• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.123-130
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• 2007

Recently, a lot of work and interest have been devoted to the development of multiaxial fatigue parameters for fretting fatigue life prediction. In this study, the fretting fatigue lift and critical location ware estimated and evaluated through the multiaxial fatigue theories in a cylinder-on-flat contact configuration far Cr-Mo steel, SCM420, the material commonly is used in gears of the automobile and rollers of the conveyor. The strain-life curve was obtained from fatigue test for SCM420. The Fretting fatigue life and critical location were estimated through stress distributions, SWT-parameters and FS-parameters obtained from FEA. This paper showed possibility of applying multiaxial fatigue theories to fretting fatigue lift prediction comparing predicted life with experimental results.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.546-554
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• 2023

The cyclical behavior of Alloy 617 was examined at 25 ℃ and high temperatures of 800, 850, 900, and 950 ℃ in air to obtain its fatigue life curves. The specimens tested at 25, 800, and 850 ℃ cyclically hardened, whereas those tested above 900 ℃ cyclically softened from the first cycle, that is, their fatigue life was reduced at high temperatures owing to loss of strength. Parameters of the typical Coffin-Manson-Basquin relationship were determined for each test temperature. Interestingly, no significant difference in fatigue life was observed for the specimens tested in the range of 800-950 ℃. Owing to the similarity in fatigue life, we determined fatigue strength and fatigue ductility exponents that could be applied for this temperature range. The parameters obtained were close to the universal slopes, although the fatigue ductility exponent was slightly different. The proposed fatigue life curves were compared with those presented in ASME code.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.43-47
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• 2000

When estimating fatigue crack growth (FCG) life of structures, the use of crack growth models and knowledge of the values of their corresponding parameters are of vital importance. Inconsistency in using models with appropriate parameters can lead to enormous errors in FCG life prediction. In this paper examples are analyzed and compared with test results to show the possible problems, Consistency checks are necessary for avoiding some pitfalls, and also necessary for verifying the correct performance and accuracy of the used computer program.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.150-155
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• 2002

En case of the fatigue life evaluation of rolling stock structures, mainly deterministic fatigue life evaluation has been carried out. But most of the parameters influencing on the fatigue life have a probabilistic distribution such as normal, log-normal, Weibull, etc. Therefore, to take probabilistic factors into fatigue life evaluation, probabilistic methods are being applied to the fatigue life evaluation of rolling stock. In this paper, probabilistic S-N analysis and methods using limit state functions are introduced. And some results of fatigue life evaluation obtained with these methods for rolling stock structures are shown.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.46-50
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• 1993

The sensitivity study to evaluate the effects of parameters on the fatigue crack propagation life under the constant loadings is executed in the previous study of the authors. It is shown that the effect of the crack opening ratio is large comparatively. The purpose of this paper is to evaluate the effects of parameters on the fatigue crack propagation life under the random loadings. A new method of evaluation of the effective stress under the random loadings is developed. The sensitivity study of parameters on the fatigue crack propagation life under the random loadings is executed by using it.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.359-360
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• 2006

Recently, a lot of work and interest has been devoted to the development of multiaxial fatigue parameters for fretting fatigue life prediction. Many of these parameters have been reviewed in the literature for simple geometries like a cylinder-on-flat contact configuration. The purpose of this study was to estimate fretting fatigue life using critical plane approach which is one of the multiaxial fatigue theories.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.393-400
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• 2011

In this study, a procedure for the inverse estimation of the fatigue life parameters of springs which utilize the field fatigue life test data is proposed to replace real test with the FEA on fatigue life prediction. The Bayesian approach is employed, in which the posterior distributions of the parameters are determined conditional on the accumulated life data that are routinely obtained from the regular tests. In order to obtain the accurate samples from the distributions, the Markov chain Monte Carlo (MCMC) technique is employed. The distributions of the parameters are used in the FEA for predicting the fatigue life in the form of a predictive interval. The results show that the actual fatigue life data are found well within the posterior predictive distributions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1448-1454
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• 1994

Data which gathered and used in the field of fatigue and fracture mechanics have a lot of uncertainties. In this case, those uncertainties will make scatter band in evaluation of fatigue life and fracture toughness. Thus, the probabilistic analysis of these data will be needed. For determining the fatigue life in mixed mode, using crack direction law and fatigue crack growth law, the problem is studied as a constrained life minimization. Stress intensity factor(SIF) is computed by approximate solution table(Ewalds/Wanhill 1984) and 0th order PFEM. The variance of fatigue life and SIF are computed by differentiation of tabulated approximate solution and 1st order PFEM. And these are used for criterion of design values, principal parameter determination and modelling. The problem of center cracked plate is solved for checking the PFEM model which is influenced by various parameters like as initial crack length, final crack length, two fatigue parameters in Paris Equation and applied stress.

• Journal of Welding and Joining
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• v.26 no.1
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• pp.69-75
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• 2008

Spot welding which use the main process for side block production of stainless steel railway vehicle is legged behind in laser welding about a quality and productivity. Although the laser welding has many potential advantages such as low heat input and aspect ratio of weld bead, its application to a new structural component still is required many engineering data including mechanical properties such as tensile, fatigue strength, etc on. Therefore, experimental analysis was carried out to understand the fatigue phenomena of different thickness stainless steel overlap joining panels by Nd:YAG laser welding. The fatigue life curves were obtained through fatigue tests with the various levels of applied load. The fatigue life is related with the parameters such as gap size and penetration depth through experiment. As the results, tensile strength and fatigue life were proportional in heat input level and gap was identified the major factor for fatigue life. Also we could know that deferent a-ferrite content at HAZ depend on welding heat input was important factor to determine a formation of initial crack and total fatigue life cycle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.89-94
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• 2006

In this paper, the effects of the system parameters on the high cycle fatigue life based on structural dynamic analysis of a turbine blade are investigated. Conventional studies have forcused on the fatigue life of turbine blades with specific system parameters. However, each parameter has statistical deviation because of inhomogeneity of material property, tolerance, and operating conditions. Therefore a methodology that estimates the effects of system parameter on the fatigue lift deviation is demonstrated.