Application of Metal Magnetic Memory Testing for Quantitative Evaluation of Stress Concentration in Ferromagnetic Steels

The objective of this research is to develop a quantitative algorithm between the magnetic parameter beta(m) and the stress concentration factor in ferromagnetic steels. Specimens of U71Mn steel were machined into smooth plates with artificial defects (circular holes and rectangular holes) to represent various stress concentration degrees. Variations of the magnetic parameter beta(m) with the stress concentration factor and the defect area were studied, respectively. The magnetic parameter beta(m) of the U71Mn steel specimen was compared with that of the X80 steel specimen. Quantitative correlations of the magnetic parameter beta(m) with the stress concentration factor and the defect area were investigated. The results show that the magnetic parameter pm is exponentially varied to the stress concentration factor and the defect area. The quantitative algorithm between the magnetic parameter beta(m) and the stress concentration factor is influenced by the defect shape and the material type. An equation was proposed to evaluate the defect area based on the magnetic parameter beta(m).