A Study on the Strain Measurements of High Temperature Objects by Electronic-Speckle-Pattern Interferometry (ESPI)

Abstract

Electronic-speckle-pattern interferometry (ESPI) using a cw Ar-laser, a video system and an image processor was applied to the strain measurements at high temperatures. Applying ESPI, several problems which caused the reduction in visibility of interference fringes were encountered. The problem on the turbulence in the hot air surrounding high temperature objects was solved by using a vacuum chamber. The background radiations from the objects were suppressed considerably by an interference filter. The problem on the oxidation of the object surface couldn't be solved. The spacings of interference fringes were calculated by FFT to avoid human error. The fringes were observable and the strains could be measured up to 1200°C. The results measured in the vacuum chamber were nearly equal to the data which have already been published, up to about 1000°C.