Constitutive Nonlinear Mechanical Behavior Of Thin-walled Cylindrical Shells

In this thesis,the nonlinear mechanical behavior of thin-walled cylindrical shells is studied.In the research process,it is assumed that the relationship between the elastic modulus and the strain in the constitutive equation is linear.The numerical method is used to obtain the numerical solution of the governing equation,and the effects of mechanical load,thermal load,nonlinear parameters of constitutive relationship,ratio of length to radius and boundary conditions on the bending deformation and neutral layer of thin-walled cylindrical shells are discussed in detail.The main tasks are:(1)Based on the Kirchhoff-Love hypothesis,the geometrically nonlinear equations of thin-walled cylindrical shells are derived using the vector method.In the constitutive equations,it is assumed that the relationship between elastic modulus and strain is linear.The equilibrium equation suitable for the large deflection problem of the shell is derived.(2)The deduced basic equations are processed in a dimensionless manner,and the numerical method is used to solve the numerical solution of the large deflection buckling problem of thin-walled cylindrical shells under different boundary conditions.The obtained results are used to analyze the influence of external mechanical load,thermal load,nonlinear parameters of constitutive relationship,ratio of length to radius and boundary conditions on the bending deformation of thin-walled cylindrical shell and the position of neutral layer.The results show that the nonlinear parameters of the constitutive relationship will affect the bending deformation resistance of the thin-walled cylindrical shell,no matter under the action of mechanical load or thermal load,and the effect is more obvious when the mechanical load is applied,the difference in the ratio of the length to the radius will also change the influence of the nonlinear parameters of the constitutive relationship on the equilibrium configuration of the thin-walled cylindrical shell and the position of the neutral layer.Regardless of the boundary conditions and the applied load,the path of the non-dimensional deflection at the midpoint of a thin-walled cylindrical shell with the increase of the aspect ratio will be divided into three stages.In the first stage,the thin-walled cylindrical shell is in a single-wave state,and the midpoint deflection is the largest at this time.In the second stage,the thin-walled cylindrical shell is in a double-wave state.At this time,as the ratio of length to radius increases,the midpoint deflection decreases.In the third stage,the thin-walled cylindrical shell is in a multi-wave state.At this time,the effect of the ratio of length to radius on the midpoint deflection of the thin-walled cylindrical shell is not obvious.