Analysis On Vibration Absorption System Of Structure With Pre-tightening Porous Silicone Rubber Cushion

Pre-tightening contacted cushion structures are usually applied in engineering components for some special application purposes. The engineering components are assemblied by applying pre-tightening force on cushion structures——gasket materials filled between outer shells(such as column shell) and components. And, the stability of cushions and components are dependent of the pre-tightening force and friction force applied on cushions by outer shells. Thus, the structures turn out into soft connected structures among several contacted deformation objects.The outer shells in the pratical case, being excited dynamically, could be treated a portion of dynamical response of whole structure system, their contact states vary from time to time between inner components and cushions or between outer shells and cushions. Pre-tightening contacted cushion structures are required frequently in compression while working in an ordinary working condition, specifically, the compressed level might be not lower some fixed levels. If contact force is lower than the fixed levels, the friction force on contact faces diminishes to some value as relative slip phenomena will be driven. What's more, inner components and cushions such as cushions and outer shells will separate so as to collide instantaneously when contact force diminishes to zero at some time. Structures are viewed to be failure when the above two conditions mentioned are satisfied for special engineering purposes. Failure of structures will bring much destractive effects on the stability and safety of inner and outer shells structures. These cases should be avoided in practivce. It is of remarkbly significance in engineering that the investigation is taken on the contact and separation among inner and outer shells and cushions, the mechanical mechanism of relative slip and the effects on the above two phenomena from mechanical parameters.Middle cushions, being the key component, are critical on the reliability of structures in the dynamical environment. The cushion material is a silicone rubber ascribed to the porous structure characters, macroscopicaly compressible in volume. The mechanical behaviors of cushion material are of geometry nonlinearity and material nonlinearity, and viscoelastic problems such as stress relaxtion, creep and environmental temperature effect in engineering application. Research work in the thesis are taken on the mechanical characters of cushion material in several chapters. Firstly, in light of the continuum mechanics and thermodynamics a bi-phasic porous medium model is established in consideration of physics structure characters of porous silicone rubber material. A strain energy density function of compressible porous rubber material is presented while as the strain energy density function may be separated into two parts of relative independence equivoluminal deformation and volume deformation, and in the latter the void ratio may be taken into account. The parameters are determined through fitting with the uniaxial compression tests of silicone rubber material. The influences of void ratio on volume deformation of porous silicone rubber are then discussed.Proceeding from the governing equations of static problem given in porous silicone rubber model, it is attained that an isotropic behavior of hyperelastic porous silicone rubber material, and a complete Lagrange format finite element analysis, the increment format of finite deformation and finite element formulation, and calculation module of stiffness matri is given out. In use of excellent opening interface and user defined subroutine in ABAQUS, the UMAT (user defined material subroutine) of silicone rubber are written with FORTRAN language. It is demonatrated that the analysis may be applied in practical design of silicone rubber materials.Viscoelastic behaviors of porous silicone rubber with high porosity at finite deformation are in the thesis dealed with. It proceeds from building up constitutive relations of relaxation function for viscoelastic property combined with constitutive relation developed for much void and nonlinear viscoelasticity of porous compressible silicone rubbers. The viscoelastic constitutive relation under finite deformation of porous compressible silicone rubbers are further developed. The finite element implemention of finite deformation viscoelasticity is investigated. A comparison of theoretical model is carried out with uniaxial compression relaxation experiments of the rubber. The effects of isochoric and volumetric deformation on stress relaxation are then discussed.Based on presented hyperelastic and finite deformation viscoelastic constitutive relations for high void ratio and porous compressible silicone rubbers, with use of the user defined material subroutine, the static and dynamic response of the structures are numerically analyzed for different practical cases and controling factors in the framework of finite element code ABAQUS. The points are placed on the influence of contact state and connection in relation with control factors. It is indicated that the results may be applied for engineering design.