FULL FIELD TENSILE STRAIN MEASUREMENT BY SHEAROGRAPHY

W. Steinchen, G. Kupfer, F. Vössing

Abstract

Digital shearography is a coherent optical method in conjunction with the digital image processing. It allows the shearogram, which depicts directly displacement derivatives, in real time to be observed and to be evaluated numerically. Strains are functions of the displacement derivatives. Thus, the shearogram contains the strain information, but usually it includes both the in-plane strain, e.g. &part;<i>u</i>/&part;<i>x</i>, and the out-of-plane component, e.g. &part;<i>w</i>/&part;<i>x</i>. In order to get the pure in-plane strain as well as the pure out-of-plane component, two linearly independent directions of illumination (usually the same but mutual and sequential illuminations) are introduced in the measuring device. The shearograms for each illuminating direction are evaluated by applying the phase shifting technique. The result by subtracting the phase maps of the two shearograms yields a new fringe pattern depicting the pure in-plane strain component and the result by adding the phase maps corresponds to the pure out-of-plane component. The theory and nondestructive tensile testing are demonstrated in this paper. Its applications for determining the strain distribution of the homogeneous and inhomogeneous material are presented.

Keywords

in-plane strain measurement, tensile test, phase shifting technique, digital shearography

Download

IMEKO-WC-2000-TC15-P431.pdf

DOI

-

IMEKO TC

TC15 - Experimental Mechanics

Back to the proceedings