Out-of-plane and in-plane strain measured by shearography

Wolfgang Steinchen; M. Schuth; Lian Xiang Yang; Gerhard Kupfer

doi:10.1117/12.221107

21 September 1995 Out-of-plane and in-plane strain measured by shearography

Wolfgang Steinchen, M. Schuth, Lian Xiang Yang, Gerhard Kupfer

Proceedings Volume 2509, Smart Structures: Optical Instrumentation and Sensing Systems; (1995) https://doi.org/10.1117/12.221107
Event: European Symposium on Optics for Environmental and Public Safety, 1995, Munich, Germany

Abstract

The shearographic interferometry is employed as a nondestructive full field, optical testing and measuring method without contact. Fringes of contant strain (so called isotase, tasis (Greek) equals strain) can be observed in real-time on the surface of the investigated machine parts and structures of any material and are represented by the shearogram. Using shearography two states of deformation are recorded by doubly exposing a Holotest film in an ordinary camera or stored by an electronic image processing system. In the objective of the camera a shearing element is integrated or the lateral Michelson shearing interferometer is used. Rigid body motions of the object are not recorded. Local deformation irregulatrites caused by a defect under or on the surface of the specimen create strain concentrations; the homogeneous surrounding is poorly superimposed by an interference pattern. The shearogram shows dark and bright fringes which are the functions of the displaceemnt derivative. The holographic interferometry measures the out of plane deformations directly. Terms of the out-of-plane strain can be determined by the shearographic method as well as the in-plane strain fringes which are described in this paper.

Citation Download Citation

Wolfgang Steinchen, M. Schuth, Lian Xiang Yang, and Gerhard Kupfer "Out-of-plane and in-plane strain measured by shearography", Proc. SPIE 2509, Smart Structures: Optical Instrumentation and Sensing Systems, (21 September 1995); https://doi.org/10.1117/12.221107

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