Determination of Residual Stress by Magnetomechanical Acoustic Emission

摘要

This paper presents a newly discovered method for residual stress measurements. It applies to ferromagnetic materials only, but has a greater depth of penetration than X-ray diffraction and other methods, and is nondestructive. Materials under test are subjected to alternating magnetic fields. When internal structures of magnetic domains are altered, ultrasonic waves are generated; that is acoustic emission. This magnetomechanical acoustic emission (MAE) depends on the level of residual stress. It is also affected by the chemical composition, microstructure (heat treatment) and prior cold working of the material. Basic behavior and dependencies of MAE are to be described. Several applications will be discussed, including MAE measurements on structural shapes, welds and railroad rails. (Author)