• Corrosion Science and Technology
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• v.22 no.2
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• pp.90-98
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• 2023

In this study, cobalt oxide (Co₃O₄) and cobalt-doped magnetite (CoFe₂O₄) nanoparticles were synthesized by a hydrothermal method. They were then used as corrosion inhibitors for corrosion protection of AA2024-T3 aluminum alloys. These obtained nanoparticles were characterized by x-ray diffraction, field-emission scanning electron microscopy, and Zeta potential measurements. Corrosion inhibition activities of Co₃O₄ and CoFe₂O₄ nanoparticles were determined by performing electrochemical measurements for bare AA2024-T3 aluminum alloys in 0.05 M NaCl + 0.1 M Na₂SO₄ solution containing Co₃O₄ or CoFe₂O₄ nanoparticles. Corrosion protection for AA2024-T3 aluminum alloys by a water-based epoxy with or without the synthesized Co₃O₄ or CoFe₂O₄ nanoparticles was investigated by electrochemical impedance spectroscopy during immersion in 0.1 M NaCl solution. The corrosion protection of epoxy coating deposited on the AA2024-T3 surface was improved by incorporating Co₃O₄ or CoFe₂O₄ nanoparticles in the coating. The corrosion protection performance of the epoxy coating containing CoFe₂O₄ was higher than that of the epoxy coating containing Co₃O₄.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.1
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• pp.255-263
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• 2001

The main purpose of this paper is to investigate strength characteristics of Aluminum 2024-T3 in high temperature environment. Tensile test of Aluminum 2024-T3 has been carried out in high temperature environment. The stress-strain relations are investigated with temperature and Young's modulus, yield strength and ultimate strength are deduced from the test results. The modulus and strength of the test are compared with those of MIL HANDBOOK and tips on structural design in high temperature environment are suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.197-204
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• 2007

Fretting is a contact damage process that occurs between two contact surfaces. Fretting fatigue reduces fatigue strength of the material due to low amplitude oscillatory sliding and changes in the contact surfaces of strongly connected machine and structure such as bolt, key, pin, fixed rivet and connected shaft, which have relative slip of repeatedly extreme low frequency amplitude. In this research, the fretting fatigue behavior of 2024-T3511 and 7050-T7451 aluminum alloys used mainly in aircraft and automobile industry were experimentally estimated. Based on this experimental wort the following results were obtained: (1) A significant decrease of fatigue lift was observed in the fretting fatigue compared to the plain fatigue. The fatigue limit of 2024-T3511 aluminum alloy decreased about 59% while 7050-T7451 aluminum alloy decreased about 75%. (2) In 7050-T7451 specimen using ATSI4030 contact pad, crack was initiated more early stage than using 2024-T3511 contact pad. (3) In all specimens, oblique cracks were initiated at contact edge. (4) Tire tracks and rubbed scars were observed in the oblique crack region of fracture surface.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.549-550
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• 2006

The corrosion performance of a powder metallurgical aluminum alloy in aeronautical environments was studied for both as sintered and heat treated states. Sintered samples were obtained by uniaxial pressing of an Al-Cu-Mg prealloyed powder followed by liquid phase sintering. The heat treatments applied were T4 and T6. Corrosion behaviour was assessed by means of potentiodynamic polarization. Results for the equivalent commercial wrought counterpart, AA2024-T3, are also presented for comparison. Similar corrosion performance was observed for both as sintered and AA2024-T3 samples, while corrosion resistance of the PM materials was improved by the heat treatment, especially in the T4 state.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.241-242
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• 2002

Wear behavior or SiC-particle reinforced aluminum matrix composites (MMC) were investigated by pin-on-disk tests in vacuum with various pressures, argon, and air with various levels of humidity. The wear rate of 2024Al and MMC increased in the following order: in a vacuum at $5.0{\times}10^{-4}$ Pa, at 1.0Pa, in argon at 0% RH, in argon at 60% RH, in argon at 90% RH, in air at 0% RH, in air at 60% RH and in air at 90% RH. In other words, the influence or environment on wear becomes stronger in the following order: moisture, oxygen, and a combination of moisture and oxygen. In various environments, the difference of the wear rate of 2024Al and MMC was compared. In argon and air at 0% RH, the wear rates of MMC were higher than that of 2024Al. In contrast, in argon and air at 60, 90% RH, the wear rates of MMC were lower than that of 2024Al.

• 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.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.1-6
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• 2001

The main objective of this study is to determine if the sources of AE in corroded specimens of aluminum could be identified iron the characteristics of the waveform signals recorded during fatigue loading. Coupons of notched 2024-T3 aluminum with or without corrosion (at the notch) were subjected to fatigue loading and the AE signals were recorded using non-resonant, flat, wide-band transducers. The time history and power spectrum of each individual wave signal recorded during fatigue crack growth were examined and classified according to their special characteristics. Five distinct types of signals were observed regardless of specimen condition. The waveform and power spectra were shown to be dependent on specimen condition. During the initial phase of crack growth, the signals obtained in the as-received specimens are most probably due to transgranular cleavage caused by extrusion and intrusion under fatigue loading. In the corroded specimen the signal are probably generated by intergranular cleavage due to embrittlement of grain boundary neat the pitting tip. The need for additional research to further validate these findings is indicated.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.124-132
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• 1993

In order to examine the effect of anisotropy and stress ratio on fatigue crack propagation rate and opening-closing behavior and also arrest behavior by single tension peak overload, the fatigue tests of constant amplitude atress and single tension peak overload adding to cycle of constant amplitude were carried out in stress ratio of -0.4, -0.2, and 0.4 with materials of T-L and L-T directions in 2024-T3 aluminum alloy plate. Crack opening-closing begavior were measured by the compliance method using COD gage and strain gage. In case of the crack opening-closing behavior was measured by strain gage, the effect of stress ratio is unchangeable. But in the case of COD gage, that is remarkably decreased. Fictitious effective stress intensity factor(U sub(f)) and effective stress intensity factor ratio(U) in L-T direction was higher than those in T-L direction and also threshold arrest overload ratio incrased as stress ratio decreased and that of T-L direction was higher than that in L-T direction.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.13-18
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• 1999

섬유강화금속적층재(Fiber Reinforced Metal Laminates. FRMLs)는 고강도금속과 섬유강화복합재료(Fiber Reinforced Composite Materials)를 적층한 새로운 종류의 하이브리드 재료이다. 국산 아라미드 섬유인 헤라크론(Heracron, 코오롱)과 국내 복합재료 제작기술(한국화이바)을 사용하여 섬유강화금속적층재를 제작하고, 이를 HERALL(Heracron Reinforced Aluminum Laminate)이라 명명하였다. HERALL(Heracron Reinforced Aluminum Laminate)의 피로균열성장특성 및 피로균열진전 방해기구를 ARALL(Aramid-fiber Reinforced Aluminum alloy Laminates) 및 Al 2024-T3과 비교해석하였다. HERALL과 ARALL은 균열진전을 저지하는 아라미드 섬유로 인해 뛰어난 피로균열성장특성 및 피로저항성을 보여주었다. 아라미드 섬유의 균열브리드징으로 인한 $K_{max}$의 감소량과 Al 2024-T3의 균열닫힘으로 인한 $K_{max}$의 증가량을 구할 수 있는 응력-COD법을 사용하여 실제로 균열성장에 영향을 준 유효응력확대계수범위를 측정하였다. 균열선단으로부터 균열을 가공하면서 COD 변화량을 측정하여 균열브리징 영역을 구하였다.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.41-46
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• 1993

This Paper aims to examine the effect of shear lip formation from cross-sections on fatigue crack propagation rate in order to study the fatigue fracture behavior of the high strength aluminum material (Al 2024-T3). The following tests were achieved from this research. 1. As a result of depressing shear lip artificially by adding a side groove to a specimen, it is shown that the propagation rate of fatigue crack is faster than that of general specimen. 2. Through the two-step load test, the phenomenon that the shear lip decreases In the part of changed load gets observed. Consequently It Is shown that the crack propagation rate gets faster.