抄録
A new extensometer has been developed that detects displacements of the marking positions on a specimen by real-time digital speckle correlation. It needs neither markings nor mechanical clips to be attached on the specimen and perfectly noncontacting to automatize tensile test. Two marking positions are illuminated by separate laser beams and imaged on separate CCD's. Each of the optical systems is installed in a separate movable probe head. For small amount of speckle displacement less than a few millimeters the optical head is fixed to output speckle displacement. A resolution of 1 μm has been attained by comparison with a laser linear encoder. Larger displacement was detected from displacement of the probe head that cancels the speckle displacement signal by feedback control of the head movement. We also conducted tensile test in a temperature chamber controlled in a range between -50℃ and 200℃ by placing the probe heads outside a window of the chamber.
