Volume 36, Issue 3 (May 2008)
Sawblade Vibration Mode Shape Measurement Using ESPI
Electronic Speckle Pattern Interferometry (ESPI) is used to measure the vibration mode shapes of circular and bandsaws. A video camera views a vibrating sawblade that is illuminated by a laser light. The image within the camera is mixed with a reference light to create an interference pattern. The reference phase is stepped by 180 degrees using a piezoelectric actuator before measuring each successive image. Subtraction of the successive images gives a contour view of the vibration mode of the sawblade. The technique is noncontacting and displays vibration mode shapes in real-time. It has the advantage over the classical Chladni method because it avoids the need to spread a powder over the sawblade surface and because it can also identify low-frequency vibrations.