• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.775-782
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• 2013

In this study, as a series of studies aimed at investigating the spatial randomness of fatigue crack growth for friction stir welded (FSWed) 7075-T651 aluminum alloy joints, the fatigue crack growth behavior of FSWed 7075-T651 aluminum alloy joints was investigated for LT orientation specimens. Fatigue crack growth tests were conducted under constant stress intensity factor range (SIFR) control for 5 specimens of the FSWed 7075-T651 aluminum alloy, including base metal (BM), heat affected zone (HAZ), and weld metal (WM) specimens. The mean fatigue crack growth rate of WM specimens was found to be the highest, whereas that of HAZ and WM specimens was the lowest. Furthermore, the variability of fatigue crack growth rate was found to be the highest in WM specimens and lowest in BM specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1109-1116
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• 2013

This study aims to investigate the spatial randomness of fatigue crack growth rate for the friction stir welded (FSWed) 7075-T651 aluminum alloy joints. Our previous fatigue crack growth test data are adopted in this investigation. To clearly understand the spatial randomness of fatigue crack growth rate, fatigue crack growth tests were conducted under constant stress intensity factor range (SIFR) control testing. The experimental data were analyzed for two different materials-base metal (BM) and weld metal (WM)-to investigate the effects of spatial randomness of fatigue crack growth rate and material properties, the friction stir welded (FSWed) 7075-T651 aluminum alloy joints, namely weld metal (WM) and base metal (BM). The results showed that the variability, as evaluated by Weibull statistical analysis, of the WM is higher than that of the BM.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.62-69
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• 1986

Fatigue surface crack growth was studied in 7075-T651 aluminum alloy plates subjected largely to bending loads. The surface crack length and its depth were measurement by the unloading elastic compliance method. The surface crack growth rate dc/dN, on the surface and da/dN, in the depth direction were obtained by the secant method. The stress intensity factor range .DELTA.K was computed by means of Newman and Raju equation. The aspect ratio a/c was presented in form of a/c=0.815-0.853(a/T). The effect of the stress ratio on the stable surface crack growth rates under increasing .DELTA.T is larger in lower .DELTA.K, while the relation between dc/dN, da/dN and the effective stress intensity factor range .DELTA.K$_{eff}$ is weakly dependent on the stress ratio.o.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.9-14
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• 1998

고강도 알루미늄 합금은 기술의 진보에 따라서 이용도가 높은 매우 중요한 재료로서, 잘 알려진 적용분야로서는 항공우주산업, 고속회전체, 항공기용재 등으로 많이 사용되고 있다. 고강도 알루미늄 합금은 Al-Cu-Mg(2000 series)를 기초로 둔것과 Al-Zn-Mg-Cu(7000 series)를 기초로 둔 것등이 있다. (중략)

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.211-216
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• 2016

Al alloys are useful materials having high specific strength and are used in machining of parts having thin-walled structures for weight reduction in aircraft, automobiles, and portable devices. In machining of thin-walled structures, it is difficult to maintain dimensional accuracy because machining deformation occurs because of cutting forces and heat in the cutting zone. Thus, cutting conditions and methods need to be investigated and cutting signals need to be analyzed to diagnose and minimize machining deformation and thereby enhance machining quality. In this study, an investigation on cutting conditions to minimize machining deformation and an analysis on characteristics of cutting signals when machining deformation occurs are conducted. Cutting signals for the process are acquired by using an accelerometer and acoustic emission (AE) sensor. Signal characteristics according to the cutting conditions and the relation between machining deformation and cutting signals are analyzed.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.91-98
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• 2014

In this investigation, the effect of crack orientation on spatial randomness of fatigue crack growth rate (FCGR) in friction stir welded (FSWed) 7075-T651 aluminum alloy joints has been statistically analyzed by Weibull distribution. The fatigue crack growth tests are conducted under three different constant stress intensity factor range (SIFR) control at room temperature with R = 0.1 and frequency 10Hz on compact tension (CT) specimen machined at base metal (BM) and weld metal (WM). The experimental fatigue crack growth rate data were obtained for two types of specimens having LT and TL orientations. LT specimens both base metal and weld metal showed higher fatigue crack growth rate as compared to TL specimens. In the lower SIFR region, FCGR were found to be almost 3 times higher in higher SIFR region. The shape parameter of Weibull both LT and TL orientation for FCGR was increased with increasing SIFR, the scale parameter was also increased with increasing SIFR. The smallest value of the shape parameter was shown in weld metal specimens having LT orientation at lower SIFR region.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.54-61
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• 1998

This paper examines the crack growth behavior of 7075-T651 aluminum alloy for small tensile overload under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investigated by compliance method. The applied initial stress ratios are R=-0.5 R=0.0 and R=0.25 Crack length, effective stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc, are inspected with fracture mechanics estimate.