• Title/Summary/Keyword: Fatigue sensitivity

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Comparative Analysis in Sensitivity of Cumulative Fatigue Damage of Mechanistic-Empirical Concrete Pavement Design Programs (역학적-경험적 콘크리트 포장설계 프로그램의 누적피로손상 민감도 비교분석)

  • Park, Joo-Young;Park, Jeong-Woo;Kim, Sang-Ho;Liu, Ju-Ho;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.14 no.3
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    • pp.15-24
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    • 2012
  • The MEPDG(Mechanistic-Empirical Pavement Design Guide) developed based on the AASHTO Design Guide helps engineers find optimal alternatives by using traffic volume, climate, material property, and pavement structure as its input parameters. However, because technical problems were found in the MEPDG, efforts to improve the program by settling the problems have been continued. Meanwhile, another mechanistic-empirical design program has been developed by the KPRP(Korea Pavement Research Program) in Korea. To develop and improve the Korean design program reasonably, it is necessary to analyze the MEPDG and then compare programs each other. For concrete pavement, fatigue cracking is predicted by using very complicated logic different from other performance indicators. Therefore, in this paper, transfer functions of the fatigue cracking used in the version of 0.5, 1.0, and 1.1 of the MEPDG were analyzed. Sensitivity of the input parameters to the cumulative fatigue damage was compared to each other by the MEPDG version and KPRP.

Performance of Cemented Carbides in Cyclic Loading Wear Conditions

  • Kubarsepp, J.;Klaasen, H.;Sergejev, F.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.887-888
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    • 2006
  • The present study describes the wear and mechanical behaviour of carbide composites in cyclic loading applications (blanking of sheet metal). Adhesive wear as well as fatigue endurance were tested, complemented by XRD studies. It was found that the blanking performance of a carbide composite is controlled by its resistance to adhesion wear and fatigue sensitivity. XRD studies revealed that fatigue damage is preceded by plastic strain in both phases of the composites

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해수환경에서 강 용접부의 환경강도평가에 관한 연구 1

  • 정세희;김태영;나의균
    • Journal of Welding and Joining
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    • v.6 no.2
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    • pp.56-63
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    • 1988
  • The effects of PWHT (poste weld heat treatment) and stress simulating the residual stress during PWHT in weld HAZ of low and high strength steels on corrosion fatigue crack growth were evaluated. The obtained results are summarized as follows. 1. Fatigue crack growth rate of HAZ in air and 3.5% NaCl solution was slower than that of parent due to the signgularity in weld HAZ. 2. In the case of HT-80, 3.5% NaCl solutio nacts to accelerate the crack growth for all specimens, and the sensitivity of as-weld to corrosion environment was the greatest among other PWHT specimens. 3. Corrosion fatigue crack growth of parent, as-weld and PWHT speciments ofr SS41 as well as SM53B was retarded in comparison with the fatigue crack growth in air. 4. There was a tendency that crack growth of PWHT specimens subjected $10kg/mm^2$ was faster than that of PWHT specimens without stress during PWHT. 5. The retardation phenomenon of crack growth in corrosion environment is attributed to the crack branching decreased .DELTA.K due to the corrosion products and multi-cracks.

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Evaluation for Probabilistic Distributions of Fatigue Life of Marine Propeller Materials by using a Monte Carlo Simulation (몬테카를로 시뮬레이션에 의한 선박용 프로펠러재의 피로수명 확률분포 평가)

  • Yoon, Han-Yong;Zhang, Jianwei
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.12
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    • pp.1055-1062
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    • 2008
  • Engineering materials have been studied and developed remarkably for a long time. But, few reports about marine propeller materials are presented. Recently, some researchers have studied the material strength of marine propellers. However, studies on parametric sensitivity and probabilistic distribution of fatigue life of propeller materials have not been made yet. In this study, a method to predict the probabilistic distributions of fatigue life of propeller materials is presented, and the influence of several parameters on the life distribution is discussed.

Sensitivity Analyses of Failure Probability of Pipes in Nuclear Power Plants using PRO-LOCA (PRO-LOCA를 이용한 원전 배관의 파손확률에 대한 민감도 해석)

  • Cho, Young Ki;Kim, Sun Hye;Park, Jai Hak
    • Journal of the Korean Society of Safety
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    • v.29 no.3
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    • pp.136-142
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    • 2014
  • Recently a new version of PRO-LOCA program was released. Using the program, failure probability of pipes can be evaluated considering fatigue and/or stress corrosion crack growth and the effects of various parameters on the integrity of pipes in nuclear power plants can be evaluated quantitatively. The analysis results can be used to establish an inspection plan and to examine the effects of important parameters in a maintenance plan. In this study, sensitivity analyses were performed using the program for several important parameters including sampling method, initial crack size, number of initial fabrication flaws, operation temperature, inspection interval, operation temperature and nominal applied bending stress. The effect of parameters on the leak and rupture probability of pipes was evaluated due to fatigue or stress corrosion crack growth.

Vibration Characterization of Cross-ply Laminates Beam with Fatigue Damage (피로 손상을 입은 직교 복합재료 적층보의 진동 특성)

  • 문태철;김형윤;황운봉;전시문;김동원;김현진
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2001.05a
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    • pp.1-4
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    • 2001
  • A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue lift of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the $90^{\circ}$-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminate. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[\textrm{90}_{2}\textrm{0}_{2}]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

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Influence of Cobalt Content on the Fatigue Strength of WC-Co Hardmetals

  • Nakajima, Takeshi;Hosokawa, Hiroyuki;Shimojima, Koji
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.623-624
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    • 2006
  • The behavior of hardmetals under cyclic loads is investigated. Unnotched specimens were employed to obtain practical information regarding fatigue in hardmetals. All the tested hardmetals exhibit an increase in the number of cycles until failure with a decrease in the maximum stress, i.e., the hardmetals exhibit a high fatigue sensitivity. The fatigue strength increases with the cobalt content. Although distinct fatigue limits, as observed in metals, cannot be observed, the calculated fatigue limit stress at $10^7$ cycles is found to be approximately 70% of the flexural strength, and the stress value exhibits a linear relationship with the flexural stress.

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Reliability based optimization of spring fatigue design problems accounting for scatter of fatigue test data (피로시험 데이터의 산포를 고려한 스프링의 신뢰성 최적설계)

  • An, Da-Wn;Won, Jun-Ho;Choi, Joo-Ho
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1314-1319
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    • 2008
  • Fatigue reliability problems are nowadays actively considered in the design of mechanical components. Recently, Dimension Reduction Method using Kriging approximation (KDRM) was proposed by the authors to efficiently calculate statistical moments of the response function. This method, which is more tractable for its sensitivity-free nature and providing the response PDF in a few number of analyses, is adopted in this study for the reliability analysis. Before applying this method to the practical fatigue problems, accuracies are studied in terms of parameters of the KDRM through a number of numerical examples, from which best set of parameters are suggested. In the fatigue reliability problems, good number of experimental data are necessary to get the statistical distribution of the S-N parameters. The information, however, are not always available due to the limited expense and time. In this case, a family of curves with prediction interval, called P-S-N curve, is constructed from regression analysis. Using the KDRM, once a set of responses are available at the sample points at the mean, all the reliability analyses for each P-S-N curve can be efficiently studied without additional response evaluations. The method is applied to a spring design problem as an illustration of practical applications, in which reliability-based design optimization (RBDO) is conducted by employing stochastic response surface method which includes probabilistic constraints in itself. Resulting information is of great practical value and will be very helpful for making trade-off decision during the fatigue design.

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Functional Relationships between Fatigue Data

  • Beiss, Paul
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.140-141
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    • 2006
  • Most PM components are exposed to cyclic loading over long periods of time, yet, the fatigue performance is often at best characterized by a fully reversed bending strength. The effects of density, deviating loading modes, external notches or mean stresses must usually be estimated. The amount of available data is nowadays sufficient to come to fact-based estimates.

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Fatigue Damage Estimation of Wide Band Spectrum Considering Various Artificial Neural Networks (다양한 인공 신경망을 적용한 광대역 스펙트럼의 피로손상 예측)

  • Park, Jun-Bum;Kim, Sung-Yong
    • Journal of Ocean Engineering and Technology
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    • v.30 no.5
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    • pp.341-348
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    • 2016
  • The fatigue damage caused by wide band loadings has generally been predicted using fatigue damage models in the frequency domain rather than a rain-flow counting method in the time domain because of its computation cost. This study showed that these fatigue damage models can be simplified in the form of normalized fatigue damage as a function of the S-N curve slope and bandwidth parameters. Based on numerical simulations of various wide band spectra, it was found that fatigue damage models in the form of normalized fatigue damage with one S-N curve slope and two bandwidth parameters( α1 , α2 ) provided less reasonable fatigue damage. Therefore, an additional bandwidth parameter needs to be considered based on a sensitivity study using various neural networks, which proved that α1-5 would be the dominant factor of a fatigue damage model as an additional bandwidth parameter.