Measurement of Residual Stress in Polymers by Digital Image Correlation Method

In this paper, the combination of digital image correlation and hole drilling methods has been used to investigate and measure the residual stress of polymer components. The bending stress was created by a three-point bending system and measured by the provided equipment. These stresses are considered in theory to be equivalent to the residual stresses within the component. Digital image correlation method utilized as a novel method to measuring released strain. In this regard, Plexiglas polymer materials in various thicknesses were analyzed under the different values of 3-point bending test. Finally, the obtained results from the introduced method in this paper, with the results of Finite element analysis and simulation have been compared and validated. Unlike the samples that have an unknown amount of residual stresses, the residual stresses in these specimens have a certain amount that can be compared and verified with the simulation and analytical results. Polymer materials have a higher released strain range than metals and it is possible to investigate the strain released by digital image correlation. The results show that the combination of digital image correlation and hole drilling techniques as innovations presented in this paper are capable of measuring residual stresses with a high accuracy less than 10% and also because of their major advantages. The method of using strain gauge would be a suitable alternative to the hole drilling whit strain gauge method for measuring residual stress in polymer samples.