Rolled pure titanium films were fatigued. The film was adhered to a through elliptical hole in a base plate and was fatigued in accordance with the displacement constraint along the hole-circumference in the base plate subjected to a cyclic stress. In this testing method, a stress intensity factor range was decreased with a crack propagation toward the hole-edge because of the difference in thickness between the film and the base plate. Consequently, the fatigue crack propagation rate was decreased and was arrested near the hole-edge under the constant stress amplitude to the base plate. As a result, fatigue cracks propagated faster in the specimen loaded to the rolling direction than in that loaded to the transverse direction and the threshold stress intensity factor ranges, Kth, are lower in the specimen loaded to the rolling direction than in that loaded to the transverse direction. Crack opening displacements were measured belong the fatigue crack and the curvature of crack tip was estimated. The fluctuation in the crack propagation rate was related to the curvature and relations between the crack propagation rate and the estimated crack tip opening displacement based on the Dugdale model were almost the same between the specimens loaded toward the rolling direction and the transverse direction.

A new DK-decreasing test method of the metal film was developed. The film was adhered to a through elliptical hole in a base plate and was fatigued in accordance with the displacement constraint along the hole -circumference in the base plate subjected to a cyclic stress. Commonly, a stress intensity factor range was increased with a crack propagation under a constant stress amplitude but was decreased toward the hole-edge because of the difference in thickness between the film and the base plate in this DK-decreasing test method.The decrease in a stress intensity factor with a crack propagation was calculated by FEM analysis and the optimum aspect ratio of an elliptical hole was determined. Using the DK-decreasing test method, the crack propagation test was conducted for metal films. As a result, the fatigue crack propagation rate was decreased and was arrested near the hole-edge under the constant stress amplitude to the base plate. The threshold stress intensity factor ranges were obtained for some kinds of metal film and the accuracy of the testing method was discussed.

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Using a fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover an circular through-hole in a base plate subjected to cyclic loads, annealed rolled commercially-pure titanium films with Anisotropy of 30μm thickness were fatigued under constant stress amplitudes with a stress ratio of R=0. In order to discuss correlation between fatigue crack propagation and change of crystal orientation, crystal orientation on the surface of the film materials was measured before and after fatigue testing. The crystallographic information of these films was analyzed using the Electron Back-scatter Diffraction (EBSD) system. As a result, fatigue cracks propagated faster in the specimen loaded to the rolling direction than in that loaded to the transverse direction. It is considered that the fatigue crack propagated by prismatic slips with screw dislocations in the specimen loaded to the rolling direction. On the other hand, the fatigue crack seems to propagate by basal slips with edge dislocations in the specimen loaded to the transverse direction.