| The stalk rubbing machine has good rubbing performance.It can rub the stalk into filaments like natural forage,which is conducive to the feeding of ruminant livestock.It is of great significance to promote the utilization of stalk as feed.However,there are problems of large vibration and noise during the operation of the rubbing machine,which cause harm to the physical and mental health of the operators and seriously affect the service life and reliability of the machine,and restrict the promotion and use of the stalk rubbing machine.Therefore,it is of great significance to study the vibration characteristics of the stalk rubbing machines and carry out the optimal design of vibration reduction.This study adopts the method of vibration test,theoretical analysis,modal test and modal simulation to explore the vibration characteristics and vibration generation mechanism of the rubbing machine;Based on these,the vibration reduction optimization design of the rubbing machine is carried out by using the foamed aluminum material and the damping ring vibration reduction method,and the vibration test of the optimized rubbing machine is carried out to obtain the influence of the vibration reduction optimization on the operation effect of the rubbing machine.The research contents and results are as follows:(1)In order to study the vibration characteristics of the stalk rubbing machine,a vibration test system is built,and the no-load and load vibration tests are carried out on the rubbing machine under different working parameters.The test results show that under different working parameters,the feeding inlet and the axial direction of the rubbing chamber vibrate more severely than other test points(the radial direction of the rubbing chamber,the vertical direction of the rubbing chamber and the frame of the feeding chain motor).The regression analysis is carried out on the time domain data of the no-load vibration signal,and it is concluded that the order of the impact on the vibration of the stalk rubbing machine is the spindle speed > the speed of the feeding chain;The regression analysis is carried out on the time domain data of the load vibration signal,and it is concluded that the order of machine vibration influence is single feeding stalk weight >spindle speed > feeding chain speed.The frequency domain analysis of no-load and load vibration signals shows that the corresponding frequency of the peak power spectral density function of each test point is the frequency doubling of the spindle speed frequency,indicating that the spindle speed contributes greatly to the vibration of the rubbing machine.Based on these,the no-load vibration test of the spindle rotor of the rubbing machine is carried out.Through the coherence analysis,it is concluded that the vibration of the feed inlet and feed chain motor frame is mainly caused by the axial vibration of the spindle,and the vibration of the spindle in the radial and vertical directions has little contribution to the vibration of the feed inlet and feed chain motor frame.Decomposition and reconstruction of the vibration signal of each test point under the no-load condition of the whole stalk rubbing machine and the spindle rotor are carried out.The decomposed signals show that the fundamental wave of the vibration signals are composed of sinusoidal signals;The reconstructed signals show obvious sinusoidal waveforms,which are superimposed by sinusoidal wavelets.(2)By analyzing the vibration characteristics of the stalk rubbing machine,mathematical models of the axial and vertical vibration of the stalk rubbing machine are established,and it is obtained that the vibration of the stalk rubbing machine is mainly affected by the eccentricity,speed and damping of the spindle rotor.When the eccentricity and rotational speed are constant,increasing the damping of the machine can reduce the vibration amplitude.The mathematical model of the spindle rotor vibration is established,and it is obtained that the damping has an obvious effect on the vibration suppression of the spindle rotor.Based on these,the mechanical model of the spindle rotor-damping ring system is established.And combined with the vibration reduction principle,the system is analyzed,and it is concluded that the larger the damping ratio after the rotor is assembled with the damping ring,the more stable the vibration reduction performance of the main spindle rotor-damping ring system.(3)Based on the multi-point excitation and multi-point response(MIMO)method,the modal tests of the whole rubbing machine and the main spindle rotor are carried out,and the natural frequencies of the whole stalk rubbing machine and the main spindle rotor are obtained.Using the MAC matrix modal confidence criterion,the correlation analysis of the two modes is carried out respectively,and it is determined that the modal parameters identified by the modal test have high reliability.The finite element model of the spindle rotor is established and the modal simulation is carried out.The free mode of the spindle rotor is basically consistent with the modal test results,which shows that the reliability of the model is good.At the same time,the vibration modes of each order of the model are analyzed,and it is found that the throwing blade,support plate and hob of the spindle rotor of the rubbing machine have a large deformation.By analyzing the Campbell diagram,the relationship between the working mode and the speed of the spindle rotor is studied,and it is obtained that the spindle rotor will not resonate when the speed is 1200 ～ 1800 r/min.(4)Based on the comprehensive analysis of the actual working conditions of stalk rubbing machine and the relevant research results of vibration reduction at home and abroad,taking into account the damping effect of aluminum foam and damping ring,a damping method for stalk rubbing machine based on aluminum foam material and damping ring is proposed,and the vibration reduction design of spindle rotor is optimized.Combined with the attenuation vibration theory,the steel ball impact vibration test is used to simulate the stalk colliding with the spindle rotor.The vibration laws of the spindle rotor before and after the vibration reduction optimization are analyzed and compared.The results show that the damping of the spindle rotor increases significantly,the vibration decreases and the vibration attenuation accelerates after the vibration reduction optimization.(5)The no-load and load vibration tests are carried out on the rubbing machine after vibration reduction optimization,and the vibration characteristics of each test point of stalk rubbing machine before and after vibration reduction optimization are analyzed and compared.The test results show that the vibration of stalk rubbing machine is improved after vibration reduction optimization.The results show that the pure working hour productivity and kilowatt hour output of the optimized stalk rubbing machine are increased by 0.56% and 10.88%,respectively.This study provides ideas and methods for the vibration characteristics study and vibration reduction optimization design of fixed rotary forage processing machinery,and is of great significance to promote the utilization of straw feed and the development of stalk rubbing machine. |
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