Detection of Sub-Cracks in Polymeric Materials using Digital Shearography Method with Thermal loading and Determination of Optimal parameters

Digital Shearography or Laser interferometry is a novel non-destructive evaluating method based on laser light which has been used and developed to directly measure the surface displacement gradients in a non-contact and full-field way. This method is equivalent to a full-area strain gauge that allows you to observe the strain distribution over a large area. Shearography is used for non-destructive inspection of various materials. In this paper, the application of Digital Shearography method in detection of subsurface cracks in lightweight polyethylene samples that are kind of polymer materials is investigated. Shearing amount, shear direction and loading are the most three effective parameters in evaluating defects by this method. In order to this purpose, after introducing and creating the setup of the mentioned method, the effect of the main parameters including the size and direction of shearing and the amount of loading for different cracks in polymer samples was investigated. The results show that the quality of fringe patterns is much higher when the shearing amount is half the crack length and perpendicular to the crack direction. Also, the loading range is different for each crack and the optimal amount must be obtained for each material.

Keywords:

non-destructive testing , digital shearography , laser interferometry , crack , polymeric material