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This paper aims to investigate the influence of material uncertainties on the postbuckling behaviour of functionally graded porous beams reinforced with graphene platelets when subjected to a thermal environment. A comprehensive deterministic, as well as stochastic study, has been done by employing the stochastic finite element methodology. The temperature-dependent (TD) and temperature-independent (TID) material properties have been considered. The homogenized effective material properties such as Young’s modulus are estimated by using the Halpin-Tsai micromechanics model and the density, and thermal expansion coefficient by Voigt’s rule of mixture. The homogenized material properties are assumed to be varying along the thickness direction in a functionally graded manner. The developed formulation is based on higher-order shear deformation theory in conjunction with Von-Kármán type geometric non-linearity for the postbuckling analysis. A C0 finite element model is developed to solve the system of non-linear governing equations, which are solved numerically using the direct iterative procedure. The convergence and validation study of the developed formulation has also been performed with an independent Monte Carlo simulation to ensure the accuracy of the formulation. The influence of material uncertainty on the thermo-mechanical postbuckling behavior of FG-GPLRC porous beams has been discussed for low variability (randomness) in material design parameters such as porosity content, amount of nanofillers, and material properties (i.e., Young’s modulus, density of metal matrix, and nanofillers) respectively. It was revealed that uncertainties in material properties can significantly affect the postbuckling response of FG-GPLRC porous beams. [ABSTRACT FROM AUTHOR]

Composite laminated thin-walled structures, widely used in high-speed aircrafts, undergo a complex thermal–mechanical coupling environment. Geometrical nonlinearities with a thermal effect bring significant challenge to finite element analysis of structures. In this paper, a novel hybrid-stress method based on the solid-shell element is proposed for nonlinear thermoelastic analysis. An eight-node solid-shell element (CSSH8) is developed based on the assumed natural strain method and hybrid-stress formulations to overcome various locking problems and achieve an effective 3D simulation for structures with a large span-thickness ratio. The Green–Lagrange displacement-strain relation is selected to take the geometrical nonlinearities into account. The modified generalized laminate constitutive model is extended to consider both the thermal expansion and temperature-dependent material properties. A temperature variation along the laminate thickness can also be assumed in the constitutive model. Nonlinear thermoelastic equilibrium equations are derived using the Hellinger–Reissner variational principle, in which five different coupling cases for thermal–mechanical loads can be fully involved. Numerical examples demonstrate that the proposed method with CSSH8 element is insensitive to various distorted meshes and numerically robust to pass the buckling point; meanwhile large step sizes can be achieved in the path-following nonlinear thermoelastic analysis. • A hybrid-stress solid-shell element is developed for nonlinear thermoelastic analysis of structures. • The modified generalized laminate constitutive model is extended to consider thermal effects. • Nonlinear thermoelastic equilibrium equations are derived for five thermal–mechanical cases. • The method is fully tested using various examples compared with displacement based FE methods. [ABSTRACT FROM AUTHOR]

In this study, nonlinear transient thermo-elastic analysis for a thick hollow 1D-FGM (functionally graded material) axisymmetric cylinder with finite length is investigated using higher-order graded finite element method. The material property gradations are along the radial direction and the power-law volume fraction and simple rule of mixture scheme are utilized to perform the effective material properties. As the cylinder exposed to high temperature, the temperature dependency of material properties is considered. So it led to nonlinear thermal conduction equation and in spite of the material distribution along one-direction by changing the temperature, the material properties are varied along two-direction with time. The nonlinear heat equation leads to 2D-temperature distribution for an axisymmetric cylinder. Also the thermal stress field would be different from an infinite cylinder which has been studied before. The temperatures, displacements and stresses for different values of volume fraction exponents along radial direction are investigated. It is revealed that the stresses and temperature in FGM cylinder are lower than the ceramic rich one. In other words, functionally graded cylinder wall gives better results in both stress and temperature cases than non-FGM cylinder. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the thermo-mechanical behavior of rotating discs made of functionally graded material (FGM) with variable thickness. The solutions are obtained by variable material property (VMP) theory. In this theory, the domain is divided into some finite sub-domains in the radial direction, in which the thermo-mechanical properties are assumed to be constant and the form of the elastic response is used to solve elastic–plastic problems. The results obtained by the VMP method are then compared with the results obtained by the finite element analysis using ANSYS software. In addition, the unloading and reverse yielding behavior of FG rotating disk are investigated and the residual stresses are then calculated with the same values of pressure and temperature by VMP theory and FE analysis. The results reveal that the mentioned methods are in very good agreement in both elastic and elasto-plastic states. Also, the effect of considering the temperature-dependent material properties is discussed. It is found that the results obtained by ignoring the temperature-dependent material properties lead to high discrepancies in comparison with those by considering that. Subsequently, the effect of various parameters including the disk geometry, temperature distribution, and boundary conditions on the stress behavior of disk is investigated. The results show that unlike the uniform rotating discs in which the yielding necessarily initiates from the inner radius, in the FG rotating discs, plasticity can be initiated from any point. [ABSTRACT FROM AUTHOR]

Mixed-mode thermal fracture of cracked AISI 304 austenitic stainless steel layers under severe thermal gradients of cryogenic and elevated temperatures is studied. Taking into account the variation of thermo-mechanical properties with temperature, the Jk-integral method, incorporating temperature-dependent material properties, is used to determine mixed-mode stress intensity factors from the results of finite element (FE) analysis. Effects of the convection heat transfer coefficient and the temperature of the contacting fluid on the mixed-mode fracture of the steel layers are investigated and it is shown that the mixed-mode stress intensity factors increase nonlinearly with these parameters. Results indicate that for accurate determination of crack tip fracture parameters when severe thermal gradients are present in the material, it is necessary to consider the variation of thermo-mechanical properties with temperature. [ABSTRACT FROM AUTHOR]

The parameters of the line heating process have significant effect on thermal history and the resulting residual deformation of the heated plate. The thermal transients are dependent on torch speed, torch height, gas pressure, and nozzle size, which in turn controls the residual deformation of the plate. In the present work, three-dimensional transient finite element thermomechanical analysis of line heating using oxyacetylene gas flame is presented. The analysis is carried out using temperature-dependent material properties, Newton's convection, and Gaussian distribution of heat. To reduce the computation time, a fine mesh was used along and near the heating line that was coarsened at the edges and away from the heating line. Numerical thermal transients and residual deformation were presented for various torch speeds, heat inputs, and different thicknesses of plate (6 mm, 8 mm, 10 mm, and 12 mm thick plates). The results compared fairly well with experimental and previously published results. The reduction in peak temperature, for similar heating conditions, and the increase in structural stiffness of thicker plates resulted in a reduction in out-of-plane deformation. In this work, the computational model for correlation of deformation pattern with heat input for a single heating line has been achieved. This model will further be extended to predict deformation patterns due to multiple parallel and oblique heating lines. [ABSTRACT FROM AUTHOR]