Research on deformation and temperature characteristics of micro negative Poisson's ratio anchor rod

Abstract

This study aims to investigate the global deformation, temperature characteristics, and their correlation during the quasi-static tensile process of micro-NPR anchor rods. The LEW-500 static tensile testing system was used to carry out the uniaxial tensile testing with three deformation rates, and the deformation and temperature of the anchor rods were studied through the DIC system and IRT system. The mechanical results indicate that the micro-NPR anchor rods have the characteristics of high elongation, high constant resistance, no yielding platform, and no obvious necking. The DIC results show that the deformation of anchor rods can be divided into the initial and accelerated differentiation stages. In the initial differentiation stage, the statistical dispersion of deformation is low and increases slowly with time. In the accelerated differentiation stage, a relatively concentrated local deformation appears, shown by the sharp rise and decline of statistical dispersion. The IRT results indicate that the surface temperature of the anchor rods also increases with deformation, and the upward trend exhibits distinct characteristics in two differentiation stages. The faster the deformation rate, the higher the temperature of the anchor rods’ surface. The correlation coefficient of axial strain and temperature difference in the anchor rods is calculated, and the correlation coefficient is maintained at a high level in the accelerated differentiation stage. The linear fitting of the standard deviation of axial strain and the temperature difference is perfect. This study provides a foundation and a new idea for future deformation patterns and monitoring analysis in on-site applications of micro-NPR anchor rods through the joint analysis of two non-contact measurement methods.