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Modeling of Cyclic Bending of Thin Foils Using Higher-Order Strain Gradient Plasticity

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Acta Mechanica Solida Sinica 2022年第4期35卷 616-631页

作者： Tong Luo Fenfei Hua Dabiao Liu School of Aerospace Engineering Huazhong University of Science and TechnologyWuhan430074China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment Wuhan430074China

The plastic behaviors of thin metallic foils,including size effect,bauschinger effect,and passivation effect,are studied under cyclic bending condition using the strain gradient visco-plasticity theory.The finite element simulations are performed on the cyclic bending of the elasto-viscoplastic thin foils with passivated and unpassivated surfaces.The study is also conducted on the transition from a passivated surface to an unpassivated one.The roles of the dissipative and energetic gradient terms are emphasized.From the results,it is found that the dissipative gradient terms increase the yield strength,while the energetic gradient terms increase the strain hardening,resulting in an anomalous bauschinger effect.Further,it is observed that the surface passivation effect increases both the normalized bending moment at initial yielding and strain hardening.The comparison between the numerical results of cases with and without passivation demonstrates that the switching of boundary conditions significantly affects the plastic behavior of the foils under cyclic bending.

关键词： Strain gradient plasticity Size effect bauschinger effect Geometrically necessary dislocations Bending

bauschinger effect and its Influence on Residual Stress of a Twinning Induced Plasticity Steel

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Bauschinger Effect and its Influence on Residual Stress of a...

Micromechanics of substrate-supported thin films

“第十届中国钢铁年会”暨“第六届宝钢学术年会”

作者： Luo Z.C. Huang M.X. Shenzhen Institute of Research and Innovation University of Hong Kong Department of Mechanical Engineering University of Hong Kong

The bauschinger effect（BE） of a twinning induced plasticity（TWIP） steel sheet was measured by shear plus reverse shear experiment. Digital image correlation（DIC） technique was used to get the corresponding stress-strain curve and then the exact yield stress was determined. Kinematic hardening of TWIP steel was about one-third of total hardening. Further, the backstress contributes about 13 percent to the total flow stress and prone to saturate with increasing strain. The effect of BE on residual stress was evaluated by the commercial finite element analysis software（ABAQUS） by using the case of cup drawing. The results showed that residual stress after forming was smaller when taking BE into consideration.

关键词： bauschinger effect TWIP steel cup drawing digital image correlation

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Acta Mechanica Sinica 2018年第2期34卷 381-391页

作者： Wei He Meidong Han Shibin Wang Lin-An Li Xiuli Xue Department of Mechanics Tianjin University Department of Engineering Mechanics Hunan University of Science and Technology

The mechanical properties of metallic thin films deposited on a substrate play a crucial role in the performance of micro/nano-electromechanical systems(MEMS/NEMS)and flexible electronics. This article reviews ongoing study on the mechanics of substrate-supported thin films, with emphasis on the experimental characterization techniques,such as the rule of mixture and X-ray tensile testing. In particular, the determination of interfacial adhesion energy, film deformation, elastic properties and bauschinger effect are discussed.

关键词： Thin films Deformation Adhesion Elastic property bauschinger effect

Strengthening and ductilization of laminate dual-phase steels with high martensite content

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Journal of Materials Science & Technology 2021年第6期65卷 29-37页

作者： Bo Gao Rong Hu Zhiyi Pan Xuefei Chen Yi Liu Lirong Xiao Yang Cao Yusheng Li Qingquan Lai Hao Zhou Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China Herbert Gleiter Institute of Nanoscience Nanjing University of Science and TechnologyNanjing 210094China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

The steels with excellent strength and ductility are expected to be achieved by tailoring the microstructural features.In this work,laminate dual-phase(DP)steels with high martensite content(laminate HMDP steels)were produced by a combination of warm rolling and intercritical annealing.Influence of rolling strain and annealing temperature on the microstructural evolution and mechanical properties of laminate HMDP steels were systematically studied.The strength of HMDP steels was significantly improved to~1.6 GPa associated with a high uniform elongation of 7%,as long as the laminate structure is maintained.The strengthening and ductilizing mechanisms of laminate HMDP steels are discussed based on the influence of laminate structure and the high martensite content,which promote the development of internal stresses and can be correlated to the bauschinger effect as measured by the cyclic loadingunloading-reloading experiments.Detailed transmission electron microscopy(TEM)observation was applied to characterize the dislocation structure in the deformed ferrite.

关键词： Dual phase steel Warm rolling Laminate structure bauschinger effect HDI stress

A STUDY OF DIRECTIONALITY OF LATENT HARDENING BEHAVIOR IN ALUMINIUM SINGLE CRYSTALS

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Acta Mechanica Solida Sinica 1996年第3期9卷 246-252页

作者： Wang, MZ Shi, L Li, CH Xiao, JM UNIV SCI & TECHNOL BEIJING DEPT MAT PHYSBEIJING 100083PEOPLES R CHINA

By defining the yield stress in a latent hardening test as the first deviation from the elastic straight line, the yielding and hardening behavior on a latent system in the positive and negative slip direction was studied in aluminium single crystals. It is shown that the yield stresses on both the positive and negative latent systems are about equal to or a little lower than the maximum resolved shear stress in the primary test, but much higher than that of the active system. The Influence of relative orientation and prestrain on latent hardening and initial work-hardening in the secondary test was also investigated, and it was found that there is a considerable effect on initial work-hardening, but none on latent hardening. With reasonable approximation, a hardening rule for single crystal could be proposed from the experimental results, that is, except for the yield stress on the system negative to the active system that is very low, hardening on the other systems is nearly the same as self-hardening.

关键词： latent hardening work-hardening bauschinger effect aluminium single crystal plastic deformation

Influence of cold forming on the tensile behavior and properties of low-carbon microalloyed steel

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Baosteel Technical Research 2010年第3期4卷 53-57页

作者： YANG Feng SU Daxiong ZHANG Wenlong Products ＆ Technique Management Department B aoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China State Key Lab of MMCs Shanghai Jiaotong University Shanghai 200240 China

The tensile behavior and properties of cold formed low-carbon microalloyed steel with its microstmcture of all ferrite and pearlite （F ＋ P） were investigated. Bending and flattening deformations were carried out in the laboratory on hot-rolled sheets in order to simulate the cold forming process of steel sheets during pipe fabrication and sampling of high frequency straight bead welding pipes. A comparison of the tensile behavior and properties of the material made before and after cold forming indicates that cold deformation alters the tensile behavior and properties of the material to a certain degree depending on the manner of the cold deformation and the degree. The research on the bauschinger effect indicates that for the steels investigated, when the plastic strain is small, the back stress increases rapidly with the increase of the plastic strain and then rapidly tends to saturation. The finite element analysis indicates that the change in the properties of the steel sheets due to cold forming is a result of the Banschinger effect and work hardening. The mechanism of the change in the properties is also given in this study.

关键词： F ＋ P steel bending deformation tensile strength bauschinger effect

Mechanical behavior of electric resistance welded pipes in pipe-making process

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Baosteel Technical Research 2010年第3期4卷 32-35页

作者： TIAN Qingchao DONG Xiaoming SHI Hongde DING Weijun Tube ＆ Pipe Technology Center Research Institute Baoshan Iron ＆ Steel Co Ltd Shanghai 201900 China HFW Plant Tube ＆ Pipe Business Unit Baosban Iron ＆ Steel Co Ltd Shanghai 201900 China

The changes in the mechanical behavior of electric resistance welded（ERW） pipes before and after the cage roll forming process were investigated through tensile experiments. It is found that the bauschinger effect does not exist in the pipe product, while the work hardening effect introduced by pipe-making is the direct cause of the mechanical changes. The prestrain introduced during different pipe-making processes are accumulative to the work hardening effect. And the increment of the yield strength for making Ф 244.48 × 8.94 pipe is approximately 45 MPa, higher than that of hot-rolled plates. It is verified that the strain ε=t/D-t is an efficient index representing the work hardening effect from the engineering viewpoint.

关键词： electric resistance welding mechanical properties work hardening bauschinger effect prestrain