International Journal of Advanced Design and Manufacturing Technology
Volume:8 Issue: 3, Sep 2015

Sandwich sheet rolling process is investigated using an analytical method (slab method) and a numerical method (finite element method). The horizontal stress distribution in the layers, the rolling pressure along the contact interface and the neutral point between the roll and the sheet are investigated. Then the affects of the parameters such as the friction between the sheet and the roll, shear yield stress ratio of the matrix and clad layers, front and back tensions on the rolling characteristics such as the pressure and neutral point position are studied. The results demonstrate that the finite element method results are very near to the slab method resultsand extra simplifying assumptions in the slab method cause low deviance in the results. In both methods As the friction coefficient increases, the rolling pressure increases and the neutral point nears the entrance of the roll gap. As the shear yield stress ratio increases, the rolling pressure increases but the neutral point doesn’t transmitted. As the front or back tensions is applied on the sandwich sheet, the rolling pressure decreases and the neutral point transmitted inverse of the tension direction.

In this article effects of friction stir welding (FSW) tool rotational and traverse speeds were studied on heat generation and temperature distribution in welding zone of AA1100 aluminium alloy. Computational fluid dynamics method was used to simulate the process with commercial CFD Fluent 6.4 package. To enhance the accuracy of simulation in this Study, the welding line that is located workpieces interface, defined with pseudo melt behaviour around the FSW pin tool. Simulation results showed that with increase of FSW tool rotational speed, the generated heat became more and dimensions of the stir zone will be bigger. The calculation result also shows that the maximum temperature was occurred on the advancing side. The computed results showed that with increasing tool linear speeds the heat generation experienced growth down trend. With increasing traveling speeds the time to reach maximum temperature in stir zone growth but the tool rotational speed dose not effect on time to reach maximum temperature. The model outcomes shows that more than 85% total heat was produced by tool shoulder and the maximum heat with selected parameters in this study was 801 kelvin degrees.

In this paper, hardness and tensile properties of welded zone of aluminum 1100 alloys by friction stir welding process was investigated and the effects of rotational and traverse speeds of tool on these parameters was studied. Also the fracture cross-section of welded samples was investigated. According the results of this paper, the hardness of weld material is higher than base material and is increased by decreasing the rate of rotational speed to traverse speed. The yields strength of weld material is 70% of base material in best conditions due to the weak thermo mechanically affected zone around weld nugget, although in some samples the tensile strength of weld material is equal to base material. Also the SEM images of fracture cross-section of welded samples showed a ductile fracture during tensile test.

In general, the aerodynamic stability of long span bridges is evaluated based on the results of wind tunnel tests in the low Reynolds number region, because in almost all wind tunnel tests, it is impracticable to satisfy Reynolds number similitude. Therefore, in order to correctly evaluate conventional wind tunnel test results, Reynolds number effects on the aerodynamic force coefficients acting on bridge decks must be carefully investigated. This paper investigate the Reynolds number effect on the aerodynamics of bridge deck section measured in the wide Reynolds number region from to based on the dimension of deck height in smooth flow. For the simulation of fluid flow, open-circuit and blowing wind tunnel was used for which the maximum nominal turbulence was 0.1%. The results show that increasing Reynolds number has less effect on the drag coefficient and Strouhal number and parameters in downstream of the model. In other words, variation of drag coefficient and Strouhal number is very small in Reynolds numbers over 20000. Increasing Reynolds number would not be followed with an outstanding change at value of velocity defect but causes to reduce half width, of course, it has no effect in rate growth of half width.

In this paper, the effects of baffle on thermal characteristics of combined convection-radiation heat transfer in laminar flow adjacent to an inclined backward facing step (BFS) in a horizontal duct are investigated. A baffle is mounted on the top wall of channel downstream side of step. In this study, the fluid is treated as a gray, absorbing, emitting and scattering medium; therefore, in the energy equation besides the convective and conductive terms, radiation term is also presented. The radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the divergence of radiative heat flux distribution inside the radiating medium. The blocked off method is employed for both fluid mechanic and radiation problems to simulate the presence of both step and baffle. The effects of height, width and location of baffle in channel and also the effects of radiative parameters on the fluid flow and heat transfer are investigated by plotting the variations of streamlines, Nusselt number and mean bulk temperature along the flow. It is revealed that, baffle and radiative parameters have great influences on flow and the thermal behaviors of systems with combined convection-radiation heat transfer.

This work deals with a numerical study on forward-facing steps situated in a supersonic flow. The primary aim of this paper is to examine the sensitivity of the velocity, density, pressure and temperature due to step-height variations of such forward-facing steps. Effects on the flowfield structure due to variations on the step height have been investigated by employing the Direct Simulation Monte Carlo (DSMC) method. The studied parameter contours for various values of step heights and profiles in three different sections of the channel are obtained. The results indicate that the fluid flow and temperature characteristics considerably depend on the step heights. The results was also compared with previous published works which showed excellent agreement.

In this study, feedback linearization (FL) for 6R manipulator is designed, simulated and implemented. The presented input-output FL controller has achieved the desired performance for the complicated nonlinear terms in the arm’s dynamic equations. Simulations were used to test the performance of the controller for point-to-point motion as well as continuous trajectory. The results of the point-to-point motion simulations and experiments were compared, where it indicates that the proposed approach preserved smooth motion in a very short process time with good accuracy. The dynamic load carrying capacity (DLCC), which is a criterion to determine FL controller performance on 6R robot, is also investigated, based on saturated torque of the motors and allowable error bounds. Moreover, it was shown that the control law is able to accurately represent closed-loop equations and simultaneously imposed desirable behavior on 6R robot.

This study presents an optimization methodology to obtain the uniform thermal conditions over the 3-D design body (DB) in 3-D radiant furnaces. For uniform thermal conditions on the DB surfaces, optimal temperature of the heater and the best location of the DB inside the furnace are obtained by minimizing an objective function. The radiative heat transfer problem is solved on the basis of the Monte Carlo method (MCM) to calculate the heat fluxes on the DB surfaces. The genetic algorithm (GA) is used to minimize the objective function defined based on the calculated and desired heat fluxes. The results indicate that thermal conditions on the DB surfaces are greatly influenced by the location of the DB and temperature of the heater. It is concluded that the introduced method is well capable to achieve the uniform thermal conditions on the DB surfaces by finding the optimal values for temperature of the heater and the best location for the DB inside the radiant furnace.

A new mechanism is presented in this paper for simulating the athlete performance and training the sportsman’s exercises, using a closed loop six degrees of freedom (DOFs) cable suspended robot. This robot cancels the necessity of presence of a sport coach for training the sportsman. Using the proposed robot, it is possible to program the robot for training the athlete limb (arm, leg and etc.) within a predefined trajectory corresponding to his special sport performance. The limb of the sportsman which is involved in the game and should be trained could be attached to the end-effector of the cable robot. Since in many sports a large environmental space needs to be covered by the athlete movement, ordinary robots are not capable to be employed for this application while cable robots are applicable since a large dynamic workspace can be covered by them. Moreover, training the sportsman limb requires a precise movement of the mentioned end-effector on a predefined trajectory. This importance could not be satisfied without using a proper closed loop controlling system since a variable external disturbing force applies on the end-effector as a result of the weight of the sportsman limb and its dynamic movement. Studio cams and automatic brancard for carrying the damaged sportsman out of the field are also of other applications of the presented closed loop cable robot. So required dynamic and control formulation of the end-effector of the cable robot is derived for handling the athlete limb on a predefined trajectory in a closed loop way. Simulation on using the MATLAB confirms the possibility of the mentioned claim for simulating the sportsman training. Finally the efficiency of the proposed mechanism in training the athletes’ limb is also proved by conducting experimental test on Iran University of Science and Technology (IUST) cable robot (ICaSbot).

Electromagnetic forming and high speed hydroforming are two new methods of tube formin. In this research, the results of expansion forming of tubes using electromagnetic forming and high speed hydroforming are compared by numerical modeling. In this study, firstly, the results of numerical solution of electromagnetic forming process in ABAQUS software are compared with experimental test results of other references. Then, results of numerical solution of high speed hydroforming in Abaqus software are compared with experimental test results. Finally, these forming methods are compared with each other in terms of displacement and thickness distribution. There is good agreement on bulge tip displacement results obtained by experimental tests and the results of numerical simulation. The results show that forming and deformation of electromagnetic forming process has been far faster than high speed hydroforming. However, a high speed hydroforming can be used in applications such as fitting of rings on tubes instead of electromagnetic forming.