镍钛基形状记忆合金因其形状记忆效应和超弹性而在工程领域得到了广泛应用。断裂损伤是镍钛基形状记忆合金在工程应用中经常出现的一种失效模式。前期研究结果表明镍钛基形状记忆合金在室温条件下塑性较差，但在包套压缩条件下可以实现较大程度的冷塑性变形，获得含有粗晶、孪晶、纳米晶和非晶的多态结构合金。这种多态结构合金在后续加工和工程应用中的断裂损伤机制目前尚不清楚。因而本项目从宏观尺度、介观尺度、微观尺度和纳观尺度出发，将塑性变形工艺实验、材料断裂力学实验、连续介质力学有限元模拟、晶体塑性有限元模拟、离散位错动力学模拟和分子动力学模拟相结合，旨在揭示基于包套压缩冷塑性变形的多态结构镍钛基形状记忆合金裂纹萌生与扩展的基本规律，探索裂尖周围粗晶、孪晶、纳米晶、非晶及各种界面结构对裂纹扩展的影响规律，获得该合金中裂纹萌生与扩展的基本机理，为镍钛基形状记忆合金在工程应用中防止断裂损伤提供科学的理论基础。

NiTi-based shape memory alloys have been widely used in the engineering fields because of their shape memory effect and superelasticity. Fracture damage is one of the most frequent failure modes in the engineering application of NiTi-based shape memory alloys. It has been found in previous studies that the NiTi-based shape memory alloys possess poor plasticity at room temperature, while they can be subjected to greater extent of cold plastic deformation in the condition of canning compression, and thus polymorphic structural alloys containing coarse grains, twins, nanocrystallines and amorphous phase are able to be obtained. So far, the fracture mechanisms for this kind of polymorphic structural alloy during subsequent manufacturing and engineering application have been unclear. As a consequence, in the present study, plastic deformation process experiment, material fracture mechanics experiment, continuum mechanics finite element simulation, crystal plasticity finite element simulation, discrete dislocation dynamics simulation and molecular dynamics simulation are combined from the macroscale, mesoscale, microscale and nanoscale perspectives. The present investigation is aimed at revealing the basic laws of crack initiation and propagation in the polymorphic structural NiTi-based shape memory alloy obtained from cold plastic deformation based on canning compression, exploring the influence rules of coarse grains, twins, nanocrystallines, amorphous phase and various interface structures surrounding the crack tip on the crack propagation, and obtaining basic mechanisms of crack initiation and propagation in the alloy, which is able to lay scientific and theoretical foundations for preventing fracture damage of NiTi-based shape memory alloy in the engineering applications.