Simultaneous measurement of three-dimensional surface temperature and strain based on speckle embedded phosphor coating

Abstract The strong coupling between temperature and strain within complex thermo-mechanical fields poses a significant measurement challenge, as existing methods lack the capability for their simultaneous, precise, and full-field 3D characterization. To address this gap, this study introduces an integrated method that combines lifetime-based phosphor thermometry (PT) with stereo-digital image correlation (DIC) in a dual-camera system. First, a phosphorescent coating with embedded speckle patterns was developed, and a phosphor-coating joint index was proposed to quantify its thermomechanical measurement accuracy. Second, a dual-camera system was developed to simultaneously measure 3D temperature and strain, utilizing phosphorescence decay under pulsed excitation for lifetime-based PT and stereo-DIC for 3D deformation analysis. Third, an intensity-temperature-view angle coupling correction method was developed to correct the grayscale distortion caused by local temperature gradients and large view angle acquisition, improving the accuracy of image matching. Subsequently, the thermal expansions of aluminium alloy samples were characterized, and the maximum deviation of measured strain compared with the reference data is within 0.322 mm m −1 from room temperature to 410 °C, proving that the developed method has good simultaneous detection capability in temperature and strain fields. Finally, the method was validated in a non-uniformly heated cylinder, demonstrating its capability for 3D temperature-deformation mapping under complex thermal conditions. This work provides a new approach for high-precision simultaneous 3D temperature–strain measurement and supports further investigation into thermo-mechanical multiphysics coupling mechanisms.