Functionally-graded materials (FGM) have recently been widely used. Furthermore, FGM are widely recommended in cylinder design. This study represents a mathematical analysis of the stresses and strains of an FGM cylinder. The paper is interested in introducing a stress analysis to an FGM cylinder where its properties vary exponentially in the r-direction. Firstly, a benchwork has been done and compared with recent works in the same field. The radial stress, the hoop stress, and the longitudinal stress on a cylinder under mechanical and thermal loading have been theoretically derived. In addition, a finite element analysis has been investigated through ANSYS software. Finally, the values of stresses obtained from the derived equations and the corresponding values of stresses obtained from ANSYS have been compared. The obtained results established the efficiency of the proposed stress distribution and the optimization model in this research, which would be helpful for understanding well the technical design of FGM vessels or related constructions.

The stationary shoulder friction stir welding (SSFSW) technique promotes new opportunities for welding material. In the current work, a special setup of SSFSW was designed and manufactured in only three parts according to the homemade friction stir welding (FSW) machine dimensions and specifications. This setup with minimum parts is easily adjustable beside it facilitates fast control of the tool pin length. This gives the design more advantages than the previous designs published for the same purpose. Two different parameters were used with the SSFSW setup to butt weld samples of AA7075-T6 of 5 mm thick. Various welding travel speeds of 25, 50 mm/min, and 75 mm/min and different values of Z-force of 20, 25 KN, and 50 KN were used to evaluate the effect of the SSFSW parameters on the joints’ quality and properties. The results confirmed that sound joints were produced without internal or surface defects. In addition, the joints are characterized with a smooth surface finish compared to the conventional FSW joints. A narrow heat affected zone around the nugget due to the elimination of heat generation by the shoulder. The tensile strength of welded samples increases with increasing the vertical force with the maximum tensile strength of 418.7 MPa at a rotational speed of 600 r/min, a welding speed of 50 mm/min, and 50 KN Z-force. This implies that the vertical applied force upon SSFSW is an important parameter in controlling the joint properties. Analysis of the hardness distribution across the weld cross-section shows slight reduction in the heat affected zone.

In this study, a closed-form analytical solution is derived to compute the stress formulations for a thick cylindrical pressure vessel made of functionally graded material (FGM) with varying parameters, which are mechanical and thermal boundary conditions. The assumed mechanical boundary condition is the time-dependent pressure acting on the internal surface of the cylinder, while the assumed thermal boundary condition is the transient temperature distribution over the cylinder thickness. The material properties are considered to be graded exponentially in the radial direction, except Poisson’s ratio which is assumed to be constant. The stress and displacement formulations are evaluated using Mathematica software for the uncoupled thermo-mechanical analysis. The results of radial, hoop, and axial stress are plotted at various times for two FGM cylinders, the SS304-Alumina FGM cylinder and the TZM-SIC FGM cylinder, to study the impact of using different materials for the same boundary conditions on the results. The results obtained in this study are beneficial as these contribute to the design and modeling of cylinders that are exposed to time-dependent internal pressure and transient temperature profiles.

Welded joints are sensitive to fatigue failure due to cyclic loading, as well as fatigue crack propagation influenced by the distribution of welding residual stress. In this study, the fatigue crack propagation rates in butt-welded joints for 304 stainless steel sheets were evaluated in the presence of welding residual stresses. The analysis consisted of two separate models: first, a 3D-finite element (FE) model was used to predict the residual stresses due to welding; second, a numerical study was undertaken to predict fatigue crack propagation in the presence and absence of residual stress using the extended finite element method (XFEM). The crack growth model (NASGRO) and available experimental data were applied to verify the simulation results. The XFEM without residual stress effects shows good agreement with the experimental data and the NASGRO model. However, in the presence of residual stress, the simulation results show less agreement with the NASGRO model. The level and the nature of residual stress have significant effects on crack growth. A faster crack propagation rate is recognized due to the effect of tensile residual stress at the crack tip, while a higher resistance to crack growth is developed due to a compressive residual stress field.