Study On Rolling-type Vibration Isolation Mechanisms Based On Elastoplastic Contact

In order to effectively eliminate the interference of environmental vibration to precision equipments,multi-degree of freedom active vibration isolator is the main way to solve the above problem.One of the important components of multi-degree of freedom active vibration isolators is the horizontal passive vibration isolation mechanism,in which the horizontal vibration isolation mechanisms of rolling type are widely concerned by scholars at home and abroad because of its low cost and simple and compact structure.The problem of huge natural frequency error is common in the application of rolling type mechanisms in micro-amplitude vibration isolation,which is comparion the experimental results with the theoretical result based on rigid contact,and the analysis shows that machining and assembly error is not the main error source.Therefore,differentting from the previous modeling researches based on rigid contact and pure rolling motion hypothesis,with the help of solid contact mechanics and wheelrail/gear transmission system researches,in the actual situation of elastoplastic contact and rolling slide motion,we consider the particularity of microvibration,and re-analyse the system's natural frequency index.Firstly,a typical mechanism of placing the ball in two spherical nests is selected as the research object.When the load of the system is small,the fully elastic contact occurs between the ball and the ball nests.Considering the microscopic sliding and elastic deformation between the contact surfaces in the rolling process,the new motion differential equations are re-established by Lagrange equation,then the natural frequency of the system can be obtained under the conditon of micro-amplitude vibration.The analysis shows that the elastic potential energy storing between the contact surfaces increases the natural frequency of the system,which is sensitive to the sliding friction coefficient,but for the vast majority of metal materials,as the sliding friction coefficient is small,the model based on fully elastic contact only improves the accuracy comparing with the previous model,rather than the main reason to cause the huge natural frequency error.Secondly,when the load on the system becomes larger,the elastoplastic contact occurs between the ball and the ball nests.Considering the problem that the ball is easier to process than the ball nests,this paper studies the general situation that the ball does not produce plastic indentation,and the spherical nests produce plastic indentation.Theoretical analysis shows that the additional stiffness caused by plastic indentation in the spherical nests can be calculated independently.By means of elastic-plastic contact mechanics and nano-indentation technology researches,on the basis of known the stress distribution on the contact surfaces,using the principle of virtual work,we can solve the left and right sides of the restoring moment of the ball,then according to the relationship of torque and power and derivation stiffness expression,and further model based on the elastic-plastic contact is set up,and the natural frequency expressions can be obained.Simulation analysis and experimens show that plastic indentation usually is the major reason leading to enormous natural frequency error.Finally,the vibration isolation experimental platform is set up,and the ball and spherical nests with various parameters are designed and processed,and the correctness and validity of the theoretical analysis are verified by measuring the natural frequency index.The experimental results show that,in the region of fully elastic contact,the model error of Zhou is less than 60%,the model error based on fully elastic contact is less than 35%.In the region of elastoplastic contact,the model error of Zhou is more than hundreds of percent,the model error based on elastoplastic contact is controlled in the 25% range.