A phase-field approach for transient thermal stress analysis of cracked and porous S-FGM rotating micro-blade under the combined effect of thermally induced vibrations and various mechanical loads

The present work is an attempt to develop a simple and accurate finite element formulation for the transient thermal stress analysis of a size-dependent cracked and porous S-FGM rotating micro-blade under the combined action of thermally induced vibrations and bending due to various mechanical loads using modified coupled stress theory in conjunction with the Phase-field theory and first-order shear deformation theory (FSDT). The bending due to the application of mechanical load is superimposed with bending due to thermally induced vibrations developed due to the application of cooling thermal shock load to study the resulting time-dependent thermal stress behaviour of a cracked and porous FGM micro-blade. For the practical analysis, a rotating cracked and porous S-FGM micro-blade is taken. The upper metallic layer made of stainless steel (SUS304) is subjected to cooling thermal shock and mechanical load, whereas the lower ceramic layer is made of carbon steel (AISI 1020), and is maintained at room temperature. Hamilton’s principle along with the Newmark average acceleration method is used to obtain the transient displacement from which the time-dependent thermal stresses are obtained. A wide range of parametric studies are carried out to investigate the combined effect of cooling thermal shock and mechanical loads, crack angle, crack depth, material scale ratio and rotational velocity on the transient thermal stress analysis of a size-dependent cracked and porous S-FGM rotating micro-blade.