セラミックス-金属系傾斜機能材料の三点曲げ負荷による破壊過程

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This paper deals with fracture process of a ceramic/metal functionally graded material (FGM) under three-point bending. The used material has a functionally graded surface layer (FGM layer) on a stainless steel (SUS 304) substrate, and the FGM layer consists of partially stabilized zirconia (PSZ) and SUS 304. In order to investigate the fracture process of the FGM, three-point bending tests of rectangular specimens and numerical analyses are carried out. On the three-point bending tests, crack initiation and unstable crack growth occur on the FGM layer, and the crack is arrested at the interface between the FGM layer and substrate. Then, the crack branches and both crack-tips grow stably along the interface with increasing deformation. After a some amount of crack growth, the both crack-tips are arrested, and a new crack is initiated and grow into the SUS 304 substrate ahead of the initial cracking of the FGM layer. The finite element analyses taking account of distribution of a PSZ volume fraction and plasticity of SUS 304 phase are carried out for each stage of fracture process. Based on the numerical results of the stress intensity factors and stress distributions, the fracture behavior of the FGM is discussed in details.
2005-01-25