| 1. |
- Hoier, Philipp, 1988, et al.
(author)
-
On assessing grindability of recycled and ore-based crankshaft steel: an approach combining data analysis with material science
- 2021
-
In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 104, s. 1601-1606
-
Conference paper (peer-reviewed)abstract
- Material-related grindability variations when grinding recycled and ore-based steel can significantly impair the process efficiency during finishing of automotive crankshafts. To address this problem and to achieve more robust grinding processes, the underlying causes of variation need to be understood. The present work investigates the feasibility of using quality data obtained during production to study grindability variations and identify material-related effects. Analysis of non-destructive inspection protocols indicates steel supplier-dependent differences in grindability. However, no systematic grindability differences between recycled and ore-based steel could be identified. Possible correlations between grindability and material characteristics obtained from supplied steel certificates are discussed.
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| 2. |
- Ahmer, Muhammad
(author)
-
Intelligent fault diagnosis and predictive maintenance for a bearing ring grinder
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- Predicting the failure of any structure is a difficult task in a mechanical system. However complicated and difficult the prediction might be, the first step is to know the actual condition of the system. Given the complexity of any machine tool, where a number of subsystems of electro-mechanical structures interact to perform the machining operation, failure diagnostics become more challenging due to the high demand for performance and reliability. In a production environment, this results in maintenance costs that the management always strives to reduce. Condition-based machine maintenance (CBM) is considered to be the maintenance strategy that can lead to failure prediction and reducing the maintenance cost by knowing the actual condition of the asset and planning the maintenance activities in advance.Grinding machines and grinding processes have come a long way since the inception of the centuries old grinding technique. However, we still have a number of challenges to overcome before a completely monitored and controlled machine and process can be claimed. One such challenge is to achieve a machine level CBM and predictive maintenance (PdM) setup which is addressed in this thesis. A CBM implementation framework has been proposed which combines the information sampled from sensors installed for the purpose of the process as well as condition monitoring. Accessing the machine's controller information allows the data to be processed with respect to different machine states and process stages. The successful implementation is achieved through a real-time and synchronized data acquisition setup that allows data from multiple sources to be acquired, stored, and consolidated. The dataset thus generated is used in a significant part of this project and is also published in Swedish National Data Service (SND).The thesis also presents the failure diagnostic model based on two step classification approach using benchmarked random forest models. The binary classifier predicts if there is a fault present in the machine based on crucial sensors data from the Idle segment of the grinding cycle. Multi-class random forest classifier diagnosis the fault condition. PdM, knowing when to trigger maintenance action, is achieved through predicting the overall quality of the produced parts from the feature set extracted from sensor data of the Spark-out segment of the grinding cycle. Combining fault diagnosis with the predicted quality information resulted in reliable and actionable maintenance decisions for the bearing ring grinder. The demonstrated setup, based on a production bearing ring grinder, is adaptable to similar machines in production.
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| 3. |
- Asgari, A., et al.
(author)
-
Magnesium alloy-silicon carbide composite fabrication using chips waste
- 2019
-
In: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 232, s. 1187-1194
-
Journal article (peer-reviewed)abstract
- Interest in Mg-based composites has grown with their potential use as engineering materials due to having a high strength-to-weight ratio, wear resistance, and creep behavior. While magnesium chips are typically considered as waste on production shop floors, there can be a promising way to fabricate Mg-based composites with carefully distributed reinforcements. This research is concerned with the reuse of AZ91 magnesium-alloy chips to fabricate Mg-based composites. The fabrication process requires to collect and clean magnesium chips and then mix them with SiC particles as reinforcements. Finally, this composition is melted and stirred by a stir casting method to fabricate the AZ91/SiC composites. The results clearly show that not only magnesium chips waste can be reused in a sustainable way, but also that they improve the reinforcement distribution substantially, leading to enhanced mechanical properties so that the composite yield strength increases by 62.7% when adding 5% SiC particles, volume percentage. Moreover, the composites with 5% reinforcements, demonstrate a hardness increase of about 46%.
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| 4. |
- Badger, J., et al.
(author)
-
Application of the dimensionless Aggressiveness number in abrasive processes
- 2021
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In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 102, s. 361-368
-
Conference paper (peer-reviewed)abstract
- The chip thickness is often used to characterize abrasive processes, particularly grinding. Unfortunately, because of the seemingly random nature of the geometrically undefined cutting points and difficulty in estimating the cutting-point density, chip thickness is notoriously difficult to quantify. Recently, the dimensionless Aggressiveness number has gained popularity because it circumvents the need to quantify the wheel topography and is applicable to any geometry in abrasive contact. This paper shows how the concept of dimensionless Aggressiveness number applies to the most common abrasive geometries and how it can be used to achieve practical results in a variety of applications.
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| 5. |
- Badger, J., et al.
(author)
-
Grinding of cermets with cup-wheels
- 2016
-
In: Materials Science Forum. - 1662-9752 .- 0255-5476. - 9783035710342 ; 874, s. 115-123
-
Conference paper (peer-reviewed)abstract
- Cup-wheels are frequently used to grind cermets, a difficult-to-grind material. An investigation was made into the transient geometry of the cup-wheel rim, grit dulling, wheel loading, and wheel self-sharpening with chip thickness. Tests were performed on a saw-tip grinding machine and specific energies, G-ratios and rim geometries were measured. Results showed that, like grinding of tungsten-carbide, loading is prevalent. However, unlike grinding of tungstencarbide, grit dulling is also prevalent and wheel conditioning is of limited use. Much better results, particularly with respect to surface finish, can be obtained if the wheel is trued to a predetermined geometry. In addition, grinding parameters must be chosen to induce wheel self-sharpening. Practical recommendations are given.
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| 6. |
- Badger, J., et al.
(author)
-
On mechanics and monitoring of plunge-roll rotary dressing of grinding wheels
- 2023
-
In: CIRP Annals - Manufacturing Technology. - 1726-0604 .- 0007-8506. ; 72:1, s. 277-280
-
Journal article (peer-reviewed)abstract
- A study is made into the mechanics and monitoring of rotary plunge-roll dressing of grinding wheels using a roll with multi-layer diamonds contained in a hybrid, metal-ceramic bond. A fundamental relationship is obtained between grinding/dressing specific energy and the dressing aggressiveness number Aggrd, revealing a distinct size effect. Results also indicate (i) a nearly linear relationship between grinding and dressing specific energy, and (ii) direct proportionality between dressing specific energy and the acoustic emission (AE) signal. SEM observations indicate that smaller Aggrd produces a grit-dulling phenomenon different from grinding-induced dulling of the grits by attrition, which causes rapid workpiece-material adhesion.
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| 7. |
- Badger, J., et al.
(author)
-
Power monitoring, Fourier transforms of power, and electron microscopy in evaluating the performance of abrasives in grinding
- 2016
-
In: International Journal of Abrasive Technology. - 1752-2641 .- 1752-265X. ; 7:4, s. 270-283
-
Journal article (peer-reviewed)abstract
- The use of electron microscopy and power-monitoring during grinding was investigated in terms of evaluating the fracture and wear characteristics and chip-formation mechanisms of abrasive grains and bond formulations. Diamond abrasives and fused, sintered and sintered triangular-shaped aluminium-oxide abrasives were evaluated. Power was shown to be a useful tool in determining the chip-formation mechanisms and the extent of grit fracture, particularly in triangular-shaped abrasive. Conclusions were supported by electron-microscope analysis. Power was also used to evaluate low-cost diamond vs. premium diamond abrasives. Practical recommendations are given for evaluating grit, wheel and bond performance both in the laboratory and in production.
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| 8. |
- Drazumeric, R., et al.
(author)
-
Mechanics of self-rotating double-disc grinding process
- 2022
-
In: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 71:1, s. 309-312
-
Journal article (peer-reviewed)abstract
- Unlike most double-disc grinding processes, which use forced workpiece rotation, some double-disc processes rely on workpiece self-rotation driven by non-uniform shear forces resulting from partial wheel-workpiece coverage. This self-rotation is poorly understood, with workpiece angular frequency remaining unknown despite its importance. This paper investigates the kinematics of self-rotation via analytical modelling of the moment-equilibrium conditions, derived from experimentally determined specific-energy values. The model showed that workpiece coverage ratio is the dominant factor governing workpiece angular frequency, allowing for the choice of optimal workpiece coverage ratios that avoid (i) workpiece-stoppage and (ii) excessive frictional heat generation. The predicted velocity was validated with acoustic-emission measurements.
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| 9. |
- Dražumerič, Radovan, et al.
(author)
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Temperature-based method for determination of feed increments in crankshaft grinding
- 2018
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In: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136. ; 259, s. 228-234
-
Journal article (peer-reviewed)abstract
- The design of a crankshaft-grinding cycle involves determining the radial infeed and axial infeed in each feed increment. A new method for determination of feed increments is developed to increase productivity while avoiding thermal damage. Analyses of the geometry, kinematics and specific-energy characteristic are made to estimate the feed-dependent distribution of maximum surface temperature along the wheel profile. It is discovered that there are two temperature maxima in the grinding zone when feeding both axially and radially. Therefore, the developed method determines the infeeds such that a predetermined burn threshold is matched in these two critical points. The new technology is validated by measurements of Barkhausen noise and residual stress. A comparison is made between the temperature-based method and the radial-plunge method previously used in production. The comparison indicates that lower cycle times are attainable with less risk of thermal damage. Results for material-removal rate and maximum surface temperature are also presented.
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| 10. |
- Drazumeric, R., et al.
(author)
-
Wheel lift-off in creep-feed grinding: thermal damage, power surge, chip thickness and optimisation
- 2017
-
In: International Journal of Abrasive Technology. - 1752-2641 .- 1752-265X. ; 8:2, s. 97 - 120
-
Journal article (peer-reviewed)abstract
- An investigation is made into the phenomenon of early lift-off in creep-feed grinding, where the wheel lifts away from the workpiece before reaching the end of cut. In single-pass operations, early lift-off can result in thermal damage. In multi-pass operations, there is a surge in material-removal rate just before lift-off, which can result in thermal damage and excess wheel wear. This study examines the current inadequate methods of dealing with lift-off. It then develops a geometric and kinematic model for analysing the lift-off phenomenon. It finally proposes a thermal-model-based optimisation method for achieving a constant maximum surface temperature, resulting in shorter cycle times and less risk of thermal damage. The power-surge model is validated experimentally in diamond grinding of tungsten-carbide rotary tools.
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| 11. |
- Grguraš, Damir, et al.
(author)
-
A novel cryogenic machining concept based on a lubricated liquid carbon dioxide
- 2019
-
In: International Journal of Machine Tools and Manufacture. - : Elsevier BV. - 0890-6955. ; 145
-
Journal article (peer-reviewed)abstract
- A novel single-channel supply of pre-mixed (a) liquid carbon dioxide (LCO2) and (b) oil – delivered via minimum quantity lubrication (MQL) – represents a significant advancement in cryogenic-machining technology. In this proof-of-concept study, an attempt is made to advance the understanding of the oil solubility in LCO2 and to analyze the oil-droplets and their impact on machining performance. The results indicate that the physical and chemical properties of oil distinctively affect its solubility in LCO2. The achieved solubility further influences the achievable oil-droplet size and distribution and tool life.
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| 12. |
- Hashimoto, F., et al.
(author)
-
Abrasive fine-finishing technology
- 2016
-
In: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 65:2, s. 597-620
-
Journal article (peer-reviewed)abstract
- Abrasive fine-finishing technology is often applied as a final finishing process, and the selection of the right technology is crucial to obtaining the desired performance of functions such as fatigue life. This paper begins with classifications of the technology along with fundamentals and brief histories of the individual methods. The material removal mechanisms, specific energies, and finishing characteristics of the various technologies are summarized giving assessments of the surfaces created by them. Guidelines developed for selecting the appropriate methods, and case studies illustrate the effectiveness of various methods. This paper ends with a discussion of the future prospects of the technology. (C) 2016
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| 13. |
- Hoier, Philipp, 1988, et al.
(author)
-
A Comparative Study of Flank Wear Characteristics When Turning 20MNCRS5 Case Hardening Steel and Allay 718 Superalloy
- 2018
-
Conference paper (other academic/artistic)abstract
- The present study deals with characterization of flank wear lands of uncoated cemented tungsten carbide (WC-Co) tools used for machining two different material types, a case hardening steel (20MnCrS5) and a heat-resistant superalloy (Alloy 718). Scanning electron microscopy (SEM) and the electron backscatter diffraction (EBSD) technique were used to investigate the flank wear lands after machining the two materials. Differences in surface topographies as well as induced strains from the machining tests are discussed with respect to the underlying tool-loads and resulting wear mechanisms during machining of the two types of materials.
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| 14. |
- Hoier, Philipp, 1988, et al.
(author)
-
An investigation into the grindability of additively manufactured 42CrMo4 steel
- 2024
-
In: CIRP Annals - Manufacturing Technology. - 1726-0604 .- 0007-8506. ; 73:1, s. 257-260
-
Journal article (peer-reviewed)abstract
- This study investigates post-processing of additively manufactured (AM) low-alloy 42CrMo4 steel (AISI 4140) produced by powder bed fusion – laser beam (PBF-LB). While the PBF-LB process produces tempered martensite by in-situ heat-treatment, resulting in superior mechanical properties, finishing by grinding remains critical for use in precision components such as automotive gears. The grindability of the AM material is compared to conventionally produced steel and reveals comparable results to most of the grindability criteria tested. However, higher wheel wear is observed when grinding the AM material. This is likely due to the lack of machinability-enhancing inclusion treatment common in conventional steelmaking.
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| 15. |
- Hoier, Philipp, 1988, et al.
(author)
-
Characterization of abrasion- and dissolution-induced tool wear in machining
- 2019
-
In: Wear. - : Elsevier BV. - 0043-1648. ; 426-427, s. 1548-1562
-
Journal article (peer-reviewed)abstract
- In the present work, a comparative study is reported on tool wear characteristics induced by machining two distinctively different types of materials: Vanadis 10 tool steel containing large amounts of MC and M 7 C 3 carbides, and 316L austenitic stainless steel which is nearly free of hard abrasive phases. Tool life tests were conducted using cemented tungsten carbide tools (WC-Co), both uncoated and TiCN-Al 2 O 3 coated. The subsequent wear characterization included scanning electron microscopy and electron backscatter diffraction (EBSD). Examination of worn WC-Co substrates and coatings revealed significantly different wear characteristics after machining the two workpiece materials. Predominantly abrasion-induced wear was revealed by micro-fragmented tool constituents as well as sub-micron sized grooves and ridges on tool substrates and coatings when machining the tool steel. Moreover, EBSD analysis indicated that the tool substrates exhibited significant superficial strains caused by localized plastic deformation during sliding contact of the tools with the carbides of the tool steel. In contrast, during machining of the stainless steel using uncoated tools, the predominantly dissolution-induced wear resulted in WC-Co substrates with smooth surfaces and absence of significant strain. The worn coatings showed signs of spalling of micro-fragments which indicated the dominant contribution of adhesive wear when machining stainless steel.
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| 16. |
- Hoier, Philipp, 1988, et al.
(author)
-
Influence of batch-to-batch material variations on grindability of a medium‑carbon steel
- 2022
-
In: Journal of Manufacturing Processes. - : Elsevier Ltd. - 1526-6125. ; 73, s. 463-470
-
Journal article (peer-reviewed)abstract
- This study addresses the influence of material variations on the grindability of crankshaft steel. Most previous studies on the effect of material microstructure on grindability involve comparisons of significantly different steel grades. This study, in contrast, is focused on batch-to-batch grindability variations for one steel grade, a scenario frequently occurring in industry where batches from different steel makers are fed into a production line. For this purpose, a batch made of recycled steel and a batch made of ore-based steel were compared with regards to microstructure and grindability under identical grinding and dressing conditions. Although both batches met the same material specifications, microstructural variations were identified in terms of grain size and micro-constituents (inclusions, carbonitrides). While specific grinding energy, residual stress and full-width at half-maximum profiles of ground surfaces were the same for both batches, the recycled batch showed different and unfavorable variation in wheel wear and Barkhausen noise (BN) response. Larger fractions of oxide inclusions and larger grain sizes (affected by carbonitrides) were present in the recycled batch, which were the likely reasons for the differences in wheel wear and BN response, respectively. These findings may aid grindability improvement by steel-grade adjustments, e.g. modification of the distribution and type of inclusions and/or amount of elements forming carbonitrides. Furthermore, the results highlight the importance of understanding and controlling material microstructure, as existing in-line quality by BN control may not always be able to correctly indicate surface integrity, which could lead to misinterpretations (e.g. false part-rejection on the assumption of grinding burn). © 2021 The Authors
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| 17. |
- Hoier, Philipp, 1988, et al.
(author)
-
Microstructural variations in 316L austenitic stainless steel and their influence on tool wear in machining
- 2019
-
In: Wear. - : Elsevier BV. - 0043-1648. ; 428-429, s. 315-327
-
Journal article (peer-reviewed)abstract
- The aim of the present study was to investigate how variations in the microstructure of 316L austenitic stainless steel influence the tool wear during machining. A detailed comparison between two workpieces of 316L, supplied by different producers was made regarding their microstructures and the resulting tool wear during machining. Machining the two workpieces resulted in distinctively different tool wear responses. During the tool life tests, machining one of the workpieces resulted in a steady increase in tool flank wear and the criterion of maximum flank wear land was reached after about 15 and 5 min at low and high cutting speed respectively. However, no significant flank wear was observed when machining the other workpiece under the same cutting conditions. Post-test characterization of the worn tool surfaces showed that tool wear by dissolution/diffusion were the main wear mechanisms for cutting both workpieces. The distinct differences in tool wear progression were linked to varying micro-constituents present in the two workpieces. Specifically, the main factor controlling the wear was attributed to differences in the composition of oxide inclusions. In the one workpiece's case, the specific composition and hence mechanical properties of the inclusions gave rise to a stable protective layer covering the tool surface. During cutting, this inclusion layer was acting as a diffusion barrier, thereby suppressing tool wear by dissolution and hence limiting the progression of flank wear. In contrast, the characteristics of the oxide inclusions present in the other workpiece did not favor the formation of a protective layer on the cutting tool surfaces.
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| 18. |
- Hoier, Philipp, 1988, et al.
(author)
-
Study of flank wear topography and surface-deformation of cemented carbide tools after turning Alloy 718
- 2018
-
In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 77, s. 537-540
-
Conference paper (peer-reviewed)abstract
- An investigation is reported on the characterization of an uncoated tungsten carbide tool used for machining of a Ni-Fe based superalloy (Alloy 718). Scanning electron microscopy (SEM) in combination with white-light interferometry (WLI) was applied to study the flank wear surface topographies both directly after the turning test and when the adhered workpiece material was removed by etching. The obtained results show that the thin layers of adhered workpiece material present on the flank wear land can obscure the wear topography. Removal of adhered workpiece material from the worn areas of interest is therefore necessary to reveal features of worn tool surfaces. SEM observations of worn WC grains revealed that abrasion is an active wear mechanism during cutting. Complementary analysis by the electron backscatter diffraction (EBSD) technique revealed that worn WC grains are additionally characterized by significant strain which suggests the contribution of plastic deformation to the flank wear. Plastic deformation of WC is likely caused by high thermal and mechanical loads acting on the tool during machining.
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| 19. |
- Hosseini, Seyed, et al.
(author)
-
Comparison of machining performance of stainless steel 316L produced by selective laser melting and electron beam melting
- 2022
-
In: Procedia CIRP. - : Elsevier B.V.. - 2212-8271. ; , s. 72-77
-
Conference paper (peer-reviewed)abstract
- Powder bed fusion processes based additively manufactured SS 316L components fall short of surface integrity requirements needed for optimal functional performance. Hence, machining is required to achieve dimensional accuracy and to enhance surface integrity characteristics. This research is focused on comparing the material removal performance of 316L produced by PBF-LB (laser) and PBF-EB (electron beam) in terms of tool wear and surface integrity. The results showed comparable surface topography and residual stress profiles. While the hardness profiles revealed work hardening at the surface where PBF-LB specimens being more susceptible to work hardening. The investigation also revealed differences in the progress of the tool wear when machining specimens produced with either PBF-LB or PBF-EB. .
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| 20. |
- Isakson, Simon, 1982, et al.
(author)
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Effect of cryogenic cooling and tool wear on surface integrity of turned Ti-6Al-4V
- 2018
-
In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 71, s. 254-259
-
Conference paper (peer-reviewed)abstract
- The aim of this work is to investigate the influence of flank wear and cutting fluid (emulsion vs. liquid nitrogen) on surface integrity in turning of titanium alloy Ti-6Al-4V. Longitudinal turning tests with pre-worn uncoated cemented carbide inserts are performed, after which the surface and subsurface layer of machined workpieces is studied. Results for residual stresses on the surface as well as in depth profiles, obtained by X-ray diffraction, are also presented. Scanning electron microscopy (SEM) is used to investigate the microstructure of the workpieces. The same tool holder was used for both cooling conditions, with the same nozzle configuration. The flow rate of liquid nitrogen was therefore limited and as a result, tool wear development was observed to be faster for cryogenic cooling than emulsion-based flood cooling. However, the results show limited differences in terms of achievable residual stresses when comparing cryogenic and conventional cooling at similar levels of tool wear. Despite an increase in tool wear rate, the cryogenic cooling conditions thus provide similar surface integrity results as emulsion cooling. The results suggest that the consumption of the cryogenic coolant can be reduced or optimized without a significant impact on surface quality.
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| 21. |
- Kadivar, Mohammadali, 1987, et al.
(author)
-
Modeling of micro-grinding forces considering dressing parameters and tool deflection
- 2021
-
In: Precision Engineering. - : Elsevier BV. - 0141-6359. ; 67, s. 269-281
-
Journal article (peer-reviewed)abstract
- The prediction of cutting forces is critical for the control and optimization of machining processes. This paper is concerned with developing prediction model for cutting forces in micro-grinding. The approach is based on the probabilistic distribution of undeformed chip thickness. This distribution is a function of the process kinematics, properties of the workpiece, and micro-topography of the grinding tool. A Rayleigh probability density function is used to determine the distribution of the maximum chip thickness as an independent parameter. The prediction model further includes the effect of dressing parameters. The integration of the dressing model enables the prediction of static grain density of the grinding tool at various radial dressing depths. The tool deflection is also considered in order to account for the actual depth of cut in the modeling process. The dynamic cutting-edge density as a function of the static grain density, the local tool deflection, elastic deformation, and process kinematics can hence be calculated. Once the chip thickness is calculated, the single-grain forces for individual abrasive grains are predicted and the specific tangential and normal grinding forces simulated. The simulation results are experimentally validated via cutting-force measurements in micro-grinding of Ti6Al4V. The results show that the model can predict the tangential and normal grinding forces with a mean accuracy of 10% and 30%, respectively. The observed cutting forces further imply that the flow stress of the material did not change with changing the cutting speed and the cutting strain rate. Moreover, it was observed that the depth of cut and grinding feed rate had the same neutral effect on the resultant grinding forces.
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| 22. |
- Kadivar, Mohammadali, 1987, et al.
(author)
-
Modeling of the micro-grinding process considering the grinding tool topography
- 2017
-
In: ISAAT 2017 - Proceedings of the 20th International Symposium on Advances in Abrasive Technology. ; 8:2, s. 157-170
-
Conference paper (peer-reviewed)abstract
- The micro topography of the grinding tool has a considerable influence on the cutting forces and temperature as well as the tool wear. This paper addresses an analytical modeling of the micro-grinding process based on the real tool topography and kinematic modeling of the cutting-edge-workpiece interactions. An approximate shape of the abrasive grains and their distribution is obtained from the confocal images, which are taken from the tool surface – determining the grain height protrusion and the probability density function of the grains. To determine the grinding forces, a transient kinematic approach is developed. In this method, the individual grit interaction with the workpiece is extended to the whole cutting zone in the peripheral flank grinding operation. Hence a predictive model of cutting forces and surface roughness in micro grinding of titanium grade 5 is developed. Finally, the simulated forces and surface roughness are validated by the experimental results.
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| 23. |
- Kadivar, Mohammadali, 1987, et al.
(author)
-
Surface integrity in micro-grinding of Ti6Al4V considering the specific micro-grinding energy
- 2020
-
In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 87, s. 13-18
-
Conference paper (peer-reviewed)abstract
- Surface integrity is one of the most significant quality aspects of micro-grinding of difficult-to-cut materials. On the other hand, specific grinding energy is a fundamental parameter for describing the micro-grinding process. This paper addresses the surface integrity of the micro-ground surface of a titanium alloy under different cutting speeds and feed-rate-to-depth-of-cut (vw/ae) ratios at the same chip thickness. Three different cutting speeds and vw/ae ratios have been chosen and the residual stress of the workpiece, as well as the specific micro-grinding energy, have been investigated. The results showed that almost the same minimum specific grinding energy was obtained at tested cutting speed and vw/aeratio. The results of the XRD analysis showed that contrary to the specific micro-grinding energy, the residual stresses of the ground surface changed by varying the cutting speed and vw/ae ratio. Higher cutting speeds resulted in lower compressive residual stress, and higher vw/ae ratios resulted in higher compressive stresses. This can be attributed to higher temperatures in the chip-formation process compared to the plastic deformation in micro-grinding at higher cutting speeds and lower vw/ae ratios which was proved via SEM micrographs.
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| 24. |
- Kadivar, Mohammadali, 1987, et al.
(author)
-
The effect of dressing parameters on micro-grinding of titanium alloy
- 2018
-
In: Precision Engineering. - : Elsevier BV. - 0141-6359. ; 51, s. 176-185
-
Journal article (peer-reviewed)abstract
- This paper is concerned with investigating the effects of dressing parameters and the effect of the cutting speed on the performance of micro-grinding of titanium Ti-6Al-4 V alloy. Extremely high dressing overlap ratios were used for the first time to dress the grinding pins, and the obtained micro-topography, measured on the surface of the pins, is found to be directly related to the grinding forces. More specifically, both the normal and tangential grinding force components increased with the dressing overlap ratio. Related effects of dressing on surface quality are also presented. Grinding with pins containing finer topography was accompanied by less loading with chips and hence a better surface finish. Moreover, down-dressing method generated rougher finished surface quality and induced lower grinding forces compared to the up-dressing. High values of the dressing overlap ratio (up to 1830) in the up-dressing method improved the surface finish significantly.
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| 25. |
- Kadivar, Mohammadali, 1987, et al.
(author)
-
The role of specific energy in micro-grinding of titanium alloy
- 2021
-
In: Precision Engineering. - : Elsevier BV. - 0141-6359. ; 72, s. 172-183
-
Journal article (peer-reviewed)abstract
- This paper is concerned with understanding the role of specific energy in micro-grinding of conventional and additively manufactured Ti6Al4V. The effects of grinding and dressing parameters, cooling-lubrication conditions, and the directions of material build-up are studied. It is demonstrated that the minimum specific energy in single grain tests is independent of the material-fabrication method. The lowest measured specific energy obtained is 11.5 J/mm3 for both workpiece materials. The direction of material build-up influenced the process only when grinding with low aggressiveness, where 20% higher specific energy was observed. Similar specific energies were obtained for oil-lubricated and dry conditions, indicating that lubrication had minimal effect. The effects of the diamond concentration in the wheel and the dressing parameters were also investigated. Comparable specific energies were observed for wheels with C150 and C200 concentrations. The specific energy was found being predominantly influenced by dressing. Coarse dressing conditions produced 18% lower specific energy and, therefore, a more efficient micro-grinding process.
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