Abstract: In a mechanical system that has periodically repeated subcomponents, premature failures or
malfunctions often occur. Due to slight irregularities of parameters of periodic systems, maximal
frequency responses of a few subcomponents become often significantly larger than those of other
subcomponents. These phenomena, called frequency response localization, need to be comprehended
for reliable designs of the periodic systems. In the present study, the effects of parameter distribution
patterns on the frequency response localization are investigated. Probabilistic results of the frequency
response localization characteristics with two distinct parameter distribution patterns are exhibited.
Abstract: The operation error of a robot that occurs inevitably due to the manufacturing tolerance
needs to be controlled within a certain range to achieve proper performance of the robot system. The
reduction of manufacturing tolerance, however, increases the manufacturing cost in return. Therefore,
design engineers try to solve the problem of maximizing the tolerance to reduce the manufacturing
cost while minimizing the operation error to satisfy the performance requirement. In the present study,
a revolute joint model considering uncertainties due to joint clearance is employed to perform a
reliability analysis of the robot manipulator operation. The reliability analysis procedure employs
single Monte-Carlo simulation and a statistical relation between the tolerance and the operation error.
Significant reduction of computing time can be achieved with the proposed method. The present
method is especially effective if sensitivity information is hard to be obtained for the analysis.
Abstract: As a number of aged fossil power plants recently increased, the precise life assessment of
critical equipments gets to be important more than ever. Despite of infrequent likelihood of failure,
the equipments in high pressure and temperature operation condition have traditionally been
considered as critical because of huge consequence of the equipments and hence life assessment of
fossil power plant has been focused on all of the severe operated equipments for past decades.
Nowadays, with Risk-Based Inspection technology being developed rapidly, most of the power plant
utilities get a chance to reduce the scope of the inspection and test and to extend the interval for the
life assessment. This paper provides methodology based on Risk-Based Inspection technology to
optimize the life assessment work scope and interval and also demonstrates the enhanced life
assessment procedure including risk assessment of equipments.
Abstract: Zirconium alloys are used for many applications in nuclear components, such as the
pressure tube material in a pressurized heavy water reactor, nuclear fuel cladding, etc. One of the
problems during the operation of a nuclear reactor is the degradation of the zirconium alloys, which is
due to an increase of the hydrogen content in the zirconium alloy. Therefore a non-destructive
determination of the hydrogen concentration in zirconium alloy is one of the important issues that
need to be addressed. The resonant ultrasound spectroscopy (RUS) technique is evaluated for a
characterization of the hydrogen concentration in Zr-2.5Nb alloy. Referring to the terminal solid
solubility for dissolution (TSSD) of Zr-2.5Nb alloy, the plot of the mechanical damping coefficient
(Q-1) versus the temperature or the deviation of the resonant frequency for the temperature (df/dT)
versus the temperature was correlated for the hydrogen concentration in Zr-2.5Nb alloy. It was found
that the temperature at an abrupt change of the slope can be correlated with the hydrogen
concentration of the Zr-2.5Nb alloy.
Abstract: This paper is focused on a probabilistic design of the honeycomb structure which is a
constituent unit of satellite. The design is considering launching and space environments by kriging
metamodel. The proposed methodology using the kriging metamodel is conducted by stochastic
step-moving method (SSMM) as the criterion of a sequential approximate optimization to satisfy the
global optimum value based on the local optimum value. Also, Design of Experiments (DOE) is used
to reduce computation costs. The honeycomb structure is analyzed for reliability. For the optimal
design, constraints are taken for natural frequency and several stresses that should be considered on
the satellite platform in launching situations. Thermal effects of space environments and wrinkling
are also considered since a structural sandwich is often poor at carrying in-plane compressive loads
and may be inflicted with instability and thermal effect.
Abstract: In-plane characteristics of a single degree of freedom frictional system with a compressed
spring are considered. The compressed spring is vertically installed to the mass moving horizontally
along the friction interface. The compressed spring can introduce a nonlinear negative stiffness into
the in-plane motion. The resulting system has a multiple equilibrium points; an unstable point at the
center and two stable points on either side. It is shown that two stable equilibrium points can be
separated far apart by increasing the compression ratio and the stiffness of the spring. The friction
system is often characterized by stick and slip motions that cause unfavorable effects such as wear,
noise, and chatter etc. It is demonstrated that increasing the compression ratio and the stiffness of the
spring results in decreasing the size of the stick regions.
Abstract: Evaluation of the ride comfort for railway vehicles can be divided into two classes; the
long-term evaluation of ride comfort and the momentary evaluation of ride comfort. In the present
paper, the ride comfort of railway vehicles are investigated for high speed trains in Korea. The
long-term ride comfort has been analyzed by a statistical method and the momentary ride comfort has
been analyzed by using the longitudinal acceleration, the jerk and the stationary lateral acceleration.
Abstract: The Korean High Speed Train (KHST) has been tested on the Kyongbu high speed line and
the Honam conventional line since 2002. A data acquisition system was developed to test and prove
the dynamic performance of the KHST, and the system has been found to be very efficient in
acquiring multi-channel data from accelerometers located all over the train. Also presented in this
paper is an analysis procedure which is simple and efficient in analyzing the acceleration data
acquired during the on-line test of the KHST. The understanding of system vibration mode for a
railway vehicle is essential to evaluate the characteristics of a dynamic system and to diagnose the
dynamic problems of the vehicle system during tests and operations. Methods based on homogeneous
linear systems are not realistic because real systems have nonlinear characteristics and are strongly
dependent on environmental conditions. In this paper an efficient method of vibration analysis has
been proposed and applied for the KHST to evaluate its vibration mode characteristics. The results
show that this method is suitable to estimate the system vibration modes of the KHST.
Abstract: Recently, the finite element absolute nodal coordinate formulation(ANCF) was developed
for large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based
on finite element procedures and the general continuum mechanics theory to represent elastic forces.
In this paper, a computational method, which predicts the dynamic and structural properties of a very
flexible beam in a multibody system, is presented based on Euler-Bernoulli beam theory and ANCF.
In order to consider the dynamic interaction between a continuous large deformable beam and a rigid
multibody system, a combined system equations of motion was derived by adopting absolute nodal
coordinates and rigid body coordinates. The efficiency and reliability of the computational results are
verified by comparison with a commercial program. These methods can be applied for predicting the
dynamic stress and fatigue life of the wire harness used in a robot system. The process of predicting
the fatigue life using the proposed method in this paper may be applied to continuous mechanical
parts of various dynamic systems.
Abstract: An Over Head Transportation (OHT) vehicle is used to transport large loads in a factory
more efficiently. To maximize productivity, the speed and load requirement for the OHT vehicle is
continually increasing. This may create a repetitive dynamic load and thus cause fatigue failure in
related components. In this paper, a computer aided engineering (CAE) method is proposed for
fatigue life prediction in the early design stage using multibody dynamic analysis and the linear
damage rule. The process of predicting the fatigue life using the proposed computer models in this
paper may be applied to structures of various mechanical systems.