• Title, Summary, Keyword: A12024-T3

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Tensile Characteristics of A12024-T3 under Rapid Heating (급속가열환경에서 A12024-T3의 인장특성)

  • Kim, Jong-Hwan;Kim, Jae-Hoon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.8
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    • pp.101-108
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    • 2004
  • The thermomechanical tensile characteristics were evaluated for A12024-T3 under heating rates from $1^{\circ}C/sec\;to\;30^{\circ}C/sec$ by using an infrared heating equipment to simulate aerodynamic heating. The rapid heating test results were compared with tensile test results after 1/2 hour exposure in terms of yield stress to investigate the influence of heating condition. A heating rate-yield temperature parameter was suggested for rapid heating based on time-temperature parameters, and master yield stress curve was obtained by using these parameter. These test results can be used for margin of safety of supersonic vehicle structures subjected to aerodynamic heating.

A study on fatigue life of aluminum plate reinforced with FRP in aircraft structure (항공기 구조물에서 FRP를 이용한 보강부재의 피로수명에 대한 연구)

  • 박원조;허정원;이광영
    • Journal of Ocean Engineering and Technology
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    • v.11 no.3
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    • pp.69-75
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    • 1997
  • A A12024-T3 plate has been reinforced with AFRP to be a Hybrid-Composite, APAL. The fatigue life of the APAL has been investigated. The effects of bonding surface, numbers of AFRP bonded and AFRP orientation on fatigue life have been compared with A12024-T3 plate. Fatigue life of APAL has been remarkedly increased compared with that of A12024-T3 plate. The fatigue life has depended on bonding surface and AFRP orientation, but no relationship could be found with numbers of AFRP laminates.

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An experimental study on the fretting fatigue crack behaviour of A12024-T4 (A12024-T4의 프레팅 피로균열거동에 관한 실험적 연구)

  • Lee, Bong-Hun;Lee, Sun-Bok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.3
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    • pp.511-518
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    • 1997
  • The technique of fretting fatigue test was developed and fretting fatigue tests of A12024-T4 were conducted under several conditions. The newly developed calibration methods for measuring surface contact tractions showed good linearity and repeatability. The plate type specimen to which tow bridge type pads were attached and vision system was used to observe the crack behaviour. The oblieque cracks appeared in the early stage of crack growth and they became mode I cracks as they grow about 1 mm. The mode I transition points were found to be longer when surface tractions are higher or bulk stress is lower. Before the crack becomes mode I crack, 'well point' where crack grow about rate is minimum, was detected under every experimental condition. The crack behaviour was found to be affected by surface tractions, contact area, bulk stress. It was also found that partial slip and stick condition is most detrimental and the crack starts from the boundary of stick and slip. For gross slip crack started at the outside edge of pad. After crack mode transition, fretting fatigue cracks showed almost same behaviour of plain mode I fatigue cracks. Equivalent stress intensity factor was used to analyze the behaviour of fretting fatigue cracks and it was found that stress intensity factors can be applied to fretting fatigue cracks.

Comparative Study on Crack Tip Opening Displacment ${\delta}_5$ R-Curve and ${\delta}_{BS}$ R-Curve (균열선단 열림변위 {\delta}_5 R-곡선과 {\delta}_{BS} R-곡선의 비교연구)

  • Kim, Eom-Gi;Nam, Seung-Hun;Jin, Uk;Go, Seong-Wi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.3
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    • pp.794-802
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    • 2000
  • Since the examination of CTOD problem revealed that the discrepancy among CTOD's was a matte., of definition, the relationships among parameters based on different definitions have been studied Particularly, the relationship between $\sigma$BS R-curve based on BS 7448 and R-curve based on the recently introduced $\sigma$5 parameter was investigated in this research. For the comparison, compact tension specimens of used 1Cr-0.5Mo steel, heat treated 1Cr-0.5Mo steel to mimic the new one, A12024-T6, and A12024-T351 were prepared and tested. Consequently, the relationship between $\sigma$5 and $\sigma$BS R-curves for tested materials were established by shifting the rotational center which could determined by rotation factor and ligament size.

Crack Growth Retardation Behavior in Aluminium 2024-T3 Alclad Alloy by Pre-Indentation (예비압입에 의한 알루미늄 2024-T3 알클래드 합금의 균열성장 지연거동)

  • 황정선;조환기
    • Journal of the Korea Institute of Military Science and Technology
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    • v.4 no.2
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    • pp.42-51
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    • 2001
  • The effects of pre-indentation technique are presented for A12024-T3 Alclad alloy using as skin material for aircraft fuselage and wing. Indentations were applied to specimens to be placed on the presumed path of fatigue crack growth before fatigue tests. Tension-tension fatigue tests were conducted on the edge cracked specimens in the L-T orientation. Test results were analyzed to investigate the effectiveness of pre-indentation with the variation of specimen's thickness, position of indentation and applied maximum stress. Fatigue crack retardation by pre-indentation is well recognized in the various conditions.

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A Study of Resistance of Fatigue Crack in Aluminum Alloy Plate Bonded with FRP (FRP 본딩한 알루미늄 판재의 피로균열 저항성에 관한 연구)

  • 윤한기;오세욱;박원조;허정원
    • Journal of Welding and Joining
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    • v.12 no.4
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    • pp.117-126
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    • 1994
  • APAL (Aramid Patched ALuminum alloy) was manufactured, which was a material that was consisting of a A12024-T3 aluminum alloy plate bonded to single-side of it with aramid/epoxy laminates. The aramid/epoxy laminates were bonded to it in condition of 1, 2 ply and fiber orientation of .+-.45, 0.deg./90.deg. Fatigue crack propagation tests were performed at stress ratio R-0.2, 0.5 with Al 2024-T3, APAL 45-1P, APAL 0/90-1P, APAL 45-2P, APAL 0/90-2P specimens to examine behavior of retardation in fatigue crack propagation. All the APAL specimens showed superior fatigue crack resistance. Number of cycle spended for crack to propagate from $a_{M}$=37 to $a_{M}$=65 mm in case of APAL 0/90-2P specimen was half that of Al 2024-T3 specimen. Fatigue crack propagation rate of APAL 0/90 specimens were retarded more compared to APAL 45 specimens and the amounts of retardation at R=0.5 were larger than that at R=0.2. It was found that the retardation in fatigue crack propagation was caused by intact fibers in the wake of crack.ack.

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Analysis of Thermal Residual Stress in Composite Patches (복합재 패춰의 열잔류응력 해석)

  • 김위대;김난호
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.63-66
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    • 2000
  • This research addresses study on thermal residual stress of a composite patch repair of the edge cracked aluminium panel of aging aircraft. Composite patch repair is an efficient and economical technique to improve the damage tolerance of cracked metallic structures. These are thermal residual stresses due to the mismatch of coefficient of thermal expansion, and these are affected by the curing cycle of patch specimen. In this study, three curing cycles were selected for F.E. analysis. This study features the effect on composite patch and aluminum by thermal residual stress during crack propagation in aluminum plate.

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A Study on Cold Working Properties of Aluminum Plates for Aircraft Structure (항공기용 알루미늄 판재의 냉간가공 특성 연구)

  • 이동석;이준현
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.3
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    • pp.165-171
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    • 2003
  • In a structure, many components are fastened together using bolts, nuts and rivets through drilled holes. Not only do these fastened joints enable easy assembly and dismantling, they are also able to transfer as well as to distribute loads applied onto the structures. The major drawback of such connections, however, is that the fatigue life of the components is reduced by the presence of the hole since the stress concentration around the hole is increased. In addition, the hole drilling process itself may introduce defects or roughness at the surfaces of the hole that may cause further decrease in fatigue performance of the components. For applications where fatigue loadings are important, one way to compensate the decrease in fatigue life of the components is by introduction of beneficial compressive residual stress around the hole using cold working. The material used for this research were A12024-T351 and A17050-T7451 using the primary member of aircraft. We present, In this paper, the characteristics of coldworking by evaluation of the hole expansion ratio, residual stress distribution, and fatigue properties.

Evaluation of Size for Crack around Rivet Hole Using Lamb Wave and Neural Network (초음파 판파와 신경회로망 기법을 적용한 리뱃홀 부위의 균열 크기 평가)

  • Choi, Sang-Woo;Lee, Joon-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.4
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    • pp.398-405
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    • 2001
  • The rivet joint has typical structural feature that can be initiation site for the fatigue crack due to the combination of local stress concentration around rivet hole and the moisture trapping. From a viewpoint of structural assurance, it is crucial to evaluate the size of crack around the rivet holes by appropriate nondestructive evaluation techniques. Lamb wave that is one of guided waves, offers a more efficient tool for nondestructive inspection of plates. The neural network that is considered to be the most suitable for pattern recognition has been used by researchers in NDE field to classify different types of flaws and flaw sizes. In this study, clack size evaluation around the rivet hole using the neural network based on the back-propagation algorithm has been tarried out by extracting some features from the ultrasonic Lamb wave for A12024-T3 skin panel of aircraft. Special attention was paid to reduce the coupling effect between the transducer and the specimen by extracting some features related to time md frequency component data in ultrasonic waveform. It was demonstrated clearly that features extracted from the time and frequency domain data of Lamb wave signal were very useful to determine crack size initiated from rivet hole through neural network.

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Biochemical Characterization of Thermophilic Dextranase from a Thermophilic Bacterium, Thermoanaerobacter pseudethanolicus

  • Park, Tae-Soon;Jeong, Hyung-Jae;Ko, Jin-A;Ryu, Young-Bae;Park, Su-Jin;Kim, Do-Man;Kim, Young-Min;Lee, Woo-Song
    • Journal of Microbiology and Biotechnology
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    • v.22 no.5
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    • pp.637-641
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    • 2012
  • TPDex, a putative dextranase from Thermoanaerobacter pseudethanolicus, was purified as a single 70 kDa band of 7.37 U/mg. Its optimum pH was 5.2 and the enzyme was stable between pH 3.1 and 8.5 at $70^{\circ}C$. A half-life comparison showed that TPDex was stable for 7.4 h at $70^{\circ}C$, whereas Chaetominum dextranase (CEDex), currently used as a dextranase for sugar milling, was stable at $55^{\circ}C$. TPDex showed broad dextranase activity regardless of dextran types, including dextran T2000, 742CB dextran, and alternan. TPDex showed the highest thermostability among the characterized dextranases, and may be a suitable enzyme for use in sugar manufacture without decreased temperature.