Distinguishing Stress Concentration or Cracking in Ferromagnetic Material Using Abnormal Magnetic Signals

Abstract

In the geomagnetic field, spontaneous magnetic signals in ferromagnetic materials can be induced by stress, which can be potentially applied to estimate the damage degree. In this research, a method of distinguishing stress concentration or cracking in ferromagnetic material was proposed. The normal component of magnetic field, H p (y), was measured on the surfaces of ferromagnetic specimens with notch. The results indicated that the shapes of H p (y) curves of stress concentration and cracking were different, there was abnormal magnetic peak in the H p (y) curve of cracking. Meanwhile, the effect of lift-off on abnormal magnetic peak was studied, and the optimal lift-off value was also presented.

Eddy Current and Metal Magnetic Memory Testing Nondestructive Evaluation for Superficial Defects of Old Cylinder Barrel

“…Eddy current testing is one of the five conventional nondestructive testing technologies, which is more mature and suitable for the detection of metal surface and near surface defects. The metal magnetic memory testing, as a novel nondestructive testing technology, can detect the stress concentration of ferromagnetic components and make the early diagnosis of components [8][9][10]. The two nondestructive testing techniques have great application prospect in the detection of cylinder defects.…”