Abstract The impact of the Portevin-Le Chatelier (PLC) effect on plasticity and fracture ahead of a severe notch is investigated by DIC field measurements for C-Mn steel. The PLC effect causes an intermittent activity of highly localized strain rate bands. This first high temperature investigation of the effect of a notch on the PLC localization bands is successfully reproduced numerically in terms of strain localization in 3D FE simulations. This thereby validates quantitatively the McCormick-type model under these complex conditions. It is found that, when the PLC effect is at play at elevated temperature (175 °C), a flat to slant crack transition is observed. In contrast, at room temperature, when only Luders bands are active, the crack remains mostly flat, i.e. normal to the loading direction of the SENT samples. This behaviour may be related to the early loss of symmetry and intermittency of the plastic zone that is found for PLC even affecting the initial Luders bands at elevated temperature. During the slant fracture at high temperature, only half the fracture energy is absorbed compared to flat fracture at room temperature. The McCormick-type model simulations predict slant strain rate bands through the sample thickness, that are consistent with the slant fracture found at elevated temperature. Accordingly, no slant bands are found for simulations outside the PLC domain. Both experiments and simulations show PLC strain localization bands that are flip-flopping up and down during crack propagation. By combining the McCormick-type model with a Rousselier porous plasticity model, the flat fracture of the sample at room temperature and the associated macroscopic curve are reproduced successfully, but the toughness at elevated temperature is overestimated.

中文翻译：

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通过 DIC 和有限元模拟研究 Lüders 和 Portevin-Le Chatelier 定位带对缺口钢试样塑性和断裂的影响

摘要 通过 C-Mn 钢的 DIC 场测量研究了 Portevin-Le Chatelier (PLC) 效应对严重缺口前塑性和断裂的影响。PLC 效应导致高度局部应变率带的间歇性活动。就 3D FE 模拟中的应变定位而言，首次对缺口对 PLC 定位带的影响进行了高温研究。这从而在这些复杂条件下定量地验证了麦考密克型模型。发现，当 PLC 效应在升高的温度 (175 °C) 下发挥作用时，观察到从平坦到倾斜的裂纹转变。相反，在室温下，当只有 Luders 带处于活动状态时，裂纹大部分保持平坦，即垂直于 SENT 样品的加载方向。这种行为可能与 PLC 发现的塑性区的对称性和间歇性的早期损失有关，甚至会影响高温下的初始 Luders 带。在高温斜断过程中，与室温下的平断相比，只有一半的断裂能量被吸收。McCormick 型模型模拟通过样品厚度预测倾斜应变率带，这与在高温下发现的倾斜断裂一致。因此，在 PLC 域之外的模拟中没有发现斜带。实验和模拟均显示 PLC 应变定位带在裂纹扩展过程中上下翻转。通过将 McCormick 型模型与 Rousselier 多孔塑性模型相结合，