Contents of Journal of Mechanical Engineering 53, 1 (2002)
J. FIALA, I. SCHINDLER, R. FORET, S. NEMECEK: Examination
of engineering materials structures and its degradation by X-ray
diffraction (in Czech) 1
M. KARAS, A. P. ZIELINSKI: Hybrid Trefftz least square element
for plane elasticity 24
B. SAMANTA, S. A. AL-ARAIMI, R. A. SIDDIQUI: A neural network
approach to estimate fatigue life of 6063 aluminum alloy 36
L. PUST, A. SKUDEROVA: Damping induced into vibrating system
by a limited energy source 45
Abstracts
Examination of engineering materials structure and its degradation by X-ray
diffraction
JAROSLAV FIALA, IVO SCHINDLER, RUDOLF FORET, STANISLAV NEMECEK
The goal of this paper is to draw attention to an X-ray diffraction (XRD)
technique which allows to obtain very useful data on the internal structure of
materials. The technique consists in the examination of the azimuthal
(lateral) diffraction line profile, i.e. the size, number and shape of
individual diffraction spots that discontinuous diffraction line consists of.
Each spot represents the diffraction image (topograph) of a definite
crystallite (the orientation of which meets the Bragg condition) and provides
information on the size, shape and orientation of this crystallite. Such an
information is not easy to obtain by other methods and can be advantageously
used in the development and optimization of technological processes. Another
domain in which this method can be usefully exploited is monitoring of
processes which degrade the materials structure in course of their service and
predicting the residual life-time of the products and construction parts made
of them. The recent development of the instrumentation technology (area
electronic position-sensitive detectors and polycapillary collimators)
provides the base for an extensive employment and a great boom in the usage of
this XRD technique for the characterization of materials structure at the
onset of the third millennium.
Hybrid Trefftz least square element for plane elasticity
MAREK KARAS, ANDRZEJ PIOTR ZIELINSKI
The Hybrid Trefftz (HT) element with the least square formulation for plane
elasticity problems is presented and compared with the well-established HT
Displacement element. The convergence of the solution is carefully studied (in
the global and local sense). Numerous tests proving the efficiency of the
element are presented.
A neural network approach to estimate fatigue life of 6063 aluminum alloy
BISWANATH SAMANTA, SAEED A. AL-ARAIMI, RAFIQ A. SIDDIQUI
A procedure is presented to estimate fatigue life of
Aluminum-Magnesium-Silicon (Al-Mg-Si) 6063 alloy using a neural network based
approach. The aluminum alloy samples were heat-treated and aged at different
combinations of temperature and time. The samples were tested to obtain
fatigue life. The normalized data of ageing conditions were used as inputs to
an artificial neural network (ANN) with the corresponding fatigue life data as
target outputs. The ANN was trained using backpropagation algorithm with a
subset of the experimental data and tested with the remaining set of data. The
results show effectiveness of the ANN in estimating fatigue life of 6063
aluminum alloy for different ageing conditions. The results of ANN are found
to be better than that of multiple regression analysis.
Damping induced into vibrating system by a limited energy source
LADISLAV PUST, ALENA SKUDEROVA
Influence of a joined engine on the mechanical system was very often studied
only from the point of stability of forced vibrations in resonance zone (so
called Sommerfeld effect). Very small attention was paid to the increased
damping of the whole system. In this paper, the dynamic properties
of a very simple torsional undamped system connected by a driving motor
with limited power are studied. The courses of the eigenfrequencies and
response curves of such a system are presented and analyzed. The induced
damping depends on the slope of the driving motor as well as on the structure
of the system, and it can reach even aperiodic damping.