Thermal fatigue test was conducted to study the failure process and failure mode of the plasma sprayed thermal barrier coating structures.The controlling factors for failure were also analyzed.Aviscoplastic constitutive model was introduced for the ceramic coat.Moreover

the thermal fatigue behavior of the coating layer was studied numerically.The analysis indicates that: mode Ⅰ crack is easily initiated at the peak position

and mode Ⅱ crack at above middle position of interfaces when TGO(thermaly growth oxides) thickness is 2 μm;the extension of transverse crack is dominated by normal stress when TGOthickness is 8 μm;high strain energy density is formed within TGOof different thickness.The process and mechanisms of crack coalescence within PS-TBC(plasma sprayed thermal grown oxides) were presented.