Abstract: In this report, the indentation method of measurement for residual stress in structural
ceramics is discussed. The residual stresses in Al2O3, Si3N4 and ZrO2 ceramics were evaluated with
the indentation method. The value obtained by the indentation method was examined as a function of
the microstructure, using Al2O3 ceramics differing in microstructure (grain size and aspect ratio). The
residual stress values in Al2O3 and Si3N4 obtained by the indentation method at 98 N agreed well with
the values obtained by the X-ray method. The residual stress value in ZrO2 obtained by the indentation
method was close to the value obtained by the X-ray method, when the indentation load was 294 N.
For estimating the residual stress in ZrO2 with the indentation method, the influence of the phase
transformation induced by the indentation is added to the original residual stress, when the
indentation is small. The value obtained by indentation method differed with the aspect ratio of the
grains in Al2O3. It was thought that the origin of the variation was the difference in crack propagation
resistance in different materials
Abstract: Bi-Te-Sb compound material was developed by spark plasma sintering process. The
electrical, thermal, thermoelectric and mechanical properties also obtained by the experiments. This
paper discusses performance and strength of the thermoelectric cooler made of Bi-Te-Sb compound
alloy. The effect of the current has been investigated. The coefficient of performance (COP) is the
primary factor to evaluate the performance of the coolers. Using the FEMLAB software package
finite element (FE) analysis was carried out with properties of Bi-Te-Sb compound alloy from
experiments. The temperature distributions, the stress distributions and the COP in the thermoelectric
cooler were obtained.
Abstract: Effects of TiAlN coating conditions on the cutting characteristics during machining high
hardened tool steel using coated ball end mill were studied in this research. KP4 steel and STD 11
steel were used as workpieces. Minimum quantity lubrication (MQL) was utilized in the cutting.
Scanning electron microscope, optical tool, and a tool dynamometer were used to measure coating
thickness and progress of tool wear. Results showed that the cutting distance using TiAlN coated
ball end mills was longer than that using WC-Co ball end mill by 2.3~5.7 times for KP4 steels and
about 2.5~4.3 times for STD11 heat treated steels. The multi layer TiAlN coated ball end mill
showed better performance of machining of hard steels than single layered coated tools.
Abstract: An effect of anisotropy on the thermoelectric properties of Bi1Sb3Te6 added with Au alloys
prepared by a mechanical alloying process has been studied. The conduction properties including
electrical conductivity and thermal conductivity were increased with Au content. The electrical
conductivity and the power factor of the perpendicular direction to the pressing direction were larger
than those of the parallel direction to the pressing direction. The intensity of (1 1 0) perpendicular
plane was larger than that of the parallel plane. It was suggested that the increase of intensity of the
(1 1 0) plane would contribute to improve the thermoelectric performance. Although the power factor
and thermal conductivity revealed the anisotropic behavior with direction, the Z value showed almost
the equal value regardless of direction. From these results, it appeared that the Z value of the
Bi1Sb3Te6 added with Au alloy prepared by powder metallurgy process was almost isotropic.
Abstract: A study has been made on the effects of antimony (Sb) and strontium (Sr) additions on the
microstructure of Mg-Al-Si alloys. Results showed that the additions of Sb and Sr can modify the
morphology of Mg2Si particles from Chinese script shape to refined polygonal shape. Tensile strength
and creep resistance were improved and tensile elongation was also increased in the modified alloy
with Sb and Sr. The addition of Sr was more effective than Sb modification of AS52 alloy for refining
microstructure and thus improving properties.
Abstract: The effect of Al content on the castability, tensile and creep properties of Mg-xAl-Zn alloy
was investigated. The molten Mg-(3~11)Al-Zn alloys of 700 °C were poured into the mould designed
to estimate castability. Tensile and creep tests were performed for the alloys. It has been shown that
creep resistance decreased while tensile strength improved with increasing Al amount. Microstructure
study revealed that morphology of Mg17Al12 is main factor determining the tensile and creep
properties of as cast Mg-xAl-Zn alloys. The final purpose of this study is to develop the heat resistant
Mg alloys to apply transportation systems such as automobile. Further study on effect of heat
treatment and additional alloying elements on the microstructure and mechanical properties of
Mg-xAl alloys is going to be performed.
Abstract: In this study, we performed fracture tests on thermally aged DLC thin films by using
micro-indentation and nano-indentation and investigated the deformation and fracture
characteristics of these films. The aged high hydrogen films have better characteristics such as thermal
and mechanical stability than low hydrogen films.
Abstract: The residual stresses in a polymeric thin film deposited on Si wafer induced during cooling
from a cure temperature down to room temperature are investigated. The laser scanning method and
the boundary element method (BEM) are employed to investigate the residual stresses. A 3 μm thick
polyimide film is deposited on a relatively thick Si wafer. The normal stress across thickness of the
thin film is estimated from wafer curvature measurements to be 20MPa . The boundary element
method is employed to investigate the whole stresses in the film. The numerical result for the normal
stress across thickness of the film, σ xx , shows good agreement with the experimental result obtained
by using the laser scanning method. The singular stress is observed near the interface corner. Such
residual stresses are large enough to initiate interface delamination to relieve the residual stresses.
Abstract: This study is conducted in order to estimate the structural characteristics for inlet port of air
breathing engine under flight condition at 12 ~ 15 km height and Mach Number 2 ~ 4. Inlet port of air
breathing engine is heated up from 307 oC to 427 oC, so that is reached plastic zone partially. The
material properties at high temperature such as young’s modulus, thermal expansion coefficients and
thermal conductivity are applied to the analysis. The transient temperature and stress analysis are
performed by the finite element method using nonlinear commercial code ABAQUS. The analysis is
performed for the two materials, Titanium alloy and AISI4130 Steel and two FEM element type, shell
and solid, to select preliminary design model for flight condition. Thermal boundary conditions are
applied at inlet port until 5 s, and these conditions are maintained until 150 s. The results of the
analysis recommend tendency of thermal stress and temperature contour. This study is expected
useful to select the structural material and to determine shape of air inlet port of air breathing engine
which satisfied the structural design safety.
Abstract: A new type of thermotropic main-chain liquid crystalline polyurethanes containing
biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene
diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate,
with 4,4′-Bis(11-hydroxyundeyloxy)biphenyl (BP11). The structure of the monomer and the
corresponding polymers were confirmed FT-IR and 1H NMR spectroscopic methods. BP11 exhibited
a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline
polyurethanes except for 1,4-phenylene diisocyanate/BP11 based polyurethane. For example,
polyurethane 2,5-TDI/BP11 exhibited monotropic liquid crystallinity in the temperature ranges from
173 to 156 °C on the cooling stage.