Ultrasonic Velocity Ratio: An Effective Tool for In-Situ Materials Characterization

Ultrasonic velocity measurements have been widely used for characterization of microstructure, texture and damage in materials. Based on ultrasonic velocity measurements in a wide range of alloy systems and data collected from literature, a new polynomial correlation between velocity ratio and ultrasonic velocity is established for isotropic solid materials. For specific materials/alloy systems, a linear increase in velocity ratio with increasing ultrasonic shear wave velocity is observed in a wide range of materials. An opposite behaviour to this is observed only for the effect of microcracks/porosity or pressure/stress on ultrasonic wave velocities. The change in velocity ratio associated with change in ultrasonic velocity is observed in all the cases. Further, as the velocity ratio does not require thickness to be measured physically, it has better potential for in-situ materials characterization applications than ultrasonic velocity. A few applications of velocity ratio for assessment of service induced degradation in materials are also discussed in the paper.