Research On The Effect Of Nonlinear Vibratory Stress Relief Parameters On Super Harmonic Resonance

Vibration stress relief(VSR)is a fast,effective and environment-friendly method to reduce the residual stress of workpiece,and it has a broad application prospect.At present,the VSR is mainly applied in the workpiece with low natural frequency.For the workpiece with higher natural frequency,it is impossible to produce enough dynamic stress by resonance of the workpiece with high stiffness,that because the excitation frequency produced by the existing ordinary vibrator can not approach the natural frequency of the workpiece,it is unable to achieve the purpose of reducing the residual stress.In order to solve this problem,a nonlinear super-resonance aging method is proposed,which uses the higher order of super-resonance vibration to achieve the natural frequency of the workpiece.But the essence of the VSR is to make the workpiece vibrate and produce enough dynamic stress to reduce the residual stress.However,the super-harmonic resonance is relatively complex,it is difficult to solve the problem that how to make the high-order vibration of the super-harmonic oscillation produce enough amplitude by modifying the parameters of the nonlinear VSR,so as to meet the demand of VSR.In this paper,the effect of parameters of the nonlinear vibratory stress relief on super harmonic resonance is further studied.Firstly,the mathematical model of the nonlinear super-resonant vibration aging system is established according to the nonlinear vibration aging method.And the relationship between the excitation amplitude and the super-harmonic resonance amplitude of the nonlinear model with strong nonlinear parameters can be obtained by analyzing the quantitative method of nonlinear vibration of the model.Because the main nonlinear component of nonlinear vibration relief system is nonlinear spring,and the parameters of nonlinear spring determine the nonlinear parameters of the whole system with a great extent.In order to further study the influence of nonlinear spring parameters on the nonlinear vibration aging system,ADAMS software was used to simulate the vibration,and the relationship between nonlinear spring and resonance amplitude of super-harmonic vibration is analyzed,and then the nonlinear super-harmonic vibration platform is built to carry out experiment with different characteristic equations and nonlinear springs.Finally,the nonlinear spring is designed based on the simulation analysis and analog experiment,and then a nonlinear super-harmonic vibration aging platform is set up.The effects of the parameters such as the magnitude of the exciting force and the support mode of the workpiece on the super-harmonic resonance are studied.The suitable vibratory stress relief parameters were selected for vibration treatment of high rigidity cylindrical workpiece.The following conclusions are drawn:(1)The nonlinear spring plays an important role in the nonlinear super-harmonic vibration system.The order of super-harmonic vibration is determined by the order of the nonlinear term in the characteristic equation.When the system is strong nonlinear vibration,the larger amplitude of resonance can be obtained by the smaller excitation amplitude.With the increase of the cubic nonlinear stiffness parameter,the resonance curve moves to the right and the resonance amplitude increases,which indicates that the nonlinear characteristics become more and more obvious.(2)Comparing the ADAMS vibration simulation results of the nonlinear super-harmonic shaking platform with the simulation test results,we can find that with the increase of the stiffness parameters of the quadratic term and the cubic term of the nonlinear spring,the resonance amplitude increases gradually,which indicates that the effect of the nonlinear super-harmonic vibration is getting stronger and stronger.The relationship between the nonlinear stiffness parameters and the resonance amplitude is same,which verifies the correctness of the simulation model.(3)Doing the sweep frequency to the nonlinear super-harmonic vibration platform before the vibration can we obtain the natural frequency of the vibrating table is 210Hz.When the excitation frequency is 70 Hz,the nonlinear super-resonant vibration platform can produce three times of the excitation frequency.It shows that the third-order super resonant vibration occurs on the nonlinear vibration platform,and the vibration platform can achieve the effect of amplifying the excitation frequency.(4)When the supporting mode of the workpiece is rigid support,the overall beating of the workpiece results in the loss of vibration energy.When the workpiece is supported by rubber pad,it can effectively centrate energy in the middle part of the workpiece and cause bending deformation.(5)The exciting force of the output of the exciter affects the frequency response of the workpiece for the super harmonic resonance.The larger the excitation force,the larger the resonance frequency of the workpiece's frequency response.When the dial angle of the exciter is 45 degrees,the effect of super harmonic resonance of the cylindrical workpiece is the best.(6)When the excitation frequencies of the non-linear super-harmonic vibration platform are 62.5HZ and 125HZ,which are respectively half of the first and second order of natural frequencies of the cylindrical workpiece of 125 Hz and 251 Hz.The acceleration amplitude curve of the cylindrical workpiece is basically the same as that of the first mode and the two mode shape curve.It shows that the second order super harmonic resonance occurred under the action of nonlinear super harmonic vibration platform of cylindrical workpiece.The nonlinear super harmonic vibration platform has achieved the super harmonic vibration aging treatment of the high rigidity workpiece.