Shrink fit process is a useful technique in order to introduce beneficial residual stress in compound pressure vessels. In this paper, the effects of geometrical tolerances on residual stresses have been studied for a compound shrink fitted pressure vessel, practically. Three layers, which are designed based on an optimum nominal thickness and overlap dimensions and tolerances, have been fitted by shrink fitting to obtain a multi-layered high pressure vessel with desirable residual stress distribution. But in the manufacturing process, variations of inner and outer diameter of each layer have been observed within the design tolerances. The geometrical tolerances considerably affect the residual stresses. In this work, experimental results for residual stress are obtained from measurements of inner diameter of innermost cylinder due to two stages of shrink fitting. Then, the residual stress distribution is compared with analytical solution and finite element method at the lower limit and upper limit of tolerance domains. It is shown that very small geometrical tolerance could have a significant effect on residual hoop stress distribution. Also, the experimental results have a good agreement with analytical and finite element results. تفاصيل المقالة

In this paper, the rolling force and reduction ratio have been investigated in multilayer strip rolling. For this purpose, two different set of multilayers have been selected which are Al/St/Al and Cu/Al/Cu layouts. At first, the validation of the numerical analysis was performed by using an experimental test. After validation of the numerical results, two set of multilayer layouts were simulated and the total rolling force and the reduction ratio of each layer have been obtained. Finally, the effect of friction factor between the strip and the roll on the rolling force and reduction ratio has been studied. The results show that stiffness of each layer and the thickness ratio (clad to core) have significant effects on the layers thickness reduction. Also by increasing the friction factor between roll and strip, the clad thickness reduction is decreased and the core thickness reduction and rolling force will be increased. تفاصيل المقالة

In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Metal Matrix Composite (MMC: AA5083/-5% Al2O3). Starting materials were roll bonded as alternate layers up to 5 rolling cycles with 300°C preheating for five minutes before each cycle. The microstructure and mechanical properties of composites have been studied after different Warm- ARB cycles by tensile test, Vickers micro hardness test and scanning electron microscopy (SEM). The results revealed that during higher Warm- ARB cycles, breaking the layers of alumina particles led to the generation of elongated dense clusters with smaller sizes. This microstructural evolution led to improvement in the hardness, strength and elongation during the Warm- ARB process. The results demonstrated that the dispersed alumina clusters improved both the strength and tensile toughness of thecomposites. Finally, Warm- ARB process allowed producing metal particle reinforced with high uniformity, good mechanical properties and high bonding strength. تفاصيل المقالة

Abstract:The equal channel angular rolling (ECAR) is one of the severe plastic deformation processes, which can develop a shear deformation into a sheet metal. In this process, internal stresses are created due to the different strain levels experienced in different locations at the same time. The incremental hole drilling method is an effective technique for the evaluation of the through-thickness residual stress distribution in the metal sheets processed by the ECAR. In this work, the residual stresses as the macro stresses have been considered by the help of the incremental method and FEM for numerical calculation of the calibration coefficients. In addition, the FE simulation has been used to investigate the residual stress profile through the thickness. It was observed that the ECARed sample was compressive at the top surface while it was in tension at the bottom surface and the stress profile was not uniform through the material thickness. A comparison between the hole drilling measurements and the FE simulation results showed a good agreement. تفاصيل المقالة

Layered alloys and composite materials have become an increasingly popular in industrial development. The roll bonding (RB) process, as a solid phase method of bonding, has been widely used in manufacturing large layered strips. In this study, aluminum alloy (AA 5083) strips were roll bonded at warm and cold temperatures. The effects of the rolling parameters such as the amount of plastic deformation by rolling and rolling temperature that create successful bonds on the bond strength and the threshold deformation between two layer strips of AA 5083/ AA 5083 were investigated. The bond strength was evaluated by the peeling test. It was found that by increasing the rolling temperature or thickness reduction, the peel strengths of the bonds increased and successful bonds with higher strength were created. Also, the threshold thickness reduction decreased with increasing the rolling temperature. Moreover, the interfaces of laminates were studied by scanning electron microscopy (SEM) in order to investigate the bonding quality. تفاصيل المقالة