EXTENSOMETER FOR MEASURING AXIAL STRAIN AND TORSIONAL DEFLECTION ON A TEST SPECIMEN

摘要

An extensometer capable of simultaneous measurement of axial strain and torsional deflection of a specimen subjected to axial or torsional load. A pair of gauge members define reference plane surfaces, one extending parallel and another extending perpendicular to the test axis. For each reference plane surface there is a follower capable of sensing only the component of relative displacement that lies in the direction normal to the reference plane surface. The sensed values of these followers represent relative axial and torsional displacement of the gauge members. The followers of the embodiment comprise cantilevers extending from ends fixed on one gauge member to ends biased against and freely riding upon the respective reference plane surfaces on the other gauge member. A calibration stand is also shown, comprising a two-part dummy specimen, the parts aligned to define a test axis. One dummy part, which is mounted for rotation on the axis and fixed against axial displacement along the axis, has a torque arm which a micrometer displaces to rotate the dummy part for calibration of the torsional sensing system of the extensometer. The second dummy part, which is fixed against rotation about the axis, is moved along the axis by a second micrometer for calibration of the axial strain sensing system of the extensometer. The parallelogram linkage of the embodiment employs resilient flexures. Clamps join the two gauge members when not in use.