Method of and apparatus for measuring elongation of a test specimen

Abstract

Method and apparatus for measuring elongation in a contactless manner capable of obtaining accurate measured value without attaching reference lines and capable of being automated, laser beams are irradiated from two sensor sections each has a laser projector and a CCD camera to prescribed reference line positions at two positions on a test specimen, laser reflection lights are photographed respectively as speckle patterns with a plurality of fringes respectively by the CCD cameras, the fringes at predetermined positions the speckle patterns are recognized on the coordinate of the CCD camera screens as targets correspondingly to the prescribed reference line positions at two positions respectively, and the moving amount on the pixel unit basis on the coordinate of the target fringes that move in accordance with the elongation of the test specimen are detected respectively to determine the elongation information of the test specimen, the fringes of the speckle patterns photographed by the CCD cameras may be image converted into the marks at the predetermined positions of the television camera screens. Stopping or disturbance of image of the speckle patterns of the CCD camera appearing just before the fracture of the test specimen may be sensed to stop the application of the tensile load on the test specimen.