Modeling And Analysis Of Rigid Flexible Coupling Dynamics Of Multi-link Mechanical Press With Clearance

Forging process has the characteristics of high efficiency,high quality and low price,which plays an important role in industrial production.Compared with other types of presses,the multi-link mechanical press has a lower speed in the process of forging,which can effectively prevent cracks in the workpiece,and improve the quality and service life of the workpiece to the greatest extent.It is widely used in machinery,transportation,military industry,aerospace and other industries.In this paper,the multi-link mechanical press mechanism is taken as the research object,and the kinematics optimization,rigid body dynamics with clearance,rigid flexible coupling dynamics and rigid flexible coupling dynamics with clearance are studied systematically.The main research contents are as follows:Firstly,the kinematic optimization of multi-link mechanical press mechanism is carried out.The structural characteristics of the mechanism are described,the kinematic model of the mechanism is established by using complex vector method,and the kinematic expression of the mechanism is derived.Taking the maximum speed and the minimum fluctuation of the slider as the design objective,the optimization model of the mechanism is established,and the size of the press mechanism is optimized by using genetic algorithm.The center of mass coordinates and rotation angles of rigid members are selected as generalized coordinates,the constraint equations of the mechanism are listed,and the rigid body dynamics model of the mechanism is established by Lagrange multiplier method.MATLAB is used to solve the model to get the dynamic response of the mechanism.Adams is used to carry out virtual simulation analysis of the mechanism to verify the correctness of the rigid body kinematics and dynamics model.Secondly,the rigid body dynamics model and analysis of the multi-link mechanical press mechanism with rotating pair clearance are carried out.Based on the "contact separation" model,a rotating pair model with clearance is established.The normal contact force is solved by using the Lankarani-Nikravesh contact force model,and the normal friction force is determined according to the improved Coulomb law.The constraint equations of the mechanism with the clearance of the rotating pair are listed,and the rigid body dynamics model with clearance is established by the Lagrange multiplier method,which is solved by the Runge Kutta method.The influence of different clearance position,clearance value and driving speed on the dynamic response of the mechanism is analyzed.Through the phase diagram,Poincare map and bifurcation diagram,the nonlinear characteristics of the multi-link mechanical press with clearance are analyzed.Thirdly,the rigid flexible coupling dynamics model and analysis of multi-link mechanical press mechanism are carried out.The generalized coordinates of rigid members and flexible members are expressed by the method of centroid coordinates and absolute node coordinates respectively.The constraint equations of the mechanism is listed,the axial elastic force and the bending elastic force produced by the flexible member are considered,and the rigid flexible coupling dynamic model of the mechanism is established by the Lagrange multiplier method,which is solved by the Runge Kutta method.Using MATLAB to solve the rigid flexible coupling dynamic model,the displacement,velocity and acceleration curves of the slider of the multi-link press mechanism are obtained.Compared with the dynamic response of rigid body,the influence of flexible member,driving speed and Young's modulus on the dynamic response of rigid flexible coupling is analyzed.Finally,the rigid flexible coupling dynamics model and analysis of the multi-link mechanical press mechanism with the clearance of the rotating pair are carried out.The clearance model of rotating pair is established.The normal contact force is calculated by the L-N contact force model,and the tangential friction force is calculated by the improved Coulomb model.The generalized coordinates of rigid members and flexible members are expressed by the method of centroid coordinates and absolute node coordinates respectively.The constraint equation of the rigid flexible coupling mechanism with the clearance of the rotating pair is listed,the dynamic model of the rigid flexible coupling mechanism with the clearance of the rotating pair is established by the Lagrange multiplier method,which is solved by the Runge Kutta method.The effects of clearance value,driving speed and friction coefficient on the rigid flexible coupling dynamic response with multiple rotating pairs clearance are studied and analyzed.