INTERNATIONAL JOURNAL OF ADVANCED DESIGN AND MANUFACTURING TECHNOLOGY
Year:2009 | Volume:2 | Issue:4 (8)|Papers Count:8

The main objective of an extrusion die is flow balancing as an unbalanced flow causes a distorted product together with residual stress. In this paper a strategy is presented for flow balancing a U-shaped profile with different wall thicknesses. For this purpose, a choker bar is provided at thicker wall to locally restrict excessive flow passing through the thicker section. For optimal design some of die dimensions are considered parametric which will be variable in three levels. The analysis of flow was performed using FLUENT software in order to get the best combination of the parameters which produces the best balance. After the optimum design was obtained, an experimental die is manufactured. It is considered in the manufacture of the die that height of choker to be variable during extrusion for finely adjusting the balance. Results demonstrate that experiments are in good agreement with simulations.

Injection molding is the most widely used process for producing plastic parts.In this process, an important issue is to predict and optimize the warpage before manufacturing. In this paper, a simulation with MOLDFLOW software is proposed to optimize the injection molding process. The optimization process aims at minimizing the warpage of the critical injection molding part in which process parameters, gate location and its shape are the design variables. Moldflow Plastic Insight software is used to analyze the warpage of the injection molding part. The mold temperature, melt temperature, injection time, packing pressure and packing time are regarded as process parameters. The results shown that to reduce warpage in plastc part not only the process parameters should be optimized but also effect of gate shape and especially its position should be considered in precise parts. Moreover the results shown that moldflow injection molding simulation software is able to accurately predict the part warpage, but it doesn’t consider the viscoelastic behaviour of plastic material in process.

In this paper the interior noise level of a vehicle due to structural vibration, named structure borne noise, as a part of NVH analysis has been investigated. First structural analysis is performed and vibrational behavior of structure carried out due to power plant excitations. Then interior acoustic cavity response for such excitation and resultant noise is determined. Vibrational analysis is performed on three dimensional structure and internal cavity, by considering all the effective components and vibrational tracks in the cabin. Finally, the acoustical behavior of the cavity in different frequencies predicted by cavity normal modes, and results are used to reduce noise level through passive noise control methods.

Springs are the  mechanical parts which have many application in industries. Static and dynamic forces cause relaxation in these parts so that they lose some of their free length and reaction force. Springs constant are very important in airplane and vailway industry since constant and variable forces are applied to them in period time, therefore it is necessary to avoid decreasing in spring constant in this condition. In this research, at first manufactured springs were stress relieved under different temperatures. In the next step constant displacements were applied to stress relieved springs by means of designed fixture. Springs constant changes and rate of these changes during different stages of the test were obtained. Results shownd that the stress relieving  at 300 ° C has the best effect on prevention of decreasing in springs constant and  free length under static long-term load.

In this paper, a multi purpose function is presented for optimum design in circular hydrostatic axial bearings. One or more parameters that are directly or indirectly dependent on given data are optimized. Usually in the local optimization methods, it is not possible to optimize several parameters simultaneously. In this research, simultaneous optimization of the power loss and the oil temperature rise as effective parameters for increase in efficiency of bearing is considered. The genetic algorithm is used in simultaneous optimization of the power and the temperature values. The accuracy of the multi purpose optimization is evaluated by a practical sample and the obtained results of simultaneous combination of parameters effect are compared with distinct functions.

An investigation has been carried out on the temperature of a biscuit on the cooling line of Razavi Food Industries Company. For thispurpose, the time variations of Biscuit’s top surface temperature in traveling from oven to packing station on the conveyor packing station by conveyors has been studied. The Fourier field equation for transient heat transfer is used as the basis for the deterministic modeling of a single biscuit. The biscuit-conveyors interface is considered as an adiabatic surface. Forced convection, natural convection and radiative heat transfer mechanisms on the top of the biscuits are investigated. The effects of cooling air temperature and also its direction on the temperature reduction of biscuit top surface has been shown. In addition validation of the numerical method has been shown by comparison with the measured data that has been obtained experimentally in the company.

In this study, as for the re-casting, surface alloying and re-solidification layer of this alloys at the work piece level machining with Wire Electro discharge machining (WEDM), changes of surface micro hardness with changes of operational parameters has been studied. Therefore, study shows using surface alloying phenomena with the diffusion of wire material into the machined surface and selection of operational parameters and suitable materials for wire cutting, surface mechanical properties can be modified simultaneously with the workpiece machining process. Also Shown in this study, by changing operating parameters such as peak power and open circuit voltage, the diffusion of wire material into the workpiece surface layer is increased, whereas with increasing pulse off time and dielectric flushing pressure, the diffusion of wire material into the workpiece surface layer is decreased. At last with increasing these parameters also change of micro hardness surface layer accompanied by a change alloy surface layer formed on the surface.

In this research between 3-dimensional and axisymmetric modeling for movement of nano-particles in passing through a aerodynamic lens, and also between these models and famous model of Wang & Liu was compared. For this purpose, output of nano-particles penetration, divergence angel, and nano-particle velocity with Wang & Liu model was compared. Geometrical model used for aerodynamic lens compared to past research is more complete and has been selected based on practical model. With regard to low density of nano-particles, hypothesis of one way interaction between liquid and molecule has been selected. That is, movement of nano-particles does not have any effect upon flowing field. Trajectory of nano-particles with diameters of 1, 2, 6, 10, 30 and 50 were investigated. Cumulative fraction of radial that shows the amount of nano-particles divergence compared to axial system for diameters of 2, 6, 10, 20, and 30 were calculated in both three dimensional model and symmetrical model and compared with Wang & Liu model. Results are shownd that nano-particles with lower diameter because of more influence from outside power become farther and this matter create difference between results of two model, since in three dimensional model, nano particles are affected in three ways by this power. These resultd show that axisymmetric modeling in nano particles movement is not accurate and exact. Also, there is a good conformity between applied model and Wang & Liu model.