Abstract:For implementing nondestructive evaluation of stress distribution inside ferromagnetic material, a magnetic testing method was developed which does not need artificial magnetizing field. This method was implemented by testing the normal component of the magnetic flux leakage above the object being tested with a constant lift-off from 1 to 10mm. The distribution of the stress inside the specimen can be gotten from that of the normalcomponent of the magnetic flux leakage. A stress concentration specimen, which is a 10mm thickness mild steel plate with a welding seam on it, was tested using this method. The stress distribution of the magnetic testing was identical with that of small hole stress testing method. It indicates that the stress distribution of ferromagnetic material can be known by the magnetic testing method.

Key words: magnetic testing; stress distribution; welding seam