Abstract

The wide application of advanced high strength steels with high specific strength in the automotive industry can significantly reduce energy consumption and contribute to carbon neutrality. Accurate prediction of the ductile fracture behavior of advanced high strength steels under complex stress states is of great significance for its application in automobile industry. In this study, the ductile fracture behavior of QP980 under complex stress states, covering shear, uniaxial tension, and plane strain tension, is investigated by conducting the hybrid experiment and simulation. The pressure-coupled Drucker yield function is chosen to characterize the effect of stress states on yielding for QP980, considering its high accuracy compared with the von Mises yield function. Failure limit of the stress states is modelled by five uncoupled ductile fracture criteria (Brozzo, Oh, Rice-Tracey, Ko-Huh, and DF2012). To improve the numerical prediction accuracy, the parameters of the constitutive model are optimized by using the inverse engineering approach. The numerical predicted results are compared with the experimental load-stroke curves with the onset of fracture. The comparison indicates that the prediction error of the DF2012 criterion is significantly lower than those of the other four criteria. In addition, the prediction accuracy is greatly improved with the parameters of the constitutive model optimized by the inverse engineering.

Highlights

  • Energy conservation is crucial to the automotive industry, which can effectively reduce the costs of automobiles and greenhouse gas emissions to promote carbon-neutral

  • A parallel groove with 3 mm was embedded for the notched specimens to avoid stress concentration and ensure the fracture initiating from the notched specimen central during deformation

  • Specimens along the rolling direction (RD), diagonal direction (DD) and transverse direction (TD) respectively were prepared for each of the four types to study the effect of anisotropy on the deformation behavior

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Summary

Introduction

Energy conservation is crucial to the automotive industry, which can effectively reduce the costs of automobiles and greenhouse gas emissions to promote carbon-neutral. With the development of computer technology, the numerical simulation method can effectively predict the plastic deformation behavior of sheet metals in forming processes, avoiding the ductile fracture under wide loading conditions. Many ductile fracture criteria have been proposed to predict the plastic deformation of sheet metals. The plastic deformation behavior of QP980 sheet metal under various stress states of shear (in-plane shear specimen), uniaxial tension (specimen with a central hole), and plane strain tension (notched specimen) was investigated by conducting experiments and simulations. It shows that the anisotropy in plastic deformation is insignificant for QP980.

Modeling of Plastic Deformation
Element Size Sensitivity
Calibration of the Constitutive Model Parameters by Using the Inverse Engineering
Fracture Prediction
Findings
Conclusions

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