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In this research, nanosized SiC and Al 2 O 3 particles were added to as-cast AZ91 magnesium alloy, and surface nanocomposite layers with ultrafine-grained structure were produced via friction stir processing (FSP). Effects of reinforcing particle types and FSP pass number on the powder distribution pattern, microstructure, microhardness, and on tensile and wear properties of the developed surfaces were investigated. Results show that the created nanocomposite layer by SiC particles exhibits a microstructure with smaller grains and higher hardness, strength, and elongation compared to the layer by Al 2 O 3 particles. SiC particles do not stick together and are distributed separately in the AZ91 matrix; however, distribution of SiC particles is not uniform in all parts of the stirred zone (SZ), which causes heterogeneity in microstructure, hardness, and wear mechanism of the layer. Al 2 O 3 particles are agglomerated in the different points of matrix and create alumina clusters. However, distribution of Al 2 O 3 clusters in all parts of the SZ is uniform and results in a uniform microstructure. In the specimen produced by one-pass FSP and SiC particles, the wear mechanism changes in different zones of SZ due to the nonuniform distribution of particles. However, in the specimen produced by Al 2 O 3 particles, the wear mechanism in all parts of the SZ is the same and, in addition to the abrasive wear, delamination also occurs. Increasing FSP pass number results in improved distribution of particles, finer grains, and higher hardness, strength, elongation, and wear resistance.

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In this article, numerical modelling of friction stir welding of copper plates is presented. The aim of this study is to implement DEFORM-3D for developing the numerical simulation. Material flow patterns are extracted using point tracking method, and mechanical/metallurgical properties of workpiece are analysed. Simulation results suggest that material particles in front of the tool pin tend to pass and settle behind the pin from the retreating side. Based on the results, a new classification of distinctive zones in the stirred zone is presented. The stir zone shape in friction stir welding is divided into five distinctive zones. In friction stir welding of copper metals, the stir zone does not lean completely towards any sides of the welding line, which was found to compare favourably with experimental observations.

The current study presents the buckling analysis of radially-loaded circular plate with variable thickness made of functionally graded material. The boundary conditions of the plate is either simply supported or clamped. The stability equations were obtained using energy method based on Love-Kichhoff hypothesis and Sander's non-linear strain-displacement relation for thin plates. The finite-element method is used to determine the critical buckling load. The results obtained show good agreement with known analytical and numerical data. The effects of thickness variation and Poisson's ratio are investigated by calculating the buckling load. These effects are found not to be the same for simply supported and clamped plates.which could be studied for FGM plates is the buckling which can occur due to the heating or under transverse loading. Thermal buckling and vibration behaviour of FGM plates have been studied by different researchers for rectangular and circular plates [7][8][9][10][11][12][13]. Buckling of FGM plates under transverse loads were also studied for circular and rectangular shapes [14][15][16]. There are also reported researches in which the behavior of FGM plates under combination of thermal, mechanical, and electrical loads have been studied [17,18]. Among them, circular plates are of particular interest because of their engineering applications under compressive loads. Elastic stability of circular plates has been investigated by several authors. Yamaki [19] studied the buckling of annular plates under uniform compression on their inner and outer edges. He found that buckling often occurs in higher buckling mode shapes. In the work done by Birman [20] and Feldman and Aboudi [21] the buckling phenomenon of functionally graded plates subjected to the uniaxial compression was investigated. Najafizadeh and Eslami [22] studied buckling of a circular plate made of FGM. They derived a closed form solution for the buckling load of such a plate under uniform compression.In most papers mentioned above, the thickness of the plate was assumed to be constant across the JMES636