Constitutive and Fracture Modeling of Biaxially Oriented Polyethylene Terephthalate Film and Its Application to Polymer-Coated Sheet Metal Forming

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Suhwan Yun ◽  
Jaebong Jung ◽  
Sungwook Jun ◽  
Jiyong Jeong ◽  
Young Hoon Moon ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Polyethylene Terephthalate ◽  
Sheet Metal ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Equivalent Material ◽  
Anisotropic Fracture ◽  
Anisotropic Mechanical Properties ◽  
Pet Film ◽  
Coated Sheet

Abstract Polyethylene terephthalate (PET) films produced by rolling and tentering have biaxial orientation and thus exhibit anisotropic mechanical properties such as yielding, hardening, and fracture. The anisotropy of film makes it difficult to analyze deformation and failures occurring during processing such as metal forming of polymer-coated sheet metals. In this work, the anisotropic yielding and hardening of the PET film were measured and an anisotropic constitutive model is developed to represent the anisotropic behavior. In addition, fracture limits of the PET film were measured using the Nakajima test. To describe anisotropic fracture behavior of the film, an anisotropic fracture criterion based on the strain energy density and the theory of isotropic equivalent material was proposed. For validation of the developed constitutive model and the fracture criterion, a deep drawing test of the PET-coated sheet metal was conducted. The film cracking predicted by the anisotropic fracture criterion agreed well with measurements.

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.

The Numerical Simulation of Multi-Stage Sheet Metal Forming Based on Modified Yoshida-Uemori Hardening Model

2016 ◽  
Vol 725 ◽  
pp. 554-559
Author(s):  
Jiang Chen ◽  
Wen Liang Chen
Keyword(s):  
Numerical Simulation ◽  
Constitutive Model ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Boundary Surface ◽  
Back Stress ◽  
Experimental Result ◽  
Multi Stage ◽  
Tension And Compression

Bauschinger effect is significant for metal forming, particularly for aluminum. A material constitutive model especially for multi-stage sheet metal forming is presented in this paper, which is improved based on Yoshida-Uemori(Y-U) model assumes that there exists different coefficient on equivalent back stress and boundary surface between stages. The prediction of this model is validated through real tension and compression test. Compared to other hardening rules, it can be shown that a more accurate result can be predicted by this model. This model is also successfully applied to be used in the numerical simulation of a multi-stage manufacturing process of an A-pillar, the experimental result demonstrates the advantage of this model in springback analysis in multi-stage simulation over other constitutive model.

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