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This paper describes the fatigue crack propagation behavior of rolled and extruded AZ31B magnesium alloys (grain size: approximately 20 and 15 mm, respectively). Fatigue crack propagation tests were performed on center cracked plate tension specimens at a stress ratio of R ¼ 0:1 and a frequency of 10 Hz at room temperature. Loading axes were parallel to the rolling and extrusion directions; fatigue cracks propagated parallel to the transverse direction (L-T specimen of rolled AZ31B), parallel to the short transverse direction (L-S specimen of rolled AZ31B), and perpendicular to the extrusion direction (E-R specimen of extruded AZ31B). The crack growth rate (da=dN) of the L-S specimen was approximately 10 times lower than that of the L-T specimen in the examined stress intensity factor (ÁK) range. Fracture surfaces of the L-T and L-S specimens showed many steps parallel and perpendicular, respectively, to the macroscopic crack growth direction. The plot of the da=dN versus the ÁK range for the E-R specimen shows two regimes with different slopes in the examined ÁK range. The fracture surface was covered by various directional steps independent of macroscopic crack growth direction, and the fracture surface roughness at low ÁK was larger than that at high ÁK. SEM-EBSD observations revealed that the c-axis direction is unfavorable for the fatigue crack propagation in rolled AZ31B magnesium alloy. Free deformation twins were observed around the fatigue crack path in the L-T, L-S, and E-R specimens.

LiNbO3 thin films with c-axis orientation were deposited on polycrystalline Si3N4 substrates by means of RF -magnetron sputtering method. Response ability to cyclic stress of the Si3N4 specimen coated by LiNbO3 thin films was evaluated by a 3-point bending fatigue test. The voltage range produced by LiNbO3 thin films in creased linearly with the maximum stress during the cyclic test. The voltage range depended on the frequen cy of cyclic stress. The position of cyclic compressional load was revealed due to the different generations of voltage signals at a multielectrode placed between the LiNbO3 thin film and Si3N4 substrate.