Investigation On Thermal Elastoplastic Buckling Of Functionally Graded Elliptical Cylindrical Shells

In this paper,elastoplastic buckling of functionally graded material elliptical shells are investigated by the semi-analytic method?The elastoplastic material properties of FGM are described by the TTO model,and the volume ratio of the constituent is in accordance with the power-law distribution.The constitutive model of FGM elastoplastic materials is given by combining J2 flow theory.Based on the assumption of uniform strain distribution in prebuckling,the theory gives the exact elastoplastic interface of the materials.Based on the FGM constitutive model and the Donnell shell theory,the buckling government equations are solved by Galerkin method,and the expression of the critical condition is given.Numerical results from the present theory are derived by an iterative procedure.By the above method,the buckling problem of elastoplastic FGM elliptical cylindrical shells subjected axially loaded and the thermal buckling of elastoplastic FGM elliptic shells are studied.With regard to the former,combined with the FGM linear hardening elastoplastic constitutive model,the elasto-plastic critical buckling load of the axial compression is obtained.The results of FGM elliptic cylindrical shells are compared with those of FGM cylindrical shells with equal perimeter.With the increase of the eccentricity,the bearing capacity decreases and the stability of the structure decreases.In terms of elastic-plastic buckling of elliptical shells under thermal load,the power law hardening elastoplastic constitutive model is adopted.In the case of the uniform,linear and nonlinear(considering the heat conduction effect)temperature rise,the critical buckling temperature is discussed.Due to the coupling of effect between material properties and temperature field,the critical buckling temperature is obtained via an iterative algorithm.Results show that temperature-dependent material properties must be considered in the thermal buckling analysis of functionally graded elliptical cylindrical shells,otherwise the critical buckling temperature would be overestimated.With the increase of temperature,the ceramic surfaces yield first and the elastic plastic interface moves from the ceramic to the metal surface.The conclusion of the uniform temperature rise is opposite?In addition,the geometric parameters of the structures and the material composition parameters have a great influence on the thermo-elastic-plastic buckling of FGM elliptical cylindrical shells.The critical buckling loads decreased with the increase of the radius-tothickness ratio.The structural buckling load and temperature difference increase with the increase of the composition of the ceramics,and the shell is prone to elastic buckling.The theoretical elastoplastic critical loads are well verified by ABAQUS coads,which includes both the material and geometrical nonlinearities.