• 한국강구조학회 논문집
• /
• 제19권2호
• /
• pp.211-221
• /
• 2007

교량의 피로파괴에 대한 Miner의 피로손상법칙을 적용하여 여러 확률변수로 표현된 피로파괴 한계상태함수에 대한 신뢰도해석을 국내에서 측정된 통행차량의 통계적 특성을 반영하여 수행하였다. 신뢰도지수의 산정에 필요한 확률변수 가운데 등가모멘트, 충격계수비, 등가하중비는 국내의 최근 측정자료를 분석하여 통계치를 산정하였으며, 피로강도, 활하중 횡분배비, 연행하중비는 국외에서 측정된 문헌자료의 통계치를 적용하였다. 신뢰도해석을 통하여 피로설계트럭의 종류, 교량수명, ADTT, 피로상세, 등가하중비, 피로설계트럭의 총중량 등의 피로손상에 관련된 여러 파라미터가 신뢰도지수에 미치는 영향을 분석하였다. 본 논문의 피로파괴에 대한 신뢰도해석 결과는 국내 LRFD 설계기준의 피로설계트럭모형과 피로한계상태의 하중계수를 결정할 때 기초 자료로 이용할 수 있을 것으로 판단된다.

• Structural Engineering and Mechanics
• /
• 제66권2호
• /
• pp.151-160
• /
• 2018

With the aim to evaluate the fatigue damage accumulation and predict the residual life of engineering components under variable amplitude loadings, this paper proposed a new strain energy-based damage accumulation model by considering both effects of mean stress and load interaction on fatigue life in a low cycle fatigue (LCF) regime. Moreover, an integrated procedure is elaborated for facilitating its application based on S-N curve and loading conditions. Eight experimental datasets of aluminum alloys and steels are utilized for model validation and comparison. Through comparing experimental results with model predictions by the proposed, Miner's rule, damaged stress model (DSM) and damaged energy model (DEM), results show that the proposed one provides more accurate predictions than others, which can be extended for further application under multi-level stress loadings.

• Structural Engineering and Mechanics
• /
• 제49권2호
• /
• pp.203-223
• /
• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2007년도 춘계학술대회
• /
• pp.378-382
• /
• 2007

To improve the reliability for a wind-turbine gearbox, the mechanical loads acting on the gearbox need to be monitored and analysed exactly. This study was conducted to identify the characteristics of torques and bending moments acting on the main shaft of the gearbox using the rainflow counting method and predict the fatigue life of the main shaft by using the modified Miner's rule. While the mean wind speed became 3.5 m/s, the life of the main shaft by the acting torques was predicted as 4.3${\times}10^6$ years, and it by the bending moments was as 2.3${\times}10^4$ years. If the life of the wind turbine was estimated as 20 years, the fatigue life of the main shaft was regarded as infinite. Also, it was suggested that the life of the main shaft must be predicted by not the torques but the bending moments.

• International Journal of Ocean System Engineering
• /
• 제3권4호
• /
• pp.209-217
• /
• 2013

This paper presents a mooring design procedure for a floating offshore wind turbine. Offshore environmental data for Jeju are taken from KHOA (Korea Hydrographic and Oceanographic Administration) and used for the environmental conditions in numerical analyses. A semi-submersible-type floating wind system with a 5-MW-class wind turbine studied by the DeepCwind Consortium is applied. Catenary mooring with a studless chain is chosen as the mooring system. Design deliverables such as the nominal sizes of chain and length of the mooring line are decided by considering the long-term prediction of the breaking strength of the mooring lines where a 100-year return period is used. The designed mooring system is verified using a fatigue calculation based on rain-flow cycle counting, an S-N curve, and a Miner's damage summation of rule. The mooring tension process is obtained from time-domain motion analyses using ANSYS/AQWA.

• 대한토목학회논문집
• /
• 제33권2호
• /
• pp.821-831
• /
• 2013

최근 연구결과 레일연마 및 장대레일화를 통해 누적통과톤수에 의한 레일교체기준의 연장이 가능한 것으로 보고되었다. 본 연구에서는 장기 사용레일에 대한 실내피로시험을 수행하였고, 파괴확률 50%에서의 장기 사용레일의 잔존수명을 표현한 S-N 선도는 적은 실험데이터에 대한 가중치 확률 해석기법을 사용하여 도출하였다. 여기서 피로시험에 사용된 레일들이 누적통과톤수가 서로 다르기 때문에 누적통과톤수를 평균하여 반복횟수를 수정하였다. 또한, 레일표면요철 및 열차속도를 고려한 레일 저부 휨응력은 기존 연구결과 도출된 레일휨응력 예측식을 사용하여 장기 사용레일의 잔존수명을 평가하였다. 따라서 본 연구를 통해 도시철도에서 레일연마를 통한 레일관리가 이루어진다면 누적통과톤수에 의한 레일교체기준(약 8억톤)보다 약 2억톤이상 연장 사용이 가능하며, 피로한도 이하의 응력범위에 대한 피로시험결과를 바탕으로 레일의 피로수명을 평가하기 위해서는 수정마이너법칙보다는 피로한도 이상에서의 S-N선도 기울기의 1/2인 하이바크법칙을 적용하는 것이 합리적이라 판단되었다.

• 한국정밀공학회지
• /
• 제33권10호
• /
• pp.851-856
• /
• 2016

Planetary gear systems have several advantages over traditional gearboxes with parallel axis gear shafts. The planetary gearbox arrangement also creates greater stability due to the even distribution of mass and increased rotational stiffness. However, gears in planetary gear systems occasionally have a short-life due to wear and breakage by repetitive load during operation time. In this study, we evaluated variables of the strength design for each part and conducted structural analysis of seven cases of the planetary gear system. The result of structural analysis was applied to shape optimization method and obtaining the weight lightening designed value. Subsequently, the planetary gear system was performed to ensure the durability of gears during operation time with miner's rule.

• 한국항공운항학회지
• /
• 제19권4호
• /
• pp.58-66
• /
• 2011

The estimation of fatigue integrity is very important for aerospace structures such as engine mount strut. The reason is that the fatigue integrity is essential analysis process to establish the structural stability in aerospace field. Therefore, in this paper, the process of fatigue analysis and test was performed for engine mount strut to prove the structural fatigue integrity. First of all, the fatigue load spectrum is constructed by considering the small aircraft operating condition. Fatigue analysis is done for the cluster near the welding zone which may have F.C.L.(fracture critical location). The fatigue life of engine mount strut was estimated by the Miner's rule which is the damage summation method. Finally, Fatigue test is performed to verify the fatigue integrity. The estimation process of fatigue integrity for engine mount strut of small aircraft may help the design.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제11권4호
• /
• pp.343-356
• /
• 2011

This paper proposes an accelerated life evaluation of drive shaft. The life test of drive shaft for independent suspension type AWD vehicle should be performed by use of the least test sample because many number of samples can't be used for the test because of its mass capacity and high price. We calculated the no failure test time by application of no failure test concept, and the already performed test data for drive shaft are applied for some kinds of reliability coefficients which are needed for calculation of life test time. And, for analysis of real driving condition of vehicle, the load spectrum is prepared using the needed road condition and vehicle data. The inverse power model is used for accelerated life test. The equivalent torque of load spectrum is achieved by use of Miner's Rule, and then the final accelerating condition is determined by decision of the accelerated test torque. This paper shows that the accelerated life test results corresponds with the target life and the proposed life test method can be very well applied to no failure life test for mass capacity machinery components.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.114-119
• /
• 2004

Endbeam is an important structural member of freight bogie for the support of service loading. In general, more than 25 years' durability is necessary. However, endbeam occur fatigue fracture in dynamic stress concentration location because comparatively strength and stiffness are low. Therefore, structure analysis is performed to evaluate structural problem of endbeam and local strain range as durability analysis. The number of cycles is extracted concerning the bogie in operation by measurement dynamic stress time history on critical part which is crack initiation in actual fact. At this time rainflow cycle counting is used to consider change of stress for operating condition. Based on the fatigue life curves and the stress analysis, the fatigue life of the endbeam is predicted and compared with the experimentally determined fatigue life, resulting in a fairly good correlation.