• Tribology and Lubricants
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• v.28 no.1
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• pp.19-26
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• 2012

Rolling contact fatigue of an urban railway wheel was analysed during its rolling. A FEM analysis was performed using a 3D modelling of rail and wheel, considering the slope of the rail and nonlinear isotropic and kinematic hardening behavior of the rail and the wheel. The maximum von-Mises stress and contact pressure between the rail and wheel were 656.9 MPa and 1111.4 MPa, respectively, under axial load of 85 kN with friction coefficient of 0. The fatigue initiation life prediction relationships by strain-lifetime (${\varepsilon}$-N) and Smith-Watson-Topper method were drawn for the wheel steel as follows: $N_i=7.35{\times}10^6{\times}SWT^{-3.56}$ and $N_i=5.41{\times}10^{-9}{\times}(\frac{{\Delta}{\varepsilon}}{2})^{-5.77}$. The fatigue lifetimes of the wheel due to rolling contact were determined to be infinite by ${\varepsilon}$-N and SWT methods.

• Culinary science and hospitality research
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• v.23 no.6
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• pp.110-117
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• 2017

This study intended to examine transitive relation among customer incivility perceived by deluxe hotel frontline employees, burnout, and deviant workplace behaviors and clarify the moderating effect of employees' stress. A total of 230 employees working in deluxe hotels in Seoul, the capital of Korea, in 2017 comprised the sample in this study. The hypothesized relationships in the model were tested simultaneously by using structural equation modelling (SEM). As results, customer incivility perceived by deluxe hotel frontline employees had significant (p<.001) positive influence on their burnout(${\beta}=.38$, t-value=4.93). Employees' burnout positively influenced their deviant workplace behaviors (${\beta}=.56$, t-value=7.22). In addition, customer incivility was found to positively affect employees' deviant workplace behaviors(${\beta}=.26$, t-value=3.90), and therefore, the moderating role of stress level was not verified. The findings of this study suggested that deluxe hotels are supposed to enhance their frontline service by providing orientation for customers through promotion materials. Limitations and future research directions of this study were also well established and discussed.

• Steel and Composite Structures
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• v.19 no.1
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• pp.93-110
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• 2015

The thermomechanical bending response of anti-symmetric cross-ply composite plates is investigated by the use of the simple four variable sinusoidal plate theory. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. The validity of the present theory is demonstrated by comparison with solutions available in the literature. Numerical results are presented to demonstrate the behavior of the system. The influences of aspect ratio, side-to-thickness ratio, thermal expansion coefficients ratio and stacking sequence on the thermally induced response are studied. The present study is relevant to aerospace, chemical process and nuclear engineering structures which may be subjected to intense thermal loads.

• Journal of Convergence Society for SMB
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• v.4 no.1
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• pp.17-29
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• 2014

The wireless capsule endoscopy played an important role as the evolutionary medical device to solving the difficulties such as diagnosing the intestine diseases. Due to the limited size and functions, it has some drawbacks. The most obstacle thing is the disability of self-motion, it means that it cannot provide the speed problem. Hence, the characteristics of human digestion system is briefly introduced, especially the intestine, to get the information of endoscopy dynamics. Next, in order to make an abstraction of the condition, a new dynamic friction model called LuGre model is introduced and clearly analysed to get the characteristics and the usage of the model. By the consideration of parameters that are tightly related with the real situation of the capsule endoscopy. The Matlab Simulink was applied to build the model and verified by the simulation to discover the features.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.439-455
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• 2018

Within a probabilistic framework, this paper addresses the determination of the static structural response of beams and frames with partially restrained (semi-rigid) connections. The flexibility of the nodal connections is incorporated via an idealized linear-elastic behavior of the beam constraints through the use of rotational springs, which are here considered uncertain for taking into account the largely scattered results observed in experimental findings. The analysis is conducted via the Probabilistic Transformation Method, by modelling the spring stiffness terms (or equivalently, the fixity factors of the beam) as uniformly distributed random variables. The limit values of the Eurocode 3 fixity factors for steel semi-rigid connections are assumed. The exact probability density function of a few indicators of the structural response is derived and discussed in order to identify to what extent the uncertainty of the beam constraints affects the resulting beam response. Some design considerations arise which point out the paramount importance of probability-based approaches whenever a comprehensive experimental background regarding the stiffness of the beam connection is lacking, for example in steel frames with semi-rigid connections or in precast reinforced concrete framed structures. Indeed, it is demonstrated that resorting to deterministic approaches may lead to misleading (and in some cases non-conservative) outcomes from a design viewpoint.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.198-204
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• 2001

The shot peening is largely used for a surface treatment of metallic components where small spherical pellets called shots are blasted onto the surface with velocities up to 100 m/s. This treatment leads to improvement of fatigue behavior due to the developed compressive residual stresses, and so it has gained widespread acceptance I the automobile and aerospace industries. The residual stress profile on surface layer depends on the parameters of shot peening, which are, shot velocity, shot diameter, coverage, impact angle, material properties etc. and the method to confirm this profile is the measurement by X-ray diffractometer only. Despite the importance to automobile ad aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, the simulation technique is applied to predict the magnitude ad distribution of the residual stress and plastic deformation caused by shot peening with the help of the finite element analysis.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.28-33
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• 2007

The objective of this paper is to investigate the relationship between the short-term creep rupture time and the creep rupture properties at three different elevated temperatures in STS304 stainless steel. Uniaxial constant stress creep rupture tests were performed on the steel to observe the creep rupture behaviors at the elevated temperatures of 600, 650 and 700, according to the testing matrix. It is very important to predict creep life in practical creep design problems. As one of the series of studies on the statistical modelling of probabilistic creep rupture time and the development of creep life prediction techniques, the relationship between applied stress and creep rupture behaviors, such as creep strain rate and rupture time, were investigated. In addition, the Monkman-Grant relationship was observed between the steady-state creep rate and the creep rupture time. The creep rupture surfaces observed by SEM showed up dimple phenomenon at all conditions.

• Tunnel and Underground Space
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• v.14 no.2
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• pp.154-166
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• 2004

A numerical stability analysis was conducted on the large oil storage caverns excavated in a rock mass under high initial horizonal stress. The behaviors of the surrounding rock mass, rockbolts, and shotcrete were analyzedr and stability of the support members were assessed. For a proper support system design, the effect of the modelling technique, cavern shape and rockbolt length on the stability of the cavern was investigated. Results show that installation timing of supports and the change in cavern shape due to stepwise excavation affect the stress induced in support members. Also found was desperate need for a numerical technique which can properly reflect the behavior of the steel fiber reinforced shotcrete.

• The Korean Journal of Applied Statistics
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• v.24 no.1
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• pp.207-216
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• 2011

Bootstrap is a resampling technique to find an estimate of parameters or to evaluate the estimate. This technique has been used in estimating parameters in linear model(LM) and generalized linear model(GLM). In this paper, we explore the possibility of applying Bootstrapping Residuals, Pairs, and an Estimating Equation that are most widely used in LM and GLM to the generalized estimating equation(GEE) algorithm for modelling repeatedly measured regression data sets. We compared three bootstrapping methods with coefficient and standard error estimates of GEE models from one simulated and one real data set. Overall, the estimates obtained from bootstrap methods are quite comparable, except that estimates from bootstrapping pairs are somewhat different from others. We conjecture that the strange behavior of estimates from bootstrapping pairs comes from the inconsistency of those estimates. However, we need a more thorough simulation study to generalize it since those results are coming from only two small data sets.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.7-13
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• 2011

The fluid-structure interaction of a towed body is simulated using a developed code, which is based on the flux-difference splitting scheme on the hybrid Cartesian/immersed boundary method. To improve the stability in the coupling between the fluid and structure domains, a scheme is used, in which the effects of structure deformation are treated implicitly. The developed code is validated for the fluid-structure interaction problem through comparisons with other results on the vortex-induced vibration of elastically mounted cylinders. To simulate behavior of a towed body, an asymmetric tension modelling for a towing cable is suggested. In the suggested model, the tension is proportional to the elongation of the cable, but the cable has no effect on the body motion whenever the distance between the endpoints of the cable is smaller than the original length of the cable. The fluid-structure interactions of a towed body are simulated on the basis of different parameters of the towing cables. It is observed that the suggested tension model predicts the snapping for a shorter towing cable, which is in accordance with the reported results.