Papers by Author: Wei Gang Zhang

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Authors: Zhi Gang Wu, Shu Hui Li, Wei Gang Zhang
Abstract: In recent years, hydropiercing technique has been used widely. In this work, its special type of hydropiercing-bend is simulated using Rice and Tracey ductile criterion based on VUMAT of ABAQUS/Explicit and verified by experiments. Hydropiercing-bend processes with different slope angles of chamfer are discussed to predict the ultimate quality. It is shown that the angle of chamfer should be less than 70º for this kind of material and technical condition in order to make the slug attached with the tube blank.
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Authors: Wen Jiao Dan, Wei Gang Zhang, Shu Hui Li
Abstract: The hardening behaviours of transformation induced plasticity (TRIP) steels depended on the martensite transformation from the retained austenite. As a key factor, pre-strain can influence martensite transformation during sheet metal multi-step processes. In order to learn about the material’s properties after pre-deformation, the effect of pre-strain on mechanical behaviours of TRIP steels has been investigated with the strain-induced martensite transformation in pre-strain condition in this study. The analyzed results show that: Hardening rate, strain hardening exponent and necking strain of TRIP steels are related to martensite transformation in deformation
857
Authors: Ai Hui Luo, Wen Jiao Dan, Wei Gang Zhang
Abstract: In this study,tensional mechanical properties of sheet metal with different heating-lines after laser forming are investigated. The basic mechanical properties of material (such as elastic modulus, yield strength, ultimate strength, TEI (total elongation index) and EIU (elongation index of uniform)) with different spacing between neighbored heating-lines and different heating-lines number are presented. The stress-strain curves are complied with a modified Swift law, where the hardening coefficient and strain hardening exponent of material are controlled by strain. The influence of heating-lines number on tensional mechanical properties of material is greater than that of the spacing between neighbored heating-lines. The results show that all mechanical properties are related to the distribution of microstructure in heat-affected zone after laser forming.
1666
Authors: Wen Jiao Dan, Wei Gang Zhang, Shu Hui Li
Abstract: Loading path is one of importance factors that influence the formability of sheet forming process. In this study, the effect of punching speed loading paths (PSLP) on forming and spring-back processes of TRIP (transformation induced plasticity) steel has been investigated. Four kinds of loading paths with three punch speeds are introduced to verify the cup drawing and U-channel spring-back processes based on a constitutive model accompanying the strain-induced martensite transformation. The results show that higher punch speed results in the thickness uniformity of drawing cup and the spring-back angle of stamping U-channel increased with the same loading path. Furthermore, a given loading path (C4) not only increases the minimum thickness of cup but also decreases the spring-back angle of U-channel.
667
Authors: Peng Hu, Lin Fa Peng, Xin Min Lai, Wei Gang Zhang
Abstract: Increasing demands for miniature metallic parts have driven the application of micro/meso forming process in various industries. The present study focuses on the size effect which appears in the micro/meso scale sheet forming process. Micro/meso scale stamping experiments and finite element simulations incorporating the CMSG plasticity theory are conducted, respectively. It is found that the numerical simulation results, with strain gradient and strain gradient path taken into account, match the experimental results better than those of conventional simulation method.
991
Authors: Zhi Gang Wu, Shu Hui Li, Wei Gang Zhang
Abstract: In the present work, the ductile fracture process of hydropiercing is simulated using Rice and Tracey ductile fracture criterion by means of the user subroutine VUMAT of ABAQUS. The simulations at different loading pressures coincide well with the experiments. Based on this criterion, the processes of hydropiercing at different technical conditions are simulated with orthogonal design and the sensitivity analysis of parameters is conducted. The sensitivity analysis shows that internal pressure plays the most important role in controlling quality of the hydropierced products, namely the sheared zone length, roll-over depth and whole coefficient Y. High pressure and better lubricant are better for all the three indexes. Large punch corner radius is better for sheared zone length and Y but worse for roll-over depth. Additionally, it is found that internal pressure and punch corner radius could be intensified each other at conditions of both larger values.
639
Authors: Wen Jiao Dan, Wei Gang Zhang
Abstract: In this study, tensional mechanical properties of sheet metal with heating-lines after laser scanning are investigated based on the thermal-microstructure-mechanical model. The phase transformations, during laser scanning of sheet metal, are calculated by coupling the thermal history from finite element analysis with a phase transformation kinetic model. The flow stresses of material are obtained from the constitutive relationship of the phases based on the mixture strain hardening laws. The results show that the influence of the heating-lines number on tensional mechanical properties of material is obvious. The mechanical properties are related to the distribution of microstructure in heat affected zone after laser scanning.
331
Authors: Wen Jiao Dan, Wei Gang Zhang, Shu Hui Li
Abstract: As an advanced high strength steels, transformation-induced plasticity (TRIP) steel has obtained more and more attentions in automotive body components forming. The TRIP effect of this steel can improve the strength of the material, which results in the spring-back angle is different with that without TRIP effect. In this paper, the spring-back process of U-channel stamping with TRIP effect is studied by deformation energy method, which is based on a constitutive model accompanying strain-induced transformation in strain rate condition. The results have shown that martensite volume fraction distribution in key parts is related to the deformation energy of material, which induces the spring-back angle higher than those without TRIP.
1265
Authors: Ti Kun Shan, Wei Gang Zhang, Zhong Qin Lin, Shu Hui Li
Abstract: The dependence of the transformation rate on the multiaxial stress state corresponding to different loading paths is investigated. On the basis of the single shear, uniaxial tension, plane strain and equibiaxial stretching tests, the influence of stress state on stability of retained austenite is analyzed and an equation of transformation kinetics is developed. In sheet metal forming, the material undergoes complicated deformation, the prediction of the volume fraction of retained austenite during forming process is essential to estimate the contribution of the TRIP effect to improving formability. To this aim, the volume fraction of retained austenite in the part’s different regions has been calculated using finite element method. The calculated results were compared with the experimental data measured in deep drawing experiments.
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