• Journal of the KSME
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• v.49 no.12
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• pp.49-53
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• 2009

이 글에서는 기계공학 분야에서 가장 널리 쓰이는 가속수명시험법의 하나인 피로시험에 최근에 개발된 확률적 피로한도를 도입한 모형과 이의 유용성에 대해 소개한다.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.1-6
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• 2004

Fatigue tests were carried out for butt welded joints with SM520-TMC steel plate with thickness between 20mm and 80mm. The test results were analysed statistically and the effect of plate thickness on the fatigue strength investigated. The fatigue strengths based on nominal stress range satisfy the requirement of the standards. Due to misalignment of the specimens, the measured stresses are higher than the nominal stresses especially for 20mm thick plates. If fatigue strengths are evaluated based on the measured stresses, then the fatigue strengths are greater than those based on nominal stresses. The results show that the thickness effect is similar to the formula proposed by Gurney.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.463-465
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• 2012

선박근무자의 피로는 해양사고의 잠재적 요인으로 혹은 인적과실에 기여하는 한 요인 정도로만으로 여겨졌으나, 최근 이와 관련한 연구에 의하면 선박근무자의 피로가 임무수행에 밀접하게 영향을 미치며, 인적과실을 유발하는 주요한 원인 중 하나라는 사실이 밝혀지게 되면서 선박 인간공학분야에서의 인간공학적 요소들의 고려 여부가 관심의 대상이 되고 있다. 선박근무자의 피로 발생원인은 명확히 밝혀져 있지 않으며, 선상작업에서 오는 스트레스, 감정 및 작업 등에 의해 영향을 받는 것으로 보이나, 통상 피로는 주로 한 가지 원인보다 복합적인 원인에 의하여 발생되는 것으로 알려져 있다. 본 연구에서는 이러한 선박근무자의 자각피로도와 직무스트레스의 효율적 관리를 위하여 선상에서 간편하게 자각피로도를 측정할 수 있는 방법을 제안하고자 한다.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.215-216
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• 2004

최근 해양구조물의 수직 칼럼부 용접 공법은 FCAW에 의한 다층 용접으로, 작업 시수와 작업자의 피로 가중 등, 생산 효율면에서 단점이 많았다. 이를 개선하기 위해 최초로 EGW에 의한 단층 용접을 적용하고자 EGW 적용시의 용접강도 및 피로 안전성을 평가하기 위한, 피로 시험을 수행하였다. (중략)

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.29-36
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• 1991

The effects of heat treatment on fatigue crack growth behavior were studied in continuously reinfored, magnesium-based composite (FP/ZE41A). Following an earlier TEM investigation, specimens were thermally aged to modify the interfacial zone between the alumina fibers and mg alloy matrix. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction(longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparision of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth than as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens. SEM observations of fiber pullout and ductile tearing on the fatigue fracture surfaces indicate that the aging weakens the strength of the fiber/matrix interface, giving rise to the observed fatigue crack growth behavior.

• The korean journal of orthodontics
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• v.35 no.4 s.111
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• pp.302-311
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• 2005

This study was performed to compare the fatigue limit of stainless steel wires and Fiber-reinforced composites (FRC) under conditions of permitting physiologic tooth movement. and to evaluate the clinical value of FRCs which was used to reinforce the anchorage unit. The stainless steel wire groups were divided into round and rectangular wire groups. The FRC groups were divided into uni-directional and woven groups, with resin coating and without resin coating in the Proximal area After the number of cycles to failure of each of the 6 groups were measured within the $5{\times}10^5\;cycle$ fatigue limit simulating the orthodontic treatment period. the fatigue limit of each group was compared with each other The findings of this study were as follows. In stainless steel wires, the fatigue limit of rectangular wires were higher than that of round wires. But there was no statistically significant difference (p>0.05). In FRCs with resin coating and without resin coating in the interproximal area, the fatigue limit of uni-directional type was higher than that of the woven type (p<0.05). In uni-directional and woven type FRCs, the fatigue limit of FRC with resin coating in the interproximal area was higher thar that of FRC without resin coating (P<0.05) As the FRCs and stainless steel wires did not fracture until the $5{\times}10^5\;cycle$ fatigue limit which clinically is useful. it is sufficient to use FRC and stainless steel wire for reinforcing anchorage. When esthetics is important and the attachment of additional devices are necessary. it seems sufficient to use FRC as anchorage reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.751-757
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• 2016

The aim of this study is to estimate the reliability of fatigue limit of the material used for crank throw components according to the staircase method. The material used for crank throw components is forged S34MnV grade steel, which is heat treated by normalizing and tempering. In this work, to predict the reliability of the design fatigue strength, axially loaded constant amplitude fatigue testing was conducted. The test specimens were loaded with an axial push/pull load with a mean stress of 0 MPa, which corresponds to a stress ratio of R=-1. The fatigue test results were evaluated by Dixon-Mood formulas. The values of mean fatigue strength and standard deviation predicted by the staircase method were 296.3 MPa and 10.6 MPa, respectively. Finally, the reliability of the fatigue limit in some selected probability of failure is predicted. The proposed method can be applied for the determination of fatigue strength for design optimization of the forged steel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1119-1129
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• 2011

Shot-peening effects on the fatigue behavior of bearing steel were investigated under the high cyclic loading. Hourglass shape specimens were made of bearing steel(JIS-SUJ2) for rotary bending fatigue tests. Two kinds of treatments were performed : a heat treatment and a shot-peened surface treatment after the heat treatment. The fracture surfaces of specimens were classified into two types of fracture mode : the surface fracture mode induced by a surface defect and the internal fracture mode induced by a nonmetallic inclusion. Inclusion depth and shape affected considerably the fatigue life. Shot-peening treatment improved much the fatigue life of the bearing steel under low and high levels of cyclic loads. Probabilistic-stress-life (P-S-N) curves were suggested for the reliable fatigue life estimation of the improved bearing steel.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.32 no.4
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• pp.176-176
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• 2019