The hardening curve for cylindrical specimens determined by conventional uniaxial tension tests generally corresponds to a relatively narrow strain range due to the occurrence of necking. To achieve the hardening curve within a large strain range, in this study, the multi-specimen tension tests with pre-torsion are developed through extrapolating the hardening curve from the stress–strain data of cylindrical specimens with various magnitudes of pre-torsion strains. The calculation of pre-strain of twisted specimen needs to be addressed for the multi-specimen tension tests. The three calculation methods on the multi-specimen tension tests are proposed, leading to their individual hardening curves for Q345 specimens. An optimal strategy for the multi-specimen tests with pre-torsion is presented by comparison with the inverse method for a single specimen tension test. The results for Q345 specimen show the strain range (0–0.6) of the hardening curve determined by the multi-specimen tension tests is significantly larger than one (0–0.04) from conventional tension test, with reasonable accuracy. Compared with the current multi-specimen tests with pre-extrusion/drawing, the proposed multi-specimen tests with pre-torsion is possessed of stronger applicability and generality, lower cost, and higher efficiency.

中文翻译：

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通过预扭转拉伸试验对圆柱试样的硬化曲线进行实验外推

由于颈缩的发生，通过常规单轴拉伸试验确定的圆柱形试样的硬化曲线通常对应于相对较窄的应变范围。为了获得大应变范围内的硬化曲线，在本研究中，通过从具有各种预扭转应变大小的圆柱试样的应力-应变数据外推硬化曲线，开发了具有预扭转的多试样拉伸试验。多试样拉伸试验需要解决扭曲试样预应变的计算问题。提出了多试样拉伸试验的三种计算方法，得出了它们各自的 Q345 试样的硬化曲线。通过与单试样拉伸试验的逆方法比较，提出了多试样预扭转试验的最佳策略。Q345 试样的结果表明，多试样拉伸试验确定的硬化曲线的应变范围 (0-0.6) 明显大于常规拉伸试验的应变范围 (0-0.04)，具有合理的精度。与现有的预挤压/拉伸多试样试验相比，所提出的预扭转多试样试验具有更强的适用性和通用性，成本更低，效率更高。