Simulation Analysis and Experiment on Bending Deformation of Slender Piston Rod Influenced by Extreme High-speed Laser Material Deposition

Extreme high-speed laser material deposition (EHLA) has become a hot research issue in the surface treatment technology of shaft parts. Aiming at the deformation of slender piston rods during the extreme high-speed laser material deposition process, experimental study and numerical simulation of thermal-structure coupling were carried out. According to the Gaussian heat source and unidirectional coupling method, a thermal-structure coupling model by EHLA of slender piston rods was established to investigate the evolution process of the transient temperature field and stress distribution under different laser power and scanning speed. Firstly, the experimental test scheme of extreme high-speed laser material deposition on slender piston rod deformation was constructed, 9 groups of laser cladding parameters were proposed. And then, the experimental test results were compared with the finite element simulation. The results showed that with the same laser power, the molten pool morphology changed with the increase of scanning speed and the isotherm at the end of the molten pool presented a comet-like shape. The temperature curve on the surface of the piston rod reached three peaks, and then became stable after cooling to room temperature. The peak temperature increased with the increase of laser power. The equivalent stress value in the molten pool region was the largest and would evolve with the axial movement of the laser source. The equivalent stress at the interface between the coating and the substrate would go through several cycles of first rising and then falling in a very short time and then tend to be stable. The equivalent stress along the axial direction of the piston rod showed the trend of high at both ends, low in the middle and maximum at the top tip, and the equivalent stress values increased with the increase of laser power. The change law of the stress difference in 9 cladding conditions corresponded to the deformation of the piston rod, and the stress difference and deformation amount were the smallest when the power was 3 500 W and the scanning speed was 25 m/min. Therefore, the thermal stress is the main factor that causes the stress distribution along the axis of the piston rod, and the difference of the equivalent stress along the axis of the piston rod determines the deformation of the piston rod. With the elastic-plastic deformation about the slender piston rods, the observations are important and necessary during experimentation and the numerical simulations. According to the analysis of the results, it is found that the axial bending deformation of the slender piston rod is related to the magnitude of the axial stress difference. This analysis reveals that greater disparities in axial stress correspond to increased bending deformation. Most importantly, in situations characterized by external loading and continuous thermal stress coupling, the von-Mises stress pattern of slender piston rods displays a discontinuous behavior. Crucially, the pressure differential between the cladding layers on both flanks and the central region directly influences axial bending deformation of the slender piston rod. The conclusions can provide guidance for the selection of extreme high-speed laser material deposition process parameters for the surface treatment of slender shaft parts. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.