A STUDY ON DAMAGE EVALUATION OF STAINLESS STEEL WITH HIGH SENSITIVITY MAGNETIC FLUX DENSITY METER

摘要

Observing the magnetic behavior of the materials is the one of the way to detect and evaluate the defects of the materials. This method, however, requires magnetizing and demagnetizing the materials. These processes need both time and money. Therefore, developing a new way to observe the magnetic behavior without magnetizing and demagnetizing the materials benefits many industries which utilize this method. In this study, we introduce the new way to observe the magnetic behavior without magnetizing the materials. We focus on the magnetic characteristics of the materials that they inherently have. We employ a high sensitive magnetic density meter to observe the magnetic behavior. In order to examine the effectiveness of the new method, we conduct a non-destructive experiment with using stainless-steel test specimens. As a result, we find there is a concave relationship between nominal strain and the magnetic density for the smooth specimen. First, the magnetic density increases linearly till its elastic limits. Then, it increases with decreasing rate. It indicates that the specimens start the plastic deformation with a constant value afterwards. In the case of the notched specimens, we also find the same tendency. Our study indicates there is a linear relationship between the stress intensity factor and the magnetic density.