A theoretical—experimental method for the identification of the modified Cockroft—Latham ductile fracture criterion

2008 ◽  
Vol 222 (9) ◽  
pp. 1869-1872 ◽  
Author(s):  
S Alexandrov ◽  
D Vilotic
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Ductile Fracture ◽  
Experimental Method ◽  
Fracture Criterion ◽  
Input Parameter ◽  
Primary Objective ◽  
Ductile Fracture Criterion ◽  
Surface Fracture ◽  
Principal Strains

The primary objective of the present study is to show that in many practical cases of free surface fracture, the modified Cockroft—Latham ductile fracture criterion is reduced to a relation between two in-surface principal strains. This finding can be combined with an appropriate set of experimental data to determine the input parameter of the criterion and/or verify it. An illustrative example is provided.

Reducibility of Stress-Based Workability Diagram to Strain-Based Workability Diagram

2016 ◽  
Vol 08 (02) ◽  
pp. 1650022 ◽  
Author(s):  
Dragisa Vilotic ◽  
Sergei Alexandrov ◽  
Aljosa Ivanisevic ◽  
Mladomir Milutinovic
Keyword(s):  
Free Surface ◽  
Ductile Fracture ◽  
Metal Forming ◽  
Strain Path ◽  
Surface Fracture ◽  
Workability Diagram ◽  
Standard Tests ◽  
Principal Strains

The strain-based and stress-based workability diagrams are often used to predict the initiation of ductile fracture in metal forming. The strain-based workability diagram is restricted to free surface fracture and postulates that the initiation of fracture is independent of the strain path. It is shown in the present paper that under these conditions the strain-based workability diagram is identical to the stress-based workability diagram. Using an available stress-based workability diagram the strain-based workability diagram is found in a much larger domain in the space of two in-surface principal strains as compared to the typical domain covered by standard tests used to determine strain-based workability diagrams. Two feasible tests are designed to determine the complete strain-based workability diagram.

Ductile Fracture in Metal Forming: A Review of Selected Issues

2012 ◽  
Vol 528 ◽  
pp. 1-11 ◽  
Author(s):  
Sergei Alexandrov ◽  
Elena Lyamina
Keyword(s):  
Free Surface ◽  
Ductile Fracture ◽  
Experimental Method ◽  
Metal Forming ◽  
Experimental Methods ◽  
Fracture Criteria ◽  
Surface Fracture ◽  
Maximum Friction ◽  
Ductile Fracture Criteria ◽  
Friction Surfaces

The paper reviews several theoretical and experimental methods for the assessment of ductile fracture criteria and for their application to the fracture prediction in metal forming processes. In particular, distinguished features of two widely used ductile fracture criteria are demonstrated in the case of free surface fracture. Conventional empirical ductile fracture criteria are not compatible with behaviour of plastic solutions in the vicinity of maximum friction surfaces. An approach to overcome this difficulty is discussed. Finally, a theoretical/experimental method to reveal a possible effect of geometric singularities on the applicability of ductile fracture criteria is reviewed.

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.

scholarly journals Finite Element Analysis of Bore-expanding Processes with Ductile Fracture Criterion

1998 ◽  
Vol 84 (3) ◽  
pp. 182-187 ◽  
Author(s):  
Hirohiko TAKUDA ◽  
Ken-ichiro MORI ◽  
Masashi KANESHIRO ◽  
Natsuo HATTA
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Ductile Fracture ◽  
Fracture Criterion ◽  
Ductile Fracture Criterion ◽  
Element Analysis

scholarly journals Forming Limit Research of 5182 Aluminum Alloy Sheet Based on Lou-2013 Ductile Fracture Criterion

2019 ◽  
Vol 55 (16) ◽  
pp. 47 ◽  
Author(s):  
YANG Zhuoyun ◽  
ZHAO Changcai ◽  
DONG Guojiang ◽  
CHEN Guang ◽  
ZHU Liangjin ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Ductile Fracture ◽  
Fracture Criterion ◽  
Alloy Sheet ◽  
Forming Limit ◽  
Aluminum Alloy Sheet ◽  
Ductile Fracture Criterion
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