Abstract A new approach was used to characterise the hardening, instability and fracture behaviour of ultra-thin (0.1 mm) stainless steel sheets under stress triaxiality ranging from 0.37 to 0.66. The Swift and the linear hardening laws were used to capture the stress–strain relationship for the complete level of plastic deformation that exceeds that achievable by a uniaxial tensile test. For this, the Virtual Field Method (VFM) was applied, which uses the strain field measured on the surface of the notched samples, to output the material hardening parameters. To determine one set of hardening parameters that fits all conditions of stress triaxiality, an upper bound of major strain was selected for the VFM fitting that optimises a single set of hardening parameters across all of the stress triaxiality conditions. The void coalescence parameter in a Gurson-Tvergaard-Needleman (GTN) fracture model was calibrated and the model results for fracture initiation were validated experimentally with a quasi-biaxial stretching test.

中文翻译：

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超薄不锈钢板的塑性失稳与断裂

摘要 一种新方法用于表征超薄（0.1 mm）不锈钢板在应力三轴度范围为 0.37 至 0.66 下的硬化、失稳和断裂行为。Swift 和线性硬化定律用于捕捉超过单轴拉伸试验可达到的塑性变形完整水平的应力-应变关系。为此，应用了虚拟场法 (VFM)，它使用在缺口样品表面测量的应变场来输出材料硬化参数。为了确定一组适合所有应力三轴条件的硬化参数，为 VFM 拟合选择了一个主要应变的上限，该上限在所有应力三轴条件下优化了一组硬化参数。