A REVIEW OF SPECIAL TECHNIQUES FOR MEASURING PLASTIC STRAIN

A review was made of strain measuring techniques other than transducer techniques, many of which are currently not widely known to engineers. The first section reviews surface strain and displacement techniques, grids, interferometry, hologram interferometry, moire fringes, photoelastic coatings and diffraction grating techniques. The second section reviews techniques for internal strain measurement, which include X-ray, microhardness, internal markers, dislocation etch pit and direct observation of dislocation techniques. In all cases accounts of the physical principles of the techniques are given and their applications and practical implications are discussed. Where possible the applications to strain distributions around notches and cracks have been presented as a common example for direct comparison. Finally, an attempt to compare the various techniques is made. (Author) NATO furnished. Presented at the Meeting of the Structures and Materials Panel (28th), Dayton, Ohio. Apr 69.