Acoustic Emission From Single-Plate Martensitic Transformation

Martensitic transformation occurs in a diffusionless manner at high velocity, with acoustic emission (AE) being generated during the process. The AE signal contains information about the dynamic process of martensitic transformation. In this analysis, a model is developed for the AE signal, or dynamic displacement, from the transformation strains and the growth process of martensitic transformation in an elastic half-space using Green’s functions. The AE signal amplitude is found to be inversely proportional to the distance between the martensite source and the sensor, and to the duration of transformation. It also depends on the orientation of the martensite plate. The spectral bandwidth increases as the duration of plate formation decreases. In addition, raising the carbon content increases the fraction of plate martensite, and consequently the signal amplitude.