Crystal plasticity-based forming limit prediction for FCC materials under non-proportional strain-path

2010 ◽  
Vol 527 (24-25) ◽  
pp. 6607-6613 ◽  
Author(s):  
Mei Yang ◽  
Xianghuai Dong ◽  
Rui Zhou ◽  
Jian Cao
Keyword(s):  
Crystal Plasticity ◽  
Strain Path ◽  
Forming Limit ◽  
Fcc Materials

Forming Limit Prediction of BCC Materials under Non-Proportional Strain-Path by Using Crystal Plasticity

2012 ◽  
Vol 201-202 ◽  
pp. 1110-1116
Author(s):  
Mei Yang ◽  
Xiao Yan Zhang ◽  
Hao Wang
Keyword(s):  
Sheet Metal ◽  
Crystal Plasticity ◽  
Strain Path ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Slip Systems ◽  
Plasticity Model ◽  
Forming Process ◽  
Crystal Plasticity Model ◽  
Microstructure Effect

In this paper, the forming limit of a body-centered cubic (BCC) sheet metal under non-proportional strain-path is investigated by using the Marciniak and Kuczynski approach integrated with a rate-dependent crystal plasticity model. The prediction model has been proved to be effective in predicting Forming Limit Diagram (FLD) of anisotropic sheet metal with FCC type of slip systems[1]. The same model has been used to study the FLD under non-proportional strain-path of BCC slip systems numerically and experimentally. The agreement between the experiments and simulations is good. With crystal plasticity model well describing the crystal microstructure effect, our model can be used to predict the FLD of BCC sheet metal under complicated strain path in plastic forming process with good accuracy.

Stress-Based Forming Limits in Sheet-Metal Forming

2000 ◽  
Vol 123 (4) ◽  
pp. 417-422 ◽  
Author(s):  
Thomas B. Stoughton
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Strain Path ◽  
Forming Limit ◽  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
The Stability ◽  
Definition Of

A strain-based forming limit criterion is widely used throughout the sheet-metal forming industry to gauge the stability of the deformed material with respect to the development of a localized neck prior to fracture. This criterion is strictly valid only when the strain path is linear throughout the deformation process. There is significant data that shows a strong and complex dependence of the limit criterion on the strain path. Unfortunately, the strain path is never linear in secondary forming and hydro-forming processes. Furthermore, the path is often found to be nonlinear in localized critical areas in the first draw die. Therefore, the conventional practice of using a path-independent strain-based forming limit criterion often leads to erroneous assessments of forming severity. Recently it has been reported that a stress-based forming limit criterion appears to exhibit no strain-path dependencies. Subsequently, it has been suggested that this effect is not real, but is due to the saturation of the stress-strain relation. This paper will review and compare the strain-based and stress-based forming limit criteria, looking at a number of factors that are involved in the definition of the stress-based forming limit, including the role of the stress-strain relation.

Orientation and Path Dependence of Formability in the Stress- and the Extended Stress-Based Forming Limit Curves

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
C. Hari Manoj Simha ◽  
Kaan Inal ◽  
Michael J. Worswick
Keyword(s):  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Stress Space ◽  
Forming Limit Diagrams ◽  
Metall Trans ◽  
Strain Paths ◽  
Strain Path Changes ◽  
Path Dependent ◽  
Forming Limit Curves

This article analyzes the formability data sets for aluminum killed steel (Laukonis, J. V., and Ghosh, A. K., 1978, “Effects of Strain Path Changes on the Formability of Sheet Metals,” Metall. Trans. A., 9, pp. 1849–1856), for Al 2008-T4 (Graf, A., and Hosford, W., 1993, “Effect of Changing Strain Paths on Forming Limit Diagrams of Al 2008-T4,” Metall. Trans. A, 24A, pp. 2503–2512) and for Al 6111-T4 (Graf, A., and Hosford, W., 1994, “The Influence of Strain-Path Changes on Forming Limit Diagrams of Al 6111 T4,” Int. J. Mech. Sci., 36, pp. 897–910). These articles present strain-based forming limit curves (ϵFLCs) for both as-received and prestrained sheets. Using phenomenological yield functions, and assuming isotropic hardening, the ϵFLCs are transformed into principal stress space to obtain stress-based forming limit curves (σFLCs) and the principal stresses are transformed into effective stress and mean stress space to obtain the extended stress-based forming limit curves (XSFLCs). A definition of path dependence for the σFLC and XSFLC is proposed and used to classify the obtained limit curves as path dependent or independent. The path dependence of forming limit stresses is observed for some of the prestrain paths. Based on the results, a novel criterion that, with a knowledge of the forming limit stresses of the as-received material, can be used to predict whether the limit stresses are path dependent or independent for a given prestrain path is proposed. The results also suggest that kinematic hardening and transient hardening effects may explain the path dependence observed in some of the prestrain paths.

Investigation of Critical Stress Concentration Factor in Analytical Stress Based Forming Limit Criterion

2009 ◽  
Author(s):  
Kyle R. McLaughlin ◽  
Tugce Kasikci ◽  
Igor Tsukrov ◽  
Brad L. Kinsey
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Failure Criterion ◽  
Concentration Factor ◽  
Critical Stress ◽  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Concentration Factors ◽  
Stress Concentration Factors

Tearing concerns in sheet metal forming have traditionally been predicted by comparing the strain state imposed on a material to its associated strain based Forming Limit Diagram. A shortcoming of this strain based failure criterion is that the Forming Limit Curves exhibit strain path dependence. Alternatively, a stress based failure criterion was introduced and shown analytically and numerically to exhibit less strain path dependence. In our past research, an analytical model was created to predict the stress based Forming Limit Curve. Inputs into the model include a material constitutive relationship, anisotropic yield criterion and a critical stress concentration factor, defined as the ratio of the effective stress in the base material to the effective stress in the necking region. This stress concentration factor is thought to be a material parameter, which characterizes a material’s ability to work harden and prevent the concentration of stress which produces the necking condition. In this paper, the critical stress concentration factors for steel and aluminum alloys were determined by comparing analytical model predictions and experimental data and found to be significantly different. A setup is then proposed to experimentally measure the critical stress concentration factors and initial results are presented.

Prediction of strain path and forming limit curve of AHSS by incorporating microstructure evolution

2020 ◽  
Vol 106 (11-12) ◽  
pp. 5085-5098 ◽  
Author(s):  
Shanta Chakrabarty ◽  
Marrapu Bhargava ◽  
Harsh Kumar Narula ◽  
Prita Pant ◽  
Sushil K. Mishra
Keyword(s):  
Microstructure Evolution ◽  
Strain Path ◽  
Forming Limit ◽  
Limit Curve ◽  
Forming Limit Curve

Forming Limit Analysis of Hexagonal Metal Considering Volume Fraction of Deformation Twinning

2019 ◽  
Vol 794 ◽  
pp. 226-231
Author(s):  
Tomoaki Koga ◽  
Yuichi Tadano
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Crystal Plasticity ◽  
Limit Analysis ◽  
Volume Fraction ◽  
Deformation Twinning ◽  
Forming Limit ◽  
Strain Paths ◽  
Homogenization Scheme ◽  
Slip Deformation

In the plastic deformation of hexagonal metals, deformation twinning plays an important role as well as slip deformation. Therefore, a modelling of deformation twinning is essential in the crystal plasticity modeling. In this study, a model considering the volume fraction of deformation twinning is presented in the framework of crystal plasticity, and it is combined with a finite element-based homogenization scheme to represent the polycrystalline behavior. The presented model is adopted to a sheet necking formulation. Plastic flow behaviors under several strain paths are evaluated using the present framework, and the effect of volume fraction of deformation twinning on the formability of hexagonal metal is discussed.

scholarly journals Effect of continuous strain path changes on forming limit strains of DP600

Strain ◽  
2019 ◽  
Vol 55 (6) ◽  
Author(s):  
Xiao Song ◽  
Lionel Leotoing ◽  
Dominique Guines ◽  
Eric Ragneau
Keyword(s):  
Strain Path ◽  
Forming Limit ◽  
Strain Path Changes

Left-Side of the Forming Limit Diagram (FLD) under Superimposed Double-Sided Pressure

2012 ◽  
Vol 472-475 ◽  
pp. 653-656
Author(s):  
Jian Guang Liu ◽  
Qing Yuan Meng
Keyword(s):  
Deformation Behavior ◽  
Strain Path ◽  
Damage Model ◽  
Forming Limit Diagram ◽  
Alloy Sheet ◽  
Forming Limit ◽  
Aluminum Alloy Sheet ◽  
The Finite Element Method ◽  
The Past ◽  
Deformation State

Over the past decades, many kinds of double-sided pressure forming processes have been proposed to improve the formability of lightweight materials which exhibit distinctly poor forming capability. In the present study, the effects of double-sided pressure on the deformation behavior of AA5052-O aluminum alloy sheet metal under tension-compression deformation state are studied numerically using the finite element method based on the Gurson damage model. It is demonstrated that superimposed double-sided pressure significantly increases the left-side of the forming limit diagram and the formability increase value is sensitive to the strain path.

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