• Title/Summary/Keyword: fatigue Model

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The fatigue analysis using cumulative damage rule (Miner's rule) for the welding areas of carbody structure (누적손상법(Miner's rule)을 이용한 철도차량 차체 용접부의 피로평가)

  • Kim, Kwang-Woo;Park, Geun-Soo;Park, Hyung-Soon
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.30-34
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    • 2007
  • Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.

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Assessment of fatigue damage in 5% chrome cold rolling work roll (5% 크롬 냉간 압연용 작업롤의 피로손상 평가에 대한 연구)

  • Kwak, G.J.;Kim, K.S.;Lee, S.W.;Yeo, W.K.;Park, Y.C.
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.316-321
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    • 2000
  • The role of fatigue on the surface damage of 5% chrome cold milling work roll is evaluated. Uniaxial and torsional fatigue tests are carried out, and the baseline data for fatigue life evaluation are established. An appropriate multiaxial fatigue parameter is developed from the fatigue data. Fatigue tests are also performed under compressive mean stresses, and a mean stress model is formulated. A computer program is developed to assess the interaction of fatigue and grinding of the roll. The fatigue damage is computed for selected servicing conditions. It is found that the fatigue damage can be an important issue when the effect of mean stress is ignored, however the fatigue damage is negligibly small when the effect of mean stress including the residual stresses currently used is fully accounted. The result indicates that spalling due to the growth of thermal shock cracks is more important than fatigue damage in roll surface failure.

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Variable amplitude fatigue test of M30 high-strength bolt in bolt-sphere joint grid structures

  • Qiu, Bin;Lei, Honggang;Yang, Xu;Zhou, Zichun;Wang, Guoqing
    • Steel and Composite Structures
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    • v.33 no.3
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    • pp.433-444
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    • 2019
  • Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High-Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.

Computer aided failure prediction of reinforced concrete beam

  • Islam, A.B.M. Saiful
    • Computers and Concrete
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    • v.25 no.1
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    • pp.67-73
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    • 2020
  • Traditionally used analytical approach to predict the fatigue failure of reinforced concrete (RC) structure is generally conservative and has certain limitations. The nonlinear finite element method (FEM) offers less expensive solution for fatigue analysis with sufficient accuracy. However, the conventional implicit dynamic analysis is very expensive for high level computation. Whereas, an explicit dynamic analysis approach offers a computationally operative modelling to predict true responses of a structural element under periodic loading and might be perfectly matched to accomplish long life fatigue computations. Hence, this study simulates the fatigue behaviour of RC beams with finite element (FE) assemblage presenting a simplified explicit dynamic numerical solution to show computer aided fatigue behaviour of RC beam. A commercial FEM package, ABAQUS has been chosen for this complex modelling. The concrete has been modelled as a 8-node solid element providing competent compression hardening and tension stiffening. The steel reinforcements are simulated as two-node truss elements comprising elasto-plastic stress-strain behaviour. All the possible nonlinearities are duly incorporated. Time domain analysis has been adopted through an automatic Newmark-β time incremental technique. The program consists of twelve RC beams to visualize the real behaviour during fatigue process and to obtain the reliability of the study. Both the numerical and experimental results indicate a redistribution of stresses along the time and damage accumulation of beam which severely affect the serviceability and ultimate capacity of RC beam. The output of the FEM analysis demonstrates good match with the experimental consequences which affirm the efficacy of the computer aided model. The controlled fatigue damage evolution at service fatigue load limits makes the FE model an efficient tool in predicting high cycle fatigue behaviour of RC structures.

Comparison of Fatigue Damage Models of Spread Mooring Line for Floating Type Offshore Plant (부유식 해양플랜트 다점 계류라인의 피로손상모델 비교)

  • Park, Jun-Bum;Kim, Kookhyun;Kim, Kyung-Su;Ko, Dae-Eun
    • Journal of Ocean Engineering and Technology
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    • v.27 no.5
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    • pp.63-69
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    • 2013
  • The mooring lines of a floating type offshore plant are known to show wide banded and bimodal responses. These phenomena come from a combination of low and high frequency random load components, which are derived from the drift-restoring motion characteristic and wind- sea, respectively. In this study, fatigue models were applied to predict the fatigue damage of mooring lines under those loads, and the result were compared. For this purpose, seven different fatigue damage prediction models were reviewed, including mathematical formula. A FPSO (floating, production, storage, and offloading) with a $4{\times}4$ spread catenary mooring system was selected as a numerical model, which was already installed at an offshore area of West Africa. Four load cases with different combinations of wave and wind spectra were considered, and the fatigue damage to each mooring line was estimated. The rain flow fatigue damage for the time process of the mooring tension response was compared with the results estimated by all the fatigue damage prediction models. The results showed that both Benasciutti-Tovo and JB models could most accurately predict wide banded bimodal fatigue damage to a mooring system.

Environmental fatigue correction factor model for domestic nuclear-grade low-alloy steel

  • Gao, Jun;Liu, Chang;Tan, Jibo;Zhang, Ziyu;Wu, Xinqiang;Han, En-Hou;Shen, Rui;Wang, Bingxi;Ke, Wei
    • Nuclear Engineering and Technology
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    • v.53 no.8
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    • pp.2600-2609
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    • 2021
  • Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

Fatigue Life Optimization of Spot Welding Nuggets Considering Vibration Mode of Vehicle Subframe (서브프레임의 진동모드를 고려한 점용접 너깃의 피로수명 최적설계)

  • Lee, Sang-Beom;Lee, Hyuk-Jae
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.7
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    • pp.646-652
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    • 2009
  • In this paper, welding pitch optimization technique of vehicle subframe is presented considering the fatigue life of spot welding nuggets. Fatigue life of spot welding nuggets is estimated by using the frequency-domain fatigue analysis technique. The input data, which are used in the fatigue analysis, are obtained by performing the dynamic analysis of vehicle model passing through the Belgian road profile and also the modal frequency response analysis of finite element model of vehicle subframe. According to the fatigue life result obtained from the frequency-domain fatigue analysis, the design points to optimize the weld pitch distance are determined. For obtaining the welding pitch combination to maximize the fatigue life of the spot welding nuggets, 4-factor, 3-level orthogonal array experimental design is used. This study shows that the optimized subframe improves the fatigue life of welding nugget with minimum fatigue life about 65.8 % as compared with the baseline design.

Assessment of Fatigue Life on Curved Self-Piercing Rivet Joint Specimen (곡률을 갖는 셀프-피어싱 리벳 접합시편의 피로수명 평가)

  • Kim, Min-Gun;Cho, Seok-Swoo;Kim, Dong-Youl
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.1
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    • pp.71-79
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    • 2010
  • One of methods that accomplish fuel-efficient vehicle is to reduce the overall vehicle weight by using aluminum structure typically for cross members, rails and panels in body and chassis. For aluminum structures, the use of Self Piercing Rivet(SPR) is a relatively new joining technique in automotive manufacture. To predict SPR fatigue life, fatigue behavior of SPR connections needs to be investigated experimentally and numerically. Tests and simulations on lap-shear specimen with various material combinations are performed to obtain the joining strength and the fatigue life of SPR connections. A Finite element model of the SPR specimen is developed by using a FEMFAT SPR pre-processor. The fatigue lives of SPR specimens with the curvature are predicted using a FEMFAT 4.4e based on the liner finite element analysis.

Effect of Ion-nitriding on Fatigue Strength (피로강도에 미치는 이온실화처리의 영향)

  • Kang, Moo-Jin;Lee, Chung-Oh
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.3 no.3
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    • pp.98-103
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    • 1979
  • The fatigue limit of an ion-nitrided steel was investigated experimentally and analytically. It is found that fatigue limit can singificantly be increased by ion-nitriding, and that the case depth is the most important parameter which determines the fatigue limit. The data indicate that fatigue limit increases with the case depth as well as the surface hardness of the nitrided steel. The fracrographs of the fracture surfaces taken by a scanning electron microscope show that the fisch-eye is located at the subsurface of failed specimens. Assuming that crack propagates from the subsurface inclusions, an analytical model is proposed to predict the fatigue limit. Taking into account the stress distrbution of a nitrided specimen, fatigue limit is predicted as a function of the case depth. The proposed semiemprical formula agrees satisfactorily with the experimental data obtained from rotating beam fatigue testing.

A Study on the Fatigue Strength Evaluation of Load-Carrying Fillet welded Cruciform Joints (하중전달 십자형 필렛 용접부의 피로강도 평가에 관한 연구)

  • Lee, Yong-Bok;Nam, Byung-Chan;Park, In-Kju;Chung, Chin-Sung;Kim, Ho-Kyung
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.200-205
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    • 2000
  • Fatigue failure modes of load-carrying cruciform weld joints are dependent on the characteristics of the fatigue crack initiation and propagation from the weld toe or the weld root. In this study, constant amplitude fatigue tests on load-carrying fillet welded specimen carried out, and fatigue strengths were evaluated. Also, an attempt is made to develop a new analytical model with more accuracy to predict the fatigue crack propagation life of fillet welded cruciform joints of SWS 490B steels containing lack of penetration defects. From the result of this study, fatigue crack growth characteristics of load-carrying fillet welded cruciform joints, containing lack of penetration defects are found to be affected by the weld geometry, stress range and microstructures of the weld zone.

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