• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.451-458
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• 2012

This study aims at the structural analysis with fatigue according to the configuration of railway vehicle wheel. Maximum equivalent stress or deformation is shown at the lower face in contact with wheel and rail. As model B has the maximum stress or deformation which becomes lower than model A, model B is shown to have more durability than model A. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of 0 to $-10^{11}$ Pa and the amplitude stress of 0 to $10^{10}$ Pa, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE Bracket history' or 'SAE transmission'. The structural result of this study can be effectively utilized with the design of railway vehicle wheel by prevention and durability against its damage.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.813-820
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• 2010

The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.154-162
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• 2005

This study investigates the fatigue life and the damage possibility of connecting rod by the fatigue tool of Ansys workbench. The case of constant fatigue loading variation 'Sine' becomes more stable than that of nonconstant loading but the magnitude of constant load becomes larger than that of nonconstant load. Among nonconstant fatigue loads, the case of 'SAE Bracket History' which is severest at the variation of load tends to be most unstable. The case of 'Sample History2' which becomes a little slow at the variation of load tends to be most stable. The maximum relative damage in case of 'SAE Bracket History' is occurred near the average stress '0' and this case can be shown to have the possibility to take more damage than another case.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.185-192
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• 2014

The riser systems for floating offshore structures are known to experience tri-modal dynamic responses. These are owing to the combined loadings from the low-frequency response due to riser tension behavior, middle-range frequency response coming from winds and waves, and high-frequency response due to vortex induced-vibration. In this study, fatigue damage models were applied to predict the fatigue damages in a well-separated tri-modal spectrum, and the resultant fatigue damages of each model were compared with the most reasonable fatigue damage calculated by the inverse Fourier transform of the spectrum, rain-flow counting method, and Palmgren-Miner rule as a reference. The results show that the fatigue damage models developed for a wide-band spectrum are applicable to the tri-modal spectrum, and both the Benasciutti-Tovo and JB models could most accurately predict the fatigue damages of the tri-modal spectrum responses.

• Membrane Journal
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• v.8 no.4
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• pp.191-202
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• 1998

The emission standards for diesel particulates have been continued to become tighter. This article reviews the pore and how to filtering characteristics and how to design the ceramic honeycomb filter which is generally used for diesel particulate filter. And the properties and fabrication methods of other particulate filters, i.e. ceramic fiber candle filter, ceramic foam filter, ceramic cross-flow filter and metal filter, are presented in this review. The results show that though the various filters have been developed and tested in the field, the more efforts are needed for the commercilaization of the diesel particulate filter.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.350-358
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• 2012

This paper deals with accuracy of accumulated fatigue damage estimation using stochastic fatigue analysis method based on Rayleigh PDF. From full scale measurement data on an 8100TEU container vessel, zero-order spectral moments for wave- and vibration-induced energy spectral densities are determined on the probability level of 99%. 80 simulation cases in total are prepared according to the variation of ratio of zero-order spectral moments and center frequency of vibration ESD. By using inverse Fourier transformation and rainflow cycle counting for the combined ESD of wave and vibration, exact fatigue damages are derived. Fatigue damages in frequency domain based on Rayleigh PDF show large conservativeness compared to exact fatigue damages in times domain. The main cause of the excessive conservativeness is analyzed by two aspects: ratio of zero crossing and peak frequencies and ratio of initial zero order spectral moments and zero order spectral moments from rainflow stress range distributions. Finally, a guideline of applicability of Rayleigh PDF is proposed for wide band processes.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.359-366
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• 2012

This is the final one of the two companion papers dealing with accuracy of accumulated fatigue damage estimation under wide band process. It is stated that four kinds of wide band models exist: typed of equivalent stress, combined PDF, correction factor, and damage combination. For the idealized ESDs from full scale measurement data on an 8100TEU container vessel, fatigue damages are compared for a narrow band prediction model based on Rayleigh PDF and five wide band fatigue prediction models of Dirlik, Wirsching-Light, Jiao-Moan, Benasciutti and DNV. DNV model consistently overestimates fatigue damages regardless of variation of ESDs. Predictions by Jiao-Moan model, which is understood as standard method for design of offshore platforms, are also in conservative side. Best accuracy is found from the results by Dirlik and Benasciutti models, but Benasciutti model is preferred since it can easily combined with narrow band fatigue damage based on Rayleigh PDF.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.11-11
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• 2017

지속적인 고령화 추세에 따라 여성과 고령층의 노동력이 차지하는 비율이 높아지고 있어, 사용하기 편리한 소형농기계의 요구가 증가하고 있는 실정이다. 본 연구에서 사용한 소형 관리기는 정식 작업 전 경운, 정지 등 다양한 작업이 가능한 농기계이다. 본 연구에서는 소형 관리기에 토크 측정 시스템을 구성하였으며, 작업 중 가장 큰 부하를 받는 구굴 작업 부하를 측정하였다. 또한, 작업 시 가장 직접적으로 영향을 받는 PTO (Power Take Off) 기어의 부하 용량(load capacity)을 기어 해석 소프트웨어를 이용하여 분석하였다. PTO 기어의 부하 용량은 안전율, 피로수명을 대상으로 평가하였다. 측정된 부하 데이터는 변동 하중이므로, 부하 크기와 빈도수의 규칙적인 신호로 단순화하기 위하여 레인플로우 카운팅 방법을 사용하였으며, SWT (Smith-Watson-Topper) 방법을 이용하여 공칭 토크를 계산하였다. PTO 기어의 안전율은 ISO 6336, 피로 수명은 마이너 법칙(Miner rule)을 이용하여 계산하였다. PTO의 변속 단수 총 2단이며, 5개의 스퍼 기어로 구성되어 있다. 시뮬레이션 결과, 소형 관리기의 주행 속도 또는 PTO의 회전속도 증가에 따라 PTO에서 발생하는 평균 부하가 크게 나타났다. 또한 주행 단수 및 PTO 기어 단수가 증가할수록 기어의 안전율과 피로 수명이 감소하였으며, 특히 PTO 기어의 안전율은 접촉 응력에서의 안전율보다 굽힘 응력에서의 안전율이 급격하게 감소하였다. 소형 관리기의 PTO 수명은 주행 단수 2단, PTO 단수 2단 일 때 가장 적게 나타났다. 따라서 소형 관리기의 주행 속도와 PTO 회전 속도를 저속으로 작업하는 것이 PTO 기어의 수명에 더 유리할 것으로 판단된다.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.133-140
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• 2012

In this study, 3 kinds of models about bike frame are simulated with static structural analysis, And fatigue life, damage and durability according to fatigue load are analyzed. A bike frame model with diamond type is compared with another model on the reinforced support with its type. In case of the reinforced support type, maximum equivalent stress or total deformation is shown with 10% or 20% more than the diamond type respectively. At both types of models, the trends of fatigue life and damage at both types are same. 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable among the cases of nonuniform fatigue loads. In case of 'Sample history' with the average stress of 0 to -1MPa and the amplitude stress of 0 to 1MPa, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE Bracket history' or 'SAE transmission'. In case of the reinforced support type, fatigue life becomes shorter and damage probability becomes larger at the right side installed with support than diamond type. The structural result of this study can be effectively utilized with the design on bike frame by investigating prevention and durability against its damage.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.1
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• pp.45-55
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• 2018

Concerns are emerging in marine industry on the additional fatigue damages induced by hydroelasticity, and large container carriers, among others, are considered to be susceptible to this hydroelastic response due to its large size, deck openings and high speed. This study focuses on the fatigue damage estimation of 9,400TEU container carrier based on the full scale measurement data via long-base strain gage installed on the ship. Some correlation analyses have been also done to check whether there was significant torsional response during the voyage. Direct cycle counting method was used to derive stress histogram and the long-term fatigue damage was estimated based upon that analyzed data. It turned out that the fatigue damage of this particular ship during the measurement period increased by more than 60% due to the hydroelastic response of the hull, and main contribution is considered to come from vertical bending mode.