6.75L급 소형 AA6061 라이너의 후방압출 및 노우징 공정에 관한 해석적 연구

강범수(B. S. Kang),구태완(T. W. Ku) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5

As one of pressure vessels, small seamless aluminum liner with inner volume of about 6.75L is considered with an initial billet material of AA6061-O. To obtain the aluminum liner, warm forging process including two sequences such as backward extrusion and head nosing is numerically simulated by using the pre-heated initial billet of about 480℃. Compression tests on the used billet material are performed with various temperature and strain rate conditions, and the obtained mechanical properties are applied to the numerical simulations. In the backward extrusion and the head nosing, tool geometries are designed based on the desired configuration of the aluminum liner. Furthermore, the tool structure integrity is evaluated to ensure the tool life, and the obtained seamless aluminum liner is estimated based on the required inner pressure endurance limit of 15Kgf/cm². Resultantly, it is confirmed that the small seamless aluminum liner of AA6061-O could be successively deformed by adopting two stage warm forging procedures without any bursting failure.

연성파괴에 기반한 다단 디프드로잉 및 아이어닝 공정에 의한 알루미늄 라이너 개발

윤여웅(Y. W. Yun),강성훈(S. H. Kang),윤춘기(C. K. Yun),이정환(J. H. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10

In this work, finite element investigations were carried out to manufacture a seamless aluminum liner without crack generation using four-stage deep drawing followed by two-stage ironing process. In order to predict the crack generation during the liner manufacturing process, the Normalize Cockroft-Latham(NCL) which is one of ductile fracture criteria was adopted. In addition, the tensile tests were carried out to obtain the critical value of NCL by comparing the experimental and FE simulation results. From this, various case studies based on FE simulation were carried to obtain the optimum die designs which can prevent the crack generation during ironing processes. Finally, the aluminum liner was successfully made using obtained die designs so that requirements were met in terms of thickness and height of the liner.

70MPa 수소가스차량용 복합소재 압력용기의 응력특성에 관한 안전성 연구

김청균(Chung Kyun Kim),김도현(Do Hyun Kim) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.1

This paper presents a stress safety of a composite pressure cylinder for a hydrogen gas vehicle. The composite pressure cylinder in which is composed of an aluminum liner and carbon fiber wound layers contains 104 liter hydrogen gas, and is compressed by a filling pressure of 70 MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 255.2 MPa of an aluminum liner is sufficiently low compared with that of 272 MPa, which is 95% level of a yield stress for aluminum. Also, the composite layers in which are wound on the surface of an aluminum cylinder are safe because the stress ratios from 3.46 to 3.57 in hoop and helical directions are above 2.4 for a minimum safety level. The proposed composite pressure cylinder wound by carbon fibers is useful for 70 MPa hydrogen gas vehicles.

35MPa 수소가스 자동차용 복합소재 압력용기의 응력특성에 관한 강도안전성 연구

김청균(Chung Kyun Kim),김도현(Do Hyun Kim) 한국가스학회 2012 한국가스학회지 Vol.16 No.2

본 논문에서는 알루미늄 라이너와 탄소섬유/에폭시 및 유리섬유/에폭시로 구성된 복합소재 압력용기에 대한 응력 안전성 연구결과를 제시하고 있다. 9.2L의 저장용량을 갖는 수소가스 자동차용 복합소재 압력용기에는 35MPa의 충전압력으로 수소가스를 압축한 경우이다. FEM 해석결과는 미국의 수소가스 압력용기에 대한 DOT-CFFC와 한국의 KS B ISO 인증기준에 기반하여 평가하였다. FEM 해석결과에서 알루미늄 라이너에 걸리는 응력 247MPa는 알루미늄 항복강도(272MPa)의 95%에 해당하는 안전기준에 비해 충분히 낮다는 결과이다. 그리고 알루미늄의 표면에 감은 탄소섬유 복합소재는 후프방향과 헤리컬방향에서 발생한 최대탄소섬유응력이 29.43%와 28.87% 수준으로 각각 나타났기 때문에 최소파열압력에서의 최대섬유응력 대비 30% 이하를 유지해야 한다는 안전기준에 부합하므로 안전하다. 또한, 탄소섬유 복합소재에 대한 응력비는 후프방향과 헤리컬방향에 대해 3.4와 3.46으로 각각 예측되었기 때문에 최소안전기준인 2.4보다 높아 안전한 것으로 나타났다. This paper presents a stress safety of a composite pressure cylinder in which is composed of an aluminum liner and composite layers with carbon fiber/epoxy and glass fiber/epoxy resigns. The composite pressure cylinder for a hydrogen gas vehicle contains 9.2 liter hydrogen gas, and hydrogen gases are compressed by a filling pressure of 35MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 247MPa of an aluminum liner is sufficiently low compared with that of 272MPa, which is 95% level of a yield stress for aluminum. And, the carbon fiber composite layers in which are wound on the surface of an aluminum cylinder are safe because the maximum carbon fiber stresses from 29.43% to 28.87% in hoop and helical directions are below 30% for a given minimum required burst pressure level, respectively. The carbon fiber composite layers are also safe because the stress ratios from 3.40 to 3.46 in hoop and helical directions are above 2.4 for a minimum safety level, respectively.

소형펀치시험법을 이용한 알루미늄 6061-T6 Type-3 용기 라이너의 파괴인성 평가

마영화(Young-Wha Ma),이승훈(Seong-Hoon Lee),윤기봉(Kee-Bong Yoon) 한국가스학회 2011 한국가스학회지 Vol.15 No.4

Type-3 용기 라이너는 두께가 5 ㎜일뿐 아니라 곡률을 가지고 있기 때문에 파괴인성시험을 위한 표준형 시편의 제작에 어려움이 있다. 따라서 용기 라이너의 파괴인성을 평가하기 위해서는 소형시편 시험기법이 도입되어야 한다. 본 연구에서는 용기 라이너의 파괴인성을 평가하기 위해 소형펀치(small punch, SP)시험법을 도입하였다. SP시험으로부터 측정된 하중-변위 곡선 결과에서 라이너 재료는 연성이 소진하여 막신장 영역에서 파손되었다. 라이너 재료는 제작공정 특성에 기인하여 소성변형량이 방향에 따라 다름에도 불구하고 등방성 파괴양상을 보였다. SP시험 데이터를 사용하여 파괴인성을 평가한 결과 J<SUB>Ic</SUB>=13.0 kJ/㎡ 이었다. 이 값은 동종재료의 파괴인성 값과 유사하다. 따라서 SP시험 데이터를 사용하여 평가한 파괴인성은 타당하며, 완성된 용기 라이너는 유효한 파괴인성 값을 유지하는 것으로 확인 되었다. Type-3 cylinder liner has a limitation of machining the standard specimen for fracture toughness test because it has approximately 5 ㎜ in thickness as well as a curvature. Hence, it needs to be employed a miniature specimen test technique to evaluate fracture toughness of the cylinder liner. In this study, small punch (SP) test method was employed to evaluate fracture toughness of the cylinder liner. Load-displacement curve result measured from the SP test showed that the liner material was failed during membrane stretching in the general SP load-displacement curve. Additionally, it was shown that liner material was isotropic although the amount of plastic deformation was different depending on the direction due to manufacturing process characteristics. Fracture toughness, J<SUB>Ic</SUB>, was evaluated using the SP test data. The value of fracture toughness obtained was 13.0 kJ/㎡. This value was similar to that of the same kind of materials. Therefore, the fracture toughness evaluated using the SP test data was reasonable.

필라멘트 와인딩법에 의한 단일 개구부 복합재료 압력용기의 개발

황병선,김병선,김병하,박승범,Hwang, Byeong-Seon,Kim, Byeong-Seon,Kim, Byeong-Ha,Park, Seung-Beom,Roger, Davidson 한국기계연구원 2000 硏究論文集 Vol.30 No.-

Double boss type composite pressure bottles have been developed widely but single boss type had not because there are some difficulty in technical point. In this paper a research was performed to develop composite pressure vessel in conjunction with design, fabrication, and test. Fiber pattern and angles were decided by CADFIL software and they are [liner/$15^{\circ}$/$15^{\circ}$/$90^{\circ}$/$18^{\circ}$/$90^{\circ}$/$21^{\circ}$/$21^{\circ}$/$90^{\circ}$]. Fabrication of bottles was done by AEA's 5-axis filament winding machine. During fabrication fiber optic sensor were embedded to measure were behavior of structure at the applied internal pressure. Even though satisfied test results were not obtained, the experimental set-up of fiber optics showed the possibility for the application of filament wound vessels. However, the conventional strain and fabrication of single boss composite bottles.

Shearography를 이용한 Aluminum Liner 내부 결함의 변형량과 변형율 측정 및 FEM 검증

최인영(In-Young Choi),홍경민(Kyung-Min Hong),고광수(Kwang-Su Ko),강영준(Young-June Kang) 한국생산제조학회 2013 한국생산제조학회지 Vol.22 No.4

Today, environmental issues have become a matter of worldwide concern. In particular, automobile industries engage in considerable research and investment to develop high-efficiency and ecofriendly cars. Most ecofriendly cars use natural gas or hydrogen gas instead of fossil fuels. In this regard, low-weight and high-pressure vessels have gradually been developed to increase the driving distance of a car. However, most pressure vessels installed in cars develop many defects over time owing to shocks sustained when the car is being driven. Such defects can cause the explosion of the pressure vessel. Therefore it is important to prevent such explosions due to internal defects. The use of shearography for measuring the internal defects of objects afford many advantages. It is a non-contact and non-destructive method, and it is not limited by the object shape. In this study, the internal defect deformation and strain of an aluminum liner that is used in a CNG bus for the fuel storage tank is measured using shearography. It is important to measure the strain and deformation in order to detect defects and repair the pressure vessel. To verify the accuracy of the shearography measurement method, the measurement results of shearography, out-of-plane ESPI, and FEM are compared quantitatively.

고체 추진기관에서 산화알루미늄 입자가 노즐 내열재의 삭마에 미치는 영향

황기영(Ki-Young Hwang),임유진(Yoo-Jin Yim),함희철(Hee-Cheol Ham) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.8

알루미늄 분말이 약 20% 포함된 2종류의 고체 추진제에 대해 원료성분, 연소실에서의 연소가스 물성치 및 산화알루미늄의 입자 크기를 비교 분석하였다. 산화제(AP/HNIW) 분말이 200과 5 ㎛로 이분양상이고 47% 부피분율을 지닌 알루미늄을 함유한 PCP계 추진제는 산화제(AP) 분말이 400, 200 및 6 ㎛로 삼분양상이고 64% 부피분율을 지닌 알루미늄을 함유한 HTPB계 추진제 보다 알루미늄들이 응집될 가능성이 크다는 것을 축소부 내열재에서 채취한 산화알루미늄 입자의 SEM 사진을 통해 확인할 수 있었다. PCP계 추진제를 적용한 고체 추진기관의 노즐 축소부 내열재에서는 큰 산화알루미늄 입자의 충돌로 인해 그레인 슬랏과 일치하는 4개 원주방향 부위에서 삭마가 크게 되었지만 HTPB계 추진제를 적용한 경우에는 원주방향으로 균일하게 삭마되었다. The compositions, the gas properties in motor chamber and the aluminum oxide (AI₂O₃) particle size for two kinds of solid propellants with approximately 20% aluminum powder have been investigated. The SEM photographs of (AI₂O₃) taken from nozzle entrance liner show that the aluminized PCP propellant with 47% volumetric fraction AP/HNIW and bimodal oxidizer 200-5 ㎛ can offer greater possibility for increasing aluminum agglomeration than the aluminized HTPB propellant with 64% volumetric fraction AP and trimodal oxidizer 400-200-6 ㎛. The nozzle entrance liner of solid rocket motor with the PCP propellant shows greater erosion at 4 circumferential sections in line with grain slots due to the impingement of large particles, but that with the HTPB propellant shows uniform erosion with circumferential angle.

차량용 복합소재 수소연료탱크의 강도안전성에 관한 연구

김청균(Chung Kyun Kim),김도현(Do Hyun Kim) 한국가스학회 2011 한국가스학회지 Vol.15 No.5

본 연구에서는 미국의 DOT-CFFC와 한국의 KS 기준에 근거하여 수소가스 복합소재 연료탱크에 대한 강도안전성을 FEM으로 해석하였다. 알루미늄 라이너 소재인 6061-T6와 탄소섬유 복합소재인 T800-24K로 적층이 형성되도록 감은 수소가스 복합소재 연료탱크는 130L의 저장용량을 갖으며, 70MPa의 충전압력으로 수소가스가 채워진다. FEM 해석결과에 의하면, 내부탱크를 형성하는 알루미늄 라이너에 작용하는 von Mises 응력 255.2MPa은 알루미늄 소재의 항복응력 대비 95%인 272MPa보다 낮기 때문에 안전하다. 또한, 복합소재 연료탱크에서 후프방향의 탄소섬유 응력비는 3.11이고, 헤리컬방향의 응력비는 3.04인 것으로 나타났다. 이들 응력비 데이터는 탄소섬유 복합소재 연료탱크에서 안전기준으로 권고한 2.4에 비해 높기 때문에 양방향 모두에서 안전하다. 따라서 70MPa의 충전압력을 갖는 130L 저장용량의 복합소재 연료탱크에 대한 강도안전성은 유용한 것으로 판단된다. This paper presents the strength safety of a hydrogen gas composite fuel tank, which is analyzed using a FEM based on the criterion of US DOT-CFFC and Korean Standard. A hydrogen gas composite tank in which is fabricated by an aluminum liner of 6061-T6 material and carbon fiber wound composite layers of T800-24K is charged with a filling pressure of 70MPa and a gas storage capacity of 130 liter. The FEM results indicated that von Mises stress, 255.2MPa of an aluminum liner inner tank is low compared with that of 95% yield strength, 272MPa. And a carbon fiber stress ratio of a composite fuel tank is 3.11 in hoop direction and 3.04 in helical direction. These data indicate that a carbon fiber gas tank is safe in comparison to that of a recommended criterion of 2.4 stress ratio. Thus, the proposed composite tank with 130 liter capacity and 70MPa filling pressure is usable in strength safety.

다구찌법을 이용한 복합소재 수소연료탱크의 최적설계에 관한 연구

김청균(Chung Kyun Kim),김도현(Do Hyun Kim) 한국가스학회 2011 한국가스학회지 Vol.15 No.6

본 연구에서는 70MPa의 충전압력을 갖는 130L 수소연료 저장탱크에 대한 최적설계를 유한요소법과 다구찌 설계법으로 고찰하였다. 6061-T6의 알루미늄 라이너의 외벽면에 T800-24K의 탄소섬유로 감아서 제조한 복합소재 연료탱크의 강도안전성을 미국 DOT-CFFC와 KS의 설계안전 규격을 기준으로 해석하였다. 70MPa용 수소가스탱크의 응력강도에 대한 FEM 해석결과에 의하면, US DOT-CFFC와 KS 규격에서 제시한 응력비 2.4의 기준값과 비교할 때 안전한 것으로 나타났다. 따라서, 다구찌 설계법에 기반한 최적설계 데이터는 설계모델 5번으로 선정할 수 있고, 여기서 제시할 수 있는 알루미늄 라이너의 두께는 6.4mm, 탄소섬유 적층에서 후프방향의 두께는 31mm, 헤리컬방향의 두께는 10.2mm이다. In this study, the optimized design for 130 liter storage fuel tank with 70MPa filling pressure has been investigated using a FEM technique and Taguchi design method. The strength safety of a composite fuel tank in which is fabricated by an aluminum liner of 6061-T6 material and carbon fiber wound composite layers of T800-24K has been analyzed based on the criterion of design safety of US DOT-CFFC and Korean Standard. The FEM computed results on the stress safety of 70MPa hydrogen gas tank were compared with a criterion of a stress ratio, 2.4 of US DOT-CFFC and Korean Standard, and indicated the safety. Thus, the optimized design elements based on the Taguchis method were recommended as an aluminum liner thickness of 6.4mm, a carbon fiber laminate thickness in hoop direction of 31mm and a carbon fiber laminate thickness in helical direction of 10.2mm, which is represented by a design model of No. 5.