Investigation of Magnetic Memory Signal of Propagation of Buried Crack under Applied Load

The timely detection of crack defects considerably helps prevent accidents caused by metal component failure. Further, magnetic memory detection technology has the advantage of detecting damage earlier than traditional nondestructive testing technology; however, the relationship between magnetic memory fields and welding cracks needs to be studied. Specimens with buried welding cracks were fabricated to study the magnetic memory field parameters of the propagation process of welding cracks. Variations in the magnetic memory signals of the crack at different loading stages were characterized. The magnetic memory detection method can effectively detect the buried welding crack defects. The magnetic field intensity gradient (dH/dx) demonstrated a regular change with the increase in the applied tensile load (P), which can be considered in two stages: In the first stage (P < 120 kN), dH/dx gradually decreased with P, and in the second stage (P > 120 kN), it rapidly increased before fracture.