• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1187-1197
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• 2000

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.110-118
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• 2000

For reasonable fatigue design and estimation of fatigue durability considered fatigue strength and stiffness of the automotive body structure, many fatigue data must be insured according to the shapes, materials, and welding conditions of the spot welded lap joints. However, because it is actually difficult problem, there is need to establish a new method to be able to predict its fatigue life without any additional fatigue tests. Therefore, In order to improve such problems, in this study, the maximum stress function presenting the $\delta\sigma_{1max}―\delta P$ relation was defined form the relation between $\delta\sigma_{1max}-N_f$ and ${\delta}P-N_f$. By using the fatigue data on the IB type spot-welded lap joints previously obtained from the fatigue test results, fatigue life of the spot-welded lap joint previously obtained from the fatigue test results, fatigue life of the spot-welded lap joint having a certain dimension was tried to predict without any additional fatigue tests. And, its result was verified by ${\delta}P-$N_f$ curves. Obtained conclusion are as follows, 1) a maximum stress function considered the relation of the maximum principal stress, fatigue load, and the effects of geometrical factors of the IB type spot-welded lap joint was suggested. 2) the fatigue life predicted by the maximum principal stress function and the relation of $\delta\sigma_{1max}-N_f$ was well agreed with the fatigue life obtained through the actual fatigue test result. 3) the fatigue life of the IB type spot-welded lap joint having a certain dimension is able to be predicted without any additional fatigue tests from the fatigue life prediction method by the maximum principal stress function.

• The Journal of Advanced Prosthodontics
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• v.13 no.4
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• pp.216-225
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• 2021

PURPOSE. The aim of this study is to evaluate the effects of canine guidance occlusion and group function occlusion on the degree of stress to the bone, implants, abutments, and crowns using finite element analysis (FEA). MATERIALS AND METHODS. This study included the implant-prosthesis system of a three-unit bridge made of monolithic zirconia and hybrid abutments. Three-dimensional (3D) models of a bone-level implant system and a titanium base abutment were created using the original implant components. Two titanium implants, measuring 4 × 11 mm each, were selected. The loads were applied in two oblique directions of 15° and 30° under two occlusal movement conditions. In the canine guidance condition, loads (100 N) were applied to the canine crown only. In the group function condition, loads were applied to all three teeth. In this loading, a force of 100 N was applied to the canine, and 200-N forces were applied to each premolar. The stress distribution among all the components of the implant-bridge system was assessed using ANSYS SpaceClaim 2020 R2 software and finite element analysis. RESULTS. Maximum stress was found in the group function occlusion. The maximum stress increased with an increase in the angle of occlusal force. CONCLUSION. The canine guidance occlusion with monolithic zirconia crown materials is promising for implant-supported prostheses in the canine and premolar areas.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.535-540
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• 2015

We propose an enhanced Green's function approach to predict thermal stresses by considering temperature-dependent material properties. We introduce three correction factors for the maximum stress, the time taken to reach maximum stress, and the time required to attain steady state based on the Green's function results for each temperature. The proposed approach considers temperature-dependent material properties using correction factors, which are defined as polynomial expressions with respect to temperatures based on Green's functions, that we obtain from finite-element (FE) analyses at each temperature. We verify the proposed approach by performing detailed FE analyses on thermal transients. The Green's functions predicted by the proposed approach are in good agreement with those obtained from FE analyses for all temperatures. Moreover, the thermal stresses predicted using the proposed approach are also in good agreement with the FE results, and the proposed approach provides better predictions than the conventional Green's function approach using constant, time-independent material properties.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1375-1386
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• 2006

In life testing, the lifetimes of test units under the usual conditions are so long that life testing at usual conditions is impractical. Testing units are subjected to conditions of high stress to yield informations quickly. In this paper, the inferences of parameters on the three step-stress accelerated life testing are studied. The two-parameter exponential distribution with a failure rate function that a log-quadratic function of stress and the tempered failure rate model are considered. We obtain the maximum likelihood estimators of the model parameters and their confidence regions. A numerical example will be given to illustrate the proposed inferential procedures.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1169-1175
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• 2009

In this paper, the inferences of data obtained from periodic inspection and type I censoring for the step-stress accelerated life test are studied. The exponential distribution with a failure rate function that a log-linear function of stress and the tampered failure rate model are considered. The maximum likelihood estimators of the model parameters are estimated and also the optimal stress change time which minimize the asymptotic variance of maximum likelihood estimators of parameters is determined. A numerical example will be given to illustrate the proposed inferential procedures and the sensitivity of the asymptotic variance of the estimated mean by the guessed parameters is investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2344-2352
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• 2000

Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.

• Journal of the Korean Data and Information Science Society
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• v.16 no.4
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• pp.791-799
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• 2005

We consider two components parallel system in which the lifetimes have the bivariate Pareto model with bivariate random censored data. We assume that bivariate Pareto model is affected by common stress which is independent of the lifetimes of the components. We obtain estimators for the system reliability based on likelihood function and relative frequency. Also we construct approximated confidence intervals for the reliability based on maximum likelihood estimator and relative frequency estimator, respectively. Finally we present a numerical study.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.293-304
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• 1999

Refinements of classical theories for entangled or crosslinked polymeric systems have led to incommensurable models for rubber networks and polymer melts, contrary to experimental evidence, which suggests a great deal of similarity. Uniaxial elongation and compression data of linear and branched polymer melts as well as of crosslinked rubbers were analyzed with respect to their nonlinear strain measure. This was found to be the result of two contributions: (1) affine orientation of network strands, and (2) isotropic strand extension. Network strand extension is caused by an increasing restriction of lateral movement of polymer chains due to deformation, and is modelled by a molecular stress function which in the tube concept of Doi and Edwards is the inverse of the relative tube diameter. Up to moderate strains, $f^2$ is found to be linear in the average stretch for melts as well as for rubbers, which corresponds to a constant tube volume. At large strains, rubbers show maximum extensibility, while melts show maximum molecular tension. This maximum value of the molecular stress function governs the ultimate magnitude of the strain-hardening effect of linear and long-chain branched polymer melts in extensional flows.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.92-100
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• 2016

Reliability analysis of tripod support structure for offshore wind turbine was performed. Extreme distribution function of peak response due to wind and wave loads was estimated by applying peak over threshold(POT) method. Then, stress based limit state function was defined by using maximum stress of support structure which was obtained by multiplying beam stress and concentration factor. The reliability analysis result was compared when maximum stress was calculated from shell element. Reliability index was evaluated using first order reliability method(FORM).