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NUMERICAL PREDICTIONS AND EXPERIMENTAL VALIDATIONS OF ductile damage EVOLUTION IN SHEET METAL FORMING PROCESSES

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Acta Mechanica Solida Sinica 2012年第6期25卷 638-650页

作者： Farhad Haji Aboutalebi Mahmoud Farzin Mohammad Mashayekhi Department of Mechanical Engineering University of Isfahan Department of Mechanical Engineering Isfahan University of Technology

Prediction of forming limit in sheet metal forming is among the most important challenges confronting researchers. In this paper, a fully coupled elastic-plastic-damage model has been developed and implemented into an explicit code. Due to the adoption of the plane stress and finite strain theories, model can predict deformation and damage of parts quickly and accurately. Also, damage initiation, propagation, and fracture in some operations are predicted and validated with experiments. It is concluded that finite strain combined with continuum damage mechanics can be used as a quick tool to predict ductile damage, fracture, and forming limits in sheet metal forming processes.

关键词： ductile damage finite strain fracture sheet metal forming

An Improved ductile Fracture Criterion for Fine-blanking Process

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Journal of Shanghai Jiaotong university(Science) 2008年第6期13卷 702-706页

作者：赵震庄新村谢晓龙 National Engineering Research Center of Die & Mold CAD Shanghai Jiaotong UniversityShanghai 200030China

In order to accurately simulate the fine-blanking process, a suitable ductile fracture is *** an evaluation strategy based on experimental and corresponding simulation results of tensile, compression, torsion and fine-blanking test is designed to evaluate five typical ductile fracture criteria, which are widely-used in metal forming *** stress triaxiality and ductile damage of each test specimen are *** results show that none of these five criteria is sufficient for all ***, an improved fracture criterion based on Rice and Tracey model, taking the influence of both volume change and shape change of voids into account, is *** characterization of this model for fine-blanking process is easily done by the tensile test and the prediction result shows good.

关键词： ductile fracture criterion finite element method fine-blanking ductile damage

Compressive failure analysis of unidirectional carbon/epoxy composite based on micro-mechanical models

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Chinese Journal of Aeronautics 2017年第6期30卷 1907-1918页

作者： Wei SUN Zhidong GUAN Zengshan LI Mi ZHANG Yongjie HUANG School of Aeronautic Science and Engineering Beihang University Beijing 100083 China

A 2D micro-mechanical model was proposed to study the compressive failure of Uni Directional（UD） carbon/epoxy composite. Considering the initial imperfection and strength distribution of the fiber, the plasticity and ductile damage of the matrix, the failure of T300/914 UD composite under longitudinal compression and in-plane combined loads was simulated by this model. Simulation results show that the longitudinal compressive failure of the UD composite is caused by the plastic yielding of the matrix in kink band, and the fiber initial imperfection is the main reason for it. Under in-plane combined loads, the stress state of the matrix in kink band is changed, which affects the longitudinal compressive failure modes and strength of UD *** failure envelope of r_1–s_（12） and r_1–r_2 are obtained by the micro-mechanical model. Meanwhile,the compressive failure mechanism of the UD composite is analyzed. Numerical results agree well with the experimental data, which verifies the validity of the micro-mechanical model.

关键词： Micro-mechanical model Unidirectional composite Initial imperfection Matrix plasticity ductile damage Kink band

Numerical simulation of ductile fracture behavior for aluminum alloy sheet under cyclic plastic deformation

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Transactions of Nonferrous Metals Society of China 2011年第7期21卷 1595-1601页

作者：胡星赵亦希李淑慧林忠钦上海交通大学机械系统与振动国家重点实验室上海200240 上海交通大学上海市数字化汽车车身工程重点实验室上海200240

A numerical analysis of mechanical behavior of aluminum alloy sheet under cyclic plastic deformation was *** limit at fracture was derived from Cockcroft-Latham ductile damage *** strain path of bending center of incremental roller hemming could be accepted as a kind of plane strain bending deformation *** rope roller hemming could be used to alleviate ductile fracture behavior by changing the stress state of the hemming-effected *** observation on the fracture surface indicates that cyclic plastic deformation affects ductile fracture mechanism.

关键词： aluminum alloy ductile damage incremental forming cyclic plastic deformation

Fracture Prediction for an Advanced High-Strength Steel Sheet Using the Fully Coupled Elastoplastic damage Model with Stress-State Dependence

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Acta Mechanica Solida Sinica 2021年第2期34卷 263-273页

作者： Kai Zhang Mingchuan Wang Weijie Liu Jianlin Liu College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580China Sino-French Engineer School Nanjing University of Science and TechnologyNanjing 210094China Institute of Applied Physics and Computational Mathematics Beijing 10094China

In this study,the numerical simulations of sheet metal forming processes are performed based on a fully coupled elastoplastic damage *** effects of stress triaxiality and Lode angle are introduced into the damage evolution law to capture the loading-path-dependent *** proposed constitutive model is implemented into the finite element(FE)code ABAQUS/Explicit via the user-defined subroutine(VUMAT).Next,the identification procedure for DP780 based on the hybrid experimental-numerical method is presented in *** numerical results of simple tests are compared with the experiments,and obvious improvement is observed for the proposed model under various loading ***,the model is applied to predict the edge fracture during sheet blanking *** predicted global load–displacement responses and crack paths have a good agreement with the experimental results,indicating that the model holds great potentials in simulation of metal forming processes.

关键词： ductile damage Full coupling Stress state Numerical simulation Edge fracture

Numerical Methodology for Metal Forming Processes Using Elastoplastic Model with damage Occurrence

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Journal of Materials Science & Technology 2006年第2期22卷 279-283页

作者： A.Cherouat H.Borouchaki K.Saanouni P.Laug LASMIS-CNRS FRE 2719 University of Technology of Troyes BP 2060-10010TroyesFrance LASMIS-CNRS FRE 2719 University of Technology of Troyes BP 2060-10010Troyes France LASMIS-CNRS FRE 2719 University of Technology of Troyes BP 2060-10010 Troyes France INRIA Rocquencourt BP 105-78153 Le ChesnayFrance

ductile damage often occurs during metal forming processes due to the large thermo-elasto （visco） plastic flow Iocalisation. This paper presents a numerical methodology, which aims to virtually improve any metal forming processes. The methodology is based on elastoplastic constitutive equations accounting for nonlinear mixed isotropic and kinematic hardening strongly coupled with isotropic ductile damage. An adaptive remeshing scheme based on geometrical and physical error estimates including a kill element procedure is used. Some numerical results are presented to show the capability of the model to predict the damage initiation and growth during the metal forming processes.

关键词： Finite elastoplasticity ductile damage Error estimation Adaptive remeshing Metal forming processes

Optimization of Clinching Tools by Integrated Finite Element Model and Genetic Algorithm Approach

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Journal of Shanghai Jiaotong university(Science) 2019年第2期24卷 262-272页

作者： WANG Menghan XIAO Guiqian WANG Jinqiang LI Zhi College of Materials Science and Engineering Chongqing University

Clinching is a convenient and efficient cold forming process that can join two sheets without any additional part. This study establishes an intelligent system for optimizing the clinched joint. Firstly, a mathematical model which introduces the ductile damage constraint to prevent cracking during clinching process is ***, an optimization methodology and its corresponding computer program are developed by integrated finite element model(FEM) and genetic algorithm(GA) approach. Secondly, Al6061-T4 alloy sheets with a thickness of 1.4 mm are used to verify this optimization system. The optimization program automatically acquires the largest axial strength which is approximately equal to 872 N. Finally, sensitivity analysis is implemented, in which the influence of geometrical parameters of clinching tools on final joint strength is analyzed. The sensitivity analysis indicates the main parameters to influence joint strength, which is essential from an industrial point of view.

关键词： mechanical clinching optimization design genetic algorithm(GA) ductile damage

Analysis of Sheet Metal Extrusion Process Using Finite Element Method

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International Journal of Automation and computing 2010年第3期7卷 295-302页

作者： Xin-Cun Zhuang Hua Xiang Zhen Zhao Department of Plasticity Technology Shanghai Jiao Tong University Shanghai 200030 PRC

Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts. However, there is still not enough know-how available. In this paper, as one of the typical sheet bulk metal forming processes, the sheet metal extrusion process was studied. A reasonable finite element method （FEM） model of sheet metal extrusion process taking the influence of flow-stress curve with wide range of plastic strain and ductile damage into consideration was established and simulated by an arbitrary Lagrangian-Eulerian （ALE） FEM implemented in ***. Validated by comparing the results with experiment, some phenomenological characteristics, such as metal flow behavior, shrinkage cavity, and the influence of different combinations of diameter of punch, diameter of extrusion outlet, and diameter of pre-punched hole were analyzed and concluded, which can be used as theoretical fundamental for the design of the sheet metal extrusion process.

关键词： Sheet bulk metal forming extrusion ductile damage arbitrary Lagrangian-Eulerian (ALE) metal flow behavior.

A LOWER BOUND APPROACH TO THE YIELD LOCI OF POROUS MATERIALS

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Acta Mechanica Sinica 1989年第3期5卷 237-243页

作者： Sun Yi Wang Duo(Department of Applied Mechanics,Harbin Institute of Technology) Department of Applied Mechanics Harbin Institute of Technology China

A lower bound approach is proposed for the first time to solve the macroscopic yield loci of porous *** results are then compared with Gurson's upper bound yield loci and those of the *** is shown that the present ana... 详细信息

关键词： constitutive equations porous materials ductile damage lower bound analysis method