Variable thickness thin-walled rotating blades made of functionally graded porous materials

Abstract

Within this study, the statics and dynamics performance of turbomachinery variable thickness rotating blades, composed of thin-walled, functionally graded metal-ceramic materials including cross-sectional distributed porosity is optimized. The pre-twisted, tapered, Thin-Wall Rotating Beams (TWRB) with constant angular velocity are considered within this context. For the optimization purpose, a genetic algorithm (GA) is implemented in a nonlinear constraint optimization problem. The goal is to exploit desirable thickness variations with improved dynamic, static, and buckling behavior of the variable thickness functionally graded material (FGM) blades. Hamilton’s principle was applied using the Euler–Lagrange dynamic system of governing equation, while the extended Galerkin’s method (EGM) was applied to solve the equations. Two variables in thickness function for each wall of the beam box (a total of eight variables) are considered in the optimization procedure. The effects of some parameters, such as the FGM volume fraction exponent, angular velocity, the pre-twist angle, porosity coefficient, and taper ratios on the mechanical behavior of the variable thickness FG beams are studied. The optimization result shows that applying the variable thickness concept can significantly increase the 1st and 2nd natural frequencies (by 60.4%, 60.22%) and reduce the weight (by 31.05%) of the system compared to the reference constant thickness beam while the increase in chordwise and flapwise deformations (by 8.16%, 9.93%) under combined loading is in an acceptable range, respectively.