• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2475-2482
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• 1993

The effects of the hole size(2R) and the specimen width(W) on the fatigue strength and the fatigue life in plain woven glass/epoxy composite plates are experimentally investigated under constant amplitude tensile fatigue loading. It is shown in this study that the notch sensitivity under fatigue loading is lower than that under static loading. It can be explained by the fact that the stress concentration is relaxed by the damage developed at the boundary of circular hole. To predict the fatigue strength at a specific cycle, the modified point stress criterion represented as a function of the geometry of the specimen(2R and W) is applied. It is found that the model used in the prediction of the notched tensile strength predicts the fatigue strength with reasonable accuracy. A model for predicting the fatigue life in the notched specimen, based on the S-$N_f$, curve in the smooth specimen, is suggested.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.134-140
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• 2014

The paper presents an overview of the present state of study on the fatigue behaviors at very high number of cycles ($N_f$ > $10^7$). A classification of materials with typical S-N curves and influencing factors such as notches, residual stresses, temperatures, corrosion environments and stress ratios are given. The microstructural inhomogeneities of materials and micro-cracks played an important roles in very high cycle fatigue behaviors. The failure mechanisms for the fatigue design of materials and components are mentioned.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.337-343
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• 2002

This study deals with evaluation of bending fatigue strength in shaving gears. The saying gears were manufactured by processes that are currently used in most gears manufacturing companies. The test gears are bobbed, then the tooth surface are treated by a combination of shaving, carburizing and shot peening. The constant stress amplitude fatigue test is performed by using an electro-hydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. In this study, the effect of shaving process and shot peening was investigated and evaluated quantitatively on the fatigue strength. The enhancement of fatigue strength due to shaving process and shot peening is clarified.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.98-109
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• 1992

In this study uniaxial cyclic loading tests were performed on Cheon-Ho Mt. Limestone specimens to investigate the fatigue failure behavior. The loading rate was kept constantly at 760kg/$\textrm{cm}^2$/sec under cyclic loading. In order to reveal the fatigue behavior for each rock type, the test results were mutually compared with previous studies carried out on Indiana Limes-tone and Seong-Ju Sandstone. Fatigue data is presented in the form of S-N curves, which illustrate the relationship of maximum applied stress(S) to the number of cycles(N) required to produce failure. For the purpose of comparing the S-N curves for each rock type, the test data were formulated up to 10$^4$cycles and the correlation coefficients(R) on Cheon-Ho Mt. Limestone and Seong-Ju Sandstone specimen are 0.886 and 0.983, respectively. All three rock specimens were found to have shorter fatigue life at higher applied stress levels. The fatigue life for each rock type was considered as no less than 81.5, 70 and 74.8%, for Cheon-Ho Mt. Limestone, Indiana Limestone and Seong-Ju Sandstone, respectively. The comparison in static strength for monotonic loaded specimens and specimens which did not fail even after 10$^4$cycles indicated that the increasing rate of strength was about 6.18 and 10.96% , for Cheon-Ho Mt. Limestone and Indiana Limestone, respectively. Poisson's ratio and volumetric strain for Cheon-Ho Mt. Limestone and Seong-ju Sandstone, tended in all the cases to rapidly increase at higher stress levels and with an increase in number of cycles. This increasing trend becomes rapid and obvious just before failure. Also Poisson's ratio and volumetric strain for each stress level were compared and analyzed at the first cycle and the cycle prior to failure.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.113-120
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• 2002

A shear connection in composite bridges with precast decks has considerable characteristics different from cast-in-place deck bridges such as shear pocket and bedding layer. Thus, it is necessary to build design basis of the shear connector in precast decks through the experiments. In order to estimate fatigue life of shear connector in precast deck bridges, push-out fatigue tests were conducted with parameter, bedding layer thickness. As a result of the tests, failure modes of shear connector were observed. Consequently, empirical S-N curve equations of stud shear connector in precast deck bridges were proposed in this paper.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.82-88
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• 2006

This assessment is concerned with the fatigue strength of the tendon porch found in TLP. Lorge-scale fatigue tests with models constructed at 30% the size of the real structures have been carried out to investigate the fatigue behavior of the API 2W Grade 50 steel recently produced by POSCO. The fatigue life for the present test models was obtained based on the concept of nominal stress. A comparison of the present test results with those obtained by a numerical approach based on the structural analysis results has showngood agreement. The present results were also compared with the design curves in DnV RP-C203.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.44-52
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• 1999

This study deals with spot weld ability of dissimilar aluminum alloy sheets in order to take advantage of its lightweight and strength. The paper also shows the relationship between weld elements(i.e. current, welding time and tip force) and weld quality on the resistance spot weld part of the same and dissimilar Al alloy. The conclusions are: (1) Because of excessive tip force, deep indentation remained at the Al 5182 side which is lower stiffness at the dissimilar Al alloy. (2) Weld quality (i.e. tensile shear strength) of dissimilar Al alloy is superior to that of the same Al 6061 alloy. (3) As long cycles, fatigue life of spot weld specimen on dissimilar Al alloy sheets was better than that of the same Al alloy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.979-986
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• 2016

The tripod shafts of constant-velocity joint are used in both the trains KTX and KTX-sanchon. It is an important component that connects the motor reduction unit and the axle reduction unit in a power bogie. The tripod shaft not only transmits drive and brake torque in the rotational direction, but also slides in the axial direction. If the drive system is loaded with an excessive torque, the fuse part of the shaft will be fractured firstly to protect the other important components. In this study, a rig was developed for conducting torsion tests on the tripod shaft, which is a type of mechanical fuse. The tripod shafts were subjected to torsional fracture test and torsional fatigue test on the rig. The weak zone of the tripod shaft was identified, and its fatigue life was predicted using finite element analysis (FEA). After analyzing the FEA results, design solutions were proposed to improve the strength and fatigue life of the tripod shaft. Furthermore, the deterioration trend and time for failure of the tripod shaft were verified using the hysteresis loops which had been changed with the advancement of the torsional fatigue test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.71-80
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• 2010

Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.635-643
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• 2017

The purpose of this study is to investigate the influence of the cold reduction rate and an ultrasonic fatigue test (UFT) on the fatigue behaviors of STS 304L. The tensile strength, yield strength, hardness value and fatigue limit in the UFT fatigue test linearly increased as thickness decreased from 1.5 mm to 1.1 mm, as the cold reduction rate of STS 304L increased. As a result of the UFT fatigue test (R = -1) of four specimens, the fatigue limit of the S-N curve formed a knee point in the region of $10^6$, and the 2nd fatigue limit caused by giga cycle fatigue did not appeared. In the case of t = 1.1 mm, the highest fatigue limit was 345 MPa, which was 64.3% higher than the original material (t = 1.5 mm). As a result of the UFT fatigue test of STS 304L, many small surface cracks occurred, grown, coalesced while tearing.