Detection of cracked position due to cyclic loading for ferromagnetic materials based on magnetic memory method

In this paper, metal magnetic memory (MMM) method is used to detect the micro-crack position on the ferromagnetic material due to the fatigue process by determining to the stress concentration zones in the metal surfaces. The MMM method was carried out on mild steel using Instron 8874 universal tensile testing machine with different values of the ultimate tensile strength (UTS) varies from 75%, 80% and 85% until the specimens fails. An equipment of stress concentration indicator was used to measure the magnetic flux leakage, Hp patterns in the specimens. The results indicated that the position of a crack on the specimen that failed due to fatigue test was correlated with the scanning interval from the magnetic flux leakage signals. Therefore, the MMM method provides the potential possibility to detect the position of fatigue damage or defect in the metal components