Research On Mechanism And Design Of Novel Vibratory Stress Relief Equipments With Strongly Nonlinear Resonance

The conventional methods adopted for relieving residual stress include natural aging,thermal annealing and vibratory stress relief(VSR).Comparing with natural aging and thermal annealing,this process of VSR has beneficial characteristics,such as no pollution,high efficiency,short treatment time,low cost and minimal energy consumption,which has been rapidly developed and widely used all over the world.It has been an intractable issue that achieving the resonance and dynamic stress so as to reduce the residual stress of higher stiffness components,as the highest vibrating frequency of traditional VSR is far lower than the natural frequency of the higher stiffness component.In order to solve the above problems,Professor Cai Ganwei first applied nonlinear vibrations to VSR and studied on mechanism and design theory of the VSR equipment with nonlinear resonance.On the basis,this study researched on the mechanism and design theory of the novel VSR equipment with strongly nonlinear resonance,which aimed to complete and promote the previous research achievements.The main contexts are as follows.Firstly,a Bernoulli-Euler beam with mass evenly distributed and uniform cross-section was taken as the object to establish a novel VSR equipment of the beam-nonlinear spring-motor system,combining the nonlinear spring and the eccentric motor.Based on the dynamic model and the generalized Hamilton principle,the dynamic equations of the novel VSR equipment were established.The strongly nonlinear characteristics of the dynamic equations were discussed.The establishments of the dynamic model and dynamic equations have built the theoretical foundation for further study.Secondly,a modified multi-scale method was presented by defining a new expansion parameter to analyze the vibration characteristics of the novel VSR equipment.According to the solvability conditions,characteristics of the main resonance,the ultraharmonic resonance and the subharmonic resonance were mainly studied.Moreover,the effects of system parameters,including stiffness coefficients,mass,locations,vibrating forces and vibrating frequencies,on the vibration characteristics of the novel VSR equipment were also considered with Newton-Raphson method.In addition,the reason of relieving residual stresses was analyzed through the relationship between stress and strain of components under VSR.The dynamic response and the effect of stress relief of ultraharmonic resonance of the novel VSR equipment was simulated by two examples based on ABAQUS.The distribution of residual stress showed obvious homogenization,the peak value decreased significantly,and the reduction rate could reach 54% by comparing residual stress before and after VSR.Finally,the novel VSR equipment was designed by selecting a conical spring.Ultraharmonic resonance of the designed VSR equipment was carried out,the ultraharmonic resonance characteristics were analyzed by experimental data under the action of the conical spring and non-conical spring,as well as the residual stress was detected by X-ray analyzer.By comparing residual stress before and after ultraharmonic resonance,the residual stress reduced up to 52%.Experimental results basically consistent with simulation results,which verified the rationality of the research on strongly nonlinear resonant VSR,and provided a new idea and a distinctive method for the traditional VSR.