ESTIMATION OF FATIGUE DAMAGE FOR AN AUSTENITIC STAINLESS STEEL (SUS304) USING A PANCAKE TYPE COIL

There are some fatigue damage estimation methods of an austenitic stainless steel that uses martensitic transformation. For instance, those are the remanent magnetization method, the excitation method, and so on. Those two methods are researched also in our laboratory now. In the remanent magnetization method, it is well known that the relationship between fatigue damage and the remanent magnetization is simple, clear, and reproducible. However, this method has the disadvantage to need a special magnetizer. Then, this method cannot be easily used at the job site such as the factory. On the other hand, as the special magnetizer is unnecessary, the excitation method can be easily used at the job site. But, this method has some disadvantages shown as follows. For instance, the output signal of this method is small. And the surface state of the specimen strongly influences the noise component of the output signal. It is well known that the inductance of a pancake type coil put on the metallic specimen changes according to the electromagnetic properties of the metallic specimen. In this paper, the method of evaluation of fatigue damage of an austenitic stainless steel (SUS304) by using a change of an inductance of a pancake type coil is shown. In addition, the fatigue evaluation performance of this method is described.