This paper presents a combined experimental and simulation approach to identify post-necking hardening behavior of ductile sheet metal. The method is based on matching a measured load-displacement curve from a continuous bending under tension (CBT) test with the curve simulated using the finite element method (FEM), while adjusting an input flow stress curve into the FEM. The CBT test depletes ductility uniformly throughout the gauge section of a tested sheet, and thus, stretches the sheet far beyond the point of maximum uniform strain in a simple tension (ST) test. Having the extended load-displacement curve, the calibrated flow stress curve is extrapolated beyond the point of necking. The method is used to identify the post-necking hardening behavior of an aluminum alloy, AA6022-T4, and two dual-phase (DP) steels, DP 980 and DP 1180. One measured load-displacement curve is used for the identification of a flow stress curve per material, and then the flow stress curve is used to simulate two additional measured load-displacement curves per material for verification. The predictions demonstrate the utility of the developed CBT-FEM methodology for inferring the post-necking strain hardening behavior of sheets. Furthermore, the results for AA6022-T4 are compared with the hydraulic bulge test data. Unlike the hydraulic bulge test, the CBT-FEM method can predict increasing as well as decreasing anisotropic hardening rate in the post-necking regime. The latter is associated with probing stage IV hardening. The proposed methodology along with the results and these key advantages are presented and discussed in this paper.

中文翻译：

---

通过拉伸试验和有限元建模相结合的连续弯曲推断板材的颈缩后应变硬化行为

本文提出了一种结合实验和模拟的方法来识别延性金属板的颈缩后硬化行为。该方法基于将来自连续拉伸弯曲 (CBT) 测试的测得载荷-位移曲线与使用有限元方法 (FEM) 模拟的曲线进行匹配，同时将输入流应力曲线调整到 FEM 中。CBT 测试在整个测试片材的规格截面上均匀地降低延展性，因此，在简单的拉伸 (ST) 测试中，将片材拉伸到远远超出最大均匀应变点。有了扩展的载荷-位移曲线，校准的流动应力曲线被外推到颈缩点之外。该方法用于识别铝合金 AA6022-T4 和两种双相 (DP) 钢 DP 980 和 DP 1180 的颈缩后硬化行为。一条测得的载荷-位移曲线用于识别每种材料的流动应力曲线，然后用流动应力曲线模拟每种材料的两条额外测得的载荷-位移曲线以进行验证。预测结果证明了开发的 CBT-FEM 方法可用于推断板材的颈缩后应变硬化行为。此外，AA6022-T4 的结果与液压胀形试验数据进行了比较。与液压胀形试验不同，CBT-FEM 方法可以预测颈缩后各向异性硬化速率的增加和减少。后者与探测阶段 IV 硬化有关。本文介绍并讨论了所提出的方法以及结果和这些关键优势。