抄録
Compressive fatigue tests and static compression tests were carried out ontwo types of giant magnetostrictive materials with different porosities. The observation of crack initiations and the classification of fragments after fractures clarified a mechanism of fatigue failure. As a result, the following were obtained: (1) Both the static and fatigue strengths showed a clear dependence on porosity. (2) The static strength σ_c was well expressed by an equation "σ_c=σ_0exp(-4_p)" with the porosity p and the strength of a pore-free material σ_0. (3) The S-N plots standardized by σ_c of the former equation distributed in a narrow band regardless of different porosities. This means that the compressive fatigue strength can be evaluated by using the porosity. (4) Many small intergranular cracks initiated from pores were observed in the fatigued test peice. The fatigue fracture results from the chain coalescence of these cracks.
