International Journal of Advanced Design and Manufacturing Technology
Volume:6 Issue: 1, Mar 2013

Hydromechanical deep drawing (HDD) is one of the most convenient processes in which a sheet metal is drawn against a counter pressure rather than a rigid die in conventional stampings. This process has been increasingly used to produce aerospace and automotive components. More recently, aerospace industry is demanding new materials with capability to produce high strength to weight ratio products. Also several investigations have been carried out on hydromechanical deep drawing, numerical considerations in order to design the process parameters to produce a cost-effective with high quality component by using this process for superalloy cups has not been investigated. Nickle-based superalloy sheet metals are more prominent in aviation and spaceflight industries. In this paper, numerical simulation of hydromechanical deep drawing for Haynes230 nickle based superalloy has been investigated. Moreover, the pressure paths which yield rupture and wrinkling have been realized. Furthermore, differences between applying uniform and gradual pressure into the pressure chamber have been detected to nominate a pressure path for successfully producing a superalloy cup made by HDD. Subsequent to that, chamber pressure against punch travel curves were depicted. For this investigation, 3-D finite element method was employed and the results obtained from numerical simulation were validated using experimental data already available in the literature.

Production and preparation of many parts of the aircraft body including wings with long length, smooth form, and large radius of curvature are amongst the most important challenges in this industry. In this paper, the effective factors in the rubber pad forming method on a pieces contain curvature radius have been investigated by finite element method. The effect of variables such as curvature radius, sheet thickness, rubber pad thickness, rubber hardness, lubrication condition, spring back phenomena have been analyzed. To validate the finite elements simulation, the experimental results were compared. Then, other above-mentioned variants were studied. The obtained results indicate that there is a close differentiation between the numerical and experimental works. Moreover, the cited parameters have different effect on part quality

Aluminium 7075- T651 alloys are widely used in the production of light weight structures requiring a high strength to weight ratio and high corrosion resistance. The effect of processing parameters on fatigue life of 7075- T651 aluminium joints produced by friction stir welding was investigated in the present study. Welding samples were made by employing rotating tool speed of 770, 900 and 1200 r.p.m, welding speeds of 70, 75 and 80 mm/min. After welding process, mechanical properties of samples were evaluated by means of fatigue testing machine at room temperature. Results were clearly illustrated that as tool speed increases, fatigue life decreases. The highest fatigue life was obtained with 80mm /min welding feed and weld speed of 1200 r.p.m

In this paper, a fully discretized bio-fidelity simulation model for bio-mechanical (kinematic) analysis of scoliosis for various patients was developed to analyze forces on vertebrae, loads acting on the intervertebral disc, corresponding angles between vertebrae, and tension in the spine muscles during lateral bending. It was further developed to study the movement limitation and muscle activation of a scoliotic subject. This system was built by using the commercial software LifeMOD. The whole spine (pre-defined by the software) was discretized into individual vertebra segments with rotational joints representing intervertebral discs. In this study, two female subjects (with 40±1.0 kg weight and 154±3 cm height), one with normal spine and the other one with scoliotic spine, were asked to do lateral bending and bend as far as they can. Motion capture data of these two subjects was obtained. Next, motion capture data was assigned to the model using a motion agent set and the inverse dynamics simulation was performed to simulate the complicated multi-body motion of lateral bending. The mobility of the ribcage, activity of muscles which are important in the lateral motion of body, as well as joint angles were analyzed using the developed simulation model. According to the obtained results, the mobility of the ribcage in scoliosis model was less than that of the normal model with the same anthropometric data. This finding is in direct agreement with the qualitative experimental results done by other researchers

Rayleigh-Taylor (RT) instability has a growing importance in many fields including aircraft industry and astrophysics. The development and the growth of RT instability were investigated using sinusoidal disturbances with different wavelength at the interface of two fluids. Numerical simulations were performed by solving Navier-Stokes unsteady equations with the VOF formulation. Results of the 2D simulation are compared with experimental results. It is shown that beyond a critical time, not captured experimentally, the mushroom shape of RT instability turns into a helical path or breaks down into a patchy shape depending on the shape of disturbance. Nonlinear instabilities responsible for such behaviour are apparent when the wavelength exceeds 10 times a length scale introduced here.

In this study, the time-average velocity in the near wake of a two-dimensional Notch-Back car model that located in the wake of a trailer has been investigated. The present experiments were carried out in an open circuit low-speed wind tunnel made by Fara Sanjesh Saba Ltd, in Iran and was used to simulate uniform air flow. Results show: at the close spacing, time- average velocity profile at the behind of car only has a maximum peak due to the interaction of the jet fluid with the wake of car, so that with increasing vehicles spacing, the jet fluid effect at the create velocity maximum pick gradually pale. In additional with increasing the vehicle spacing we see that the velocity in the wake of car started to grow from the lower height.To measure the drag coefficient it was preferred to use wake–survey method and also the equation recently derived by Van Dam. The dimensionless distance between vehicles derived based on the length of the front one ranges from 0.1 to 3. It was observed that the value of car drag coefficient experiences a rising trend in the beginning and then a descending one along dimensionless distance of 0.1 to 1.3 compared to individual condition. In further distances it will be less than the individual condition.

In this study we consider PCF (Plane Couette Flow) which is introduced by two parallel planes which have same velocity in opposite direction and the distance between them is filled by viscoelastic fluid. By this way we have modeled viscoelastic damper. The constitutive equation of JS (Johnson-Segalman) has been used for dynamic analysis of viscoelastic damper’s behavior. By using this equation we can examine normal stress which is existed in the fluid and achieve more accurate results about stability of flow between two planes. At first problem formulation is covered. The general conservation and constitutive equations, as well as the boundary and initial conditions are covered for a JS fluid. The Galerkin projection is applied, using Chandrasekhar functions, for 1-D disturbance from the base (Couette) flow. An arbitrary number of modes are included, to lowest order, the formulation leads to a six-dimensional system. Linear stability analysis around the base flow and nontrivial steady-state solution branches is carried out. The influence of inertia on transient flow is studied. Discussion and concluding remarks are finally given. This study has been done specially for PCF of fluids with high molecular weight such as combination of a Newtonian solvent and a polymer solute.

This paper is a computational study of the behavior of aerodynamics characteristics of an airfoil with blunt trailing edge and studies the effects aerodynamic performance caused by modifications made to the trailing edge. Blunt trailing edge airfoils are of interest in the engineering of large wind turbine blades because they allow for a strong structure with a high aerodynamic lift to structural weight ratio. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as decreased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Also vortex shedding in this airfoils, induces fluctuating loads and radiated noise. In the present investigation, we tested the effects of two cavities on the base drag and wake of an airfoil with blunt trailing edge. In two-dimensional subsonic flows, any method that increases the base pressure of the airfoil with blunt trailing edge consequently reduces the base drag. When the cavity is introduced to the trailing edge, the base pressure increases. Also the cavity caused trapping and stabilizing the vortex

This work presents a numerical study to investigate the heat transfer characteristics of a 2-D rectangular composite porous radiant burner (CPRB). In the construction of porous burner, the porous layer is considered to be composite consisting of upstream and downstream layers with equal thickness but with different physical and radiative properties. In the present work, a two dimensional rectangular model is used to solve the governing equations for porous medium and gas flow. In order to analyze the thermal characteristics of the CPRB, the coupled energy equations for the gas and porous medium are solved numerically and the discrete ordinates method is used to obtain the distribution of radiative heat flux in the porous media. Finally, the effects of the various factors on the performance of CPRB are determined. Computational results show that the high porosity and low scattering coefficient for downstream porous layer are desirable for maximizing the CPRB efficiency in comparison to homogeneous one. Comparison between the present results with those obtained by other investigators shows a good agreement.

Pulsed Current Plasma Arc Welding (PCPAW) is one of the most widely used welding processes in sheet metal manufacturing industry. In any fusion arc welding process, the weld bead geometry plays an important role in determining the mechanical properties of the weld and hence quality of the weld. Moreover, the geometry of weld bead involves several simultaneously multiple quality characteristics such as front width, back width, front height and back height, which must be closely monitored, controlled and optimized. This paper presents the optimization of the PCPAW process by using the grey relational analysis considering the aforementioned quality characteristics. The specific targets are maximum front width and back width, minimum front height and back height. Experiments were performed under different welding conditions such as peak current, back current, pulse rate and pulse width using AISI 304L stainless steel sheets of 0.25mm thick. An Response Surface Method (RSM) based Central Composite Design (CCD) experimental design is used to conduct experiments. Optimal welding parameters were determined by the grey relational grade obtained from the grey relational analysis. Optimal results have been verified through confirmation experiments.

There are many parameters that affect the sheet hydroforming process such as fluid pressure, material properties, interfacial friction between blank and tool surfaces, etc. In this paper, a FEM-based Taguchi method is used to determine the effects of forming parameters on the quality of part formability in the process of hydrodynamic deep drawing assisted by radial pressure. Four important forming parameters, fluid pressure, friction coefficient at blank/punch interface, die entrance radius and the amount of gap between die rim block and blank holder are considered in this investigation. In order to have more comprehensive study, three different workpieces are used as the case studies. Three-dimensional FE models are developed for simulating the forming process. After experimental validation, these models are used for performing the set of experiments designed by Taguchi’s orthogonal array. The signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) techniques are used to calculate the contributions of each of the mentioned parameters to the output characteristic. The results indicate that fluid pressure in the die cavity and friction coefficient at blank/punch interface are the most influential parameters. Also, die entrance radius and the amount of gap between die rim block and blank holder have considerable effect on the part formability. The obtained results may provide useful guidance on determining forming parameters. Also, further optimization of the forming parameters can be done based on the degree of importance of the parameters on the sheet hydroformability.