Association Reconstruction of Inner Wall of Cylinder Head Based on Hybrid Thermal Field Pattern

The present study was envisaged to address the problem of poor reconstruction of associated images of the inner wall of cylinder head caused due to changes in the thermal field gradients. By introducing the idea of multiscale in this study, a method for the associated reconstruction of inner wall of the cylinder head based on hybrid thermal field pattern was proposed. Initially, the characteristics of the thermal field distribution in the inner wall of the cylinder head were analyzed. The inner wall of cylinder head was divided into 7 areas based on each nose bridge area, the surrounding areas of the nozzle and the cylinder head, and then subdivided according to the shape of the area. Subsequently, numerical simulation was performed on the thermal field using finite element software to calculate the variation range and gradient of the thermal field in each area, and the minimum interval of the thermal field and its thermal field resolution was determined according to the area. Further, the thermal field at some positions of the inner wall of cylinder head was measured by thermocouple thermometry. Thermal field pattern was constructed in this procedure based on the study of filling method of thermal field on different resolutions. Finally, the constructed thermal field pattern was correlated with the thermal radiant energy of outer wall of the cylinder head, and the inner wall image was reconstructed. The reconstruction results of the single-scale thermal field pattern were compared and analyzed. The experimental results show that the structural similarity of the reconstructed image obtained using hybrid thermal field pattern constructed based on the multiscale idea was 12.5–77.01% higher than that of the single-scale thermal field pattern with same correlation algorithm. The results indicated that the proposed method was more appropriate for discriminating the cracks and other defects caused by the thermal fatigue damage.