Ultrasonic Defect Localization Correction Method under the Influence of Non-Uniform Temperature Field

In ultrasonic non-destructive testing of high-temperature industrial equipment, sound velocity drift induced by non-uniform temperature fields can severely compromise defect localization accuracy. Conventional approaches that rely on room-temperature sound velocities introduce systematic errors, potentially leading to misjudgment of safety-critical components. Two primary challenges hinder current methods: first, it is difficult to monitor real-time changes in sound velocity distribution within a thermal gradient; second, traditional uniform-temperature correction models fail to capture the nonlinear dependence of material properties on temperature and their effect on ultrasonic velocity fields. Here, we propose a defect localization correction method based on multiphysics coupling. A two-dimensional coupled heat transfer–wave propagation model is established in COMSOL, and a one-dimensional steady-state heat transfer condition is used to design a numerical pulse–echo experiment in 1020 steel. Temperature-dependent material properties are incorporated, and the intrinsic relationship between sound velocity and temperature is derived, confirming consistency with classical theories. To account for gradient temperature fields, a micro-element integration algorithm discretizes the propagation path into segments, each associated with a locally computed temperature from the steady-state heat conduction solution. Defect positions are dynamically corrected through cumulative displacement along the propagation path. By integrating heat conduction and elastic wave propagation in a multiphysics framework, this method overcomes the limitations of uniform-temperature assumptions. The micro-element integration approach enables dynamic tracking of spatially varying sound velocities, offering a robust strategy to enhance ultrasonic testing accuracy in high-temperature industrial environments.