Method and means for determining fatigue damage and surface stress

摘要: The test specimen is mounted on a movable table, ultrasonic surface waves are caused to travel across the by transducer fed from CW signal source, laser beam passed through splitter, one portion being reflected onto photo-detector measuring amplitude, an output compared with of and shifted in phase 90 DEG , these outputs measure difference, at points along specimen; second mirror attached table back screen where interference pattern formed as moved, photo detectors sense changes determine displacement.