目的 研究再制造件涂层内部不同形状、尺寸的裂纹扩展行为。方法 利用扩展有限元和内聚力单元结合的方法，通过设定断裂能G值作为控制裂纹扩展的参数，对三点弯曲试验以及拉伸试验下涂覆层内部的裂纹进行模拟，并通过实验进行验证。结果 随着载荷的增加，涂层中的垂直裂纹和45°倾斜裂纹均沿着涂层厚度方向扩展，到达界面时裂纹发生偏转，沿着界面继续扩展而并没有越过涂层-基体界面向基体扩展。模拟得到三点弯曲试验下初始长度为0.2 mm的垂直裂纹和45°倾斜裂纹开裂的临界载荷分别为3.47 kN和4.49 kN，裂纹长度增加至0.3 mm时，临界载荷降低为3.29 kN和4.31 kN。裂纹越靠近试件中心，临界载荷越小，越易发生裂纹扩展现象。另一方面，在拉伸试验下，0.2 mm的垂直裂纹的临界开裂载荷（3.47 kN）小于投影长度相同的倾斜裂纹的临界载荷（5.21 kN），而与拉应力平行的裂纹并未扩展。实验得到0.2 mm的垂直裂纹在弯曲试验下的平均临界载荷为3.49 kN，而倾斜裂纹为4.46 kN。结论 三点弯曲试验下，垂直裂纹比倾斜裂纹更危险，初始长度越长、越靠近试件中心的裂纹越易发生裂纹扩展现象。在拉伸试验下，与拉应力平行的裂纹并未扩展，最安全。模拟结果与实验相近，验证了模拟的正确性。

The work aims to study crack propagation behavior in different shape and size in the remanufactured coating. Cracks in the coating layers subject to three-point bending test and tensile test were simulated and validated by experiment by setting fracture energy G value as parameter for controlling cracks by combining extended finite element method and cohesive element method. As the load increased, vertical crack and 45° inclined crack in the coating extended along coating thickness. The cracks deflected at the interface and further extended along the interface without extending toward the substrate over the coating-substrate. Simulation showed that critical load at which vertical crack and 45° inclined crack with initial crack length of 0.2 mm under the three-point bending test were acquired were 3.47 kN and 4.49 kN, respectively. When the crack length increased to 0.3 mm, the critical load was reduced to 3.29 kN and 4.31 kN. The closer the crack was to the center line of the test piece, the lower the critical load was, the more prone to crack propagation would be. On the other hand, under the tensile test, critical crack load of the 0.2 mm vertical crack (3.47 kN) was less than that of the same inclination crack of the same projection length (5.21 kN), and the crack parallel to tensile stress did not expand. The experiment showed that average critical load of 0.2 mm vertical crack under bending test was 3.49 kN, and for inclined crack, 4.46 kN. Under the three-point bending test, vertical crack is more dangerous than inclined crack. Cracks of longer initial length closer to testpiece center are more likely to be subject to crack propagation. The crack parallel to the tensile stress does not expand under tensile experiment, which is the safest. The simulation results are close to the experiment results, and simulation correctness is verified.