The monitoring of stress and microstructure by magnetoacoustic emission : Proceedings of the 16th European Working Group on Acoustic Emission Conference, London (United Kingdom), 13–18 Sep. 1987, pp. 3076–3082. Edited by C.B. Scruby and R. Hill, Proceedings of the 4th European Conference on Non-Destructive Testing, London (United Kingdom), 13–17 Sep. 1987, Vol. 4, Pergamon Press, 1988

Abstract

ABSTRACT Magnetoacoustic emission (MAE) is generated by localised magnetostrictive strains when domain walls move in ferromagnetic materials. MAE amplitude is a function of internal and applied stresses: however it is also dependent upon the microstructure so that these two effects must be separated for practical applications. Using the ratio of MAE at high and low fields, there is good sensitivity to stress in certain mild steel microstructures (e.g. ferritic/pearlitic) and much lower sensitivity to heat treatment. In rapidly cooled microstructures however, there is a much greater sensitivity to microstructure. In a separate study MAE has been used to monitor the subtle microstructural changes that accompany neutron irradiation of steels. It is concluded that MAE should be developed further as a nondestructive method for measuring stress and monitoring microstructure.