Contents of Journal of Mechanical Engineering 57, 1 (2006)
PALENČÁR, R., GROS, P., HALAJ, M.: Evaluation of the positional deviation
of numerically controlled axes 1
SINGH, S., MAHESHWARI, S., PANDEY, P. C.: An experimental investigation
into Abrasive Electrical Discharge Machining (AEDM) of Al2O3
particulate reinforced Al-based metal matrix composites 13
BEITHOU, N.: Heat transfer aspects in bottom flow mixing of cold water
and hot water in domestic hot water storage tank 34
SARANJAM, B., BAKHSHANDEH, K., KADIVAR, M. H.: Dynamic behaviour of
a beam with non-uniform linear varying cross-section under moving load 45
Abstracts
Evaluation of the positional deviation of numerically controlled axes
RUDOLF PALENČÁR, PETER GROS, MARTIN HALAJ
Modern production machines must meet different criteria related to their performance.
The positional deviation (difference between the actual and target position) belongs to the
important criteria that describe the performance of numerically controlled axes. The
procedure for determination of such deviation is described in the international standard ISO
230-2: 1997. This standard provides calculation of the positional deviation only in several
discrete (measuring) points. Moreover it does not consider effects of the measuring instrument
on the obtained results. The following paper introduces the procedure for estimation of the
positional deviation in any point of the axis travel, together with the uncertainty of such
estimate.
An experimental investigation into Abrasive Electrical Discharge Machining
(AEDM) of Al2O3 particulate reinforced Al-based metal matrix composites
SHANKAR SINGH, SACHIN MAHESHWARI, POORN CHANDRA PANDEY
Modern industrial ultra-demanding applications have been increasing rapidly leading to the
development of advanced materials having specific set of properties. Machining of these advanced
materials such as metal matrix composites, superalloys, and engineering ceramics is difficult to
carry out due to their design requirements, which demand for complex geometry to be machined
having high precision, high surface finish, and less machining costs. The conventional machining
applied to these materials typically results in low stock removal, surface damage and rapid wear of
the cutting tool. General appearance of machined surface with conventional EDM is matt surface
with the work material being subjected to a Heat Affected Zone (HAZ) and the top surface layer
comprising of recast (white) layer due to spark discharges. This recast surface layer is generally
removed by supplementary processes such as hand polishing, etching or heat treatment, leading to
increased cost and time. Research on EDM is taking a new orientation by the development of
Abrasive Electrical Discharge Machining (AEDM) process, in which free abrasive grains are mixed
in the dielectric fluid. It is a hybrid process, which is characterized by the mutual assistance of
mechanical interaction (abrasion) and thermal interaction (electrical spark erosion) for the removal
of material from the workpiece, resulting in good machinability and improved surface finish giving
a polished look.
This paper presents the details and results of an experimental investigation carried out on
work specimen 6061Al-Al2O3 p-20% cast aluminium metal matrix composites using AEDM process
with addition of SiC abrasive powder in dielectric and using copper tool electrode. The work
specimens have been manufactured by one of the Liquid Metal Processing technique known as Stircasting method.
The machining parameters or control factors considered are
Heat transfer aspects in bottom flow mixing of cold water and hot
water in domestic hot water storage tank
NABIL BEITHOU
This study is a part of a project, aimed to create a deep understanding of how
to use effectively the available hot water resources. The current study is directed to
analyse the mixing nature of the cold and hot water inside the storage tank for bottom
supply of cold water. An experimental rig consisting of hot water reservoir, cold
water reservoir, water pump, flow meter, hot water storage tank, and a PC with Lab-View
data acquisition system, was constructed to collect the necessary data for
analyses. Four different flow rates 3, 6, 8, and 9 l/min have been taken under
consideration.
It has been observed that high turbulent mixing occurs especially at 8 l/min
and 9 l/min as a result of the high flow rates; this resulted in higher heat transfer rate
and less available hot water for customs use. At higher flow rates it was clear that
turbulent mixing is dominant, this means that a small amount of hot water can be used
in such cases and the rest of the hot water comes to be with a low temperature, which
can be not usable.
It is important not to mix the available hot water by cold water, which will
accelerate the heat transfer rate. There is a need to stop the turbulent mixing in the
case of bottom cold water supply. A current study for ending the high turbulent
mixing of the hot and cold water in the case of bottom cold water supply is to cover
the cold water inlet by a metallic cup which will distribute the entering water onto a
horizontal plan thus ending the turbulent mixing in bottom flow supply of cold water.
Dynamic behaviour of a beam with non-uniform linear varying
cross-section under moving load
BAHADOUR SARANJAM, KAMBIZ BAKHSHANDEH, MOHAMMAD HASSAN KADIVAR
In this study, the dynamic behaviour of a beam with non-uniform linear varying cross-section
subjected to a single force travelling at a constant velocity has been investigated by use
of finite element method. Initially the finite element method (FEM) is validated by analytical
result of a simply supported uniform beam. With verification of FEM, the dynamic study of
non-uniform cross-section beam under the action of moving loads is carried out by this method.
For investigation of material effectiveness, two materials are considered (steel and aluminium).
This study shows that the magnification factor is a function of force travelling speed and
cross-section variation angle (tapering angle). Maximum dynamic magnification factor is occurred at
a tapering angle, which is named critical tapering angle. The MSC.Nastran is used for finite
element analysis.