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Zhengyi Jiang - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Surface Asperity flattening based on two different methods
Continuum Mechanics and Thermodynamics, 2016Co-Authors: Andreas Öchsner, Dongbin Wei, Zhengyi JiangAbstract:The stress state is an important parameter in metal forming processes, which significantly influences the strain state and microstructure of products, affecting their Surface qualities. In order to make the metal products have a good Surface quality, the Surface stress state must be optimised. In this study, two classical methods, the upper bound method and the crystal plasticity finite element method, were investigated. The differences between the two methods were discussed in regard to the model, the velocity field, and the strain field. Then the related Surface roughness is deduced.
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Study on Surface Asperity flattening in cold quasi-static uniaxial planar compression by crystal plasticity finite element method
Tribology Letters, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xiaoming Zhang, Dianyao Gong, Jiangtao HanAbstract:In order to study the Surface Asperity flattening in a quasi-static cold uniaxial planar compression, the experimental results of atomic force microscope and electron backscattered diffraction have been employed in a rate-dependent crystal plasticity model to analyze this process. The simulation results show a good agreement with the experimental results: in this quasi-static deformation process, lubrication can hinder the Surface Asperity flattening process even under very low deformation rate. However, due to the limitation of the model and some parameters, the simulation results cannot predict all the properties in detail such as S orientation {123} , and the maximum stress in sample compressed without lubrication. In addition, the experimental results show, with an increase in gauged reduction, the development of Taylor factor, and CSL boundaries show certain tendencies. Under the same gauged reduction, friction can increase the Taylor factor and Σ = 7.
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Crystal plasticity finite element modelling of the effect of friction on Surface Asperity flattening in cold uniaxial planar compression
Applied Surface Science, 2015Co-Authors: Andreas Öchsner, Dongbin Wei, Zhengyi JiangAbstract:Abstract During uniaxial planar compression of annealed aluminium alloys, a novel approach to determine the Surface Asperity flattening (roughness R a ) is employed by analyzing the evolution of the Surface's micro-texture. With an increase in compression strain, the Surface Asperity tends to be flattened, and strain hardening increases. Lubrication can constrain the Surface Asperity flattening process and hinder the progress of grain Surface flattening. The development of Surface texture shows an obvious dependency: under the influence of friction, the normal deformation texture component (brass orientation { 0 1 1} 〈1 1 2〉) can be generated easily, while lubrication can hinder this texture component generation. Simulated results show a good agreement with experimental results which predicated brass orientation. However, due to the limitation of the FCC Taylor model, the other orientation components cannot be predicted.
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Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy in a quasi-static cold uniaxial planar compression (CUPC)
Applied Surface Science, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xingjian Gao, Xiaoming ZhangAbstract:Abstract In a quasi-static cold uniaxial planar compression, Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy are carried out by employing Atomic Force Microscope (AFM) and Electron Backscattered Diffraction (EBSD) methods. Strain rate affects the Surface Asperity evolution obviously. While lubrication can hinder the Surface Asperity flattening by constraining the Surface localized deformation. Lubrication can accelerate the crystallization in CUPC process. It also impedes the activation of some orientation components by hindering the activation of related slip systems in light metal Al alloy.
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Influence of Friction on Surface Asperity Flattening Process in Cold Uniaxial Planar Compression (CUPC)
Tribology Letters, 2014Co-Authors: Hejie Li, Zhengyi JiangAbstract:Atomic force microscope and electron back-scattering diffraction measurement methods were used to study the effects of friction on Surface Asperity flattening and Surface texture during the uniaxial planar compression of annealed aluminum alloy. With an increase in gauged reduction, Surface Asperity tended to be flattened. Friction could boost the Surface Asperity flattening process by reducing the flow stress in deformation. The development of Surface Asperity features demonstrated that friction can effectively hinder the development of the Goss orientation component {011} and clearly promote the generation of brass orientation {011} orientation. Regardless of whether the sample was compressed with lubricant or not, a few S orientation component {123} formed in sample edge area.
Dongbin Wei - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Surface Asperity flattening based on two different methods
Continuum Mechanics and Thermodynamics, 2016Co-Authors: Andreas Öchsner, Dongbin Wei, Zhengyi JiangAbstract:The stress state is an important parameter in metal forming processes, which significantly influences the strain state and microstructure of products, affecting their Surface qualities. In order to make the metal products have a good Surface quality, the Surface stress state must be optimised. In this study, two classical methods, the upper bound method and the crystal plasticity finite element method, were investigated. The differences between the two methods were discussed in regard to the model, the velocity field, and the strain field. Then the related Surface roughness is deduced.
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Study on Surface Asperity flattening in cold quasi-static uniaxial planar compression by crystal plasticity finite element method
Tribology Letters, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xiaoming Zhang, Dianyao Gong, Jiangtao HanAbstract:In order to study the Surface Asperity flattening in a quasi-static cold uniaxial planar compression, the experimental results of atomic force microscope and electron backscattered diffraction have been employed in a rate-dependent crystal plasticity model to analyze this process. The simulation results show a good agreement with the experimental results: in this quasi-static deformation process, lubrication can hinder the Surface Asperity flattening process even under very low deformation rate. However, due to the limitation of the model and some parameters, the simulation results cannot predict all the properties in detail such as S orientation {123} , and the maximum stress in sample compressed without lubrication. In addition, the experimental results show, with an increase in gauged reduction, the development of Taylor factor, and CSL boundaries show certain tendencies. Under the same gauged reduction, friction can increase the Taylor factor and Σ = 7.
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Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy in a quasi-static cold uniaxial planar compression (CUPC)
Applied Surface Science, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xingjian Gao, Xiaoming ZhangAbstract:Abstract In a quasi-static cold uniaxial planar compression, Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy are carried out by employing Atomic Force Microscope (AFM) and Electron Backscattered Diffraction (EBSD) methods. Strain rate affects the Surface Asperity evolution obviously. While lubrication can hinder the Surface Asperity flattening by constraining the Surface localized deformation. Lubrication can accelerate the crystallization in CUPC process. It also impedes the activation of some orientation components by hindering the activation of related slip systems in light metal Al alloy.
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Crystal plasticity finite element modelling of the effect of friction on Surface Asperity flattening in cold uniaxial planar compression
Applied Surface Science, 2015Co-Authors: Andreas Öchsner, Dongbin Wei, Zhengyi JiangAbstract:Abstract During uniaxial planar compression of annealed aluminium alloys, a novel approach to determine the Surface Asperity flattening (roughness R a ) is employed by analyzing the evolution of the Surface's micro-texture. With an increase in compression strain, the Surface Asperity tends to be flattened, and strain hardening increases. Lubrication can constrain the Surface Asperity flattening process and hinder the progress of grain Surface flattening. The development of Surface texture shows an obvious dependency: under the influence of friction, the normal deformation texture component (brass orientation { 0 1 1} 〈1 1 2〉) can be generated easily, while lubrication can hinder this texture component generation. Simulated results show a good agreement with experimental results which predicated brass orientation. However, due to the limitation of the FCC Taylor model, the other orientation components cannot be predicted.
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study on the influence of temperature on the Surface Asperity in micro cross wedge rolling
THE 11TH INTERNATIONAL CONFERENCE ON NUMERICAL METHODS IN INDUSTRIAL FORMING PROCESSES: NUMIFORM 2013, 2013Co-Authors: Dongbin Wei, Zhengyi Jiang, X M ZhaoAbstract:When the common deformation processes are scaled down to micro/meso dimensions, size effect is the particular phenomena in microforming, which is related to the dominant influence of single grains inside the micropart. The conventional cross wedge rolling (CWR) is introduced into the micro scale in order to take the advantages of CWR. The micro cross wedge rolling (MCWR) has to confront with the phenomena of size effect that occurs in the common microforming processes inevitably. One of the approaches to compensate size effect is to increase the deforming temperature. An increased formability is achieved because more slip systems of polycrystal metal are activated at the elevated temperature. This reduces the anisotropic material behavior resulting in a more homogeneous forming with improved reproducibility. In this study, a YAG laser beam is applied to heat the workpiece. Finite element model (FEM) associated with a material constitutive formulation considering dislocation mechanics is set up to simulate...
Xiaoming Zhang - One of the best experts on this subject based on the ideXlab platform.
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Study on Surface Asperity flattening in cold quasi-static uniaxial planar compression by crystal plasticity finite element method
Tribology Letters, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xiaoming Zhang, Dianyao Gong, Jiangtao HanAbstract:In order to study the Surface Asperity flattening in a quasi-static cold uniaxial planar compression, the experimental results of atomic force microscope and electron backscattered diffraction have been employed in a rate-dependent crystal plasticity model to analyze this process. The simulation results show a good agreement with the experimental results: in this quasi-static deformation process, lubrication can hinder the Surface Asperity flattening process even under very low deformation rate. However, due to the limitation of the model and some parameters, the simulation results cannot predict all the properties in detail such as S orientation {123} , and the maximum stress in sample compressed without lubrication. In addition, the experimental results show, with an increase in gauged reduction, the development of Taylor factor, and CSL boundaries show certain tendencies. Under the same gauged reduction, friction can increase the Taylor factor and Σ = 7.
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Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy in a quasi-static cold uniaxial planar compression (CUPC)
Applied Surface Science, 2015Co-Authors: Zhengyi Jiang, Dongbin Wei, Xingjian Gao, Xiaoming ZhangAbstract:Abstract In a quasi-static cold uniaxial planar compression, Surface Asperity evolution and microstructure analysis of Al 6061T5 alloy are carried out by employing Atomic Force Microscope (AFM) and Electron Backscattered Diffraction (EBSD) methods. Strain rate affects the Surface Asperity evolution obviously. While lubrication can hinder the Surface Asperity flattening by constraining the Surface localized deformation. Lubrication can accelerate the crystallization in CUPC process. It also impedes the activation of some orientation components by hindering the activation of related slip systems in light metal Al alloy.
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Microtexture based analysis of Surface Asperity flattening behavior of annealed aluminum alloy in uniaxial planar compression
Tribology International, 2013Co-Authors: Zhengyi Jiang, Dongbin Wei, Xiaoming ZhangAbstract:During the uniaxial planar compression of annealed aluminum alloy, a novel approach to determine Surface Asperity flattening (roughness Ra) is employed by analyzing the evolution of Surface microtexture. With an increase in gauged reduction, Surface Asperity tends to be flattened, and strain hardening increases. Lubrication can constrain the Surface Asperity flattening process. Development of Surface Asperity features shows the obvious dependency on [111] orientation. In-grain slips contribute significantly to the evolution of Surface microtexture. Influence of deformation twins (brass orientation) on the evolution of microtexture is not obvious under our current experimental conditions.
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A new approach to the investigation of mixed lubrication in metal strip rolling
2012Co-Authors: Mohammad N Khan, Liangchi Zhang, Haihui Ruan, Xianming Zhao, Xiaoming ZhangAbstract:Mixed lubrication is an important lubrication mode, and if controlled properly, can improve the performance of metal rolling. However, understanding the mechanisms of mixed lubrication is still a big challenge in the discipline because of the complexity caused by the fluid-solid interaction and random Surface Asperity deformation in a rolling process. A complete solution to mixed lubrication with full resolution down to the microscopic Asperity level is formidable although the fundamental fluid and solid mechanics have been established. A practical approach is to solve the problem in the framework of continuum mechanics with the ingredients of microscopic Asperity contacts and the lubricant flow at the interface. This paper aims to take such challenge by establishing an integral approach to reveal the mechanisms of the mixed lubrication in metal strip rolling. This new approach analyses the overall strip deformation with explicit finite element method, but introduces an equivalent interfacial layer to capture the microscopic interface mechanics including the random Asperity deformation using a statistical formulation and the effect of lubricant using the modified Reynolds equation. It was found that this approach can effectively predict the contact pressure, shear traction and friction in metal strip rolling processes.
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Study on Surface Roughness Muring Metal Manufacturing Process
Advanced Materials Research, 2011Co-Authors: Zhengyi Jiang, Dongbin Wei, Shu Jun Wang, Haibo Xie, Xiao Dong Wang, Xiaoming ZhangAbstract:In the paper, a crystal plasticity finite element method (CPFEM) model was developed based on ABAQUS to analyse the Surface roughness transfer during metal manufacturing. The simulation result shows a good agreement with the experimental result in the flattening of Surface Asperity, and the Surface roughness decreases significantly with an increase of reduction with considering friction effect. Lubrication can delay Surface Asperity flattening. The effect of Surface roughness on produced metal defect (crack) was also studied, and the Surface roughness affects the crack initiation significantly in cold strip rolling. In addition, the Surface roughness variation along the metal plate width contributes to stress distribution and then inhibition of crack nucleation.
Tadao Tsukada - One of the best experts on this subject based on the ideXlab platform.
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An evaluation of Surface Asperity profile changes in truncation processes using optical interferometric microscope
International Journal of Machine Tools & Manufacture, 2001Co-Authors: Kazuyuki Sasajima, K Naoi, Tadao TsukadaAbstract:Abstract The truncation process as running-in wear was applied to evaluate Surface Asperity changes as removal at the top of its Asperity profile. The measurement was done using an optical interferometric microscope. Whole Surface profile was measured by the microscope supported by the stitching technique. The specimen was relocated on the microscope utilizing Hirth coupling as a hardware technique. Data obtained from a truncated specimen were precisely relocated to the original untruncated specimen by computer software in three dimensions. Then the profile change was obtained by deducting truncated data from the original data. The profile change was calculated as removed volume. The volume changes are plotted against a sliding length. As the software relocation technique needs the unchanged profile of a valley part, the evaluation is limited to where the truncation height is higher than −1.28 sigma (the standard deviation of untruncated original profile height). The present research can detect very little volume change that cannot be measured by other conventional methods, such as the gravimetric method. The advantages of the present method are as follows. It is possible to compare the truncated Surface profile with the original untruncated Surface profile in three dimensions. Thus, the inclination of the truncation Surface can be evaluated and any other local changes can also be assessed. From this information the profiles of truncated Surfaces will be linked to functions, and new parameters for truncation profile will be presented.
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A software-based relocation technique for Surface Asperity profiles and its application to calculate volume changes in running-in wear
Wear, 2000Co-Authors: Kazuyuki Sasajima, K Naoi, Tadao TsukadaAbstract:Abstract Evaluation of truncated Surface asperities is critically important in many industrial applications. Any discussion of truncation processes such as wear mechanisms and plateau honing requires a comparison of the original profile with the truncated one. In order to compare profiles, it is necessary to accurately relocate the truncated profile with respect to the original one. However, there is a limitation to relocation using hardware. To achieve accurate relocation, the authors propose a software-based relocation technique. In this paper, we present newly two software-based relocation techniques that examine the correspondence between untruncated areas in the truncated profile and the same untruncated areas in the original profile. In the first technique, the correspondence is measured by a collation index that is determined for the two profiles and calculated in an optimization method. In the second technique, the height probability distributions of two profiles are calculated and the profiles are then relocated in order to obtain the minimum degree of difference. Furthermore, the applicability of these techniques is discussed using simulation data and actual measurement data. These techniques are effective in the range that the truncated Surface height is higher than −1.28σo (σo is the standard deviation of untruncated original Surface height) from experiment, and are useful for measuring very little wear volume changes in contrast with measuring mass changes.
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A development of three-dimensional Surface measurement on cylinder
International Journal of Machine Tools & Manufacture, 1998Co-Authors: Kazuyuld Sasajima, Tadao TsukadaAbstract:We developed a new measuring equipment of three-dimensional Surface on cylinder. This system can measure all of Surface forms from cylindrical form error to local Surface Asperity profile continuously. The system consists of static air bearings mainly and gets discrete data in cylindrical coordinates. Any areal data are regressed by some references and expressed by contour maps. This system is useful for estimation of roller bearing, etc.
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Measurement of fractal dimension from Surface Asperity profile
International Journal of Machine Tools and Manufacture, 1992Co-Authors: K. Sasajima, Tadao TsukadaAbstract:Abstract This paper presents differences of fractal dimension between calculating memethods of it. It is shown that fractal dimension changes between 1 and 2 in two-dimensional profile, the dimension changes with changing vertical/horizontal magnification ratio of profile according to the conventional dividing procedure. It is also shown that fractal dimension changes between same range with changing aspect ratio of reticular cell in calculating the dimension with reticular cell counting method. Then we propose normalized reticular cell counting method, length in the measuring direction is normarized by auto-correlation length and height by standard deviation of height in two different directions. Fractal dimension must be valued with its calculating method and conditions.
Robert L. Jackson - One of the best experts on this subject based on the ideXlab platform.
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elastic and elastic perfectly plastic analysis of an axisymmetric sinusoidal Surface Asperity contact
Tribology - Materials Surfaces & Interfaces, 2020Co-Authors: Swarna Saha, Robert L. JacksonAbstract:ABSTRACTClosed-form finite-element empirical models are available for elastic and elastic–plastic spherical and sinusoidal contact. However, some of these models do not consider the effect of inter...
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Perfectly Elastic Axisymmetric Sinusoidal Surface Asperity Contact
Journal of Tribology, 2016Co-Authors: Swarna Saha, Robert L. JacksonAbstract:This work presents a finite element (FE) study of a perfectly elastic axisymmetric sinusoidal-shaped Asperity in contact with a rigid flat for different amplitude to wavelength ratios and a wide range of material properties. This includes characterizing the pressure required to cause complete contact between the Surfaces. Complete contact is defined as when there is no gap remaining between two contacting Surfaces. The model is designed in such a way that its axisymmetric and interaction with the adjacent asperities are considered by the effect of geometry at the base of the Asperity. The numerical results are compared to the model of curved point contact for the perfectly elastic case (known as Hertz contact) and Westergaard's solution. Once properly normalized, the nondimensional contact area does not vary with nondimensional load. The critical pressure required to cause complete contact is found. The results are also curve fitted to provide an expression for the contact area as a function of load over a wide range of cases for use in practical applications, such as to predict contact resistance. This could be a stepping stone to more complex models.
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Elastic-plastic axisymmetric sinusoidal Surface Asperity contact
2016 IEEE 62nd Holm Conference on Electrical Contacts (Holm), 2016Co-Authors: Swarna Saha, Robert L. JacksonAbstract:Closed-form finite-element empirical solutions are available for elastic-plastic spherical and sinusoidal contact. However, some of these models do not consider the effect of interaction with adjacent asperities or require extensive numerical resources because they employ a full 3-D model. The present work has considered these factors during modeling. The current finite element model (FEM) represents an axisymmetric elastic-plastic sinusoidal Surface in contact with a rigid flat for a wide range of material properties and different values of the amplitude to wavelength ratio. The numerical results are compared with the existing elastic-plastic spherical contact model. Empirical equations are derived for the critical pressure at which two Surface will reach complete contact. Complete contact occurs when there is no gap remaining between two contacting Surfaces. An equation for the critical value of the amplitude of the sinusoidal Asperity below which it will deform completely elastically from initial to complete contact is also established. The current study finds that for the cases which have amplitudes that fall below the critical value, and are elastic in nature, that the previously published perfectly elastic model can be used. The results are applicable for almost all kinds of metallic materials.
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Perfectly elastic axisymmetric sinusoidal Surface Asperity contact
2015 IEEE 61st Holm Conference on Electrical Contacts (Holm), 2015Co-Authors: Swarna Saha, Robert L. JacksonAbstract:This work presents a finite element study of a perfectly elastic axisymmetric sinusoidal shaped Asperity in contact with a rigid flat for different amplitude to wavelength ratios and a wide range of material properties. This includes characterizing the pressure required to cause complete contact between the Surfaces. Complete contact is defined as when there is no gap remaining between two contacting Surfaces. The model is designed in such a way that it is axisymmetric and interaction between adjacent asperities are considered. The numerical results are compared to the model of curved point contact for the perfectly elastic case (known as Hertz contact). Once properly normalized, the non-dimensional contact area does not vary with non-dimensional load. The critical pressure required to cause complete contact is found. The results are also curve fitted to provide an expression for the contact area as a function of load over a wide range of cases for use in practical applications, such as to model rough Surface contact and predict contact resistance.
