Abstract

This paper is concerned with accurate prediction on the fracture strain and fracture forming limit curve (FFLC) by calibrating the material constants by the specimens with reasonable shapes and sizes. The Lou–Huh ductile fracture criteria (DFC) in analytic and integral forms were adopted, and the theoretical formulas in various stress states were derived. The process and basis for calibrating the material constants of DFC by hybrid experimental–numerical method were described in detail. Moreover, the material constants calculated by different test groups including the uniaxial tensile, plane strain and shear specimens with different shapes and sizes vary enormously, and the optimal test group was determined to calibrate the material constant of DFC. Meanwhile, it can be found that the different material constants greatly impact on the magnitude and shape of the fracture strain and FFLC, and the effect of each material constant on the fracture strain and FFLC was analyzed and compared in this paper. Finally, the FFLCs theoretically calculated by DFC in analytic and integral forms were verified by the experimental forming limiting data of the bulge test.

Graphic Abstract

中文翻译：

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最优实验设计对延性断裂准则的标定及铝合金薄板成形极限的预测

摘要

本文通过对具有合理形状和尺寸的试样的材料常数进行校准，来准确预测断裂应变和断裂极限曲线（FFLC）。采用解析和积分形式的Lou-Huh韧性断裂准则（DFC），并推导了各种应力状态下的理论公式。详细介绍了通过混合实验-数值方法校准DFC的材料常数的过程和基础。此外，由不同形状和尺寸的单轴拉伸，平面应变和剪切试样等不同测试组计算出的材料常数相差很大，并确定了最佳测试组以校准DFC的材料常数。同时，可以发现，不同的材料常数对断裂应变和FFLC的大小和形状有很大的影响，并对每种材料常数对断裂应变和FFLC的影响进行了分析和比较。最后，通过凸出试验的实验成形极限数据验证了DFC理论上以解析形式和积分形式计算出的FFLC。

图形摘要