Effects of Carbon and Plastic Strain on Stress Measurement of Steel Based on the Law of Approach to Saturation Magnetization

This paper is concerned with the application of the law of approach to saturation magnetization for nondestructive evaluation (NDE) of stress in carbon steels. In our previous paper, we have deduced the formula m=A+Bσ for stress measurement based on the law, where m is a magnetic parameter in a high field region, σ is the applied stress, and A and B are constants. In this paper, we have examined the effect of carbon content ranging from 0% to 0.45% in the specimen on the constants A and B, and also the effect of the plastic strain up to 10%. The experiments show that the stress sensitivity B decreases almost linearly with increasing carbon content and it decreases with increasing plastic deformation, saturating in the region above 2% of the plastic strain.