構造用セラミックスの破壊強度に及ぼすショットピーニングの効果の評価

抄録

To investigate the effects of shot peening (SP) on the fracture strength of structural ceramics, bending tests on alumina-silicon carbide (Al₂O₃/SiC) ceramic composites were performed. A semi-elliptical surface pre-crack was introduced on the surface of the specimens with a Knoop indenter. Specimens with and without a surface pre-crack were subjected to SP. The X-ray diffraction analyses showed that a large compressive residual stress of approximately 1376 MPa was generated on the surface by SP, reaching a maximum compressive residual stress of 1410 MPa at a depth of 3 μm. The effects of SP on the Weibull distributions of the fracture strength of specimens without pre-crack were investigated. It was found that the scatter of the fracture strength of SP specimens was reduced compared to that found in samples not subjected to SP (non-SP specimens). The locations where the fracture originates shifted from the surface to interior of specimen or unpeened areas (edge of specimen) where the compressive residual stress was small. The fracture strengths of the pre-cracked specimens were significantly improved by SP. Using the evaluation equation based on process zone size fracture criterion and the √area parameter model, the fracture strengths of pre-cracked non-SP specimens were successfully predicted. However, the predicted fracture strengths were lower than the experimental values of pre-cracked SP specimens.