This study was performed to estimate the stretch-flangeability of two important advanced high strength steel (AHSS) sheets, i.e. DP980 and TRIP1180, using hole-expansion test (HET). Moreover, the effect of hole edge-quality on stretch-flangeability of both steels was analyzed by adopting two different methods, (i) shearing and (ii) wire cutting, to create the central hole on test specimens. Formability of the sheets was measured in terms of fracture strain and hole expansion ratio, under the influence of two different edge-qualities. A detailed characterization at both micro- and macro-scale was carried out to analyze the fracture behavior of both steels. Experimental results showed that the role of localization and shear in addition to edge-quality is crucial to fracture behavior of both the steels. Apart from the macro- and micro-scale characterization, a finite element study was also carried out to model the HET numerically. Finally, a suitable fracture criterion was used to predict the onset of fracture during the test.

中文翻译：

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先进高强钢扩孔试验的断裂特性

本研究旨在使用扩孔试验 (HET) 来评估两种重要的高级高强度钢 (AHSS) 板材，即 DP980 和 TRIP1180 的拉伸法兰性能。此外，通过采用两种不同的方法（i）剪切和（ii）线切割在试样上创建中心孔，分析孔边缘质量对两种钢的拉伸法兰性能的影响。在两种不同边缘质量的影响下，根据断裂应变和扩孔率测量板材的成形性。在微观和宏观尺度上进行了详细的表征，以分析两种钢的断裂行为。实验结果表明，除了边缘质量外，局部化和剪切的作用对两种钢的断裂行为都至关重要。除了宏观和微观尺度的表征外，还进行了有限元研究以数值模拟 HET。最后，使用合适的断裂标准来预测试验期间断裂的发生。