Transient thermal stress analysis of imperfect functionally graded material folded plate under thermal shock loading

Purpose The purpose of this study is to investigate the effect of geometric imperfections on the transient thermal stress response of functionally graded material (FGM) folded plates subjected to thermal shock loading, which is motivated by the need to enhance the structural reliability and safety of FGM components having complex shapes, such as folded plates, when exposed to sudden high temperatures, where manufacturing defects like imperfections can significantly affect their performance. Design/methodology/approach An eight-noded isoparametric finite element, based on the first-order shear deformation theory (FSDT) and incorporating von Kármán-type geometric nonlinearity, is employed to develop the finite element formulation. The upper surface of the imperfect FGM folded plate is subjected to thermal shock loading, while the lower surface is maintained at room temperature. A nonlinear temperature variation is assumed across the thickness of the plate, and the material properties are considered to be temperature-dependent. The governing equations are formulated using a total Lagrangian approach and solved through the Newmark average acceleration method in conjunction with a modified Newton–Raphson iterative scheme. Findings The findings presented in the present work highlight that the magnitude of transient thermal stresses in a double-fold imperfect FGM plate is lower than that in configurations with a single fold. Furthermore, the sine-type imperfection results in the highest transient thermal stresses, followed by the global type, while the local type exhibits the lowest stress levels across imperfect FGM plate configurations with single and double folds. As the crank angle of the folded plate increases, the magnitude of transient thermal stresses also increases for configurations with single and double folds. Originality/value In this study, the transient thermal stress response of imperfect FGM folded plates subjected to thermal shock loading is analyzed, and to the best of the author’s knowledge, such studies are limited in the literature. A few formulations are reported in the literature where the combined effect of geometric imperfections and material gradation of FGM under thermal shock loading is investigated in a simple and generalized manner that is applicable to single and double folds, as presented in this study. The uniqueness of the present formulation also lies in its applicability to perform a wide range of parametric studies that include investigating the effect of crank angle, geometrical imperfection, volume fraction index and intensity of thermal shock on transient thermal stress analysis of FGM folded plate.