scholarly journals An Efficient Approach for Identifying Constitutive Parameters of the Modified Oyane Ductile Fracture Criterion at High Temperature

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Sergei Alexandrov ◽  
Yusof Mustafa ◽  
Mohd Yazid Yahya
Keyword(s):  
High Temperature ◽  
Ductile Fracture ◽  
Computational Models ◽  
Fracture Criterion ◽  
Fracture Initiation ◽  
Material Model ◽  
Material Behavior ◽  
Ductile Fracture Criterion ◽  
Path Dependent ◽  
Constitutive Parameters

The paper presents the theoretical part of a method for identifying constitutive parameters involved in the modified Oyane ductile fracture criterion at high temperature. Quite a general rigid viscoplastic model is adopted to describe material behavior. The ductile fracture criterion is in general path-dependent and involves stresses. Therefore, the identification of constitutive parameters of this criterion is a difficult task which usually includes experimental research and numerical simulation. The latter requires a precisely specified material model and boundary conditions. It is shown in the present paper that for a wide class of material models usually used to describe the behavior of materials at high temperatures, the criterion is significantly simplified when the site of fracture initiation is located on traction free surfaces. In particular, this reduced criterion does not involve stresses. Since there are well established experimental procedures to determine the input data for the reduced criterion, the result obtained can be considered as a theoretical basis for the efficient method for identifying constitutive parameters of the modified Oyane ductile fracture criterion at high temperature. The final expression can also be used in computational models to increase the accuracy of predictions.

Failure Prediction in Drawing Processes of Mg Alloy Sheet by the FEM and Ductile Fracture Criterion

2011 ◽  
Vol 264-265 ◽  
pp. 813-818 ◽  
Author(s):  
Sang Woo Kim ◽  
Young Seon Lee ◽  
Beom Soo Kang
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Elevated Temperatures ◽  
Failure Prediction ◽  
Fracture Initiation ◽  
Tensile Tests ◽  
Alloy Sheet ◽  
Fe Analysis ◽  
Uniaxial Tensile ◽  
Ductile Fracture Criterion

In this work, in order to predict the forming failure of AZ31 magnesium alloy sheet in drawing process at elevated temperatures, a series of square cup tests at various temperatures and FE analyses were carried out. The critical damage values and the mechanical properties dependent on strain rates and temperatures were evaluated from uniaxial tensile tests and those were utilized to the forming failure prediction using FE analysis. Based on the plastic deformation history obtained from FE analysis and Cockcroft and Latham’s ductile fracture criterion, the fracture initiation time and location were predicted and verified with the experimental results.

Evaluation of prediction error resulting from using average state variables in the calibration of ductile fracture criterion

2017 ◽  
Vol 27 (8) ◽  
pp. 1231-1251 ◽  
Author(s):  
Xincun Zhuang ◽  
Yehui Meng ◽  
Zhen Zhao
Keyword(s):  
Ductile Fracture ◽  
Prediction Error ◽  
Fracture Criterion ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Equivalent Strain ◽  
State Variables ◽  
Ductile Fracture Criterion ◽  
Series Of Experiments ◽  
Relationship Of

In order to evaluate the prediction error resulting from using average state variables in the calibration procedure of the ductile fracture criterion, a series of experiments and corresponding simulations were performed to extract the evolution of fracture-related state variables such as stress triaxiality (η), Lode parameter, and equivalent strain to fracture at the fracture initiation points. The average stress triaxiality, average Lode parameter, and equivalent strain to fracture were used to calibrate the Lou-Huh (L-H) ductile fracture criterion. The average induced prediction error was evaluated by comparing the accumulated damage value, which was computed with the calibrated L-H ductile fracture criterion at the fracture initiation point, with the critical threshold value. Comparisons based on a series of experiments covering a wide range of values for stress triaxiality indicated the existence of an average induced prediction error for the compression tests, and demonstrated that different values of embedded-constants C1 and C2 of L-H ductile fracture criterion resulted in entirely different average induced prediction errors. Thus, a parameter study was performed to investigate the influences of C1, C2, the relationship of η and equivalent plastic strain ([Formula: see text]), and the internal function of the integral formula on the average induced relative error. The influence of the relationship of [Formula: see text] could be represented by the influence of the exponent a, the intercept for the stress triaxiality, and the allocation of equivalent strain for the segmented function. Among these influence factors, the value of C2, the value of the exponent a, and the value of the negative intercept for stress triaxiality contributed significantly to an increase in relative error.

Application of Coupled Ductile Fracture Criterion to Plane Strain Plates

2018 ◽  
Vol 382 ◽  
pp. 186-190 ◽  
Author(s):  
František Šebek ◽  
Petr Kubík ◽  
Jindřich Petruška
Keyword(s):  
Aluminum Alloy ◽  
Ductile Fracture ◽  
Fracture Criterion ◽  
Material Model ◽  
Plastic Behavior ◽  
Ductile Fracture Criterion ◽  
User Subroutine ◽  
Aa 2024 ◽  
Stress States ◽  
Subsequent Propagation

The paper presents a complex material model which covers the elastic-plastic behavior, material deterioration and ductile fracture. The calibration of such model was conducted for Aluminum Alloy (AA) 2024-T351 using specimens with various geometries and loading which covers various stress states. The model was then applied to the simulations of tensile test of plates. The computations were carried out in Abaqus/Explicit using the user subroutine Vectorized User MATerial (VUMAT), where the crack initiation and subsequent propagation was realized using the element deletion technique. The results were compared to the experimental observation in the end.

Effect of Intensive Plastic Deformation Near Frictional Interfaces on Ductile Fracture

2012 ◽  
Vol 586 ◽  
pp. 306-309
Author(s):  
Sergei Alexandrov ◽  
Dragisa Vilotic ◽  
Elena Lyamina ◽  
Yeau Ren Jeng
Keyword(s):  
Plastic Deformation ◽  
Ductile Fracture ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Fracture Initiation ◽  
Experimental Results ◽  
Ductile Fracture Criterion ◽  
Special Design ◽  
Upsetting Test ◽  
Ductile Fracture Initiation

A layer of intensive plastic deformation often appears in the vicinity of frictional interfaces in metal forming processes. The paper presents a study to reveal a possible effect of intensive plastic deformation in such a layer on ductile fracture. To this end, an upsetting test of special design is used to move the site of ductile fracture initiation to the friction surface independently of the effect of intensive plastic deformation on the occurrence of ductile fracture. Experimental results obtained are compared to the theoretical prediction based on a conventional empirical ductile fracture criterion. It is shown that there is some deviation of the fracture conditions predicted theoretically from the experimental results.

Prediction of Fracture Strains for DP980 Steel Sheets Using a Modified Lou–Huh Ductile Fracture Criterion

2014 ◽  
Vol 626 ◽  
pp. 347-352 ◽  
Author(s):  
Namsu Park ◽  
Hoon Huh
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Pure Shear ◽  
Equivalent Plastic Strain ◽  
Material Behavior ◽  
Loading Path ◽  
Ductile Fracture Criterion ◽  
Steel Sheets ◽  
Wide Range ◽  
Dp980 Steel

This paper is concerned with the prediction of fracture strains for DP980 steel sheets using a modified Lou–Huh ductile fracture criterion. The usage of DP980 steel is significantly increasing in the automotive industry for weight reduction, enhancement of crashworthiness and safety of car body. The material behavior of AHSS show unpredictable and sudden fracture during sheet metal forming process. A modified Lou–Huh ductile fracture criterion is utilized to predict the formability of AHSS because the conventional FLD constructed based on necking is unable to evaluate the formability of AHSS. Fracture loci were extracted from 3D fracture envelopes by assuming the plane stress condition to evaluate equivalent plastic strain up to the point of fracture at a wide range of loading paths. Three different types of specimens such as pure shear, dog-bone and plane strain grooved specimens were used for tensile tests to construct 3D fracture envelopes of DP980. Fracture strain of each loading path was evaluated to show that there is little deviation between predicted fracture strains and experimentally acquired ones. From the comparison, it is concluded that the 3D fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets in complicated loading conditions including the pure shear condition.

scholarly journals Comparison of Modified Mohr–Coulomb Model and Bai–Wierzbicki Model for Constructing 3D Ductile Fracture Envelope of AA6063

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

AbstractDuctile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar tension tests, compression tests and torsion tests. These tests cover a wide range of stress triaxiality (ST) and Lode parameter (LP) to calibrate the ductile fracture criterion. Plasticity modeling was performed, and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments. Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr–Coulomb (MMC) model and Bai-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

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