Evaluation of Residual Stress in Modified and Pure HDPE Materials Based on Thermal Diffusivity and Terahertz Phase Spectroscopy

Residual stress significantly affects the mechanical properties, physical properties, and durability of materials. It is meaningful to evaluate the residual stress using non-destructive methods. However, existing techniques are expensive and have low accuracy and narrow applicability. In this paper, both infrared and terahertz techniques were used to quantitatively evaluate the residual stress of high-density polyethylene (HDPE) under tensile loading. For the terahertz technique, a new theory based on stress-optics law and Poisson’s effect is proposed. For the infrared technique, line-scan thermographic (LST) was used to extract the thermal diffusivity of HDPE. The residual stress caused by plastic deformation is quantitatively related to thermal diffusivity. Conclusively, THz-TDS shows an obvious improvement in residual stress detectability.