Elastoplastic Buckling Of Functionally Graded Structures In Thermal Environment

Functional graded materials(FGM)are new composite materials composed of two or more materials,and their composition and structure vary continuously with certain gradients.The new composite materials are developed to complete the repeated normal work in the extreme thermal environment,then meeting the needs of modern aerospace industry and other high-tech fields.Under specific working conditions,the heat resistance and crack resistance of this composite can be changed by adjusting the basic material properties and gradient index so as to meet the specific needs.Therefore,in recent years,the research on functional gradient materials has become a hot topic.In this paper,the elastoplastic buckling of FGM beams and FGM cylindrical shells in thermal environment is studied.The details are as following:(1)The elastoplastic buckling behaviors of functionally graded material(FGM)beams under axial compression loading are studied in consideration of temperature dependence of material properties.Firstly,elastoplastic material properties are obtained on the basis of bilinear hardening model and temperature dependence,meanwhile the elastoplastic constitutive equations of the FGM are established as well.Then introducing the Hamilton principle,the elastoplastic buckling behaviors of FGM beams are transformed into solving the eigenvalues in symplectic space.At the same time,the buckling critical loads corresponding to the generalized eigenvalues of the canonical equations can be calculated by the bifurcation conditions.Finally,the influence of material gradient,structural geometric parameters and environmental temperature on the critical loadings and elastoplastic interface is discussed in detail through analyzing the data.(2)Considering the temperature dependence of the material,the elastoplastic buckling behavior of FGM cylindrical shells under uniform axial compression is studied.Based on the bilinear mixed hardening elastoplastic model,the materialproperty formulas and elastoplastic constitutive equations of FGM cylindrical shell are given.Then,the Hamilton principle is introduced to transform the elastoplastic buckling behavior of FGM cylindrical shell into solving the eigenvalue in symplectic space.Furthermore,the critical buckling loads corresponding to the generalized eigenvalues of the canonical equations are calculated by using the bifurcation condition.At the same moment,the positions of the elastoplastic interface and the relative elastoplastic interface of the buckled shells are obtained by combining the yield condition.Finally,the effects of the environmental temperature,the material gradient and the structural geometry parameters on these parameters are discussed.