| Viscoelastic damping technology is a new passive seismic control technology in recent years.According to the actual needs in the engineering,a variety kinds of dampers have been developed,such as plate-type viscoelastic damper,cylinder-tube viscoelastic damper,wall-type viscoelastic damper and viscoelastic damping walls,etc.It has been greatly concerned because of its advangtages as high energy dissipation capacity,good working stablity,simple in fabrication,low in cost,and having wide application ranges.However,the development of viscoelastic damper involves many fields,such as mechanics,seismic vibration control,polymer materials science,fracture mechanics and etc.,which makes the research of viscoelastic damping and equipment development more difficult.At present,the commonly used plate viscoelastic dampers are mainly vulcanized and bonded under high temperature and high pressure or by using epoxy resin at room temperature.But due to the limited bonding strength of the adhesive,the interface damage happens easily in the production process,which leads to the crack occurance on the interface between viscoelastic layer and steel plate before the damping material stress reaches its shear failure strength.Therefore,it is necessary to design the bonding structure between the viscoelastic layer and the steel plate to improve the interface bonding strength and dynamic properties of the damper.Based on this reseaon,this paper firstly proposes an improvment method to design the interface bonding structure of the viscoelastic damper,and carries out mechanical performance tests to study the dynamic properties differences of the damper with different interface bonding forms;secondly,the three-dimensional models of the dampers with conventional,grooved and baffled interfaces are established with ABAQUS finite element software,and the dynamic performance and energy dissipation capacity of the dampers with different interface bonding forms are compared and analyzed;finally,a new mechanical model of viscoelastic material based on micro molecular chain structures is proposed,and the parameters of the proposed model are obtained by data fitting and the numerical results are compared with the experimental data of the dampers in Chapter 2.The main contents of present work are shown as follows:（1）Experimental study on bonding interface of the viscoelastic damperTwo bonding interface structures are designed: 1)the contact area between steel plate and viscoelastic materials is increased by grooving the steel plate on the contact interface;2)inspired by the cylindrical damper,the triangular steel baffles are set on both sides of the viscoelastic layer to constrict the displacement.The damper specimens are fabricated with different bonding processes（high temperature and high pressure vulcanization and epoxy adhesive bonding）and different interface bonding forms（conventional,grooved and baffled interfaces）,then the dynamic properties of these dampers are tested.The effects of ambient temperature,excitation frequency and displacement amplitude on the dynamic mechanical properties of the damper are studied,and the dynamic properties differences of viscoelastic dampers under different processing technology and interface forms are compared.The results show that temperature,frequency and displacement have significant influence on the dynamic properties of the viscoelastic damper.For the grooved damper,its energy dissipation capacity with high temperature and high pressure vulcanization process is similar to that with epoxy adhesive bonding process at room temperature,but at high and low temperature conditions,its energy dissipation capacity is better with epoxy adhesive bonding.For the baffled dampers,the dynamic mechanical properties and energy dissipation capacity of the damper with high temperature and high pressure vulcanization process are better than that with epoxy adhesive bonding process.With high temperature and high pressure curing process,the dynamic mechanical properties of baffled dampers are better than that of grooved dampers.With epoxy adhesive bonding process,the grooved dampers can obtain greater equivalent stiffness and storage modulus,but the damper with baffles can obtain greater loss factor.（2）Interface failure analysis of the viscoelastic damper based on finite element methodABAQUS finite element software is used to establish the three-dimensional model of viscoelastic dampers with three different interface bonding forms: conventional,grooved and baffle,and the dynamic properties and energy dissipation capacity of the damper with different bonding forms are analyzed.The effects of three different interface bonding forms on the dynamic mechanical properties and energy dissipation capacities of vulcanized viscoelastic dampers are compared and verified.The differences of hysteretic curve,storage modulus,loss modulus,loss factor,hysteretic energy consumption of single loop,equivalent stiffness and equivalent damping between viscoelastic dampers with grooved and baffled interface and conventional viscoelastic damper are studied.Finally,the cracking failure of viscoelastic dampers with different interface bonding forms is numerically analyzed,and the effects of different interface configurations on the interface cracking failure and dynamic performance of viscoelastic dampers are studied.（3）Equivalent fractional order three-layer molecular chain network model of viscoelastic damperBased on the micro molecular network chain structures,different types of micro molecular chain structures in viscoelastic materials are described with the help of fractional order mechanical model.Combined with the temperature-frequency equivalent principle,the influence of temperature is studied,and an equivalent fractional order three-layer chain network model based on micro molecular chain structures is proposed.The parameters of the proposed model are obtained by fitting and the numerical results are compared with the experimental data of damper dynamic properties test in Chapter 2.The results show that the proposed model can well characterize the effects of ambient temperature,loading frequency and material microstructures on the dynamic properties of viscoelastic dampers,and the relationship between the macro properties and microstructures of viscoelastic materials are established.The innovation of this paper is as follows:（1）Two new interface bonding forms are proposed,and the effects of different damper manufacturing processes and interface bonding methods on the dynamic properties and energy dissipation capacity of the viscoelastic damper are studied.For the baffled viscoelastic dampers,the dynamic properties and energy dissipation capacity of the dampers with high temperature and high pressure vulcanization process are better than that with epoxy adhesive bonding process.Under high temperature and high pressure curing process,the dynamic mechanical properties of dampers are better than that of grooved damper.For epoxy adhesive bonding process,the grooved damper can obtain greater equivalent stiffness and storage modulus.（2）An equivalent fractional order three-layer molecular chain network model of viscoelastic dampers based on micro molecular chain structures is proposed.The model can well describe the effects of ambient temperature,loading frequency and material microstructures on the dynamic properties of viscoelastic dampers,and the relationship between the macroscopic properties and microstructures of viscoelastic materials are established. |
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