Investigation on Effective Factors in Thermoelastic Analysis of FGM Rotating Drum in Air Turbine Engine under Nonlinear Thermal Loading

Introduction 1. n recent years, with the increasing growth of various industries, the development of advanced industrial structures has been widely increased in many industries such as aerospace, turbines, reactors, and other rotary machines. One of the most applicable rotating structures in this type is rotating drum in air turbine engines, which is very important due to the thermo-mechanical loads applied on it. The drum is a rotary structure that in recent years has been widely used in various sectors such as aerospace industries and nuclear facilities and has a very similar geometry to a thick-walled circular cylinder. This structure is under thermo-mechanical loads. Analysis of rotating drum stresses and investigating effective parameters including loadings at inner and outer radius, rotating speed, and using advanced materials like FGMs instead of homogenous materials is very important in the design of air turbine engine drums. A bunch of useful materials are FGM materials with a non-homogeneous coefficient which is suitable for redesigning a drum with lower stresses and higher safety factor. FGM materials are special types of composites and their properties can change steady and slowly in one or more arbitrary directions. These materials have high mechanical strength at high temperatures against applied loads, which makes them an appropriate selection in the above activity. In 2013, the elastic analysis of the FGM thick-walled cylindrical pressure vessels was analytically investigated [10]. In I 107 B. Shahriari, M. S. Sadeghi Nezhad Mechanics of Advanced and Smart Materials Journal Vol.1, Issue 2, (2022) 106 – 135 2015, thermoelastic analysis of a hollow circular cylinder for an FGM material with arbitrary properties distribution was studied [16]. In 2018, an investigation on an FGM rotating disk considering arbitrary changes in material properties and using the finite element method is carried out [19]. In this paper, analyzing a rotary drum and investigation on effective parameters including rotating speed, types of loading carrying on internal and external surfaces, thickness, and type of material has been studied. In order to investigate the drum, a thermoelastic analytical solution is performed for both homogenous and FGM states under internal and external loading conditions. The material properties are assumed to vary nonlinearly in the radial direction and the Poisson’s ratio is assumed constant. At first, differential equation of motion for FGM material is derived by assuming the properties functions exponentially and thermal gradients as an arbitrary function of radius. Then the equation is solved analytically using MATLAB engineering software. Stresses and displacements were calculated in clamp-clamp ends boundary conditions. Then, the governing thermal differential equation of the drum was solved and the response was replaced with an arbitrary thermal function considered at first stage of the analysis. After calculating the displacements and stresses applied to drum for FGM and homogeneous states, a study on effective parameters was carried out. Changes in the values of different parameters affecting the stresses and displacements, including rotation speed, magnitude, and type of loading on internal and external surfaces in the same working conditions on homogenous and FGM with nonhomogeneous coefficients have been investigated. Results clearly show the significant effects of loading conditions, drum rotating speed, and materials deployed to improve the drum behavior. Methodology 2. Schematic of investigated FGM thick-walled rotating drum under desired loading conditions is depicted in Figure 1. Figure 1. Representation of a thick-walled rotating drum under internal and external loads By applying equilibrium relations in radial direction, the governing equilibrium equation of motion in the drum was obtained as follows: In the following, considering the drum properties function in FGM state, including the modulus of elasticity, density, thermal expansion coefficient, thermal conductivity, and yield strength, which is considered as an exponential function and variable in radial direction as follows: