Abstract
This paper discusses material aging diagnosis what uses a non-destructiveness evaluation system. The diagnosis is based on magnetic characteristics of material. It is well known that the magnetism of strong magnetic materials is extremely sensitive with respect to the change of microstructure and to residual-stress variation. For example, coercive force and minor-loop coefficients have shown a linear relationship with rolling reduction. We have proposed a method what is an impedance measurement of a sensor. The method needs a magnetizer with one coil and an impedance meter. The method is simpler than a method what use coercive force. We have compared the method with a method what is a measurement of coercive force. Relationship between strain of carbon steels and experimental results of using coercive force or impedance measurements has measured. Carbon steel sample specimens with some strain loading in the experiment have been used. The experimental results have shown that the method can detect strain of steel just like a method of using a coercive force measurement.