Creep deformation and stress analysis in rotating disks of composite materials

Abstract

The present study is an attempt to investigate the steady state creep behavior of a rotating disk made of isotropic composite containing aluminum/aluminium alloy matrix reinforced with silicon carbide particles or whiskers. The creep behavior of the composite is described by a threshold stress based creep law. The creep parameters appearing in the law have been extracted from the experimental uni-axial creep data available for Al?SiCp. In the first segment of the study, the effect of stress exponent, appearing in the creep law, has been studied on the steady state creep of a constant thickness rotating disk made of isotropic Al?SiCp composite. The stresses and strain rates have been estimated by assuming the values of stress exponent as 3, 5 and 8. The study reveals that the values of stresses and strain rates in the disk are significantly affected by varying the stress exponent. The steady state creep rates in the disk increases by about two orders of magnitude with the increase in stress exponent from 3 to 8. The next segment of the study investigates steady state creep in a variable thickness rotating disk made of Al-SiCp. The creep stresses and creep rates have been estimated in the composite disks having linear and hyperbolic thickness profiles. It is revealed that the stresses and strain rates in the disk could be reduced significantly by varying the disk thickness profile. The composite disk having linearly varying thickness exhibits the lowest stresses and strain rates than that observed in hyperbolic or uniform thickness disk. The third segment of the study deals with the analysis of creep behavior in a rotating disk made of functionally graded composite and having linearly varying thickness. The content of SiCp reinforcement in the FGM disk is assumed to decrease linearly from the inner to the outer radius. The study indicates that with the increase in SiCp gradient in the disk, the radial stress increases over the entire radius..