Abstract: Recently, the use of composite material to railway vehicles is gradually increasing due to its
light weight. The concept of light weight design will be very helpful for the tilting train to travel
around a curve at a faster speed because the light weight car body makes the center of gravity lower.
The impact characteristics of composite materials should be investigated because the impact property
of composites is very important for the design and repair of a tilting train. This paper investigates the
low-velocity impact and damage characteristics conducted on woven carbon/epoxy laminates for a
tilting train. Low-velocity impact tests were carried out at different energy levels on woven type of
laminates using a drop-weight apparatus. The impact-induced delaminations are examined by
ultrasonic technique such as C-Scan. Those delaminations are also examined by laser technique such
as ESPI (Electronic Speckle Pattern Interferometry). Experimental results show that the type of
damage is dependent on the impact energy level and the delamination area becomes larger as the
impact energy increases.
Abstract: Several nondestructive evaluation (NDE) techniques, including ultrasonic C-scan, X-ray
computed tomography (CT), and infrared (IR) thermography, were employed on ceramic matrix
composites (CMCs) to illustrate defect information that might effect mechanical behavior and to
analyze structural performance of CMCs. Prior to tensile testing, through C-scan and CT analyses
results, the qualitative relationship between the relative ultrasonic transmitted amplitude and porosity
based on CT was exhibited. An IR camera was used for in-situ monitoring of progressive damages
and to determine temperature changes during tensile testing. Moreover, scanning-electron
microscopy characterization was used to perform microstructural failure analyses. This paper
describes the use of nondestructive evaluation (NDE) techniques to facilitate the understanding of
tension behavior of CMCs.
Abstract: To analyze the stress distribution and the crack initiation due to the location of the defects,
artificial defects were made on the different locations of the high strength monolithic Al and GLAss
fiber REinforced laminate (GLARE). Experimental study shows that the defect location in the
vicinity of the circular hole was changed from ° = 90 4 θ to ° = 0 1 θ , the stress concentration was
increased. The stress concentration of GLARE was about 15% higher than that of the monolithic Al.
When the defect was at ° = 30 2 θ , Multi Site Damage (MSD) crack was found in the monolithic Al but
not in GLARE. Instead of MSD crack, a delamination was made in GLARE and that it resulted in the
prevention against the second crack initiation.
Abstract: Bolted joints are widely used for composite structures. As is well known, excessive
bearing load gives rise to bearing failure at hole boundaries. Detecting bearing failure is important
for assuring integrity of composite structures. Since conventional nondestructive inspection
methods are expensive, cumbersome, time-consuming, and not suitable for health monitoring, a
simple, low-cost inspection method for bearing failure must be developed. Authors have
demonstrated the feasibility of detecting bearing failure by using an electric resistance change
method. In this study, more detailed analyses were carried out to investigate the detectability in
terms of the damage size and the distance between damage and electrodes. The results show that
bearing failure of less than 10mm square causes the electric resistance change of a few hundred
ppm and thus can be easily detected, and that the electrodes can be mounted more than 10 mm far
from a bolt hole.
Abstract: In this paper, a smart skin, i.e. a conformal load-bearing antenna structure, which is a
multi-layer sandwich structure composed of carbon/epoxy, glass/epoxy and dielectric material,
designs, analyses, fabrications and tests are conducted. Mechanical properties of each structural layer
of the designed smart skin are obtained from experimental tests. Tests and analyses are conducted to
study the deformation behavior of the smart skin under compressive loads. The measured data are
compared with the numerical results from geometrically linear/nonlinear finite element analyses.
Numerical prediction for the buckling load of the smart skin agreed well with the experimental data.
Abstract: For improving quality of a carbon fiber reinforced composite material (CFRP) by
preventing defects such as delamination and void, it should be inspected in fabrication process. Novel
non-contacting evaluation technique is required because the transducer should be contacted on the
CFRP in conventional ultrasonic technique during the non-destructive evaluation and these
conventional contact techniques can not be applied in a novel fiber placement system. For the
non-destructive evaluation of delamination in CFRP, various methods for the generation and
reception of laser-generated ultrasound are applied using piezoelectric transducer, air-coupled
transducer, wavelet transform technique etc. The high frequency component of laser-generated
guided wave received with piezoelectric sensor disappeared after propagating through delamination
region. Air-coupled transducer was tried to be adopted in reception of laser-generated guided wave
generated by using linear slit array in order to generate high frequency guided wave with a frequency
of 1.1 MHz. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled
transducer and linear slit array. Transmitted laser-generated ultrasonic wave was received on
back-wall and its frequency was analyzed to establish inspecting technique to detect delamination by
non-contact ultrasonic method. In a frequency spectrum analysis, intensity ratio of low frequency and
center frequency was approvable parameter to detect delamination.
Abstract: Ultrasound techniques have recently been widely used for the characterization of articular
cartilage (artC) in vitro and in vivo. The sound speed in artC plays an important role either as an
indicator for the artC degeneration or for the calculation of other parameters such as tissue thickness
or stiffness. Previous studies on artC have been carried out in bathing saline solutions with different
concentrations to investigate swelling behaviors of artC. There is a lack of information in the
literature about the effect of bathing saline concentration on the sound speed of artC. In the present
study we measured sound speed in artC under different saline concentrations ranging from 0M to
2.5M at the room temperature temperature (21±1°C). ArtC specimens from bovine patellar models
(n=20) were used in these in-vitro studies. Results demonstrated that the sound speed in artC ranged
from 1681±50 m/s to 1816±54 m/s when the saline-concentration varied from 0M to 2.5M, while the
sound speed in saline changed from 1521± 3 m/s to 1674 ± 3 m/s. The sound speed linearly (r2 = 0.99,
p <0.001) increased with the increase of the saline concentration at a rate of 55 m/s per mole change.
It is concluded that the variations of the bathing saline concentration significantly affect the sound
speed in artC and should be well documented in the ultrasonic studies of artC.
Abstract: PMN-PT, a piezoelectric single crystal, has been known to be a better material for
transducer arrays due to its high electromechanical coupling coefficient (k33) and high dielectric and
piezoelectric constants. It may also be good even for high frequency single element transducers using
relatively high kt and low attenuation and velocity dispersion. However, it’s challenging to fabricate
high frequency transducers using PMN-PT since it is easily breakable and requires small area and
thickness of the transducer. A KLM model was used to simulate a 40 MHz single element transducer
including 2 matching layers and a conductive backing. The simulation showed that the PMN-PT
transducer turned out to be better in sensitivity and bandwidth than a 40 MHz LiNbO3 transducer. A
40 MHz PMN-29%PT transducer was fabricated and the pulse echo signals were obtained and
analyzed. Its sensitivity was found to be –48 dB and –6dB bandwidth was about 48 %.
Abstract: Pressure distributions on the buttocks and thighs by the functional electrical stimulation on
the gluteus maximus, sartorius and hamstring in the seating posture were analyzed for ten healthy
young volunteers in order to determine which muscle can be stimulated for pressure ulcer prevention.
Muscles were stimulated every 5 seconds over 30 seconds by the MP150 stimulator. Pressure
distribution and ground reaction forces on the stimulated buttocks and thighs increased when the
gluteus maximus was stimulated. Pressure on the stimulated thigh slightly decreased
when stimulating sartorius and hamstring individually. With a simultaneous stimulation of the
gluteus maximus and sartorius, pressures on the stimulated buttocks and thighs increased
significantly, but pressure on the opposite buttock decreased significantly. With a simultaneous
stimulation of the sartorius and hamstring, both pressure on the stimulated thigh and the ground
reaction force significantly decreased.
Abstract: The purpose of this study is to quantitatively evaluate foot motions in the normal and hallux
valgus(HV) patients using a proposed multi-segment foot model. Results showed that HV patients
exhibited relatively smaller flexion/extension, especially in terminal stance. An early abduction at the
ankle during terminal stance was also noted in HV patients, which resulted in an excessive abduction
in subtalar joint. In HV patients, medial MP joints exhibited excessive amount of adduction during
terminal stance. In HV patients, hallux MP joint and talocrural joint exhibited excessive external
rotation over the whole period of gait cycle. Understanding the detailed foot motions by the present
multi-segment foot model would be very useful to diagnose and to treat patients with various foot