• Title/Summary/Keyword: Striation Height

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Nano-Scale Observation of Fatigue Striations for Aluminum Alloy (알루미늄 합금 피로 스트라이에이션의 나노 스케일 관찰)

  • Choi, Sung-Jong;Kwon, Jae-Do;Ishii, Hitoshi
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.153-158
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    • 2000
  • Atomic Force Microscope (AFM) was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights $(SH,\;SH_h)$ were measured from the cross sectional Profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of $10^{-5}$ mm/cycle. (2) The relation of $SH={\alpha}(SW)^{1.2}$ was obtained. (3) The ratio of the striation height to its width SH/SW and did not depend on the stress intensity factor range ${\Delta}K$ and the stress ratio R. From these results, the applicability of the AFM to nano-fractography is discussed.

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The Observation of Fatigue Striations for Aluminum Alloy by Atomic Force Microscope(AFM) (원자력 현미경(AFM)에 의한 알루미늄 합금의 피로 스트라이에이션 관찰)

  • Choe, Seong-Jong;Gwon, Jae-Do
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.4 s.175
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    • pp.955-962
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    • 2000
  • Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM) was shown to be the powerful tool for nano-scale characterization of a fracture surface . AFM was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights (SH) were measured from the cross sectional profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of 10-5 mm/cycle. (2) The relation of SH=0.085(SW)1.2 was obtained. (3) The ratio of the striation height to its width SH/SW did not depend on the stress intensity factor range K and the stress ratio R. (4) Not only the SW but also the SH changed linearly with the crack tip opening displacement (CTOD) when plotted in log-log scale. From these results, the applicability of the AFM to nano-fractography is discussed.

Nano-Scale Observation of Fatigue Striations for Aluminum Alloy (알루미늄 합금 피로 스트라이에이션의 나노 스케일 관찰)

  • Choe, Seong-Jong;Gwon, Jae-Do;Ishii, Hitoshi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.7
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    • pp.1047-1054
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    • 2001
  • Atomic Force Microscope (AFM) was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths(SW) and heights (SH, SH(sub)h, SH(sub)ι) were measured from the cross sectional profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) The relation of SH=$\alpha$(SW)(sup)1.2 was obtained. (2) The ratio of the striation height to its width SH/SW, SH(sub)h/SW and SH(sub)ι/SW did not depend on the stress intensity factor range ΔK and the stress ratio R( =P(sub)min/P(sub)max = K(sub)min/K(sub)max). (3) Effect of precipitate on the morphology of striation was changed by the relative dimensional difference between the striation width SW and the precipitates. From these results, the applicability of the AFM to nano-fractography is discussed.

A Study on Failure Analysis of Turbine Blade using AFM and FEM (AFM과 유한요소법을 이용한 터빈 블레이드의 파손해석에 관한 연구)

  • 최우성;이동우;홍순혁;조석수;주원식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.489-493
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    • 2000
  • Turbine blade has trouble of cracking at root region. Fracture surface of blade root is surveyed by SEM and AFM to clear relation between fracture mechanical parameter and surface parameter (striation width and surface roughness). Service stress is predicted by maximum height roughness $R_{max}$, on fractured surface and stress analysis on turbine blade. It is to thought that turbine blade is fractured by abnormal condition such as incorrect fittings between pin and pin hole but isn't fractured by normal service conditions such as steam pressure, centrifugal force and torsional force.

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