Research on Magnetoinductive NDE Techniques to Measure Tensile Strength and Fracture Toughness in Steels as They are Manufactured

摘要

The project investigated the interrelationship between mechanical properties and magnetic properties by developing an understanding of how microstructure interconnects the two properties, and tested whether nonlinear harmonics of the magnetic induction could be used to nondestructively determine tensile strength and fracture toughness. The project has been the first to show the following: (1) via magnetic hysteresis modeling, how inverse grain size and dislocation density affect the parameters controlling magnetic hysteresis; (2) that with coils wrapped around the specimen, harmonic amplitudes decrease with increasing dislocation density and inverse grain size, and hence with increasing tensile strength; (3) distinguish important differences in microstructural dependences of magnetic properties between hysteresis loops of the same maximum field intensity H(sub max) and hysteresis loops of the same maximum magnetic induction B(sub max); and (4) the first to investigate whether or not correlative relationships exist between NLH and fracture toughness. In technology transfer, a pilot program was set up under a separate program to test the use of NLH to nondestructively monitor tensile strength in moving steel sheets in a German steel plant. The report includes a list of papers published in peer-reviewed journals; papers presented at meetings, but not published; manuscripts submitted, but not published; and technical reports submitted to ARO. The appendix contains the paper 'Modeling Microstructural Effects on Hysteresis Loops with the Same Magnetic Flux Density.' (2 tables, 2 figures).