• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.167-175
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• 1988

The principle objective of this study is to evaluate the fatigue behavior of structural steel components of highway bridges subjected to service stresses. The main aspects of this investigation are; 1) a measurement and statistical analysis of service stress cycles observed in highway bridge. 2) fatigue tests under equivalent constant-amplitude(CA) loading and simulated variable-amplitude(VA) loading 3) a evaluation of the fatigue behavior under VA-loading by eqivalent root mean cube (RMC) stress range. Theoretically, the RMC model is adequate in evaluation of fatigue behavior under VA-loading, because the regression coefficient (m) of crack growth rate is 3 approximately. The result of fatigue test shows that the RMC model is fitter than the current RMS model in fatigue evaluation under VA-loading. The interaction effects and sequence effects under VA-loading affect little fatigue life of structural components. As the transition rate of stress ranges is higher, the crack growth rate is higher.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.11-22
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• 2006

Message Signs (VMS) structures offer an increase in traffic safety through their ability to relay massages to motorists for warnings of hazards ahead, traffic congestion, accidents, and lane closings. The geometry of these signs sometimes results in the significant cyclic loading of the supports structure due to wind gusts, which can result from passing trucks or from natural wind. This study presents the results of analytical and experimental investigations of VMS structures. The commercially available softwareGTSTRUDL (2003) was used to perform space-frame structural analyses of these welded tubular structures. Fatigue evaluations were performed using stress ranges from field measurements and from structural analyses. Based on the results of the structural analyses that were conducted, where fatigue design loadings that had been derived from AASHTO Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals (2001) were used, the structures that had been studied were found not to have infinite fatigue life. According to the limited measurements that were made in this study, the fatigue design loadings derived from AASHTO Specifications (2001) appear to be conservative, but they are not overly conservative. The results of this study should be used to make a reasonable design of VMS structures, and to maintain their standards.

• Journal of the Korea Convergence Society
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• v.5 no.3
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• pp.17-22
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• 2014

The stress between work piece and end mill at the use of end mill at machining and the structural deformation due to the and the pressure are investigated by simulation analysis of three end mill models in this study. These results are achieved with structural and fatigue analyses. Model 1 has the deformation less than model 2 or model 3. As the maximum equivalent stress of model 1 is shown to become the least among all models, model 1 can endure the highest load by comparing with other models. It is useful to estimate the damage prevention and the durability by applying this study result into the design of end mill.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.306-313
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• 2011

The damage tolerance analysis is required to guarantee the structural safety and the reliability for aircraft components. The damage tolerance method, which evaluate the life considering the initial crack, considers a fatigue design model of the aircraft main structure. The fatigue crack growth life should be calculated in damage tolerance analysis and the inspection time to define the replacement cycle. In this paper, the damage tolerance analysis is performed for a turbine wheel which has complex geometry. The equation of the stress intensity factor for complex geometry is hard to know, so that they are usually processed by finite element analysis which takes long time. To solve this problem, the stress intensity factors at specified crack are obtained by the FEA and the crack growth life is evaluated using the surrogate model which is generated by the regression analysis of the FEA data. From the results, the efficiency of the crack growth life calculation and the damage tolerance analysis could be increased by taking the surrogate model.

• Journal of the Korea Convergence Society
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• v.11 no.1
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• pp.169-174
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• 2020

Side bolster is a part of the vehicle seat that holds the passenger's body from the side to make it more stable when the passenger is seated in the seat. In this study, the structural and fatigue analyses of the side bolsters at a car seat were carried out with two models of A and B. The heavily loaded parts, the damage by fatigue at driving a car and the difference of durability due to the structure were examined and the distributions of stress and deformation, and the fatigue lives were seen. Also, the strength and durability were examined. This study result is thought to be devoted to decrease the fatigue damage and increase the fatigue life and durability according to the design of bolster. This result is able to improve the product by applying the design of automotive side bolster practically. And it is thought to be the advantage to apply this study result to the convergence research with esthetic sense.

• Computational Structural Engineering
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• v.6 no.3
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• pp.113-123
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• 1993

Most of the ship structures and offshore structures are constructed through the welding and they are always subjected to variable loads. In this study, fatigue and stress concentration of the various types of welding connections due to the variable loads are investigated by using numerical approach, and comparisons between numerical analysis and experiments are performed. Fillet weld, full penetration weld and partial penetration weld characteristics are studied by using parameters such as penetration length, welding leg length, size and penetration angle. Based on this study, it is suggested that the fillet welding can be replaced with the penetration welding in some cases. The results of this study can be used as guidelines for actual welding problems in the shipyards.

• Computational Structural Engineering
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• v.5 no.3
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• pp.97-103
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• 1992

Since many design problems in the railroad, aerospace and machine structures involve considerations of the effect of cyclic loading, manufacturing and quality control processes much fully account for fatigue of critical components. Due to the sensitivity of the Paris law, it is very important to calculate .DELTA.K numerically to minimize the error of predicted fatigue life in cycles. However, it is shown that the p-version of FEM based on LEFM analysis is far better suited for computing the stress intensity factors than the conventional h-version. To demonstrate the proficiency of the proposed scheme, the welded T-joint with crack problems of box car body bolster assembly and a crack problem emanating from a circular hole in finite strip have been solved.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.832-835
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• 2011

최근까지 용접구조물의 피로설계는 용접품질 수준에 따라 공칭응력 또는 핫스팟 응력에 의한 S-N선 도로부터 수행하였다. 본 연구에서는 유한요소망의 크기에 덜 민감하면서 기존의 하중모드형식, 두께 효과 및 용접결합형식에 상관없는 등가구조응력(E2S2) 접근법을 이용한 Master S-N선도로부터 철도차량 대차프레임의 피로수명을 평가하고자 한다. 또한 합리적인 철도차량 용접대차프레임의 피로해석 연구일환으로서, 다축피로조건인 EN규격의 피로시험조건하에 이의 피로수명을 평가하고자 한다.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.2
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• pp.155-160
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• 2006

합성상판을 시공하는 경우 교축방향에 분할된 저강판을 접합 일체화해야 한다. 본 논문에서는 강 콘크리트 합성상판을 대상으로 3종류의 배력철근 방향 이음구조를 제안하며, 보 공시체에 의한 정적 정점피로 실험한다. 그 결과 보의 피로실험 결과 저강판 혹은 고력볼트가 피로파단 하였으며, 3차원 FEM해석에 이음부의 휨 강성도 및 피로강도에 대해서 해석적으로 검토된다.

• Journal of the KSME
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• v.28 no.4
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• pp.322-327
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• 1988

용접구조물의 파괴는 단순 역학적인 차원을 넘어서 재료공학적 검토와 시공상의 각종 변수를 고려해야만 정확하게 이해할 수가 있으며 방지할 수 있다. 용접도중에 발생되는 미소파괴(균열) 는 적절한 재료의 선정과 적당한 시공법으로 해결할 수 있으며, 사용도중 발생되는 거시적 파 괴는 사용조건에 유의하고 발생된 용접결함을 제거할 수 있다면 방지할 수 있다. 결론적으로 용접구조물의 파괴는 용접도중에 결함을 발생시키지 않는 방법으로 방지하는 것이 가장 효과적 이기 때문에 시공법의 선정 및 실시는 충분한 검토와 주의가 필요하다. 용접품의 파괴현상을 해석하는 데는 현재까지 잘 연구되어진 각종 파괴역학적 및 피로역학적 해석이 적용될 수 있 으나 용접부의 불균일한 조직형성에 따른 기계적 성질의 불균일성과 잔류응력 등을 추가로 고 려해야 하는 것이 약간 다를 뿐이다. 현재 용접부의 취성 및 피로파괴에 대한 다방면의 연구가 활발하게 이루어지고 있는 형편이며 향후에는 용접구조물의 수명예측을 포함한 가족 파괴해석 기술이 확립될 것으로 생각된다.