Volume 3 Issue 1
Authors: Sanaz Mirzaparikhany; Mortaza Yari; Mehran Abdolalipouradl
Abstract: In this study, entropy generation of fluid flow in axially moving micro-concentric cylinders for the Couette-Poiseuille slip flow was studied. Fully developed laminar flow was considered with uniform heat flux at the walls. The effects of slip velocity, temperature jump at the walls, and viscous dissipation were taken into consideration. The velocity and temperature profiles were obtained analytically and used to compute the entropy generation. The obtained results were compared with the available data in the literature and an excellent agreement was observed. Effects of Knudsen number, cylinder moving velocity, cylinders radius ratio, Brinkman number and Br/Ω on the entropy generation were also investigated. It was found that by increasing the Knudsen number and cylinder moving velocity the entropy generation is decreased, while any increase in cylinders radius ratio, Brinkman number, and also Br/Ω causes the entropy generation to be increased. It was also found that the fluid friction is the main reason for the entropy generation for flow in the annulus region.
Keywords: Entropy Generation Minimization; Second Laws of Thermodynamics Analysis; Viscous Dissipation; Slip Flow and Temperature Jump; Couette-Poiseuille Flow
Authors: Ali Taghizadeh Armeki; Jafar Bazrafshan
Abstract: In recent years, hydroforming process has been applied in different industries such as aerospace, automotive industry and military industry due to its advantages, like high dimensional accuracy, capability of forming complicated-shaped parts and high drawing ratio. Hydrodynamic deep drawing with radial pressure is one of the hydroforming processes. In this paper, forming of cylindrical cups in hydrodynamic deep drawing with radial pressure was investigated and the effects of pressure path on the cup thickness distribution and punch force were studied. In this study two pressure paths (liner pressure with maximum pressure or step pressure) were used and their thickness distributions were compared. The results of this study showed that by choosing the step pressure path, the quality of the formed cup increases and more uniform thickness distribution will be obtained.
Keywords: Deep drawing; Sheet hydro forming; Thickness distribution; Cylindrical cup
Authors: Sameh S. Habib
Abstract: In the present research, electrical discharge machining (EDM) of carbon fiber reinforced plastic (CFRP) material was studied. The selection of optimum electrical discharge machining parameters combinations for the purpose of obtaining higher cutting efficiency and accuracy is a challenge task due to the presence of a large number of process variables. This paper presents an attempt to develop an appropriate machining strategy for a maximum process criteria yield. A feed-forward back-propagation neural network was developed to model the machining process. The three most important parameters-material removal rate, tool electrode wear rate and surface roughness-were considered as measures of the process performance. A large number of experiments were carried out over a wide range of machining conditions to study the effect of input parameters on the machining performance. The experimental data was used for the training and verification of the model. Testing results demonstrated that the model is suitable for predicting the response parameters accurately as a function of most effective control parameters, i.e. pulse duration, peak current and tool electrode rotational speed.
Keywords: Electrical Discharge Machining (EDM); CFRP; Neural Network Technique; Metal Removal Rate; Tool Electrode Wear Rate; Surface Roughness