膜材の疲労破壊特性評価に関する研究

膜疲労試験法と膜厚さの影響

抄録

A new fatigue testing method was developed by which fatigue cracks can be initiated and propagated in the film adhered to cover a circular hole in a base plate subjected to push-pull cyclic loads. The Boundary Element Method Analysis for this testing showed that the stress was constant in the film until crack initiation and the stress intensity factor was almost constant during the greater part of crack propagation. When the commercial-grade iron films of 100, 50 and 40μm thickness were used, the data of fatigue crack propagation rate under various stress amplitudes gathered together in a narrow band showing a power law of stress intensity factor range, but strictly speaking a little higher side for the thinner film. Also, a residual plastic layer was left considerably in the wake of the crack propagation. It was found that the stress intensity factor estimated from the crack opening displacement was smaller and the slip/crack initiation life was shorter for the thinner film.