Research on the evolution law and control mechanism of residual stress under vibration stress relief

Vibration stress relief (VSR) can effectively eliminate residual stress and stabilize the dimensional accuracy of components. However, most of the mechanism of VSR studies focus on the macroscale, and the research from the microscale or mesoscale is not yet clear. In this paper, the influence of process parameters on the VSR effect was systematically investigated through experiments. VSR experiments have found that the peak acceleration has no direct impact on the VSR effect, usually through changing the frequency or amplitude has an indirect effect on the residual stress relief. On this basis, a single-crystal mechanical model composed of multiple unit cells was established through the spatial lattice structure of iron crystals. The mechanical behavior of steel materials under tensile, compressive, and cyclic vibration was simulated and the relationship between stress, strain, dislocation structure, and energy during the process was explored. Besides, the mechanical principle and micro-essential model of residual stress relaxation were established, and the intrinsic driving stress of VSR to relieve the residual stress was revealed. The results of microscopic simulation and mechanism analysis show that dislocation multiplication is the main reason for the mutation of stress, and the energy of atoms decreases obviously when dislocation slides or pile-up starts. VSR is realized by the continuous release of internal elastic strain energy through microplastic deformation caused by changes in dislocations within some grains. Under the action of vibration cycle stress, the residual stress showed a decreasing trend at the beginning, and then the peak value of the stress tended to a stable value, and the minimum value of the stress was close to zero. With the increase of the excitation stress, the yield of the iron material becomes more obvious, and dislocation slip is more likely to occur. The results reveal the law and mechanism of residual stress relief and homogenization and provide theoretical references for the application of VSR.