• 한국생산제조학회지
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• 제26권3호
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• pp.292-298
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• 2017

Numerical analysis for various design parameters should be preceded by optimal design of composite materials. Numerous studies have been conducted on the bolting of interconnecting beams. In this study, the response surface method was applied to optimize the design of bolted joints connected by laminated wood composite beams. The response surface was created by combining the FEA code for composite analysis and the algorithm for forming the response surface. Optimization on this response surface was performed with a genetic algorithm to derive the results. The determination of the optimum bolt-hole position for the connection of composite beams is an optimization problem. Tsai-Wu composite failure index, maximum deflection, and simple von Mises stress are set as the objective functions. It has been proved that the design results of the optimized bolt-hole are superior to the design performance of the existing conventional bolt-hole position.

• 열처리공학회지
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• 제15권5호
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• pp.213-218
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• 2002

In order to develop the economic and environmental water-soluble black coloring agent, some adequate chemical mixtures were mixed and this solution was applied to coat quenched and tempered 51B20 steel bolt. Some basic properties of the solution and characteristics of the coated film in addition to the corrosion resistance were investigated. The developed 100 kg of water-soluble black coloring agent solution was a chemical mixture consisted of 10 kg of aqueous coloring agent, 40 kg of surface active agent, 0.3 kg of anti-foam agent and $50{\ell}$ of water. The coated film of the bolt was composed of hard layer of about $2{\mu}m$ and the disbondable soft layer of about $4{\mu}m$ above the hard layer. Many surface active agents peaks and a few hydrophilic peaks were observed in the coated film. Surface roughness value of the coated bolt was lower than that of the non-coated bolt. Corrosion resistance of the coated bolt considerably improved and also relatively showed a good polarization resistance at test condition of $40^{\circ}C$ colorizing temperature and 5% the solution concentration in 3% NaCl anodic polarization test. Initial appearance time of the surface rust was greatly retarded owing to the coated film in salt spray test.

• 한국강구조학회 논문집
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• 제12권2호통권45호
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• pp.177-185
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• 2000

본 논문에서는 대기 중에 폭로한 내후성강재의 고장력볼트 마찰이음부 미끄럼계수 평가를 위한 실험연구를 수행하였다. 표면 상태는 흑피 부착된 시험체와 숏브라스트로 흑피를 제거한 시험체를 각각 3개월 및 6개월 폭로한 후 수동솔질, 전동솔질 및 청소하지 않은 표면 등을 고려하였다. 또한, 6개월 폭로 시험편의 각 표면 상태에 대하여 600 시간 동안 볼트축력 감소율을 측정하였다. 실험으로부터 모든 시험체에서 폭로 기간에 따라 미끄럼 계수는 증가하였으며 흑피부착 표면을 전동솔질로 청소한 경우를 제외하곤 모두 0.6 이상의 값을 보였다. 볼트 축력 감소율 역시 초기 비폭로 시험체에 비해 폭로한 시험 체에서 증가하였으며 최대 감소율은 약 10%에 이르렀다.

• 열처리공학회지
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• 제36권1호
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• pp.15-21
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• 2023

Recently, ultra-high strength bolts have been developed for weight lightening of a vehicle and fuel efficiency. However, some amount of diffusible H is absorbed into the bolt during its manufacturing process so that H embrittlement (HE) often occurs particularly in high strength bolts with a tempered martensitic microstructure. This brings attention to ultra-high strength pearlitic bolts with a high resistance to HE. Therefore, in this study the HE resistance of the 1.6 GPa grade pearlitic bolt was evaluated through tightening tests and slow strain rate tests (SSRTs), and fracture surfaces of failed bolts were comparatively observed. A critical H content for the tightening test turned out to be ~0.23-0.35 mass ppm. The bolt with a diffusible H content of ~0.35 mass ppm was fractured during the tightening test, showing a quasi-cleavage fracture surface, indicating the occurrence of HE. In addition, the bolt underwent premature elastic failure during the SSRT. This implies that the HE resistance of high strength bolts can be evaluated by both tightening test and SSRT.

• 대한토목학회논문집
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• 제26권3A호
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• pp.513-521
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• 2006

최근에는 고장력볼트 마찰이음의 다양화에 대해서 실무적 관점에서부터 각종 실험적 연구가 실시되고 있지만, 이러한 연구 결과가 시방기준의 개정에 반영된 것은 거의 없는 실정이다. 특히 강교량에 있어서는 최근 합리화의 추진이 강하게 대두되고 있으며, 이에 따라 강교의 설계 및 시공상 가장 중요한 부분의 하나인 고장력볼트 이음부의 합리화의 필요성이 커지고 있다. 따라서 본 연구는 고장력볼트 이음부의 설계 및 시공의 합리화를 위한 방향을 제시하고, 설계기준으로의 반영을 위한 기초자료를 제시하기 위하여 고장력볼트 이음부에 관한 국내외의 설계기준을 비교, 검토하여 설계에서 가장 중요한 인자인 미끄러짐 계수, 그리고 볼트 구멍의 크기에 대한 규정을 분석하였다. 한편 과대공 및 축력감소의 영향을 평가하기 위하여 고장력볼트 연결부에 대한 미끄러짐 시험을 실시하여 미끄러짐 거동을 평가하였다. 또한 최근에 수행된 고장력볼트 마찰이음에 관한 연구결과를 토대로 접촉면의 상태에 따른 미끄러짐 계수의 차이, 과대공의 영향, 채움판의 적용, 모재 틈새간격의 영향, 방청볼트의 사용성 등을 평가하였다. 이로부터 미끄러짐 계수의 경우 국내의 시방기준에서는 접촉면의 처리상태에 따라 일률적으로 적용되고 있는데 비하여 외국의 시방기준에서는 접촉면의 처리상태에 따라 세분화하여 규정하고 있다. 따라서 국내의 시방기준에도 접촉면의 처리상태에 따라 미끄러짐 계수를 세분하여 규정하여 설계의 합리화를 추진할 필요가 있을 것으로 판단된다. 또한 외국의 시방기준에서 적용하는 정도의 과대공을 설계에 반영하면 시공의 효율성을 증대시킬 수 있을 것으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.244-249
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• 2008

It happened a failure on special bolt which supported main landing gear actuator up-lock rod of 00 aircraft. Fracture was occurred at end of center drilled hole and thread machined on bolt. Metallographic, fractographic, and other characteristics of embrittlement analysis and experiments carried out on the failed bolt to find out the reason. Bolt surface was cadmium electroplated(EP) to give lubrication and provide excellent corrosion resistance. Resultly, Bolt was failed due to cadmium embrittlement occurred during baking treatment as well as center drilled hole. for the failure that are relevant to failure analysis and prevention. For their successful functional application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and is complete with no center drilled hole

• 대한금속재료학회지
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• 제49권1호
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• pp.1-8
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• 2011

To measure the sensitivity of the hydrogen embrittlement from plated high strength bolts (SWCH18A, F11T), the bolt was stressed by a corresponding to the amount of tensile strain of 5% and 20%, and then the bolt developed a crack on the surface. The bolt that didn't have concentrated hydrogen, even though it was stressed by a corresponding the amount of tensile strain of 5% and 20%, no crack developed. However, the bolt that had concentrated hydrogen, developed cracks from the thread crest to the root. It is impossible to measure the hydrogen amount from plated high strength bolts using Hydrogen-Determinator, because of the limitation of the minimum sample size (about 1g as a mass or $5{\times}5{\times}5 mm^3$ as a volume). Therefore, the sensitivity of hydrogen embrittlement can be measured by observing the presence of cracks on the surface of plated high strength bolts which are stressed by a corresponding to the amount of tensile strain of 5% and 20%.

• 대한기계학회논문집
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• 제13권3호
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• pp.353-361
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• 1989

본 논문에서는 유한 요소법을 이용하여 접촉을 고려한 나사 체결 문제를 해석하고 여러 다른 체결조건이 각 나사산에 걸리는 하중 분담율에 미치는 영향을 살펴보고, 이 하중 분담율이 보다 균일화 될 수 있는 체결 조건을 찾고, 또 그때의 응력 분포를 살펴보는 것을 목적으로 한다.

• 한국기계가공학회지
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• 제18권2호
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• pp.14-21
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• 2019

In recent years, the use of composite structures has become commonplace in various fields such as aerospace, architecture, and civil engineering. In this study, A method is proposed to find optimal position of bolt hole for fastening of composite structure. In the case of composites, stress distribution is very complicated, and design optimization based on this phenomenon increases difficulty. In selecting the optimum position of the bolt hole, the response surface method(rsm), which is a method of optimization, was applied. A response surface was created based on design points by multiple finite element analyzes. The position of the bolt hole that minimizes the stress when bolting on the response surface was found. The distribution of the stress at the position of the optimal hole was much lower than that of the initial design. Based on the results of this study, it is possible to increase the design safety factor of the structure by appropriately selecting the position of the bolt hole according to various load types when designing the structure and civil structure.

• 한국표면공학회지
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• 제44권1호
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• pp.21-25
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• 2011

This test focuses on the correlation between the lubrication, ductility and strength through the change of nut lubricant which decides joining angle for A490 bolt sets required in the AASHTO (American Association of State Highway & Transportation Officials). Because the lubrication of high tension bolt, nut, washer sets becomes an important factor to ductility and joining load, the quality improvement is required for improving reliability and securing enough lubrication of maker and user. This study examines the quality characteristics required in the specification through tests because only this standard specifies joining quality in the extreme conditions (as much about two times of the joining angle on site as normal condition). Moreover, this study is limited to the test on joining axial force required in the AASHTO for the three nut lubrication conditions of A490 bolt set. It is concluded that the nuts should be coated or waxed enough for the improvement of the joining axial force and ductility of bolts required in the standards. It is shown that in the case of plain high tension bolt sets, a rust preventing lubricative oil shall be applied and the torque coefficient value for A490 bolt sets should be maintained below 0.175.