Abstract: Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the
tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause
oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which
causes fretting wear in contact parts of tube-support. The fretting wear of tube-support can threaten
the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of
tube-support is required. The fretting wear tests were performed with supporting grids and cladding
tubes, especially after corrosion treatment on tubes, in water. The tests were done using various
applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube
materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick
phenomena the wear depth was changed as increasing load and temperature. The maximum wear
depth was decreased as increasing the water temperatures. At high temperatures there are the regions
of some severe adhesion due to stick phenomena.
Abstract: Wear and scuffing tests were conducted using friction and wear measurement of piston
rings and cylinder blocks for the low friction diesel engine. Scuffing, described as sudden
catastrophic failure of lubricated sliding surfaces, usually characterized by a sudden rapid increase
in friction, temperature and noise, is an important failure mode on sliding surfaces. In this study, the
frictional forces, wear amounts and cycles to scuffing in boundary lubricated sliding condition were
measured using the reciprocating wear tester. The cylinder blocks with several values of surface
roughness were used as reciprocating specimens, and a piece of piston ring was used as fixed pin.
As increasing load by several steps in lubricated sliding, the friction signals indicated the state of
surface interactions, such as friction forces, changes of lubricating films and scuffing. There were
some rapid increases in friction forces just before the scuffing would occur. It was found that there
was the optimum value of initial surface roughness to prolong the wear life of sliding surfaces. As
decreasing the surface roughness of cylinder blocks, the wear amounts were decreased due to
increasing the contact area. There was also the optimum surface roughness to reduce the friction
and to prolong the scuffing life.
Abstract: It is studied the deformation process by IN SITU surface morphology observation for Mg
alloy AZ31 sheet in an SEM. It is found that the deformation starts phenomenologically from
twinning process, making out of the first twinning in both intact crystallite grains and existing
twinned bands by rolling process, and the secondary twinning in original twinned bands. As the
plastic strain increases the twinned bands turn to transverse direction (TD) of the sheet in all three
tensile directions: rolling direction (RD), TD and 45° to rolling direction (45). The turning
characteristic of grain boundaries were dealt with as well.
Abstract: New laminate design for improved toughness in hexacelsian-alumina composite is
introduced. The composite is based on crack deflection in a weak interphase in the alumina matrix and
hexacelsian interphase. The strength and toughness of the laminated composite were studied both
qualitatively by electronic microscopy and measuring flexure strength. The metastable hexacelsian
interphases had partially microcracks to provide crack deflection in the composite, and the crack
deflection noticeably proceeded along the meta-stable hexacelsian interphase. Load-deflection curve
for the laminate showed improved work of fracture of 2.23 kJ/m2.
Abstract: This research aims to investigate strain rate effect on the out of plane shear strength of
unidirectional fiber composites. Both glass/epoxy and graphite/epoxy composites were considered in
this study. To demonstrate strain rate effect, composite brick specimens were fabricated and tested to
failure in the transverse direction at strain ranges from 10-4/s to 700/s. Experimental observations
reveal that the main failure mechanism of the specimens is the out of plane shear failure taking place
on the plane oriented around 30 to 35 degree to the loading direction. The corresponding out-of-plane
shear strength was obtained from the uniaxial failure stress through Mohr-Coulomb strength analysis.
In addition, the associated shear strain rate on the failure plane was calculated through the coordinate
transformation law. Results show that the out-plane shear strength increases with the increment of the
shear train rates. A semi-logarithmic function expressed in terms of the normalized shear strain rate
was employed to describe the rate dependence of the out-plane shear strength.
Abstract: A finite element model is proposed to determine the residual strength and the evolution
of damage area of indented sandwiches structures with Nomex honeycomb core and metallic skins
indented by a spherical indenter under longitudinal compression load (CAI). The honeycomb is
represented by a grid of non-linear springs which its behavior law is obtained by performing simple
transverse uniform compression test on a block of honeycomb alone.The comparisons between
computation and test result show that the model can simulate accurately the form of damage
geometry during indentation, its residual print when the load is relieved (relaxation) and the residual
strength and the evolution of damage geometry during CAI.
Abstract: Pt-IrOx and Au-V2O5 thin films were created by magnetron co-sputtering from multiple
targets in an Ar-O2 mixture. Successful Pt-IrOx production required high O2 partial pressure and
slow deposition rate followed by post-annealing in pure O2. In contrast, deposition of Au-V2O5
films required relatively low O2 partial pressure, and did not need any post-anneal. These different
strategies for forming oxide dispersion strengthened films in a multi-target reactive sputtering
configuration are directly related to the thermodynamic characteristics of the two materials systems.
The most important characteristics are the low equilibrium oxygen solubility in Pt and Au, and the
different degrees of oxygen affinity by Ir and V.
Abstract: The quality of surface of the product of metal forming processes depends on physical
processes in the vicinity of frictional interfaces between the material and tool. It is well known that
material properties in a narrow layer in the vicinity of such interfaces are usually quite different
from the properties in the bulk. It is therefore necessary to develop a special approach to account for
this feature of the distribution of material properties. A possible approach is proposed in the present
paper. It is based on the concept of strain rate intensity factor.
Abstract: Thin metal films often play an important role as structural elements or reflective surfaces
in MEMS applications. Mechanical properties of the films are important due to their influence on
the performance of MEMS devices that involve bending or stretching metal parts. In order to gain a
better understanding of the mechanical behavior of thin metal films, we have developed a novel
bulge system and measured mechanical properties of aluminum thin films. The thin films were
prepared by e-beam evaporation of high purity Al onto 2 or 3mm ×12 mm rectangular silicon
nitride membrane windows in silicon frames. N2 gas was used to pressurize and thus bulge the
membranes. The bulge height was measured based on changes of capacitance between the
membrane and a fixed, closely spaced electrode. This apparatus provides resolution of
approximately 50 nm in bulge height at a data acquisition rate of 100/sec and provides strain rates
in the membrane up to 10-5/sec. The stability of the apparatus allows stress relaxation measurements
to be made to times of many hours. Time dependent elastic modulus changes of 1 m Al films were
measured over periods of times under constant stress.
Abstract: In this paper, the pumping performance of a piezoelectric micropump is simulated with
commercial finite element analysis (FEA) software COMSOL Multiphysics 3.2a. The micropump is
composed of a 4-layer piezo-composite actuator (LIPCA), a polydimethylsiloxane (PDMS) pump
chamber, and two diffusers. The piezoelectric domain, structural domain and fluid domain are
coupled in the simulation. Water flow rates are numerically predicted for geometric parameters of
the micropump. Based on this study, the micropump is optimally designed to obtain its better