VOID EVOLUTION BEHAVIOR AND CLOSURE CRITERION INSIDE LARGE SHAFT FORGINGS DURING A FORGING PROCESS

Yongxing Jiao; Cunlong Zhou; Jiansheng Liu; Xuezhong Zhang; Wenwu He

doi:10.17222/mit.2020.172

Yongxing Jiao School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China
Cunlong Zhou School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China
Jiansheng Liu School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China
Xuezhong Zhang School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China
Wenwu He School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China

DOI: https://doi.org/10.17222/mit.2020.172

Keywords: large shaft forgings, void evolution, finite elements, void-closure model

Abstract

In this study, the effects of different void positions, void shapes and sizes on the evolution of voids were discussed in detail using experiments and simulations. The results show that the influence of the void size on the void closure can be ignored, while the void position and void shape have a great influence on the closure of a void. Considering the complexity of the void-shape change in a forging process, we proposed a quantitative expression of the void-shape coefficient, which is affected by the effective stress and effective strain. Meanwhile, the void-shape evaluation parameter, defined as a function of the stress deviator, effective strain and effective stress, was proposed to describe the changes in the void aspect ratio. Finally, WHF (wide die heavy blow) forging experiments were conducted using a 5MN hydraulic press to verify the numerical-simulation results. Based on the experimental and simulation results, a new mathematical model for void-closure determination was established during a forging process of large shaft forgings. The experimental results were consistent with the simulation results, showing that the void-closure model can accurately determine whether a void is closed or not.

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