A Note on Ductile Fracture Criteria in Metal Forming

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Sergei Alexandrov ◽  
Lihui Lang
Keyword(s):  
Ductile Fracture ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Ductile Fracture Criterion ◽  
Hot Metal ◽  
Fracture Criteria ◽  
Material Models ◽  
Analysis And Design ◽  
Ductile Fracture Criteria ◽  
Forming Analysis

This paper deals with some general properties of a ductile fracture criterion, which generalizes two ductile fracture criteria conventionally adopted for metal forming analysis and design. The results are valid for a wide class of material models applicable to both cold and hot metal formings. It is expected that the theoretical features of the fracture criterion emphasized in the present paper can be useful for its experimental verification or for determining its parameters from the experiment.

Fracture Prediction in Sheet Metal Stamping Based on a Modified Ductile Fracture Criterion

2015 ◽  
Vol 639 ◽  
pp. 543-550
Author(s):  
Rong Zeng ◽  
Liang Huang ◽  
Jian Jun Li
Keyword(s):  
Ductile Fracture ◽  
Sheet Metal ◽  
Fracture Criterion ◽  
Fracture Prediction ◽  
Uniaxial Tensile ◽  
Ductile Fracture Criterion ◽  
Fracture Criteria ◽  
Sheet Metal Stamping ◽  
Ductile Fracture Criteria ◽  
Metal Stamping

Sheet metal stamping is an important manufacturing process because of its high production rate and low cost, so the fracture prediction of stamping parts has become important issues. Recent experimental studies have shown that the quality of stamping parts can be increased by using ductile fracture criteria. This paper proposed a modified ductile fracture criterion based on the macroscopic and microscopic continuum damage mechanics (CDM). Three-dimensional (3D) explicit finite element analysis (FEA) are performed to predict the fracture behaviors of sheet metal stamping process. An approach to determine the material constants of modified ductile fracture criterion is presented with the help of uniaxial tensile tests and compressive tests. The results show that the modified ductile fracture criterion enables precise cup depth and fracture location of sheet metal stamping under nonlinear paths. Compared with typical ductile fracture criteria, the results predicted with modified ductile fracture criterion correlate the best with the experimental data.

Evaluation of Seven Ductile Fracture Criteria for Failure Prediction of AZ31 Sheet in Warm Forming

2012 ◽  
Vol 482-484 ◽  
pp. 1947-1950 ◽  
Author(s):  
Jian Guang Liu ◽  
Wei Liu
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Alloy Sheet ◽  
Mg Alloy ◽  
Ductile Fracture Criterion ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria ◽  
Element Simulation ◽  
Az31 Mg Alloy ◽  
Az31 Sheet

Seven commonly used ductile fracture criteria are briefly reviewed and the validity of predicting the failure of AZ31 Mg alloy sheet by using these ductile fracture criteria is evaluated. Through fitting the experimental FLCs, the damage parameters for these ductile fracture criteria are determined firstly. Integrating these seven ductile fracture criteria into Abaqus/Explicit via VUMAT subroutine, the warm deep drawing process of AZ31 Mg alloy sheet is simulated. The limit drawing ratios (LDR) of AZ31 Mg alloy sheet at different temperature are predicted. The comparison of predictions with the experimental results has shown that the combination of the finite element simulation and the ductile fracture criterion is useful for predicting the fracture occurred in warm deepdrawing of AZ31 Mg alloy sheet.

The Evaluation of Ductile Fracture Criteria (DFC) of 6061-T6 Aluminum Alloy

2010 ◽  
Vol 44-47 ◽  
pp. 2837-2841 ◽  
Author(s):  
Ying Tong
Keyword(s):  
Aluminum Alloy ◽  
Ductile Fracture ◽  
Metal Forming ◽  
True Strain ◽  
Mutual Support ◽  
Fracture Criteria ◽  
Forming Process ◽  
Forming Simulation ◽  
Ductile Fracture Criteria ◽  
Metal Forming Process

As one of the principal failures, ductile fracturing restricts metal forming process. Cockcroft-Latham fracture criterion is suited for tenacity fracture in bulk metal-forming simulation. An innovative approach involving physical compression experiments, numerical simulations and mathematic computations provides mutual support to evaluate ductile damage cumulating process and ductile fracture criteria (DFC). The results show that the maximum cumulated damage decreases with strain rate rising, and the incremental ratios, that is damage sensitive rate, vary uniformly during the upsetting processes at different strain rates. The damage sensitive rate decreases rapidly, then it becomes stability in a constant 0.11 after true strain -0.85. The true strain -0.85 was assumed as the fracture strain, and the DFC of 6061-T6 aluminum alloy is almost a constant 0.2. According to DFC, the exact fracture moment and position during various forming processes will be predicted conveniently.

Analysis and Study of Damage of Forging Cracks

2011 ◽  
Vol 189-193 ◽  
pp. 2735-2741 ◽  
Author(s):  
Xing Wang Duan ◽  
Jian Sheng Liu ◽  
Xiu Zhi Zhang ◽  
Xiao Dong Zhao
Keyword(s):  
Ductile Fracture ◽  
Damage Mechanics ◽  
Fracture Criterion ◽  
Future Research ◽  
Fracture Parameter ◽  
Fracture Criteria ◽  
Existing Problems ◽  
Ductile Fracture Criteria ◽  
Mesoscopic Models ◽  
Scope Of Application

This paper dealt with the outstanding problems which were forging cracks existing in the process of forging.The forming reasons of forging cracks were analyzed. From the perspective of damage mechanics, the conventional mesoscopic models and fracture criteria of ductile metal material damage were introduced. The problems in recent research of forging cracks were pointed out. Some corresponding suggestions for the future research of forging carcks were put forward based on the existing problems. The existed ductile fracture criteria have only predicted the damage of specific process yet ,while the diversities of metal forming processes require ductile fracture criterion to have wide scope of application,so,for reason given above,the emphasis is placed on the necessity of establishing new ductile fracture criteria and fracture parameter library with the method of combination of theory and experiment and numerical simulation.

Prediction and analysis of ductile fracture in sheet metal forming—Part I: A modified Ayada criterion

2014 ◽  
Vol 23 (8) ◽  
pp. 1189-1210 ◽  
Author(s):  
HS Liu ◽  
MW Fu
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Ductile Fracture ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Ductile Fracture Criterion ◽  
Wide Range ◽  
Stress States

A modified ductile fracture criterion is proposed based on the traditional Ayada criterion and coded into the finite element simulation platform of VUMAT/ABAQUS for prediction and analysis of ductile fracture in metal plastic strain processes. In this modified ductile fracture criterion, stress triaxiality is taken into account, and more importantly, the exponential effect of the equivalent plastic strain on the damage behavior, which is generally ignored in other ductile fracture criteria, is also considered. The material related constants in the modified ductile fracture criterion are determined by tensile tests together with finite element simulations. The applicability and reliability of the ductile fracture criterion in ductile fracture prediction in two types of classic stress states, viz. shear stress, tensile stress in sheet metal forming, are investigated based on the deformation behavior and fracture occurrence in two case studies with two typical types of materials, i.e. Al 6061 and T10A. The materials have a wide range of plasticity. The simulation and experimental results verify the applicability and reliability of the developed ductile fracture criterion in prediction of the ductile fracture with and without necking in different stress states of plastic strain.

Prediction of ductile fracture for Al6016-T4 with a ductile fracture criterion: Experiment and simulation

2019 ◽  
Vol 29 (8) ◽  
pp. 1199-1221 ◽  
Author(s):  
Saijun Zhang ◽  
Yanchun Lu ◽  
Zhaohui Shen ◽  
Chi Zhou ◽  
Yanshan Lou
Keyword(s):  
Ductile Fracture ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Stress Triaxiality ◽  
Yield Function ◽  
Isotropic Hardening ◽  
Ductile Fracture Criterion ◽  
Fracture Locus ◽  
Hardening Law ◽  
Tension Tests

The key point in this paper is the prediction of the onset of ductile fracture with a newly proposed ductile fracture criterion in various stress state ranging from shear to uniaxial tension. A series of tension tests with different material orientations are carried out up to fracture. The anisotropic Drucker yield function with an isotropic hardening law is identified to describe the elastic–plastic behaviors of Al6016-T4 aluminum alloy. The uncoupled ductile fracture criterion is calibrated and then utilized to construct the fracture locus of Al6016-T4, which is implemented into the ABAQUS/Explicit to validate the prediction of ductile fracture criterion by comparing experimental results to numerical ones. The validation demonstrates that the ductile fracture criterion can accurately predict the onset of ductile fracture for Al6016-T4 in medium stress triaxiality ranging from 0.1 to 0.44 where most ductile fracture occurs in sheet metal forming.

Incorporation of a Fracture Criterion in Ideal Flow Design

2016 ◽  
Vol 713 ◽  
pp. 143-146 ◽  
Author(s):  
Elena Lyamina ◽  
Sergei Alexandrov
Keyword(s):  
Ductile Fracture ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Design Method ◽  
Stress And Strain ◽  
Preliminary Design ◽  
Ductile Fracture Criterion ◽  
Ideal Flow ◽  
Ideal Plastic ◽  
The Ideal

The theory of sheet and bulk ideal plastic flows is used for the preliminary design of metal forming processes. The present paper develops an approach to incorporate the Cockroft and Latham ductile fracture criterion in this design method for stationary bulk flows. In particular, it is demonstrated that the initiation of ductile fracture can be predicted without having the ideal flow solution for stress and strain in the plastic zone (it is only necessary to know that the solution exists). Using the approach proposed the initiation of ductile fracture in axisymmetric drawing is predicted.

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