Research On Wear Process Modeling And Life Prediction For Revolute Joint With Clearance

In the steering system used by military equipment such as submarines and ships to control the course,due to the influence of reciprocating impact,seawater corrosion and other factors,the wear and failure process of the revolute joints will be significantly accelerated.Once the failure of a revolute joint occurs,the steering accuracy will be reduced,the operating noise will be increased,and the stealth performance of equipment will be lowered.Even worse,a severe accident may take place during sailing.Also,it is difficult to maintain or replace the revolute joint after sailing.Only preventive maintenance can be carried out before the voyage to eliminate potential dangers.However,there is currently a lack of relevant research on the wear process modeling and life prediction methods of revolute joints in those mentioned equipment.Therefore,to ensure the safe and reliable operation of submarines,ships and other equipment after sailing,it is urgent to clarify the wear and failure rules of revolute joints and carry out wear life prediction,providing key technical support for structural optimization and preventive maintenance of revolute joints.This paper starts from the practical engineering requirements of equipment preventive maintenance and reliability assessment,takes the revolute joint structure as the research object,conducts in-depth research in the aspects of wear failure mechanism analysis,wear process simulation and wear life prediction,etc.,and provides theoretical methods and technical support for preventive maintenance and reliability evaluation of revolute joint structures.The research content includes:1.Mathematical models of planar and spatial revolute pair with clearance were developed based on three-state model,and then the characteristics and application scope of different contact force models were analyzed.After that,modeling method for multi-rigid-body system dynamics under the condition of ideal constraints and the wear analysis method based on finite element were introduced.Finally,a wear simulation analysis for a typical journal-bearing structure was carried out.The influence of journal rotation speed,journal radius and load on the wear distribution on the bearing inner surface was studied.2.Based on surface discretizing method and L-N(Lankarani-Nikravesh)contact force model,the wear prediction models of planar crank slider and planar four-bar mechanisms with revolute clearance joint were established.The influences of five key parameters,including the number of discrete points on the bearing inner surface,Baumgarte stability coefficient,crank speed,external load and clearance size,were analyzed.A wear prediction model of planar revolute clearance joint considering time-varying friction coefficient and wear rate was proposed.On the basis of the models,the numerical simulations of planar crank slider and planar four-bar mechanisms with clearance were carried out using "Cycle-update" contour updating strategy.3.Considering the radial and axial clearance,a geometrical model of a revolute joint with spatial clearance was established based on surface discretizing method.An improved L-N contact force model considering time-varying contact stiffness was proposed.The differential form of Archard wear model was applied to calculate wear depth.A wear process modeling framework of revolute joint with spatial clearance was put forward by integrating dynamic analysis and wear process.The test platform of four-bar mechanism with spatial revolute clearance joint was built and the wear test scheme was designed.The ADAMS dynamics model of the revolute joint with spatial clearance was established,and the 3D finite element wear model based on ABAQUS/Standard environment was established by using the axis trajectory,which verified the correctness of the numerical simulation results.In order to verify the results of numerical simulation and finite element simulation,wear experiments of revolute joint with spatial clearance were carried out based on DIC(Digital Image Correlation)method.Motion characteristics and surface profile of bearing with diameters of 15.6mm and 16.0mm were measured before and after wear.The experimental results prove that the distribution of wear on the inner surface of the bearing is irregular in both axial and radial directions,which verifies the accuracy of the simulation results.The measured motion data also indicates that the wear has a negative effect on the dynamic performance of the system.4.To solve the problem of the difficulty of observing the wear state and the long acquisition period of wear process data,a staged wear life prediction method of a revolute joint based on LSTM network was proposed.The vibration signal was used as input and combined with simulated wear data to predict the remaining life of the revolute joint,and finally the validity of the method was verified on a four-bar test platform.5.On the basis of the foregoing research,this thesis starts from the actual engineering needs of wear life prediction for the revolute joint structure in a certain type of electric steering system,established a dynamic model of the electric steering system,and analyzed the effect of the wear degradation process on the system dynamics response based on ADAMS software.Finally,the wear life prediction method of revolute joint based on LSTM(Long-Short Term Memory)network proposed in this paper was used to carry out the application verification in the electric steering system.The results show that the method proposed in this paper has a good prediction effect in the wear life prediction of the revolute joint in the electric steering system.In summary,funded by the "13th Five-Year Plan" equipment pre-research project,this paper establishes a planar and spatial revolute joint wear model with clearance,and proposes a planar revolute wear model that takes into account time-varying parameters.An improved L-N contact force model considering time-varying contact stiffness is proposed,and a wear prediction model of a revolute joint with spatial clearance is established based on the contact force model.A staged wear life prediction method of a revolute joint based on LSTM network is proposed.The research results can provide theoretical and technical support for preventive maintenance and reliability evaluation of revolute joint structure in steering system of military equipment,and can also be extended to wear process modeling and life prediction of revolute joint structure in other mechanical systems.