature on DSA and DP is the main mechanism controlling the stress-strain response. At temperature above room temperature, DP in the intense slip bands inhibits cyclic softening and the samples harden until the on-set of crack growth. At lower temperatures, the rate of DP is too slow to compensate for the softening in the slip bands and the stress amplitude saturates or decreases. The stress amplitude development is shown to primarily be a result of the evolution of the effective stress associated with dislocation-precipitate interactions.
  •  
49.
  • Hörnqvist Colliander, Magnus, 1979, et al. (författare)
  • Fatigue crack growth in Ti-6242 under elasto-plastic loading conditions
  • 2010
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 2:1, s. 223-229
  • Konferensbidrag (refereegranskat)abstract
    • The applicability of LEFM is investigated in this paper. Experiments with loads corresponding to load controlled LEFM conditions and LCF strain controlled conditions were carried out and the crack propagation was monitored. The experiments were evaluated according to standard procedures for crack propagation testing, ASTM E 647. The results from the LCF experiments were evaluated using linear elastic representation of the load in the crack vicinity i.e. KI. The results show that although essentially elastic stress response is observed the use of LEFM and material data obtained under LEFM loading situations resulted in non conservative crack propagation rate predictions for LCF loads. However, the LEFM methodology could be used to accurately describe the fatigue crack growth behavior using material data from the LCF tests but further work is needed for such methodology to be implemented in a life calculation system. © 2010 Published by Elsevier Ltd.
  •  
50.
  • Hörnqvist Colliander, Magnus, 1979, et al. (författare)
  • Fatigue crack growth testing using varying R-ratios
  • 2010
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 2:1, s. 155-161
  • Konferensbidrag (refereegranskat)abstract
    • A method to generate high temperature fatigue crack growth data for multiple R-ratios during a single or only a few tests for surface crack specimens was developed. Two tests were performed; one with 0≤R≤0.8 and one with -1≤R≤0. The crack growth was monitored using the potential drop method. It was shown that the results from tests with varying R-ratio gave very similar results to test with constant R. Fatigue crack growth predictions with data from varying R-test were generally slightly more conservative compared to predictions using data obtained from conventional testing. © 2010 Published by Elsevier Ltd.
  •  
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