| The sprag clutch is widely used for its low manufacturing cost,high power density,and excellent durability and reliability.In practical applications,the inner and outer rotors are often used directly as the inner and outer rings of the sprag clutch,which together form the sprag clutch-rotor system.With the development of rotating machinery towards high speed,high power density and high reliability,the sprag clutch-rotor system shoulders the key responsibility of transmitting and cutting off torque at the high-speed drive end.The complexity of the working conditions urgently requires dynamic design of the sprag clutch,and special attention should be paid to the impact,deformation and non-linear contact during dynamic engaging,and the significant elastic deformation and vibration of the inner and outer rotors under high-speed operating conditions.Most of the existing design and analysis methods for the sprag clutch still based on static iterative calculation,lacking of theoretical support for dynamic design and evaluation of the overall vibration performance.In order to solve the above problems,this paper takes the sprag clutch-rotor system as the research object,and carries out the dynamic modeling for engaging process;the optimization design of macro and micro parameters of the system considering the profile modification;the research and experiment of the overall vibration characteristics of the system considering the rotor flexibility,and dimension reduction and analysis of nonlinear vibration models.Aiming at the dynamic engaging process,considering the contact,structural defor-mation and friction state of the contact surface of each component,a segmented engaging dynamic model of the sprag clutch-quasi rigid rotor system(SC-QRRS)is established.Based on this model,and taking the two types of compound profiles SC-QRRS of multiple arcs and logarithmic spirals as objects,their engaging dynamic model is established and compared with the ABAQUS model from two aspects of torsional stiffness and dynamic radial contact force.It is found that there is a jump phenomenon of torsional stiffiness at the tangent point of the arc.To further verify the model,under different combinations of preload torque and sinusoidal excitation torque,the engaging slip characteristics of the system are analyzed,and the results obtained are consistent with the conclusions of theexisting literature.Therefore,the dynamic model of engaging process established in this paper can reflect the dynamic engaging behavior under different friction states.In order to dynamically design SC-QRRS during the dynamic engaging process,a macro-micro parameter optimization design method considering the modification of sprag roller is proposed.A three-parameter logarithmic function is used to axially modify the sprag roller,and a Kriging approximate model of Hertz contact deformation is estab-lished,and then the engaging dynamic model of the system considering the modification is obtained;the calculation methods of constraint conditions such as the self-locking angle,the maximum total deformation limit,the circumferential stress and the anti-overturn limit are dis-cussed,at the same time,the minimization of the maximum contact stress in the engaging process is selected as the optimization goal,and the system optimization model is established.In order to improve the optimization speed,a Kriging approximation model of maximum radial force and maximum angle of rotation of the sprag roller are established,and the macro and micro parameters of the system are optimized using genetic algorithms.It is found that the maximum contact stress during dynamic engaging is greatly reduced.To study the overall vibration characteristics of a sprag clutch-flexible rotor system(SC-FRS)under high-speed operating conditions,based on the proposed calculation method of the stiffness clutch stiffness matrix,a SC-FRS finite element model considering rotor flexibility and support stiffness is established.Based on this model,from the twoaspects of natural frequency and modal vibration mode,the model calculation results and ANSYS calculation results are compared and verified.It is found that the introduction of the sprag clutch increased the system's new natural frequency in the torsional direction.At the same time,under the effect of unbalance,the system's bending-torsion coupling vibration and the dynamic load of inter-shaft bearing are analyzed,and it is found that the resonance peak in the torsional direction and the resonance peak in the bending direction have the same resonance frequency.Through the established rotor test,the model is tested and verified,and the results show that the SC-FRS finite element model can describe the vibration characteristics of the system more accurately.To consider the effect of bearing radial clearance on the vibration characteristics of SC-FRS,a dimension reduction model of nonlinear vibration of SC-FRS is established and the nonlinear characteristics is analyzed.Based on the fixed interface modal synthesis method,the inner and outer rotors are used as the substructures,respectively,and their dimensionality reduction models are derived;Through the connection of the inter-shaft bearing and the sprag clutch,the dimensionality reduction vibration equation of SC-FRS is obtained.Based on this model,by comparing the calculation results of the reduced dimensional models with different reserved main modes with the original model,the reserved main modes are selected.At the same time,the effects of radial clearances of different bearings on the system's amplitude-frequency response,as well as the effects of radial clearances of different bearings and unbalances on the dynamic load of the inter-shaft bearings are analyzed.The study found that the sensitivity of radial clearances of different bearings to the system's amplitude-frequency response is different,and amplitude jumps and frequency hysteresis phenomena appear at the resonance peak. |
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