Ultrasonic measurement was carried out in synchronization with a fatigue cycle during the fatigue testing of aluminum alloy plates 2024-T3 with a circular hole. A water bag was used to obtain the surface acoustic wave (SAW) reflected from a fatigue crack propagating from the hole edge. When the SAW was irradiated at the crack side, no considerable change was observed in the echo intensity from the crack side in a loading cycle. When the SAW was irradiated at the crack front, however, considerable change was observed in the echo intensity; the echo intensity increased successively with the crack propagation and also showed the sinusoidal change in a loading cycle following the change in the crack opening.

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Stud welding plays a key role in making electronic device cases using magnesium alloy sheets. The welding of magnesium is a rather difficult process because of its high thermal conductivity and easy oxidizability. When magnesium alloy sheets are thin, boss forming becomes more difficult. Therefore an effective method for the non-destructive testing of magnesium stud welding is desired to perform a 100-percent inspection. We propose a new method, in which a stud is excited electromagnetically and the vibration of the stud head is measured by a laser velocimeter. We applied this method to two groups of magnesium alloy stud specimens, one welded with the optimum energy and the other welded with insufficient energy. The cross-sectional area of those weldings was evaluated by X-Ray CT. A difference appeared in the amplitude spectrum of the displacement at the stud heads. We introduced a parameter K which is the average amplitude between zero and 70 kHz in the amplitude spectrum. The two welding groups can be distinguished with an accuracy of 90% by using the parameter K.

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Two approaches were taken to improve the precision of the non-destructively diagnosed stress in a piping system with a bent pipe and tangent pipes on both ends using the magnetic anisotropy sensor developed by Sakai et al. As a result, an effective method is proposed to distinguish whether or not there is a flattening of a cross section by using the amplitude in the equation determined by regressing the measured values with the magnetic anisotropy sensor to the equation: Y=a+b cos (2X-c). And also, it was clarified that the method proposed by Iimura and Sakai, to distinguish only the stress by the external loading produced in a bent pipe, was applicable to a bent pipe that has over a 45 degree angle.

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