Contents of Journal of Mechanical Engineering 62, 4 (2011) 




TANCSICS, F.,GERGYE, T.,HALBRITTER, E.: Using up-to-date software in
technological improvement and optimization of multiple-cavity forging 
                                                                       191                                                      

ZHU, L., JEN, T.-C., YIN, C.-L., KONG, X.-L., YEN, Y.-H.: Experimental
verification of the feasibility and effectiveness of heat pipe cooling 
in drilling applications                                               205

AREFI, M., RAHIMI, G. H.: General formulation for the thermoelastic 
analysis of an arbitrary structure made of functionally graded 
piezoelectric materials, based on the energy method                    221                      

ARAFAT A. BHUIYAN, SADRUL ISLAM, A. K. M.: CFD analysis of different 
fin-and-tube heat exchangers                                           237



Abstracts



Using up-to-date software in technological improvement and optimization of multiple-cavity forging

F. TANCSICS, T. GERGYE, E. HALBRITTER

Forging is a technology frequently used in production of vehicle parts. Shape and dimensions of the blank and occasionally of the finished work piece are provided, and mechanical properties of the starting material are improved by forging. In production of vehicle parts competitiveness is getting more and more important. Frequently, competitiveness can only be increased by making the product to strict deadlines by improving the quality and by reducing the production costs.
These complex requirements can only be met by quicker, more exact and more reliable production planning. Our work is aimed at setting an example for improvement as well as at elaborating an optimization method, at presenting the results gained in order to increase potential to enter the markets. In improvement of mechanical properties, the good grain flow free of folds is very important. A case of folds in grain and its elimination will be presented through an industrial task. In multiple-cavity forging process the blank has significant influence on how much force and work are required in forming. A blank which requires less work in forming is considered more favourable. In making comparisons it is required that various blanks have the same volume. Various blanks were designed with Pro/Engineer software and the same volumes were provided by optimization restricted within the design software. By taking the blank areas into account, in restricted optimization we tried to find a solution how to realize gradual forming beside constant volume of various blanks. The optimization method we have elaborated will also be presented through an industrial task.


Experimental verification of the feasibility and effectiveness of heat pipe cooling in drilling applications

L. ZHU, T.-C. JEN, C.-L. YIN, X.-L. KONG, Y.-H. YEN

This paper presents an experimental investigation to verify the feasibility and effectiveness of heat pipe cooling in drilling operations. The basic idea is to insert a heat pipe at the center of the drill tool with the evaporator close to the drill tip, and the condenser at the end of the drill. Consequently, the heat generated at the tool-chip interface can be removed by convection heat transfer. Experimental studies were involved in three cases, including dry drilling, fluid cooling and heat pipe cooling. Drilling tests were conducted on a CNC machining center with full immersion cutting. The cast iron square block was used as the work-piece, and the high-speed steel was chosen for the drill tool material. End-mill tip temperature was measured with an infrared temperature meter. Flank wear is considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker's microscope. The tests were conducted until the drill was rejected when an average flank wear greater than 0.10 mm was recorded. The results demonstrate that heat pipe cooling in the drilling applications can effectively perform thermal management comparable to the flooding coolant cooling used pervasively in the manufacturing industry, extending the tool life of the drill.


General formulation for the thermoelastic analysis of an arbitrary structure made
of functionally graded piezoelectric materials, based on the energy method

M. AREFI, G. H. RAHIMI

This study deals with the thermoelastic analysis of an arbitrary structure using the energy method. The structure is loaded under the temperature gradient. This structure can be subjected to other external loads such as rotational load and also inner and outer pressures. In this issue, energy method is used for the general thermoelastic analysis of the piezoelectric structures. Energy equation with considering the classical terms cannot predict the thermal behavior of a piezoelectric structure as true as previous methods. The present study proposes a novel term that is introduced as additional energy. This term is necessary energy for increasing the temperature for those sections of structure expanded due to external loads. Final derived equation includes the equilibrium and Maxwell's equations. This procedure indicates that the Maxwell's equation can be derived independently from the energy equation. As an applied problem in the context of the piezoelectric structures, thermoelastic analysis of a FGP rotating pressure vessel is analyzed using the energy method.


CFD analysis of different fin-and-tube heat exchangers

ARAFAT A. BHUIYAN, A. K. M. SADRUL ISLAM

The objective of this numerical investigation is to examine the effect of heat transfer and pressure drop characteristics inside a three-dimensional, four-row fin-and-tube heat exchanger allowing for staggered and in-lined tube array of plain and wavy fin for laminar (400 £ ReH £ 1200) and turbulent (1300 £ ReH £ 2000) flow range using the commercial Computational Fluid Dynamics (CFD) code ANSYS CFX-11. For transitional flow, the k-w turbulence model has been used. Results are presented in the form of streamline patterns, velocity vectors, and temperature and pressure distributions. Code validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) to experimental results from the literature. This study reveals that the flow distinction between plain and wavy fin has an intense influence on the heat transfer and pressure drop performance. Wavy fin shows greater heat transfer and pressure drop performance compared to plain fin arrangements. On the other hand, for a particular Reynolds number (ReH), the efficiency is higher in in-line arrangement than in the staggered case.