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The Mechanical Crack Tip Opening Displacement fracture criterion in Piezoelectric Ceramics

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The Mechanical Crack Tip Opening Displacement Fracture Crite...

Investigation on fracture criterion of Sheet-Metal based on Laser Shock Forming

第16届全国疲劳与断裂学术会议

作者：薛存雍华东周又和兰州大学西部灾害与环境力学教育部重点实验室兰州大学土木工程与力学学院力学与工程科学系

In order to interpret the two different kinds of experimental results of the effect of applied electric fields on the critical load in piezoelectric ceramics at present,a new fracture criterion,the mechanical crack tip opening displacement fracture criterion,is proposed in this *** mechanical crack tip opening displacement is calculated in two cases based on the mechanical and electrical strip yielding *** order to obtain simple and valid results,the simplified

关键词： Crack opening displacement fracture criterion Piezoelectric ceramics

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Investigation on Fracture Criterion of Sheet-Metal based on ...

An Energy Gradient fracture criterion Based on Virtual Crack Vector Model with Application to T-Stress Problem

第三届北京国际快速成形及制造会议暨第二届北京国际生物制造会议

作者： Jiang Yinfang1 Shi Chaoyang1 Ren Xudong1 Wang Fei1 Zhu Yuanyou2 1.School of Mechanical Engineering,Jiangsu University,Zhenjiang,Jiangsu 212013,China 2.Department of Mechanical Engineering,Nanjing Institute of Technology,Nanjing Jiangsu 210013,China

Laser shock forming(LSF)of sheet metal is a novel technology in plastic *** is necessary to correctly predict fracture of metal sheet in LSF of sheet *** on the he fracture criterion of 3003H16 aluminum alloy sheet metal in traditional punching theory,the reduction of thickness is displayed obviously in the process of fracture of metal sheet,so thickness parameters can judge whether metal sheet is fracture,the basic parameters are found by experiment and simulation,the fracture criterion of 3003H16 aluminum alloy sheet metal is founded and verified by numerical simulation and LSF *** result shows that this failure criterion can be used in the LSF numerical simulation to predict the thickness thinning state,which is used to judge the forming characteristics of LSF of metal sheet;this failure criterion is basically suitable for fracture criterion of LSF of metal sheet.

关键词： Aluminum alloy Laser shock forming(LSF) Maximum thickness reduction rate fracture criterion

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An Energy Gradient Fracture Criterion Based on Virtual Crack...

Effect of fracture Criteria on Taylor Impact fracture

中国科学院地质与地球物理研究所2004学术年会

作者： D.A Liu~1,L.Y.Li~2 Q.F.Yuan~3 and D.X.Cheng~1 1 Key Laboratory of Engineering Geomechanics,Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing 100029,P.R.China 2 China University of Mining and Technology(Beijing Campus),Beijing 100083,P.R.China 3 University of Science and Technology Beijing,Beijing 100083 P.R.China

A virtual crack vector model is proposed in this paper to simulate the branched crack propagation and simplify its calculation of energy release *** energy gradient fracture criterion is constructed based on this *** can take account of the effects of biaxial loads or T-stress on brittle mixed mode fracture and agrees well with the test data of biaxial tensile fracture and the specially conducted experiment of the influences ofσ on the mixed mode fracture of *** its advantage of predicting initial propagation angle and critical fracture stress independently without the determination of the core region radius,it can be used as a practical fracture criterion for brittle mixed mode fracture under biaxial tension.

关键词： fracture criterion Energy release rate Energy gradient Virtual crack vector Biaxial Loading experiment T-stress Branched crack propagation

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Journal of Harbin Institute of Technology(New Series) 2013年第1期20卷 63-67页

作者： Wei Zhang Gang Wei Xin-Ke Xiao Zi-Tao Guo Hypervelocity Impact Research Center Harbin Institute of Technology

Taylor impact test on aluminum alloy 7A04-T6 presented in a previous study has been numerically evaluated using the finite element code ABAQUS/Explicit in this paper. The influence of fracture criterion in numerical simulations of the deformation and fracture behavior of Taylor rod has been studied. The following fracture criterions, included a modified version of Johnson-Cook, the Cockcroft-Latham(C-L), the constant fracture strain, the maximum shear stress and the maximum principle stress fracture models, have been used in this paper. Model constants for each criterion are calibrated from material tests. The modified version of Johnson-Cook fracture criterion with the stress triaxiality cut-off idea used can give good prediction to the Taylor impact fracture behavior. However, the C-L fracture criterion with only a constant required for calibrating by a simple test is found to give reasonable predictions. Unfortunately, the other three criteria are not able to repeat the experimentally obtained fracture behavior. The result indicates that the stress triaxiality cut-off idea is necessary to predict the Taylor impact fracture.

关键词： Taylor impact fracture fragmentation fracture criterion

Theoretical and experimental study of 3-D initial fracture and its significance to faulting

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Earthquake Science 2011年第3期24卷 283-298页

作者： Shiyu Li Taiming He Chunkai Teng Xuyao Zheng Kuksenko Viktor Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China A F Ioffe Physical-Technical Institute Russian Academy of Sciences St. Petersburg 194021 Russia

The experimental results of 3-D fracture under compression are introduced in brief and the theory of stress criterion of 3-D fracture is studied. Methods to imitate initial fractures are developed. It is pointed that there are important defects in the extreme value （EV） method ever proposed by Palaniswamy and Knauss. The major defect lies in that only two Euler angles （2EA） are considered, but another one is neglected. If the variation of all the three Euler angles （3EA） are considered, one can get better result which is consistent with the observation of faulting that extends on curved surfaces but not on planes. The method of evaluating maximal normal stress direction vector （NSDV） is proposed and further proved to be equivalent to the 3EA method. It is proved that the NSDV method can be further optimized to the method of composition of the first principal differential plane （CFPDP）. The results from CFPDP method can fit the curved surfaces of initial growth observed in the experiments of 3-D fracture. The CFPDP method can also be used to interpret the 3-D fractures of the slipping section between the asperities in the buried fault plane that is modeled as ellipse crack. The results of 3-D fracture can be applied to interpreting the related problems of faulting including the mechanism of a lot of shatter rocks with different dimensions, the cause of earthquakes occurred at the edge of plate under low shear stress, and the mechanism of anisotropy caused by the extensive dilatancy anisotropy （EDA） cracks.

关键词： fracture mechanics 3-D fracture fault fracture criterion

FEM Modeling of Crack Propagation in a Model Multiphase Alloy

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Journal of Materials Science & Technology 2006年第1期22卷 59-65页

作者： Lihe QIAN Seishi NISHIDO Hiroyuki TODA Toshiro KOBA YASHI Department of Production Systems Engineering Toyohashi University of Technology Toyohashi 441-8580 Japan IT Promotion Department Aisin Takaoka Co. Ltd. 1 Tennoh Takaokashin-machi Toyota 473-8501 Japan

In this paper, several widely applied fracture criteria were first numerically examined and the crack-tip-region Jntegral criterion was confirmed to be more applicable to predict fracture angle in an elastic-plastic multiphase material. Then, the crack propagation in an idealized an elastic-plastic finite element method. The variation dendritic two-phase AI-7%Si alloy was modeled using of crack growth driving force with crack extension was also demonstrated. It is found that the crack path is significantly influenced by the presence of α-phase near the crack tip, and the crack growth driving force varies drastically from place to place. Lastly, the simulated fracture path in the two-phase model alloy was compared with the experimentally observed fracture path.

关键词： Al-Si alloys fracture criterion fracture path Numerical simulation Finite element method (FEM) Multiphase microstructure

A constitutive model coupling damage and material anisotropy for wide stress triaxiality

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Chinese Journal of Aeronautics 2020年第12期33卷 3509-3525页

作者： Rui LI Mei ZHAN Zebang ZHENG Hongrui ZHANG Xiaolei CUI Wei LV Yudong LEI State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Laboratory of Aero-engine High-Performance Manufacturing School of Mechanical EngineeringNorthwestern Polytechnical UniversityXi'an 710072China

A constitutive model that can describe the damage evolution of anisotropic metal sheets during the complex forming processes which experience wide stress triaxiality history is essential to accurately predict the deformation and rupture behaviors of the *** this study,a modified Lemaitre damage criterion which couples with the anisotropic Barlat 89 yield function is *** effects of stress triaxiality,Lode parameter and shear stress on damage accumulation are considered in the constitutive *** model is numerically implemented and applied to fracture prediction in tensile tests with different stress triaxialities and a complex deformation process with wide stress triaxiality *** good consistency of predictions and experiments indicates that the modified Lemaitre damage model has excellent fracture prediction ***,the accuracy of the model is analyzed and discussed.

关键词： Constitutive model Damage evolution fracture criterion Material anisotropy Stress triaxiality

RANDOM-FUZZY MODEL FOR THE DUCTILE/BRITTLE TRANSITION

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Applied Mathematics and Mechanics(English Edition) 2003年第10期24卷 1158-1167页

作者：吕震宙岳珠峰冯蕴雯 Department of Aircraft Engineering Northwestern Polytechnical University Department of Engineering Mechanics Northwestern Polytechnical University

Based on a large experimental sample, the influence of stress triaxiality and temperature have been studied on the growth of micro voids and the ductile/brittle transition (DBT) of 40Cr steel. Ductile and brittle fractures have been investigated simultaneously. The experiments show that the ductile fracture is controlled by the micro void mechanism,and the critical void growth ratio can be used as the criterion of ductile fracture. The brittle fracture is modeled by an embedded penny crack, and a micro stress intensity with a characteristic length can be used as the criterion of the brittle fracture. The DBT is the result of the competition of the two mechanisms. Which exists in the fracture of all specimens simultaneously. The distributions of model parameters were measured experimentally. A random model and a random-fuzzy model for DBT were presented. The comparison between the calculated and experimental results shows that the random-fuzzy model can model the DBT satisfactorily.

关键词： ductile/brittle transition (DBT) fracture criterion randomness fuzziness

ANALYSIS OF A CRACK IN A FUNCTIONALLY GRADED STRIP WITH A POWER FORM SHEAR MODULUS

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Acta Mechanica Solida Sinica 2009年第5期22卷 465-473页

作者： Jinju Ma Zheng Zhong Chuanzeng Zhang School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China Department of Civil Engineering University of Siegen D-57068 Siegen Germany

The plane strain problem of a crack in a functionally graded strip with a power form shear modulus is studied. The governing equation in terms of Airy＇s stress function is solved exactly by means of Fourier transform. The mixed boundary problem is then reduced to a system of singular integral equations and is solved numerically to obtain the stress intensity factor at crack-tip. The maximum circumferential stress criterion and the strain energy density criterion are both employed to predict the direction of crack initiation. Numerical examples are given to show the influence of the material gradation models and the crack sizes on the mode-I and mode-II stress intensity factors. The dependence of the critical kink-angle on the crack size is examined and it is found that the crack kink-angle decreases with the increase of the normalized crack length, indicating that a longer crack tends to follow the original crack-line while it is much easier for a shorter crack to deviate from the original crack-line.

关键词： functionally graded material crack stress intensity factors fracture criterion