Integral Operators: Remarks and Definitions

Abstract

Measurement of elastic anisotropy of materials is expected as method to evaluate, indirectly, various mechanical properties of materials. For the measurement of elastic anisotropy, ultrasonic velocity measurement is utilized, and laser ultrasonic technique is suitable for the measurement, because it is free from coupling medium of ultrasound and applicable for small region. In experiments, laser ultrasonic technique with pico-second pulse laser for ultrasonic short pulse generation, and two-wave mixing interferometer with photo-refractive crystal for high frequency ultrasonic detection on rough surface of specimen was used for precise measurement ofultrasonic anisotropy of steels with ultra-fine grain size(< lmicron) produced by various making processes. As results of the measurement, anisotropy of longitudinal waves were obtained, and those indicated microstructure of the steels shows strong elastic anisotropy, and difference of the microstructures made by the various processes shows remarkable difference in elastic anisotropy. For example, steels made with same elements, and made by same mechanical process (groove rolling) in different processing temperature, showed different grain size and different tensile strength, have evident relation between grain size and elastic anisotropy between rolling direction and traverse direction. In conclusion, it was induced that ultrasonic anisotropy measurement has capability for evaluation of mechanical properties such as tensile strength brought by microstructures of the steels.