Dynamic And Progressive Failure Analysis Of Composite Cylindrical Shells

Nuclear energy utilizationis gaining extensive attention as the strong demand of clean energy in 21 st century.During the whole industrial chain of nuclear power utilization the production of nuclear fuel is essential.Currently centrifugal separationis the mainstream way to enrich uranium isotopes,and the supercritical centrifugal technology is the leading edge and the most efficient.The main concern in centrifugal separation is to promote the separative workunit of every single machine.In mechanical and dynamic aspect there are two ways: using the high strength-density ratio materials to obtain high line speed and increasing the length of rotors.Nowadays CFRP materials are commonly utilized in centrifugal rotors.Under constant rotor materials and diameter the supercritical centrifugal technology is necessary to increase the rotor length.In this paper the study is based on the integral type rotor instead of the multi-segment type,namely the CFRP composite laminated cylindrical tubes.From acceleration to operational state of the composite rotor,there will be some critical frequencies;and it is necessary to obtain these frequencies to balance the rotor.Composite materials offer high strength-density ratio as well as obvious viscoelasticity;damping in rotors has an effect on passing critical frequencies and rotor instability,so it is also necessary to study on the material damping.When operating steadily the composite rotor is under large centrifugal forces;some small cracks may propagate by these forces and lead to explosives further,so the study on progressive failure analysis of the composite rotor is essential.In thisdissertation the first section is static analysis of the modal frequency and damping of the composite cylindrical tube.The governing equation of composite cylindrical tube is obtained using Timoshenko beam theory and Love's first order shell theory;by implementing the complex modulus method and modal strain energy method in beam and shell theories respectively;the modal frequency and damping is obtained using the wave propagation approach to taking every kind of boundary conditions into consideration.Based on above-mentioned studies the influence of aspect ratio,boundary conditions etc.on vibration and damping properties and comparison of beam and shell theories are discussed.The modal experiment of composite cylindrical shells is performed and the results of bend modes are in a good agreement with theoretical studies.The second section is rotordynamics analysis of the composite cylindrical tube including the damping properties.By inducing rotating differential operators in shell theory the frequency and damping results under simply supported boundary condition are obtained using the series method.The effect of aspect ratio and circumferential number on frequencies and damping are discussed.Theexperiment platform of supercritical integral type rotor is set up with a signal acquisition and analysis system.Dynamic properties of this platform are analyzed using the transfer matrix method within viscoelasticity and the theoretical results are compared with the speed up & down process.A good agreement is achieved and the influence of every kind of damping is discussed.The last section of this dissertation is on researches of progressive failure analysis of short composite cylindrical tubes with holes under radial loadings.The progressive failure analysis is coded using FE software ANSYS-APDL;failure capacity and damage path of composite cylindrical samples with different diameter holes are obtained.Based on a tensile machine the experimental facility is designed and manufactured to apply radial loadings.The FE results are compared with experiment and a good agreement is obtained.The influence of different diameter holes on failure capacity and the mechanism of damage path are discussed.