Abstract
Estimation of the applied stress to the fractured component is important in failure analysis in fatigue fracture accident in order to determine the cause of fracture and to prevent another failure. The estimation using striation spacing achieved success in the very limited range of ΔK. The objective of this study is development of estimation methods, which are applicable in the wide range of ΔK from crack propagation threshold to striation formation. Electric impedance method and fracture surface hardness one were examined. Electric impedance of fatigue fracture surface was measured within the plastic deformation layer by using high frequency current. The impedance increased with increase of the K value. Micro Vickers hardness was measured on the fatigue fracture surface. The hardness was defined as the area of indentation mark to reduce the effect of the roughness of fracture surface. The hardness increased with increase of the K value.
