Study On Dynamic Modeling And Vibration Characteristics Of Composite Thin-Walled Shaft

The composite thin-walled shaft has an extensive application prospect in the mechanical systems,therefore eatablishment of dynamic analysis model to study vibration characteristics of the composite thin-walled shaft can provide a theoretic foundation and technique support for its structural design and performance optimization.The establishment of advanced model is an important basis for the dynamic analysis and design of composite thin-wall shaft,and the high efficiency numerical analysis method is an effective guarantee to improve the dynamic analysis and design efficiency of thin-walled shaft.The generalized differential quadrature method is a numerical solution technique for initial and/or boundary problems.The GDQM does not rely on functional and variational principles.It has the advantages of simple mathematical principle,fast convergence speed,high calculation accuracy,small calculation amount and less memory demand,etc.So the high-precision numerical solution of the differential equation can be obtained with less grid points and less calculation amount.In this dissertation,five kinds of dynamic models of composite thin-walled shafts were established according to the typical application situation.The vibration characteristics of composite thin-walled shafts were studied by using the GDQM.The main achievements derived in this dissertation are listed as follows:The dynamic model of the cylindrical composite thin-walled shaft is established based on the dynamic modal of the rotating composite shaft with constant angular speed considering shear coefficient.The structural model of the composite thin-walled shaft considers warping effects on the cross section which caused by torsion,tension,shear and bending.The free vibration equations of the shaft are derived and the GDQM is used to discretize the equations of the shaft and the numerical calculation program is written using MATLAB.The effects of rotating speed,fiber orientation,ratios of length to radius,ratios of radius to thickness and three boundary conditions(clamped,simply supported,cantilever)on natural frequencies and critical speeds are studied.The results show that the GDQM can effectively solve the coupled kinematics equation of flexural-transverse shear of the rotating shaft,and it is easy to deal with the boundary conditions,and the calculation precision is satisfactory.The dynamic model of composite thin-walled shaft-disk system including disk and bearings is established based on the cylindrical composite thin-walled rotating shaft and the dynamic equations of the shaft are derived.The GDQM is used to discretize the equations of the system and the numerical calculation program is written.The effects of rotating speed,fiber orientation,ratios of length to radius and ratios of radius to thickness on natural frequencies and critical speeds are studied.Aiming at the vibration and stability of the tapered composite thin-walled shaft,the dynamic model of the tapered composite thin-walled shaft is established and the free vibration equations are derived.The GDQM is used to discretize the equations of the shaft and the numerical calculation program is written.The natural frequencies and critical speeds of the tapered composite thin-walled shaft with clamped,simply supported,cantilever are analyzed.The effects of taper,fiber orientation,rotating speed,ratios of length to radius,ratios of radius to thickness on natural frequencies and critical speeds are studied.A dynamic model is proposed of the tapered composite thin-walled rotating shaft embedded with SMA wires in order to realize the active control of the shaft.The axial force generated by SMA wires is introduced into the vibration equations of the tapered composite thin-walled shaft model,and equations are discretized and solved by using the GDQM,then the vibration frequencies are obtained.The effects of SMA wires on the dynamic characteristics of tapered composite thin-wall shaft were studied compared with without SMA wires.Based on Timoshenko beam theory and Hamilton's principle,the dynamic model of the composite thin-walled shaft with curvilinear fibers is established.The governing equations for the free vibration of the shaft are derived.The natural frequencies of the shaft are then obtained by solving the governing equations by using the GDQM and the numerical calculation program is written.The effects of fiber paving paths,stacking sequence,ratios of length to radius,ratios of radius to thickness on natural frequencies of the shaft with different boundary conditions are investigated through numerical examples.In this dissertation,the calculated results based on the composite thin-wall shaft dynamic models and the vibration analysis method using the GDQM are in good agreement with those obtained by using ANSYS analysis and in related literatures.Experimental study on vibration characteristics of the cylindrical composite thin-walled shaft was carried out,which proves the correctness and feasibility of the dynamic models and the analysis method.Therefore the research has theoretical significance and practical value.