• 항공우주시스템공학회지
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• 제16권6호
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• pp.8-17
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• 2022

항공기 날개에 사용되는 스킨-스트링거 패널은 기계적 체결과 접착 체결로 인하여 응력 집중과 접착 분리가 발생할 수 있다. 이를 고려하여, 3차원 직조 복합재료를 이용해 스킨과 스트링거를 일체시킨 패널을 설계하였다. 본 논문에서는 일체형 패널의 기계적 물성을 예측하기 위하여 기하학적 모델링 기법을 제안하였다. 시편의 기하학적 변수를 측정하고 섬유 다발의 패턴을 함수식으로 정의해 기하학적 모델링을 수행하였다. 이를 검증하기 위하여 iso-strain, iso-stress 가정을 사용한 가중평균모델을 통해 각 부재의 기계적 물성을 예측하고 유한요소해석을 수행해 압축시험 결과와 비교하였다. 제안한 기하학적 모델링 기법을 통해 스킨-스트링거 일체형 패널의 기계적 물성을 실험적 방법보다 효율적으로 예측하였다.

• 한국기계가공학회지
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• 제19권12호
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• pp.56-61
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• 2020

Fuel economy has always been a major issue in the automobile industry, especially owing to the associated environmental concerns. It is widely known that only 5-20% of the energy generated by automobiles running on internal combustion engine engines is used as power, while the rest is consumed because of friction between components. The main components of the reciprocating piston type compressor used in vehicles, such as the shaft, swash plate, piston, and cylinder, cause severe energy loss owing to frictional contact between each other. The wear contact between the main shaft and the other components is particularly severe. Most quality issues arise owing to the sticking phenomenon that occurs between these parts. In this study, a coating solution to reduce friction is prepared by mixing adhesive solid lubricant, organic binder-polyadimide, inorganic binder (Binder), and graphite in four different ratios, and the best combination is determined.

• Structural Engineering and Mechanics
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• 제6권5호
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• pp.485-496
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• 1998

Standard finite element wave propagation codes are useful for determining stresses caused by the impact of one body with another; however, their applicability to a laminated system such as architectural laminated glass is limited because the important interlayer delamination process caused by impact loading is difficult to model. This paper presents a method that allows traditional wave propagation codes to model the interlayer debonding of laminated architectural glass subject to low velocity, small missile impact such as that which occurs in severe windstorms. The method can be extended to any multilayered medium with adhesive bonding between the layers. Computational results of concern to architectural glazing designers are presented.

• 항공우주시스템공학회지
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• 제1권1호
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• pp.25-35
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• 2007

In this paper, the interlaminar crack problems of a fiber metal laminate (FML) under generalized plane deformation are studied using the theory of anisotropic elasticity. The crack is considered to be embedded in the matrix interlaminar region (including adhesive zone and resin rich zone) of the FML. Based on Fourier integral transformation and the stress matrix formulation, the current mixed boundary value problem is reduced to solving a system of Cauchy-type singular integral equations of the 1st kind. Within the theory of linear fracture mechanics, the stress intensity factors are defined on terms of the solutions of integral equations and numerical results are obtained for in-plane normal (mode I) crack surface loading. The effects of location and length of crack in the 3/2 and 2/1 ARALL, GLARE or CARE type FML's on the stress intensity factors are illustrated.

• 항공우주시스템공학회지
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• 제15권1호
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• pp.86-94
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• 2021

PCB 기반 전개형 태양전지판은 경량화 및 전기적 연결의 용이성으로 주로 큐브위성에 사용되나, 태양전지판의 면적이 증가할수록 발사환경에서 유발되는 굽힘거동이 증가하기 때문에 태양전지셀의 구조건전성 보장에 한계가 있다. 종래에는 태양전지판의 강성증가를 통해 굽힘거동을 최소화하고자 알루미늄 및 복합재 기반의 보강재를 또는 태양전지판을 적용하였지만, 태양전지판의 부피 및 무게 증가로 제한적인 설계요구조건을 가진 태양전지판의 단점으로 작용한다. 본 연구에서는 점탄성 테이프로 다층 박판을 적층하여 고댐핑 특성 구현이 가능한 6U 규격의 고댐핑 적층형 태양전지판을 제안하였다. 제안된 태양전지판의 기본특성파악을 위해 자유감쇠시험을 수행하였으며, 인증수준의 발사진동시험을 통해 설계유효성을 입증하였다. 또한, 시험결과를 토대로 일반 PCB 태양전지판과 고댐핑 적층형 태양전지판의 진동특성을 예측하고 비교분석을 수행하였다.

• Tribology and Lubricants
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• 제23권1호
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• pp.14-18
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• 2007

SCM415 alloy was implanted with nitrogen ions using plasma source ion implantation (PSII), at a dose range of $1{\times}10^{17}\;to\;6{\times}10^{17}N^{+}cm^{-2}$. Auger electron spectrometry (AES) was used to investigate the depth profile of the implanted layer. Friction and wear tests were carried out on a block-on-ring wear tester. Scanning electron microscopy (SEM) was used to observe the micro-morphology of the worn surface. The results revealed that after being implanted with nitrogen ions, the frictional coefficient of the surface layer decreased, and the wear resistance increased with the nitrogen dose. The tribological mechanism was mainly adhesive, and the adhesive wear tended to become weaker oxidative wear with the increase in the nitrogen dose. The effects were mainly attributed to the formation of a hard nitride precipitate and a supersaturated solid solution of nitrogen in the surface layer.

• 한국재료학회지
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• 제34권3호
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• pp.125-137
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• 2024

Composite laminates are used in a wide range of applications including defense, automotive, aviation and aerospace, marine, wind energy, and recreational sporting goods. These composite beams still exhibit problems such as buckling, local deformations, and interlaminar delamination. To overcome these drawbacks, a novel viscoelastic autoclave bonding with tapered epoxy reinforcement polyurethane films is proposed. In existing laminates, compression face wrinkling and interlaminar delamination is caused in the sandwich beam. The unique viscoelastic autoclave spunbond interlayer bonding is designed to prevent face wrinkling and absorb and distribute stresses induced by external loads, thereby eliminating interlaminar delamination in the sandwich beam. Also, the existing special reinforcement causes stress concentrations, and the core is not effectively connected, which directly affects the stiffness of the beam. To address this, a novel tapered epoxy polyurethane reinforcement adhesive film is proposed, whose reinforcement thickness gradually tapers as it enters the core material. This minimizes stress concentrations at the interface, preventing excessive adhesive squeeze-out during the bonding process, and improves the stiffness of the beam. Results indicate the proposed model avoids the formation of micro cracks, interlaminar delamination, buckling, and local deformations, and effectively improves the stiffness of the beam.

• 품질경영학회지
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• 제42권3호
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• pp.325-338
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• 2014

Purpose: The purpose of this study was to explain de-painting phenomenon of KUH-1 tail blade and to propose useful solution of it by test. The proposed solution was evaluated by real flight, and then it applied to mass product to improve the paint qual ity of KUH-1 tail blade. Methods: This study investigated an adhesive ability of primer following surface sanding condition. The cross cut and scratch test were conducted to evaluate the adhesive strength. And the water flow test was designed to simulate a real flight condition under rain. Through water flow test, an optimal condition of tail blade to prevent a de-painting phenomenon was deduced. Finally, the improvement method was evaluated by real flight under rain. Results: The results of this study are as follows; The sequential polishing was most excellent method in primer painting quality. The results of test including cross cut, scratch and water flow showed that MIL-DTL-53039 paint with epoxy primer has excellent adhesive ability. To proof the effect of improvement, a real flight during a rain condition was conducted. Finally, the comparison between original and improved configuration was conducted. Conclusion: The painting quality of KUH-1 tail blade was improved through deriving an optimal painting condition. In detail, a condition of optimal sanding and a sort of primer and paint was showed. Finally, the reliability of tail blade was guaranteed through improving the quality of painting.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1222-1228
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• 2002

This research is the development of a flexible tactile sensor array for service robots using PVDF (polyvinylidene fluoride) film for the detection of a contact state in real time. The prototype of the tactile sensor which has 8${\times}$8 array using PVDF film was fabricated. In the fabrication procedure, the electrode patterns and the common electrode of the thin conductive tape were attached to both sides of the 281$\mu\textrm{m}$ thickness PVDF film using conductive adhesive. The sensor was covered with polyester film for insulation and attached to the rubber base for a stable structure. The proposed fabrication method is simple and easy to make the sensor. The sensor has the advantages in the implementing for practical applications because its structure is flexible and the shape of the each tactile element can be designed arbitrarily. The signals of a contact force to the tactile sensor were sensed and processed in the DSP system in which the signals are digitized and filtered. Finally, the signals were integrated for taking the force profile. The processed signals of the output of the sensor were visualized in a personal computer, and the shape and force distribution of the contact object were obtained. The reasonable performance for the detection of the contact state was verified through the sensing examples.

• 항공우주시스템공학회지
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• 제16권1호
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• pp.12-16
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• 2022

유도 용접은 비접촉식으로 깨끗하고 빠른 공정으로 현재 주목받고 있다. 하지만 열가소성 수지는 전자기장에 영향을 받지 않기 때문에 유도 용접은 서셉터(Susceptor)라는 발열체가 필요하다. 고품질 접합을 목표로 연구가 진행되고 있지만, 결국 발열체라는 이물질이 들어가기 때문에 기준이 필요하다. 시편의 제작과 시험은 ASTM D5868에 근거하여 진행된다. 본 논문에서 평가 기준은 용접된 접합면의 상태와 기공률, 전단강도로 총 3가지를 근거로 판단할 것을 제안한다. 용접되는 접착면은 용융되고 냉각되면서 고형화가 되기 때문에 급격한 온도 변화는 기공을 발생시킬 수 있다. 또한 가열이 균일하지 않다면 원하는 성능을 기대하기 힘들다. PA6 (CF 30%) 엔지니어링 플라스틱을 이용하여 서셉터 제작과 유도 용접 그리고 성능 검증으로 진행하였다.