Study On Nonlinear Aerothermoelastic Of The Irregular Structures

Vibration problems often occur in the use of the various instruments,mechanical equipment and all kinds of engineering structures,then their life and precision will be greatly affected by the vibration.The plate structure and the non-smooth structure are the main components among them,so its vibration characteristics have attracted great attention.Aiming to research the plate structure,most of the previous researches are concentrated on study the vibration characteristics of rectangular thin plate structure,but in reality,the plate structure is often processed into various irregular shapes and used in different environments.Therefore,it is of great practical significance to research the vibration characteristics of irregular plate structures considering the various using environments.Aiming to research the non-smooth structure,the most important thing is to study the influence of clearance on the vibration characteristics,and it can be provided analytical methods and theoretical guidance for the design of mechanism,the prediction of the real dynamic behavior of mechanism and the related experimental research.In this paper,the nonlinear aerothermoelastic properties of the irregular composite laminated plates in thermal field and hypersonic airflows are investigated.And the dynamic behaviors of two discontinuous beams connected by a joint with clearance are studied.The main contents of this dissertation are as follows:The nonlinear vibration behaviors of the trapezoidal composite laminated plate are analyzed.Based on the von Karman's large deformation theory,the finite element method(FEM)and Hamilton's principle are used to establish the equation of motion of the composite laminated trapezoidal plate.The effects of the ply angle and the length-high ratio on the nonlinear vibration frequency ratios of the trapezoidal plates are discussed,and the nonlinear forced vibration characteristics are analyzed for the different ply angles and harmonic excitation forces.The thermal effects on the buckling,postbuckling and nonlinear vibration behaviors of the trapezoidal plates are studied.Aiming at the complex plate structure and to simulate the temperature distribution of the plate,the FEM and Galerkin principle is employed to establish the temperature equation of the composite laminated trapezoidal plate,thence,the temperature distribution of the plate is obtained.And the FEM and Hamilton's principle are combined used to establish the thermoelastic equation of motion of the trapezoidal composite laminated plate.The effects of the temperature and ply angle on the thermal buckling,postbuckling and nonlinear vibration behaviors of the composite laminated trapezoidal plates are discussed.The aerothermoelastic properties of the composite laminated trapezoidal plates are investigated.Considering the compressibility of supersonic airflow and shockwave(SW),the first order piston theory containing the effect of arbitrary flow direction is employed to evaluate the aerodynamic pressure.In view of the irregular structure of composite laminated plate and the complex temperature distribution of the plate due to aerodynamic heating,the heat conduction equation and the aerothermoelastic coupled equation of motion of the composite laminated trapezoidal plate are established using the FEM.The temperature distribution of the plate is obtained by the heat conduction equation,and the aerothermoelastic behaviors of trapezoidal plates are investigated by combining the aerothermoelastic equation of motion.From the numerical simulation,the effects of the aerodynamic heating and ply angle on the natural frequencies and modes of the trapezoidal plate are studied.The thermal effects on the buckling,postbuckling and nonlinear vibration behaviors of the trapezoidal plates are researched.The buckling of the plate caused by the thermal effect and the flutter caused by the airflow are discussed considering the influences of various parameters.And the coupling interaction of the thermal and the aerodynamic forces is analyzed.Moreover,the effect of aerothermal elasticity on the stability of the plate is also considered.The dynamic behaviors of two discontinuous beams connected by a joint with clearance are investigated.A new equivalent joint model using the transverse and torsion spring systems with a clearance is developed to express the joint.Based on the FEM and Hamilton's principle,the equations of motion of the two jointed beams with clearance are established.A modified numerical solution method is presented based on the Newmark integration method to solve the equations with the nonlinearity of clearance type.The influences of the clearance size and stiffness on the amplitude-frequency response are discussed.The effects of the clearance on the vibration transfer between two beams and the impact force of the joint are investigated.