• 문화기술의 융합
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• 제7권2호
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• pp.405-410
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• 2021

본 연구에서는 레일체결장치용 방진패드의 사용수명 및 스프링강성을 평가하고자 비선형 재료모델 및 피로하중조건을 적용한 유한요소해석을 수행하였다. 피로해석 결과, 초기조건 대비 스프링강성의 변화율은 약 16%로 나타나 피로경화가 발생된 것으로 분석되었다. 방진패드의 길이방향으로 발생되는 응력은 중앙부와 외곽부(Edge)의 발생응력의 차이가 약 10배 이상 발생되었다. 또한 중앙부 보다 외곽 경계부의 등가응력이 2배 이상 크게 발생하는 것으로 분석되었다. 따라서 실제 사용조건에서 방진패드의 손상 및 변형 취약부는 방진패드의 모서리부분인 것으로 분석되었다. 피로해석을 통해 산출된 반복횟수에 따른 방진패드의 등가응력을 이용하여 방진패드의 피로수명선도를 도출하였다. 본 연구에서 도출한 방진패드의 피로수명선도를 이용하여 향후 다양한 하중조건에서 방진패드의 등가응력을 산출하여 해당조건에서의 피로수명을 예측하는 데에 활용이 가능할 것으로 판단된다.

• Design & Manufacturing
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• 제14권4호
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• 한국재난정보학회 논문집
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• 제20권2호
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• pp.411-418
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• 2024

연구목적: 본 연구에서는고인장 합금재를 활용하여 기존 철근콘크리트 기둥의 내진성능 향상이 가능한 새로운 형식의 볼트 체결식 내진보강재를 개발하고자 한다. 연구방법: 고인장 합금재인 SUS304 및 일반 구조용 강재인 SS275를 이용하여 T형 단면 강판을 제작하고 이를 SCM435의 고장력 볼트로 체결한 내진보강재 실험체를 제작하여 휨 실험을 통해 재료적 특성이 내진 보강성능에 미치는 영향에 대해 비교 분석한다. 연구결과: SUS304를 사용한 실험체가 7% 높은 최대 강도와 22% 높은 항복 강도를 보이며, 360MPa 더 높은 압축응력을 나타낸다. 또한 중립축의 변화도 더 미소하여 더 우수한 내력을 가진 것으로 판단된다. 결론: 동일한 단면에서 SUS304를 사용한 내진보강재가 휨 강도, 항복강도, 인장강도, 중립축 변화, 연성능력 측면에서 더 우수한 것으로 판단되며 추후 연구에서 철근콘크리트 기둥 실물 실험체에 적용함으로써 기둥-보강재간 일체 거동에 대한 실험이 필요하다고 사료된다.

• 한국해양공학회지
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• 제29권1호
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• pp.34-44
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• 2015

A hydraulic tensile test machine (HSTM) is one of the devices used to obtain the flow stress of a material during high-speed elongation. This paper first describes some features of a newly built HSTM. The improvement histories of the upper and lower jigs, which are the most vital parts of the HSTM, are also presented. We have frequently witnessed test failures with 1st generation jigs and specimens due to slip between the jig and specimen. 2nd generation jigs provide more stable test results, but the use of a longer upper jig induces excessive vibration and consequently makes it difficult to attach an environment chamber. 3rd generation jigs have some advances in terms of the symmetric fastening between the upper jig and specimen, as well as an exemption from direct contact between the lower jig and specimen. The performance of an environment chamber is verified by high and low temperature tests. A high-speed displacement measurement system is introduced based on a high-speed camera and motion-tracking software with aid of a surface grid device for the specimen.

• 대한치과보철학회지
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• 제40권3호
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• pp.246-261
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• 2002

The screw loosening is one of the complications that happen frequently in dental implant prostheses. The purpose of this study was to evaluate the changes of reverse/loosening (opening) torque of the screw according to the surface modifications by sandblasting and 24K gold electroplating as well as to determine the possibility of the clinical use of a washer in dental implant. The reverse torque of 4 experimental conditions(control, sandblasted, use of washers, electroplasted) was measured by digital torque gauge (Model MGT50Z, Mark-10 Corp., 458 West John Street Hicksville, NY 11801 USA). Electronic torque controller (Nobel Biocare DEA 020) was used in fastening the gold screws into abutment replicas. Mixed Linear Model Analysis method was used for statistical analysis. To examine the changes of screw thread surface, microphotographs were taken by Olympus PME-3 metallurgic microscope (Olympus Optical Co. Ltd., Tokyo, Japan). Within the limitations of this study, the following results were drawn: 1. The surface modifications of the gold screws and the use of a washer have significantly affected the reverse torque value compared to the control group (P<0.01). 2. Sandblasting and electroplating treatments demonstrated significantly higher reverse torque value than that of control group. 3. The use of a washer may be one of the useful clinical methods that prevent the screw loosening. However, further studies are necessary for the material selection and design of the washer.

• 복식
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• 제66권5호
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• pp.133-148
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• 2016

This study examined dahoe(多繪-braided cord) and mangsu(網綬-ornament of husu for ceremonial dress) used in myeon gwan(冕冠), daedae(大帶), and husu(後綬) among royal formal dresses in the Joseon Dynasty(1392-1910) based on historical materials including literature, relics, and paintings. The results of this study are as follows. In myeon-gwan, dahoe was used for cap strings, goeing(紘) and yeong(纓). Cap strings were applied to the king, the Crown Prince, and the eldest son of the Crown Prince regardless of their status, and they showed differences among the periods. Both goeing and yeong were used during the early period of Joseon, and then only yeong was used in the late period. As goeing was removed and only yeong was used in the late period, patterns combining goeing and yeong, in color and wearing method, appeared. Dahoe used in cap strings is dongdahoe(童多繪-a kind of braided cord). In daedae, 'nyuyak(紐約)' was tied up to its fastening part. The material of nyuyak was changed from dongdahoe in the early Joseon Dynasty to guangdahoe(廣多繪-a kind of braided cord) in the late period, and the method of using it was also changed. Husu was imported from Beijing in China during the early period of the Joseon Dynasty, but in 1747, it was regulated to be woven in Joseon, and at that time, King Yeongjo attempted to restore the institution of weaving husu with "320 su(首)," namely, 6,400 strands as specified for the status of a prince of the Ming Dynasty.

• 한국컴퓨터정보학회논문지
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• 제25권11호
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• pp.167-178
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• 2020

본 연구는 소재 특성, 맞음새, 여밈 등을 고려하여 변화되고 있는 신한복 저고리의 패턴을 비교 분석해봄으로써 시판 신한복 브랜드 간의 저고리 패턴의 차이를 알아보고자 하였다. 6개 제품을 구매, 분해한 후 분해 패턴을 가지고 분석을 실시하였다. 저고리 형태의 경우, 1, 3, 6브랜드의 경우 다트가 없는 형태를 나타냈고 5브랜드는 프린세스라인으로 인체의 입체감을 표현하였다. 외관 평가결과, 5브랜드가 앞품너비의 여유량, 뒤소매진동의 군주름을 제외한 대부분의 항목에서 가장 높게 평가되어 외관이 가장 우수한 것으로 분석되었다. 의복압은 1브랜드의 경우 다른 브랜드의 제품보다 가슴둘레가 작고 어깨폭이나 길이도 짧아 착용 후 당김 현상이 발생하였다. 신한복에 대한 수요가 증가됨에 따라 기성복화하여 사이즈 체계에 대한 확립이 필요할 것으로 생각된다.

• Design & Manufacturing
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• 제14권1호
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• pp.42-48
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• 2020

Titanium alloy has been in the spotlight as a core material in high-tech industries that require high strength and light weight because it has excellent strength and corrosion resistance and strength is higher than that of steel. Therefore, in various industries, existing steel products are intended to be replaced with titanium alloys. Titanium alloys can cause cutting tool breakage during cutting, and heat generated during cutting does not dissipate, accumulates in tools and workpieces, resulting in large wear and tear on thin workpieces. In addition, since titanium alloy is a metal with high chemical activity, the wear of the tool becomes more severe when the cutting speed is high, so machining of titanium bolt through cutting is very disadvantageous in terms of productivity. Therefore, the production of bolts using titanium alloys is being produced through a forging process to improve productivity and product quality. In this paper, hot forging molding analysis was performed on bolts used for fastening automobile parts using Ti-6Al-4V alloy, which is the most commonly used titanium alloy.

• 한국기계가공학회지
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• 제20권5호
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• pp.76-84
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• 2021

In this study, an optimal stiffness model of the C-frame, which was supporting the mold and tool load, was proposed to obtain quality self-piercing riveting (SPR) joining. First, the load path acting on the C-frame structure was identified using topology optimization. Then, a final suggested model was proposed based on the load path results. Stiffness and strength analyses were performed for a rivet pressing force of 7.3 [t] to compare the design performance of the final proposed model with that of the initial model. Moreover, to examine the reliability of continuous and repeated processes, vibration analysis was performed and the dynamic stiffness of the final proposed model was reviewed. Additionally, fatigue analysis was performed to ascertain the fatigue characteristics due to simple repetitive loading. Finally, stiffness test was performed for the final proposed model to verify the analysis results. The obtained results differed from the analysis result by 2.9%. Consequently, the performance of the final proposed model was superior to that of the initial model with respect to not only the SPR fastening quality but also the reliability of continuous and repetitive processes.

• 한국구조물진단유지관리공학회 논문집
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• 제23권4호
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• pp.145-151
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• 2019

급속공사 현장에 사용되는 속경성 보수모르타르의 내구성능 증진을 위해 사용재료의 물리적 성능을 평가하였다. 이를 위해 염화물 확산 억제 성능을 보유한 페로니켈 수쇄슬래그 잔골재와 급결제, EVA계 폴리머를 모르타르에 치환시켜 급결성능과 기초적 성능을 평가하였다. 그 결과 FNS잔골재 및 RS잔골재 사용에 따른 압축강도, 휨강도, 부착강도가 증가되었다. 속경성 폴리머 모르타르의 염화물 이온 촉진시험의 결과 FNS를 50%이하 사용 시 재령 7일에서 재령 28일간 염화물 억제 성능이 유지되었으며, FNS잔골재 및 RS잔골재 사용에 따른 내구성 저하는 발견되지 않았으나, 건축 및 토목용 대체골재로 사용하는데 경제성 및 장기 내구성에 대한 추가 검토가 필요할 것으로 판단된다.