Research of Residual Stresses in Polymer Parts Using the Combined Bridge Curvature and Optical Scanning Method

The article presents the results of a study of the possibility of reliably determining residual stress-strain state in polymers and composites using a combination of bridge curvature, optical scanning and FEM (finite element method) methods. A three-factor experiment was conducted to determine the strength of printed PLA plastic products. The influence of residual stresses on the strength of printed products was assessed. When comparing the values of the same strength stresses, a relationship was revealed between the nature of the stresses and the strength of the samples. There was an obvious tendency for the negative effect of tensile stresses and, conversely, the strengthening effect of compressive stresses, so with the same values of the tensile strength of the tensile stress fracter, the residual stress value of 42.9 MPa is lower than when compressing fibers at a value of 88.9 MPa. The proposed new methods for determining residual stresses allow us to obtain a complete picture of the stress state of the material in the studied areas of products, which may be necessary when validating calculation models of residual stress-strain state, clarifying strength criteria and evaluating the quality of selected technological modes of manufacturing products.