喷丸强化对车辆传动齿轮裂纹扩展影响的研究综述

Fatigue fracture is one of the main failure modes of the transmission gear of heavy duty vehicles. The service life of the transmission system of vehicles will be shortened due to the expansion of fatigue cracks at the bottom of the teeth, and serious accidents will occur. The generation of residual compressive stress is the main method to delay crack propagation. Shot peening technology is a surface strengthening process of cold working. When the plastic strain is generated on the surface of parts, the residual compressive stress is introduced on the surface and inside, so as to improve the crack closure effect and achieve the strengthening effect of delaying crack propagation. In order to better reveal the influence of the residual compressive stress introduced by shot peening on fatigue crack propagation, the surface of the transmission gear is usually susceptible to a variety of alternating loads, such as external thermal loads and force loads. Compared with static loads, the non-uniformity of the internal structure of the material under alternating loads has a greater influence on the fatigue damage resistance of the material. Fatigue causes tooth breakage. Based on the strength factor, J-integral and crack closure effect, the theory of fatigue crack growth on the transmission gear surface and the relationship between compressive residual stress and fatigue crack growth rate were introduced. The introduction of compressive residual stress could reduce the crack growth rate, improve the fatigue resistance index of fatigue crack, and reduce the stress intensity factor at the crack tip. The new methods of particle shot peening, laser shot peening and ultrasonic shot peening, which were beneficial to the conversion of residual tensile stress to compressive stress, were summarized. The particle shot peening was to use a smaller diameter projectile to impact the surface of a part at high speed, which could not only introduce compressive residual stress on the surface of the part, but also achieve higher surface finish requirements. Laser shot peening adopted shock wave to carry out high-speed impact, so there would be no additional mechanical damage and surface phase change on the surface of parts. The surface depth after ultrasonic shot peening was much higher than that after traditional shot peening. However, due to its high price or small applicability, it has not been widely used in the surface strengthening of vehicle transmission gears. In the future development, it is necessary to design the shot peening technology with high efficiency, high adaptability, low cost and less energy consumption. At the same time, the relationship between the new shot peening method and the traditional mechanical shot peening technology was described. In addition, based on the numerical simulation and experimental results, the influence of the selection of five process parameters including shot peening speed, shot peening Angle, shot diameter, shot material and coverage rate on the improvement of residual compressive stress introduced on the transmission gear surface was emphatically reported. The compressive residual stress did not increase with the increase of incident velocity and projectile diameter, but tended to be stable when it exceeded a certain limit. Large residual compressive stress could be introduced when the projectile vertically incident impacted the surface of the transmission component. On the other hand, the residual compressive stress increased with the increase of the projectile diameter in the range of 0.2-3.4 mm. Steel shot had a better ability to improve the fatigue strength, ceramic shot after shot peening could achieve better surface smoothness, the final residual compressive stress increased with the increase of shot peening coverage, but the surface coverage was also saturated value. Finally, the future research direction of shot peening technology in transmission gear was prospected, and the technological innovation was further carried out in combination with the use requirements of heavy-duty vehicles, so as to promote the sustainable development of shot peening technology to delay crack propagation. The special simulation of shot peening technology mainly focuses on the selection of single shot peening process parameters of gear, while the analysis of combined parameters is less. However, in practical application, it is necessary to comprehensively consider the influence of coupling effects of various parameters on the gear. Therefore, in future numerical simulation, it is necessary to combine the optimal combination of process parameters to further study the surface integrity of the gear surface after shot peening, such as corrosion resistance, wear resistance and oxidation resistance.