• Title/Summary/Keyword: Cumulative damage

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A cumulative damage model for extremely low cycle fatigue cracking in steel structure

  • Huanga, Xuewei;Zhao, Jun
    • Structural Engineering and Mechanics
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    • v.62 no.2
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    • pp.225-236
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    • 2017
  • The purpose of this work is to predict ductile fracture of structural steel under extremely low cyclic loading experienced in earthquake. A cumulative damage model is proposed on the basis of an existing damage model originally aiming to predict fracture under monotonic loading. The cumulative damage model assumes that damage does not grow when stress triaxiality is below a threshold and fracture occurs when accumulated damage reach unit. The model was implemented in ABAQUS software. The cumulative damage model parameters for steel base metal, weld metal and heat affected zone were calibrated, respectively, through testing and finite element analyses of notched coupon specimens. The damage evolution law in the notched coupon specimens under different loads was compared. Finally, in order to examine the engineering applicability of the proposed model, the fracture performance of beam-column welded joints reported by previous researches was analyzed based on the cumulative damage model. The analysis results show that the cumulative damage model is able to successfully predict the cracking location, fracture process, the crack initiation life, and the total fatigue life of the joints.

Cumulative Damage Characteristics of Concrete Subjected to Variable Amplitude Loadings (반복하중을 받는 콘크리트의 누가손상 특성)

  • Byun, Keun Joo;Kim, Moon Kyum;Han, Sang Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.1
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    • pp.43-54
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    • 1987
  • Cumulative damage characteristics of concrete, on which rapetitive loads are applied, are investigated. Preliminarily, a series of uniaxial compression tests on cylindrical specimens of plain concrete is carried out to find out that, among various factors, stress levels of repetitive loadings and loading order are the most governing factors of cumulative damage of concrete. Based on this preliminary study, fatigue tests are carried out applying two levels of stresses, stepwisely. As a result, it is found that characteristics of cumulative damage of concrete are governed by nonlinear relationships and do not follow Miner's linear theory. It is also observed that cumulative damage characteristics and static strengths of concrete vary with loading history of stresses. Empirical equations which may be useful in predicting fatigue characteristics and remaining life of concrete stuctures are proposed for concrete subjected two stress levels.

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The Fatigue Cumulative Damage and Life Prediction of GFRP under Random Loading (랜덤하중하의 GFRP의 피로누적손상거동과 피로수명예측)

  • Kim, Jeong-Gyu;Sim, Dong-Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.12
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    • pp.3892-3898
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    • 1996
  • In this study, the prediction of the fatigue life as well as the extimation of the characteristics of fatigue cumulative damage on GFRP under random loading were performed. The constant amplitude tests and the ramdom loading test were carried on notched GFRP specimens with a circular hole. Random waves were generated with a micro-computer and had wide band spectra. Since it is useful that the prediction of fatigue life ot the given load sequences is based on S-N curves under constant amplitude loading, the estimation of equivalent stress is done on every random waves. The equivalent stress wasat first estimated by Miner's rule and then by the proposed model which was based on Hashin-Rotem's comulative damage theory regarding nonlinear fatigue cumulative damage behavior. The fatigue lives were predicted from each equivalent stress evaluated. And each predicted fatigue llife was compared with experimental results. The number of cycles of random loads were counted by mean-cross counting method. The reuslts showed that the fatigue life predicted by proposed model was correlated well with the experimental results in comparison with Miner's model.

Seismic reliability analysis of structures based on cumulative damage failure mechanism

  • Liu, Qiang;Wang, Miaofang
    • Earthquakes and Structures
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    • v.18 no.4
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    • pp.519-526
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    • 2020
  • Non-stationary random seismic response and reliability of multi-degree of freedom hysteretic structure system are studied based on the cumulative damage failure mechanism. First, dynamic Eqs. of multi-degree of freedom hysteretic structure system under earthquake action are established. Secondly, the random seismic response of a multi-degree freedom hysteretic structure system is investigated by the combination of virtual excitation and precise integration. Finally, according to the damage state level of structural, the different damage state probability of high-rise frame structure is calculated based on the boundary value of the cumulative damage index in the seismic intensity earthquake area. The results show that under the same earthquake intensity and the same floor quality and stiffness, the lower the floor is, the greater the damage probability of the building structure is; if the structural floor stiffness changes abruptly, the weak layer will be formed, and the cumulative damage probability will be the largest, and the reliability index will be relatively small. Meanwhile, with the increase of fortification intensity, the reliability of three-level structure fortification is also significantly reduced. This method can solve the problem of non-stationary random seismic response and reliability of high-rise buildings, and it has high efficiency and practicability. It is instructive for structural performance design and estimating the age of the structure.

Development of Accelerated Life Test Method for Machanical Parts Using Cumulative Damage Theory (누적손상이론을 이용한 기계류부품의 가속수명시험법 개발)

  • Kim, Dae-Cheol;Lee, Geun-Ho;Kim, Hyeong-Ui
    • 연구논문집
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    • s.32
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    • pp.35-43
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    • 2002
  • This study was performed to develop accelerated life test method of machanical parts using cumulative damage theory that used to model the fatigue of parts that receive variable load. The cumulative damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the cumulative damage theory, because test time can shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7. This accelerated test method was used to develop accelerated test method of gear reducer, hydraulic hose and bearing as well as agricultural tractor transmission and it is considered to be applied comprehensively to machanical parts the fatigue of which is happened by load or pressure etc.

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On a Special Case of a Problem in the Cumulative Damage Model (누적(累積), 손상(損傷), 모형(模型)의 특이(特異)한 경우(境遇)에 관(關)한 연구(硏究))

  • Lee, Hyo-Seong
    • Journal of Korean Institute of Industrial Engineers
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    • v.7 no.1
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    • pp.33-36
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    • 1981
  • An equipment is subject to shocks which occur randomly according to a Poisson process. The equipment fails when the total cumulative damage reaches a certain prescribed level. An optimal preventive replacement policy is presented when the level of cumulative damage cannot be checked. Renewal theory is used to obtain the results and a case example is presented.

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A Probabilistic Analysis for Fatigue Cumulative Damage and Fatigue Life in CFRP Composites Containing a Circular Hole (원공을 가진 CFRP 복합재료의 피로누적손상 및 피로수명에 대한 확률적 해석)

  • 김정규;김도식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1915-1926
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    • 1995
  • The Fatigue characteristics of 8-harness satin woven CFRP composites with a circular hole are experimentally investigated under constant amplitude tension-tension loading. It is found in this study that the fatigue damage accumulation behavior is very random and history-independent, and the fatigue cumulative damage is linearly related with the mean number of cycles to a specified damage state. From these results, it is known that the fatigue characteristics of CFRP composites satisfy the basic assumptions of Markov chain theory and the parameter of Markov chain model can be determined only by mean and variance of fatigue lives. The predicted distribution of the fatigue cumulative damage using Markov chain model shows a good agreement with the test results. For the fatigue life distribution, Markov chain model makes similar accuracy to 2-parameter Weibull distribution function.

Fatigue analysis of pressure vessel in view of wind and seismic loads (풍력과 지진하중을 고려한 압력용기의 피로해석)

  • 박진용;황운봉;박상철;박동환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.596-603
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    • 1991
  • Fatigue life prediction of pressure vessel is studied analytically using cumulative damage models and linear elastic fracture mechanics method. The stresses are analyzed by finite element method. During operation, the maximum stress occurs at the outside of neck region while fatigue analysis indicates that the bottom of nozzle part has the shortest fatigue life. Previously proposed fatigue life prediction equation and cumulative damage model are modified successfully by introducing reference fatigue modulus. It is found that the modified life prediction equation and damage model are useful for lower stress level application.

Comparison of Calculation Methods of Cumulative Damage of Breakwater Armor Layer (방파제 피복층의 누적 피해 계산 방법의 비교)

  • Suh, Kyung-Duck;Chang, Eun-Seok
    • Ocean and Polar Research
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    • v.25 no.spc3
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    • pp.417-421
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    • 2003
  • In the reliability design of the breakwater armor layer, it is often necessary to calculate its damage accumulated over the life of the breakwater. In this paper comparison is made between the two methods proposed by Hanzawa et at. in 1996 and Melby and Kobayashi in 1998 to calculate the cumulative damage of the breakwater armor layer. Tn the case where a severe damage occurs at the beginning of the life or toe breakwater, the two methods do not show significant difference, but in general the farmer predicts a cumulative damage several times larger than the latter.

Comparison of Cumulative Damage Models by predicting Fatigue lives of Aircraft Flaperon Joint (손상누적모델의 비교를 통한 플래퍼론 연결부의 피로수명 예측)

  • Park, Tae-Young;Park, Jung-Sun
    • Journal of Aerospace System Engineering
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    • v.3 no.4
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    • pp.27-34
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    • 2009
  • This paper deals with the lifetime prediction of Aircraft Flaperon Joint made of AISI 4130 steel. Reviews are performed on the published damage models at first. And three different damage models are used for predicting the fatigue life of the structure subjected to variable amplitude fatigue loading. These models require no increase in complexity of use, nor do they require additional material property or mission loading information to achieve the improved accuracy. Finally a comparison among the fatigue results is performed. It is observed that the Miner's rule could predict longer life than other cumulative damage models which take into account loads below the endurance limit.

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