In this study, the effect of geometrical parameters of Rectangular vortex extrusion die, including twist angle (𝜑 ), reduction in area (𝑅 𝐴 ), and twist zone length (𝐿 ), on deformation inhomogeneity is investigated using the finite element analysis and response surface methodology. Analysis of variance (ANOVA) was used to determine the primary parameters and accuracy of the mathematical model obtained from response surface methodology results. The results showed that the suggested mathematical model predicts the strain inhomogeneity with high accuracy. Additionally, it revealed that the input parameters of 𝜑 , 𝑅 𝐴 , 𝐿 , the interaction between 𝜑 and 𝑅 𝐴 (𝜑 × 𝑅 𝐴 ), and interaction between 𝑅 𝐴 and 𝐿 (𝑅 𝐴 × 𝐿 ) are the main significant factors affecting the inhomogeneity. Perturbation plots and 3D surface diagrams were used to check the results of ANOVA, the sign, and the magnitude of the coefficient of the suggested mathematical model.

vortex extrusion (VE) is a severe plastic deformation technique which is based on the synergies between high strain accumulation and high hydrostatic pressure. Such a high amount of pressure places a mandate to seek the method for investigation of the load under processing conditions. For this, kinematically admissible velocity field and upper bound terms based on Bezier formulation are developed in order to investigate relative pressure in the VE process. Effects of reduction in area, relative length, twist angle, and friction factor in power dissipation terms are systematically analyzed. It is demonstrated that the increase in twist angle, area reduction and friction factor in the VE process increases the relative pressure, which the rates of these increase vary with twist angle. Moreover, the effect of the relative length is different in various frictional conditions. Results of conventional extrusion (CE) are in good agreement with those found by Avitzur for the effect of slug length and friction factor on the relative extrusion stress.

Rectangular S-duct diffusers are widely used in air-intake system of several military aircrafts. A well-designed diffusing duct should efficiently decelerate the incoming flow, over a wide range of incoming conditions, without the occurrence of stream wise separation. A short duct is desired because of space constraint and aircraft weight consideration, however this results in the formation of a secondary flow to the fluid within the boundary layer. The axial development of these secondary flows, in the form of counter rotating vortices at the duct exit is responsible for flow non-uniformity and flow separation at the engine face. Investigation on S-shaped diffusers reveals that the flow at the exit plane of diffusers is not uniform and hence offers an uneven impact loading to the downstream components of diffuser. Experiments are conducted with an S-shaped diffuser of Rectangular cross-section at Re=1.34´105 to find out the effects of the corners (i.e. sharp 90o, 45o chamfered etc.) on its exit flow pattern. A ‘fishtail’ shaped submerged vortex generators (VG) are designed and introduced at different locations inside the diffusers in multiple numbers to control the secondary flow, thereby improving the exit flow pattern. It is found that the locations of the VG have a better influence on the flow pattern rather than the number of the VG used. The best combination examined in this study is a 45o chamfered duct with 3´3 VG fixed at the top and bottom of the duct inflexion plane.The results exhibit a marked improvement in the performance of S-duct diffusers. Coefficient of static pressure recovery (CSP) and coefficient of total pressure loss (CTL) for the best configuration are reported as 48.57% and 3.54% respectively. With the best configuration of VG, the distortion coefficient (DC60) is also reduced from 0.168 (in case of bare duct) to 0.141.

Stir casting (vortex technique) is one of the simplest methods for producing metal matrix composites. Due to the formation of agglomerated particles and large amounts of porosities, these fabricated composites have very low mechanical properties. The effects of hot extrusion and warm ECAP on the microstructure and mechanical properties of these composites have been investigated in this study. The experimental results indicated the appreciable effects of these secondary processes on the tensile and ultimate strengths, ductility, relative density, hardness, and microstructures of the as-cast composites. In addition, it was revealed that warm ECAP (at 200oC) and hot extrusion (at 500oC) have completely different effects on properties of as-cast composites.

The effect of geometrical parameters involved in vortex extrusion (VE) die design, on AA1050 aluminium alloy processed by VE were investigated using finite element analysis (FEA) and response surface methodology (RSM). For this, VE die length (L), reduction in area (RA), twist angle (𝜑 ), and position of control points in Beziers' formulation (C1) were considered as input parameters and strain inhomogeneity was considered as a response. Both standard deviation (S. D) and inhomogeneity index (Ci) were used to quantify the strain inhomogeneity from FEA results. Analysis of variance (ANOVA) was used to determine the significant parameters and to mathematically model the strain inhomogeneity. It was concluded that standard deviation (S. D) is not a good choice for examining the strain inhomogeneity distribution in VE technique. ANOVA results showed that 𝜑 , RA, and interaction between 𝜑 and RA are the most significant parameters affecting the strain inhomogeneity.

There are several ways to increase heat transfer in mini-channels, like adding a vortex generator. In this paper, the effect of the presence of the hole on vortex generators on the heat transfer parameters is examined. In this study, a 50 mm long minichannel with eleven Rectangular vortex generators, with holes with area of 5 to 60% of the vortex generator area, was analyzed with water-based fluid under constant flux in the range of Reynolds numbers 200-1000. The results showed the presence of holes on the vortex generators reduced the pressure drop resulting from the obstruction against the fluid flow and 34.7% decrease in pressure drop is observed for minimum and maximum area of holes in Reynolds number 1000. The Nusselt number is increased by existence of a hole in the Reynolds numbers range and then is decreased by increasing the size of the hole due to the reduction of the vortex size behind the obstacle, so that in the maximum Reynolds number by increasing hole size, 34.3% decrease is observed.

The aim of the present study is to determine the feasibility of making a Rectangular twist waveguide used to rotate electromagnetic waves. For this purpose, the process of fabricating an aluminum Rectangular twist waveguide was simulated by making use of finite element method and Deform software. The optimum length and angle of the twist die for manufacturing a twist waveguide with inner cross sectional dimensions of 22. 86 mm × 10. 16 mm and a length of 50 mm and twisting angle of 90 degrees were investigated. Moreover, the effect of certain factors such as the length, thickness, cross section dimensions of the waveguide and friction on the optimum length of the twist die and cross sectional distortion was studied. The results of this study indicated that the length of the twist die had an influence on the amount of twisting, while friction was of no importance. In addition, comparing the values of effective stress and flow stress at the cross section of the workpiece behind the twist die depicted that the workpiece would not yield behind the twist die due to smaller values of effective stress.

vortex extrusion (VE) is a new severe plastic deformation method that simultaneous reduction in area and twisting around the longitudinal axis of the workpiece, within the fixed convergent die, leads to the accumulation of high amounts of strain on the sample. Due to the many capabilities of this process such as creating high strain in a pass, simplicity and no need for complex equipment and homogeneity of strain distribution, in this paper, the simultaneous effect of reduction in area, twist angle and curvature of slip lines on the mean effective strain, maximum damage factor and the steady state load of the process were investigated. The results showed that the mean effective strain value increased with increasing reduction in area and twist angle and there is a significant interaction between mentioned factors. The maximum damage factor was observed at the surface of work piece, which according to the values of positive mean stress in these points it can be said that the possible initiated cracks propagate under tensile state of stress. Reduction in area and twist angle are the effective factors on steady state load of process but the curvature of the slip lines does not have much effect on it. Maximum of damage factor was determined for VE die with curved streamlines, reduction in area equal to 30% and twist angle of 30 degree.

In this research, in order to investigate the effect of the piezoelectric patch which is used as a sensor or actuator in rotating flexible structures such as a helicopter blade, the free vibrations of the rotating Rectangular sheet with and without the piezoelectric patch have been presented. First-order shear deformation theory is considered for plate displacement and piezoelectric field. Considering the effect of Coriolis acceleration, centrifugal acceleration and centrifugal in-plane forces, the equations of motion are derived from Hamilton's principle and the electromechanical couple equation is obtained from Maxwell's equation. For piezoelectric, two electrical conditions, open circuit and closed circuit, which are used in sensors and actuators, respectively, have been considered. The equations are discretized with the help of the numerical method of generalized differential squares and the matrices of inertia mass, eccentricity, Coriolis and stiffness matrix are obtained. Natural frequency values for beam and rotating plate have been compared in Abaqus software. Also, the values obtained from the numerical solution in MATLAB have been verified with articles and ABAQUS, which have high accuracy. The effect of parameters such as hub radius, rotation speed, sheet thickness, aspect ratio, piezoelectric patch thickness and applied voltage on the natural frequency of the system has also been investigated.

Flow-induced vibration is the effective factor in mechanical destruction of structures that are exposed to fluid flow. In this study, random vortex- boundary element methods (RVM-BEM), is used to simulate two-dimensional laminar fluid flow around four one/two-degrees-of-freedom cylindrical cylinders in a Rectangular arrangemen. Hydrodynamic force coefficients, streamlines and cylinder displacements were plotted. The vorticity distribution is separated into blob-vortexes and its changes are studied by tracking these vortexes in the Lagrangian approach by considering two mechanisms of convection and diffusion in each time step. Satisfying no-slip boundary condition, vortex sheets were created on boundary. The cylinder vibrations were modeled as a system of mass, spring, and damper. The results showed that for 1 and 2DoF compared to the stationary cylinder, the average drag coefficient changes are 0.84 and 0.97, respectively. The rear cylinders vibrations amplitude were less than in the front cylinders. The y-amplitude was three times larger than x-amplitude. The maximum x-amplitude vibration of 1DoF cylinders was 1.51 times larger than 2DoF ones. Solving flow over 2DoF single cylinder by BEM(no need for homodis mapping or considering the vortexe images) with a similar solution in Ansys-Fluent software, showed 25% reduction in runtime and 2.3% increase in calculations accuracy.