Structural Dynamic Analysis Of Composite Boring Bar Considering Different Factors

The composite material has high specific strength and specific rigidity,better fatigue resistance and vibration resistance,and excellent damping characteristics,which makes them have greater advantages in light weight and vibration resistance of parts and components.With the increasingly common application of deep hole machining in the design of transmission shafts for advanced aerospace equipment and various vehicles,higher requirements are placed on the vibration stability and operational reliability of composite boring bars.Due to the different materials,shapes,and fastening methods of the boring bar,the reliability and dynamic characteristics of the work are also different.Therefore,it is of great significance to establish a precise dynamic model of the composite boring bar and analyze the dynamic characteristics of the boring bar under the influence of different conditions.In this paper,based on the constitutive relation of the composite material and the basic equation of the strain-displacement relationship,based on the Euler-Bernoulli beam theory,the vibration model of the composite material boring bar with three different boundary conditions is established.According to the equations of motion and boundary conditions,the characteristic equation of vibration is deduced by using the method of separation of variables and transformation matrix.Through numerical calculation,the curves and forms of the natural frequency and dynamic stiffness of the composite boring bar with different boundary conditions are obtained with the change of the layer angle.The effects of the layer material,the different clamping methods and the layer mode on the natural frequency and the dynamic stiffness are revealed.The dynamic characteristics of composite boring bar with damping core are discussed and studied.Based on the theory of material mechanics,a model of composite boring bar with damping core is established.The influence of different types of fiber composite material,layer mode,damping core and length diameter ratio on natural frequency is revealed,and the influence of the selection of the above parameters on the dynamic stiffness is also studied.On the basis of the above research,taper parameters are introduced to study the dynamic characteristics of variable cross-section composite boring bar.According to Euler-Bernoulli beam theory and Lagrange equation,the dynamic equation of conical boring bar of composite material is established.Then,the hypothetical modal method is used to approximate the above equations.The effects of taper,fiber ply angle and length diameter ratio on the dynamic characteristics of conical boring bar are studied.