Materials degradation and altering influence on ultrasonic scattering by the light statistical approach in austenitic thermal loaded materials

Materials degradation is a complicated process including multiple phenomena. Degradation is most critical in the near surface areas. These areas contain many types of defects and material phase changes, which are also caused by the degradation of the material. The information received from those material properties are measured with special ultrasonic probe optimised for surface measurement and with a 0° longitudinal wave probe. With help of combining measured data from large area and calculating depths of interest in the sound path (RF‐signal) information can be gained to improve potential estimation of degradation levels. The technique is based on combination of three factors: using back scattered ultrasonic signals and induced leaky Rayleigh wave information (1), and simple statistical data analysis (2) in combination with optimised ultrasonic transducer (3). The back scattered ultrasonic signal is a measure of the amount of geometrical reflectors such as micro‐pores, inclusions, precipitations, segregations, micro‐cracks and cracks as well as of back‐scattering from phase boundaries during fatigue damaging and increase of degradation inside the material. The leaky Rayleigh wave component is sensitive to surface properties as known from normal Rayleigh wave probes. Especially cracks cause strong effect on leaky Rayleigh wave. If the crack is deep it cancels the leaky Rayleigh wave signal totally.