International Journal of Advanced Design and Manufacturing Technology
Volume:9 Issue: 3, Sep 2016

Accommodation of mechanism with human being’s physical characteristics creates the possibility of safe and efficient interaction between human being and robot. Regarding the fact that amputation of a limb in human beings causes several mental, economical and social difficulties and problems, need to a substitute limb which has the most efficiency for the person after amputation is a vital need. The cable robots are the kinds of robots that the cable is used instead of rigid link. The cable robots have a simple appearance that some cables connect the motors to the final organ. In this research a robot with cable mover is designed and modeled as a tool in the case of creating movement with the most accordance for an artificial organ below the knee. In addition, in this mechanism some advantages are also considered including creating movement in two axes, its cheapness and lightness. In this research at first a primary design of the artificial organ is presented. The forward and inverse kinematic relations which are dominant on system are explained, in fact you can find different features with kinematic robots like dexterity, global condition, local condition, etc, and finally we study the available workspace for the system. Workspace in cable robots is different from other parallel robots, in this paper, first description about some methods for finding work­space in cable-driven-robots and then use of force-closure workspace to find workspace for this system are presented.

Expansion equal channel angular extrusion (Exp-ECAE) is a severe plastic deformation (SPD) operation for processing bulk materials. In the current study, AA7075 Al was SPD-processed by expansion equal channel angular extrusion (Ex-ECAE) at various temperatures and ram velocities. Then, using split Hopkinson pressure bar (SHPB), the severely deformed products were compressed at room temperature and strain rates of 0.1~3000 s-1. Both the strain rate sensitivity (SRS) and the apparent activation volume (AAV) were determined for all deformed samples. The results revealed that the Ex-ECAE operation has noticeably increased the SRS. The tensile strength at a strain rate of 3000 s-1 was 6 times increased by conducting Ex-ECAE at 100 °C and with a ram velocity of 7 mm/min. Ex-ECAE was also capable of considerably decreasing the AAV. The results showed the yield stress of both the Exp-ECAE and the annealed samples increased with increasing the strain rate. Also, the results showed that after the Exp-ECAE process, the AAV reached to 6.3 b3 from the initial values of 118.5 b3 in the annealed state.

In this paper, the temperature distribution in workpiece and microstructure of welded zone in friction stir welding of aluminum 1100 alloys and the effect of the tool rotational speed on these parameters have investigated experimentally. Also feed forward back propagation neural network has been used to predict the temperature of the workpiece during the welding process by considering the process time and tool rotational speed as input parameters of the neural network.
For this purpose, the Taguchi design of experiments has been used and the network with minimum mean squared error was selected. This way of neural network selection is very formal and effective than the existing methods. The selected network mean squared error with this approach, is 0.000388, its most differences with experimental inputs is 0/770997 ºC and its regression R values is 0.99113. Also according to experimental results, increasing tool rotational speed leads to higher plastic deformation in materials and also causes increasing the friction between tool and workpiece which leads to higher workpiece temperature.

In this paper, fluid flow between two parallel flat plates that are partially filled with two-dimension porous media is investigated numerically using single relaxation time (SRT) lattice Boltzmann method (LBM) at pore scale. The considered obstacles are random, circular, rigid and granular with uniform diameters. Single component and single-phase viscous Newtonian fluid are considered as working fluid. There are no overlaps between obstacles. It supposed incompressible, steady and laminar flow and no chemical reaction performed in porous media. Velocity vectors and streamlines in this domain depicted. The effect of varying Reynolds number on the pressure drop or pressure gradient and Darcy drag are studied. Dimensionless permeability calculated as a function of porosity and Knudsen number. To vary porosity, obstacles diameter changed but their places considered constant. With increasing Knudsen number, the dimensionless permeability is increased. In addition, effect of domain resolution on pressure gradient investigated. The results demonstrate that lattice Boltzmann method will be very useful in fluid flow simulation through porous media

All the producing and assembling processes exert residual stress on the pieces that may lead to structural failure. Therefore, calculating the residual stress in such structures has been common in recent years. In this article, distribution of temperature and residual stress resulting from arc welding in three-pass butt joint in P91 austenitic stainless steel pipes is calculated and estimated using the finite element method and experimental data. Simulating the welding process has been carried out three- dimensionally using Abaqus software. Distribution of the arc thermal flux has been identified based on the Goldak two-elliptical model using DFLUX subprogram in Abaqus software. The numerical method has been employed by doing thermoelastoplastic analysis and the technique of birth and death of the elements to model the welding passes and the melted elements. Then, using central hole drilling method, residual stress gradient of the thickness at distance 3mm from the welding line on the pipe is measured. Finally, the maximum percentage of error, through the results obtained from experimental measurements and finite element method, was reported 27% which is scientifically reasonable .The results show that the residual environmental stress in the internal surface of the pipe from the welding central line to 8.7mm varies with the gradient of 610MPa from 296MPa to -314MPa. Such a drastic stress distribution leads to genesising some cracks on the welded pipes.

Gears are one of the most critical components in power transmission system of an automobile and also many rotating machinery. Many studies have been conducted on optimum gear design. The main objective is to design different aluminium metal matrix composite spur gears before and after optimization. Aluminium metal matrix material composites are preferred mostly due to their low density. Also the high specific mechanical properties make these alloys one of the most interesting material alternatives for the manufacture of lightweight parts for many types of vehicles. With wear resistance and strength equal to cast iron, 67% lower density and three times the thermal conductivity, aluminium MMC alloys are ideal materials for the manufacture of lightweight automotive and other commercial parts. In the present work materials considered are Al 6061-T6, Al 6106-T6, Al 7075-T651, and Al 7050-T7451. Finite element analysis is performed on different spur gears using above materials and the results will be compared.

Cable driven parallel manipulator (CDPM) is a special class of parallel manipulator in which the rigid extensible links are replaced by actuated cables. It is necessary to take into consideration the cable dynamics, i.e.; its mass, flexibility and curved shape for manipulating a long-span CDPM. These terms complicate governing equation of motion in a way that special tactic are applied for simulation and solving this problem. Flexibility and mass of cablesimpose vibration and error in path trajectory planning.Effect of varying stiffness in precise performance of CDPM is surveyed.The cables are modelled, in ADAMS software to illustrate the dynamical behaviours of the manipulator for comparison with the simulated results. Moreover, an algorithm is developed to study the effects of velocity and acceleration of the end-effector on the dynamics of CDPMs. Moreover it is shown that the evolutionary computing algorithms are so effective in solving complicated nonlinear dynamic path trajectory planning. Simulations for different trajectories of two CDPMs are included to demonstrate the efficiency of the proposed algorithm.

In this study, the problem of determining an optimal trajectory of a nonlinear injection into orbit problem with minimum time was investigated. The method was based on orthogonalpolynomial approximation. This method consists of reducing the optimal control problem to a system of algebraic equations by expanding the state and control vector as Chebyshev or Legendre polynomials with undetermined coefficients. The main characteristic of this technique was that it converted the differential expressions arising from the system dynamics and the performance index into some nonlinear algebraic equations, thereby greatly simplifies the problem solution. Our research effort focuses on applying a Chebyshev series expansion to optimize the trajectory profile of a point-mass Satellite Launch Vehicle (SLV).This paper is divided as follows: first, the Chebyshev and Legender series expansion to optimization are introduced. Then, the flight mechanics model of the point-mass SLV is given. Next, our optimization problem is described and optimization results are presented and discussed.

The satellite battery pack is one of the important and vital parts that are required for conducting special design with multiple capabilities. Some parameters like the minimum weight, lack of outgassing of parts, avoiding from short- circuit in batteries inside battery pack, the possibility for making series connection in batteries, and prevention from destroying battery pack structure caused by vibrations due to displacement of missile upon launching of a satellite are included in some requirements for design and manufacture of satellite battery pack. In the present essay we have studied on design and manufacture of battery pack structure by considering the above- mentioned requirements in mind. In order to determine the authenticity of design and manufacture of battery pack in real conditions for launching and vacuum conditions, several environmental test of thoroughness such as Thermal Vacuum Testing and Vibration Tests have been carried out on the manufactured structure so the results of batteries performance be purposed within these tests. The results obtained from environmental test and conducted on satellite battery pack structure suggest the fully successful and innovative achievement in design and manufacture of battery pack structure.

Severe plastic deformation (SPD) methods were developed for producing of metals and alloys with ultrafine grained (UFG) microstructures having high strength. Parallel tabular channel angular pressing (PTCAP) as a noble severe plastic deformation (SPD) method was used to produce ultrafine grained (UFG) and nanostructured Cu-30%Zn tubes. In this paper, the effect of PTCAP process temperature on the deformation microstructures and mechanical properties were investigated using experimental tests. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to evaluate microstructural evolutions and fractured surface analysis. Microhardness and tensile tests were employed to mechanically characterize the PTCAP processed samples. The results showed the strength and the hardness decrease with increasing process temperature up to 100 ℃, but at 200℃, strength and hardness increase in comparison to that in 100℃. The rise in the strength and hardness of the sample processed at 200℃ compared to that at 100℃ is because of the partial recrystallization, forming new fine grains with high angle boundaries and twin boundaries. Twinning is dominant deformation mechanism of brass material in order to low stacking fault energy (SFE). Observations revealed that the failure mode in PTCAPed brass was a ductile rupture with the existence of deep dimples. It also indicates that the temperature has no obvious effect on the fracture mood.

In this paper, the conjugate gradient method coupled with adjoint problem is used in order to solve the inverse heat conduction problem and estimation of the time- dependent heat flux using the temperature distribution at a point in a three layer system with none homogeneous boundary conditions. Also, the effect of noisy data on final solution is studied. For solving this problem the general coordinate method is used. We solved the inverse heat conduction problem of estimating the transient heat flux, applied on part of the boundary of an irregular region. The present formulation is general and can be applied to the solution of boundary inverse heat conduction problems over any region that can be mapped into a rectangle. The obtained results for few selected examples show the good accuracy of the presented method. Also the solutions have good stability even if the input data includes noise. Applications of this model are in the thermal protect systems (t.p.s.) and heat shield systems.

The accuracy of stereolithography (SL) product is very essential for meeting the intended functional applications. The parameters like layer thickness, hatch spacing, hatch overcure contribute significantly to the accuracy of the SL parts. In this paper an attempt has been made to identify the process parameters that influences on the accuracy of the parts made with CIBA TOOL 5530 and optimize the process parameters. A standard test specimen is designed for this study. A process model between the geometric tolerance (parallelism, perpendicularity, angularity, radius fillet), surface roughness and the above mentioned process parameters (layer thickness, hatch spacing, hatch overcure) have been developed. It is found that parallelism, perpendicularity, angularity, radius fillet and surface roughness are influenced significantly by hatch spacing, layer thickness, hatch overcure, hatch spacing and layer thickness respectively. The percentage deviation between the experimental and process model values have also been calculated to validate the developed process model.