The severe nonlinear behavior caused by the martensitic transformation (MT) and subsequent plastic deformation (PD) of detwinned martensite leads to a complex local stress redistribution at the location of stress risers of superelastic shape memory alloy (SMA) components. Nevertheless, in the literature, the simple linear elastic fracture mechanics (LEFM) equations are widely used in the evaluation of the fracture response of superelastic components which has resulted in obvious conflicts between the conclusions regarding the effect of MT on the fracture parameters, i.e. stress intensity factor (SIF) and material toughness. Furthermore, the linear elasticity method is frequently used in the literature to calculate the stress intensity range ([Formula: see text]) when the fatigue crack growth rate dependence on [Formula: see text] ([Formula: see text]) is being evaluated. Moreover, the PD followed by MT is poorly considered in the fracture mechanics of SMAs. This paper presents a numerical investigation on the role of both MT and PD, as well as the notch acuity, on the evolution of notch-tip stresses and strains and stress concentration factor ([Formula: see text]) upon the incremental application of the macroscopic tensile load on a thin NiTi notched superelastic ribbon, to mimic the effects of MT and PD on the SIF of superelastic parts. It is revealed that MT results in drastic deviations of the notch-tip stress, as well as the stress concentration factor ([Formula: see text]), from that obtained in LEFM. Due to the heterogeneous evolution of MT, the trend of the deviations is not regular and unique upon monotonic external loading. Accordingly, the results represent the ineffectiveness of the LEFM method in the evolution of the stress concentration factor (hence, the SIF) and toughness in monotonic loading, as well as the stress intensity range ([Formula: see text]) under fatigue loading in SMA components.

中文翻译：

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马氏体相变和塑性变形对薄缺口超弹性镍钛带应力集中系数影响的有限元分析

由脱孪马氏体的马氏体转变 (MT) 和随后的塑性变形 (PD) 引起的严重非线性行为导致在超弹性形状记忆合金 (SMA) 部件的应力上升位置处出现复杂的局部应力重新分布。然而，在文献中，简单的线性弹性断裂力学（LEFM）方程被广泛用于评估超弹性构件的断裂响应，这导致关于MT对断裂参数（即应力）影响的结论之间存在明显的矛盾。强度因子（SIF）和材料韧性。此外，文献中经常使用线弹性法计算疲劳裂纹扩展速率依赖于[公式：见文本]（[公式：见文本]）时的应力强度范围（[公式：见文本]）见文本]) 正在评估中。此外，在 SMA 的断裂力学中很少考虑 PD 和 MT。本文介绍了 MT 和 PD 的作用以及缺口锐度对缺口尖端应力和应变的演变以及应力集中因子（[公式：见文本]）的作用的数值研究。薄镍钛缺口超弹性带上的宏观拉伸载荷，以模拟 MT 和 PD 对超弹性零件 SIF 的影响。结果表明，MT 导致缺口尖端应力以及应力集中因子（[公式：见文本]）与 LEFM 中获得的值有很大偏差。由于 MT 的异构演化，在单调外部加载时，偏差的趋势不规则且唯一。因此，