Time-varying dynamic characteristics analysis of machine tool structural components under residual stress dissipation

The gradual release of residual stress during the service of large machine tool structural components leads to the evolution of their natural frequencies, thereby affecting the overall dynamic performance of the machine tool. Based on elastic bending vibration theory, this study establishes a theoretical model for the natural frequency of structural components by considering two aspects: the variation in elastic modulus induced by residual stress and the additional internal force effect caused by residual stress. By coupling the evolution of elastic modulus with dynamic corrections, a natural frequency calculation method capable of characterizing the service state of structural components is proposed. Finite element simulation results demonstrate a high level of agreement with the theoretical model. The release of tensile residual stress increases the natural frequency, whereas the release of compressive residual stress leads to a decrease in natural frequency. When only the additional internal force induced by residual stress is considered, the influence trend is consistent with that of elastic modulus variation, but the effect magnitude is relatively small. Furthermore, a free-boundary experimental platform is constructed, and residual stress is obtained using the ultrasonic pulse-echo method, followed by natural frequency testing under different residual stress levels. The experimental results show good agreement with the theoretical predictions, verifying the reliability and accuracy of the proposed model. This study provides valuable theoretical and engineering references for maintaining the dynamic performance of machine tool structures and for residual stress regulation.