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The initial induced compressive residual stresses relax during component operating life and it is important to consider the relaxation phenomenon in the design of the component. In this study, 2024-T 351 aluminium alloy specimens were shot peened under three different shotpeening intensities. Cyclic tests for two load magnitudes were performed for 1, 2, 10, 1000 and 10,000 cycles. The initial and final residual stresses and the cold work after each loading cycle were measured for the three shot-peening intensities and for the two load magnitudes using X-ray diffraction. The initial and final microhardnesses after each loading cycle load were also measured for the three shot-peening intensities. The results showed that the reduction in the residual stress, microhardness and cold work are dependent on the applied load. An empirical model was proposed to estimate the residual stress relaxation. The presented model incorporates parameters including the degree of cold work, initial induced residual stress and the number of applied loading cycles.

A theoretical solution for thermoelastic analysis of functionally graded (FG) rotating disk with variable thickness based on first-order shear deformation theory (FSDT) is presented. Material properties and disk thickness profile are assumed to be represented by power law distributions. A semi analytical solution for displacement field is given under two types of boundary conditions applied for solid and annular disks. The effects of the material grading index and the geometry of the disk on the stress and displacement fields are investigated. Mechanical responses homogeneous disks versus FG disks are compared and verified with the known results in the literature. It is seen that the transverse displacements in FG solid disks with roller support condition at the outer surface remain between the minimum displacement value for the full-ceramic disk and the maximum displacement value for the full-metal disk. It is found that the transverse displacements in FG mounted disks with free condition at outer surface may not lie in between the displacement values for full-metal and full-ceramic disks. It is observed that the absolute moment resultant for FG mounted disk with concave profile is lowest compared to the FG mounted disk with linear or convex profile. It can be concluded that the gradation of the metal-ceramic components and the geometry of the disk are significant parameters in the thermomechanical responses of FG disks.

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