• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.1978-1988
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• 2004

Hybrid finite element analysis was used to analyze the influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors. The effects of changes in stiffness were similar for most of the manufacturing errors. State variables were most affected by the stiffness of the planet ,bearings. Floating either the sun or carrier helps to equal load sharing and minimizes the critical tooth stress. The effects of a floating sun and carrier are similar, but it is not recommended that both float, because this can induce greater critical tooth stress. Planet bearing stiffness should be optimized. Both load sharing and critical tooth stress should be considered to determine optimal bearing stiffness.

• Communications for Statistical Applications and Methods
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• v.6 no.1
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• pp.89-98
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• 1999

In this paper we estimate the reliability of parallel system with two components. We assume that the strengths of these components follow bivariate exponential(BVE) models proposed by Marshall-Olkin(1967) Block-Basu(1974) Freund(1961) and Proschan-Sullo(1974) These two components are subjected to a normally distributed random stress which is independent of the strength of the components. If the strengths ($\textit{X}_1$, $\textit{X}_2$) are subjected to a stress($\textit{Y}$) then the system reliability ($\textit{R}$) is given by $\textit{R}=\textit{P}[\textit{Y} We present some numerical results and compare the bias and the mean square error of the maximum likelihood estimator and proposed estimators for a moderate sized samples when $(\textit{X}_1, \textit{X}_2)$ follow BVE of Marshall-Olkin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.3010-3017
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• 2000

For integrity evaluation of cracked or damaged structures, fracture toughness test results in ASTM are widely used. The fracture toughness values of the structures are used as an effective design criterion in nuclear plants and aircraft structures. Sometimes the difference of P-$\delta$ curve trend during the unloading /reloading cycle in the fracture toughness test using partial unloading compliance was observed. The phenomenon as a possible source of error in determining fracture toughness may be caused by the residual stress during unloading work-hardening and bucking of a specimen. Therefore, we evaluate the effect of bucking and compressive residual stress during the K-R and J-R testing using a finite element method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.955-962
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• 2006

This paper has the objects of deciding dynamic instability regions of thick plates on Pasternak foundation by finite element method and providing kinematic design data for mats and slabs of building structures. In this paper, dynamic stability analysis of tapered opening thick plate is done by use of Serendipity finite element with 8 nodes considering shearing strain of plate. To verify this finite element method, buckling stress and natural frequencies of thick pate with or without in-plane stress are compared with existing solutions. The results are as follow that this finite element solutions with 4x4 meshes are shown the error of maximum 0.56% about existing solutions, and obtained dynamic instability graph according with variation of opening positions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.4
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• pp.119-126
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• 2017

High-precision wire is one of the most important components of lead production. However, no studies have been performed on the dimensional tolerance of these wires, and their capabilities have been deduced through trial and error. Therefore, PIANO, a commercial PIDO tool, was used to systematically determine the optimal parameters for stress minimization. The values obtained from the optimum design were modeled and analyzed using LS-Dyna, a finite element analysis program. Maximum stress was reduced by about 10% compared to its initial values, and the wire now satisfies dimensional tolerance ($10{\mu}m$).

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.188-194
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• 2009

Consolidation settlement, a crucial parameter in geotechnical design of soft ground, has not been computed in a unique way due to different computation methods in practice. To improve computational error in calculating consolidation settlement, a number of researches has been attempted. Conventional 1-dimensional consolidation theory assumes the center of the clay layer as the representative point to obtain effective stress in calculation, which could resort to erroneous results. To calculate exact solutions considering initial distribution of effective stress, diving a stratum into multi-layers could resort to wasting time and effort. In the study, a novel methodology for calculating consolidation settlement via Guassian quadrature is developed. The method generally is capable of computing settlements in any case of the stress conditions encountered in fields.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.1-6
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• 2000

In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor, ${\Delta}K_{th}$. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the ${\Delta}K_{th}$ in the standard test method but the ${\Delta}K_{th}$ can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the ${\Delta}K_{th}$ due to regression analysis method and to evaluate the relative error range of the ${\Delta}K_{th}$ in same fatigue crack growth test data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.831-836
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• 2010

In this paper, Plasma Enhanced Chemical Vapor Deposition (PECVD) $SiO_2$ film properties are modeled using statistical analysis and neural networks. For systemic analysis, Box-Behnken's 3 factor design of experiments (DOE) with response surface method are used. For characterization, deposited film thickness and film stress are considered as film properties and three process input factors including plasma RF power, flow rate of $N_2O$ gas, and flow rate of 5% $SiH_4$ gas contained at $N_2$ gas are considered for modeling. For film thickness characterization, regression based model showed only 0.71% of root mean squared (RMS) error. Also, for film stress model case, both regression model and neural prediction model showed acceptable RMS error. For sensitivity analysis, compare to conventional fixed mid point based analysis, proposed sensitivity analysis for entire range of interest support more process information to optimize process recipes to satisfy specific film characteristic requirements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.678-684
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• 2008

A general treatment is to restore abfraction lesions with dental filler materials to reduce stress concentration. A material should be selected from various dental products based on long term experiences of dentist or personal preference concerning filler methods. A quantitative criterion is necessary to make an evaluation of the results as dentists decide treatment methods and dental materials relying on their clinical experiences. The purpose of this study is to find an optimal restoration method and material for noncarious cervical lesions using the finite element method. An objective function was defined to minimize the sum of tension or compression stress. Trial-and-error and approximation were used to find an optimal restoration method. An optimal solution was to fill TetricFlow inside the lesion and Z100 in the remaining region. The most desirable thickness ratio of the two filler materials was 0.125 with trial-and-error and it was similar to the results of approximation, 0.121 and 0.132.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.465-472
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• 2003

Creep Poisson's ratio reported by previous experimental studies on multiaxial creep of concrete was controversial. The Poisson's ratio is very sensitive to small experimental error that is inevitably induced, and the sensitivity may cause the controversy. It is difficulty to find out the properties on multiaxial creep of concrete. Therefore, a new approach method to analyze the test results is needed to precisely understand the properties on multiaxial creep of concrete. In this study, microplane model is used as a new approach method in analyzing the multiaxial creep test data. The six data sets extracted from the literature are fitted from regression analysis. Double-power law as a model representing volumetric and deviatoric creep evolutions on microplane is used, and six parameters in volumetric and deviatoric compliances are determined on the assumption that the volumetric and deviatoric creep strains are linearly proportional to corresponding stresses. The optimum fits give very accurate description of the test data. The Poisson's ratio calculated from the optimum fits varies with time and does not depends on the stress states, namely, uniaxial, biaxial, and triaxial stress states. Regression analysis is also performed on the assumption that the Poisson's ratio remains constant with titre. The constant Poisson's ratio can be use in practice without serious error.