マグネシウム合金スタッド溶接の振動解析による非破壊検査

概要

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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 <I>K</I> 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 <I>K</I>.
一般社団法人日本非破壊検査協会の論文