• Title/Summary/Keyword: 잔류두께

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Analysis and Measurement of Residual Stress of Al 7175 Ring Rolls after Quenching and stress Relieving (고강도 알루미늄 7175 합금 링롤재의 급냉 및 응력제거처리후 잔류응력 유한요소해석 및 측정)

  • 박성한;구송회;이방업;은일상
    • Journal of the Korean Society of Propulsion Engineers
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    • v.1 no.1
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    • pp.104-110
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    • 1997
  • To predict the effect of ring expansion and ring compression on residual stress relief of Al 7175 ring rot]s, 2-D axisymmetric thermal analysis and elastoplastic analysis were performed. The residual stress distributions along the thickness of T73, T7351 and T7352 treated rings were measured using three step sectioning method. The measured results were compared to numerical ones for quenched and stress relieved rings. After quenching, calculated hoop and axial residual stresses were similar to measured ones for T73 treated rings. The residual stresses of T7351 and T7352 treated rings were decreased remarkably compared to T73 treated rings. The effect of axial residual stress relief was superior to that of hoop one, and also ring compression to ring expansion. It was concluded that ring compression is advantageous over ring expansion in view of stress relief effect and practicality, and vice versa in view of dimensional control and press power.

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Statistical Evaluation for Residual Strength of Impacted Composite Materials (충격손상 복합재료의 잔류강도저하거동에 대한 통계적 평가)

  • Kang, Ki-Weon;Lee, Seung-Pyo;Lee, Jin-Soo;Koh, Byung-Kab
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.2
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    • pp.426-434
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    • 2010
  • This study is experimentally performed to evaluate the strength reduction behavior and its statistical properties of plain woven glass/epoxy composites. The results indicate that the major impact damage of plain woven glass/epoxy composites is the fiber breakage and matrix crack, whereas the dominant impact damage of unidirectional carbon/epoxy laminates is the delamination, which depends on the stacking sequence. The residual strength prediction models, previously proposed on unidirectional laminates, are applied to evaluate the residual strength of plain woven glass/epoxy composites with impact damage. Among these models, the results by Caprino and Avva's model have a good agreement with the experimental results. To investigate the variability of residual strength of the impacted composite materials, a statistical model was proposed and its results were in conformance with the experimental results regardless of their thickness.

Local Buckling and Inelastic Behaviour of 800 MPa High-Strength Steel Beams (800MPa급 고강도강 보 부재의 국부좌굴 및 비탄성 거동)

  • Lee, Cheol-Ho;Han, Kyu-Hong;Kim, Dae-Kyung;Park, Chang-Hee;Kim, Jin-Ho;Lee, Seung-Eun;Ha, Tae-Hyu
    • Journal of Korean Society of Steel Construction
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    • v.24 no.4
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    • pp.479-490
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    • 2012
  • Flexural tests on full-scale H-shaped beams, built up from high-strength steels (HSB800 and HSA800) with a nominal tensile strength of 800 MPa, was carried out to study the effect of flange slenderness of high-strength steel on flexural strength and rotation capacity. The primary objective was to investigate the appropriateness of extrapolating current stability criteria (originally developed for ordinary steel) to high-strength steel. The performance of high-strength steel specimens was very satisfactory from the strength, but not from the rotation capacity, perspective. The inferior rotation capacity of high-strength steel beams was shown to be directly attributable to the absence of a distinct yield plateau and the high yield ratio of the material. Residual stress measurements reconfirmed that the magnitude of the residual stress is almost independent of the yield stress of the base metal.

Magnetic Interaction and Magnetic Properties of Electrodeposited CoPt Magnetic Films with Different Thickness (전기도금법으로 제작한 CoPt 자성막의 자기상호작용과 자기적 성질)

  • Kim, Hyeon-Soo;Lee, Jong-Duck;Jeong, Soon-Young;Lee, Chang-Hyeong;Suh, Su-Jeong
    • Journal of the Korean Magnetics Society
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    • v.21 no.5
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    • pp.151-156
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    • 2011
  • The influence of thickness on magnetic interaction and magnetic properties in electrodeposited CoPt magnetic films was investigated from the analysis of the magnetic remanence curves and the magnetic hysteresis loops. As the thickness of the CoPt film is increased, the perpendicular coercivity and the saturation magnetization are increased but the squareness is considerably decreased. The analysis results of the magnetic remanence curves and the magnetic hysteresis loops exhibited that the dipolar interaction is the main interaction mechanism for all samples, but the strength of the dipolar interaction gradually increased with increasing sample thickness.

A Study on the Bonding Residual Thermal Stress Analysis of Dissimilar Materials Using Boundary Element Method (경계요소법에 의한 이종재료 접합 잔류열응력의 해석)

  • Yi, Won;Yu, Yeong-Chul;Jeong, Eui-Seob;Yun, In-Sik
    • Journal of the Korean Society for Nondestructive Testing
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    • v.15 no.4
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    • pp.540-548
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    • 1996
  • In general residual stress is measured by X-ray diffraction method but in case of bonding residual thermal stress it is inadequate technique to examine the stress singularity. Therefore Two-dimensional elastic boundary element analyses were carried out to investigate the residual thermal stress and stress singularity of bonding interface in Al/Epoxy. This boundary element results were compared with the strain gauge measurements. The effects of different interface models, sub-element and adherend thickness are presented and discussed. On the basis of the obtained results, interface delamination causing by normal stress is expected and stress singularity is observed more intensively increasing with adherend thickness. It is concluded that the bonding strength of Al/Epoxy interface can be estimated correctly by taking into account the stress singularity at the edge of the interface.

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Sintering of Layer Structure Materials: Effect of Starting Material on Sintering Defects and Residual Stress (층상구조 재료의 소결: 출발물질이 소결결함 및 잔류응력에 미치는 영향)

  • 정연길
    • Journal of the Korean Ceramic Society
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    • v.36 no.1
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    • pp.61-68
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    • 1999
  • To analyze several defects and residual stress in sintering of layer structure materials, multiayer materials with TZP/SUS and ZT/SUS, and bilayer materials with porcelain/alumina and porcelain/Y-TZP were fabricated by sintering method. Multilayer materials prepared by pressureless sintering show the sintering defect such as warping, splitting, cracking originated from the difference of sintering shrinkage between each layer, which could be controlled by the adjustment of number and thickness in interlayer. In tape casting, a certain pressure given during sintering relaxed the sintering defects, specially warping. The residual stress in bilayer was examined with Vickers indentation method. A small tensile stress in porcelain/alumina and a large compressive stress in porcelain/Y-TZP were generated on the porcelain interface due to the thermal expansion mismatch, which affected the strength of bilayer materials. As a consequence, the sintering defects of multilayer materials and the residual stresses of bilayer materials were dominantly influenced on material design and starting material constants.

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Si 함유 DLC 필름의 탄성특성 평가

  • 정진원;조성진;이광렬;고대흥
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.136-136
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    • 1999
  • 박막의 탄성특성을 평가하는 방법으로 nano-indentation, Brillouin light scattering measurement, ultrasonic surface wave measurement, bulge test, vibration membrane method 등 여러 가지가 제시되어 왔다. 최근에는 탄성특성을 평가할 수 있는 간단한 방법으로 기판 식각 기법을 이용한 freehang, bridge 방법이 제시되었다. 이중에서 bridge 방법은 간단한 식각 기법을 이용하여 얇은 박막에서도 탄성 특성을 평가할 수 있는 방법으로 제시되었다. 그러나 식각 과정에서 발생하는 patch 부분의 under-cut으로 인해 정확한 bridge의 길이를 측정할 수 없게 되어 오차가 발생하고 있다. 본 연구에서는 bridge 방법에서 발생하는 오차를 줄이기 위한 방법으로, patch 부분에 etch-stop을 제작해 줌으로서 식각 과정에서 발생하는 under-cut을 효과적으로 제거시켰다. Etch-stop은 2장의 mask를 align key를 이용하여 제작하였다. 먼저 산화막이 형성되어 있는 Si 기판위에 mask 1을 이용하여 patch 부분을 lithography 작업하고, 습식 식각 공정을 한 뒤 DLC 필름을 증착시킨다. 다음으로 mask 2를 이용하여 bridge pattern을 제작하고, DLC 필름을 증착시킨 후 lift-off 기술과 산화막 등방식각 공정을 통해 bridge를 제작하였다. 이렇게 제작된 bridge를 통해 필름이 기판에 부착되기 위해 필요한 변형률을 측정하고, 독립적으로 측정된 필름의 잔류응력과 함께 박막의 응력-변형률 관계식에 적용시켜 biaxial elastic modulus, E/(1-v)를 구할 수 있었다. Sidl 첨가된 DLC 필름은 rf-PACVD 장비를 이용하여 증착하였다. 이때 전극과 플라즈마 사이의 바이어스 음전압은 -400V로 합성압력은 10mTorr로 고정하였다. 사용한 반응가스는 벤젠(C6H6)과 희석된 실렌(SiH4:2H=10:90)이며, 희석된 실렌의 첨가량을 조절하여 필름 내에 함유된 Si의 양을 조절하였다. 각각의 조건에서 증착시간을 조절하여 필름의 두께를 조절하였다. 필름의 잔류응력은 압축잔류 응력에 의해 발생한 필름/기판 복합체의 곡률을 laser 반사법을 이용하여 측정하고, 이 결과를 Brenner 등에 의해 유도된 식을 대입하여 계산하였다.

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A Study on the expectation of residual layer thickness in roller pressing imprint process (롤러 가압 임프린트 공정에서 잔류막 두께 예측에 관한 연구)

  • Cho, Young Tae;Jung, Yoon-Gyo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.12 no.1
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    • pp.104-109
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    • 2013
  • In order to apply nano imprint technology in large area process, roller pressing is promising because of its low cost and high productivity. When pressing mold by roller, liquid resin is locally squeezed between mold and substrate. In this study, the main focus is to understand which process parameter affects residual layer. To do this, a simple analytical model was introduced. Especially, we consider the aspect ratio of patterns as essential cause of variation of the thickness in the equation. As a result, when the aspect ratio of pattern in the mold increases, the thickness of residual layer also increases. In conclusion, we show that the uniformity of residual layer could be accomplished by the control of velocity and pressing force in roller pressing imprint process.

Analysis of Residual and Applied Stresses of Thin-walled U tubes (얇은 두께로 된 U 전열관의 잔류응력 및 부하응력 해석)

  • 김우곤;김대환;류우석;국일현;김성청
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1999.05a
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    • pp.163-169
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    • 1999
  • Residual stresses causing stress corrosion cracking (SCC) of thin-walled steam generator U tubes were investigated. The residual stresses were measured by hole drilling methods, and the applied stresses resulting from the internal pressure and the temperature gradient in the steam generator were estimated theoretically. In U-bent regions, the residual stresses at extrados were induced with compressive stress(-), and its maximum value reached -319MPa in axial direction at $\phi$= $0^{\circ}$ in position. Maximum tensile residual stress of 170MPa was found to be at the flank side at position of $\phi$= $90^{\circ}$, i.e., at apex region. Hoop stress due to the pressure and temperature differences between primary and secondary side were analyzed to be 76 MPa and 45 MPa, respectively.

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Residual stresses on plasma sprayed zirconia coatings (플라즈마 용사법에 의한 지르코니아 코팅에서의 잔류응력에 대한 연구)

  • 류지호;강춘식
    • Journal of Welding and Joining
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    • v.7 no.4
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    • pp.46-55
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    • 1989
  • Zirconia coatings are performed by the plasma spraying on the substrate of Al-Si alloy. In case of plasma sprayed ceramic coatings, it is important to control properly residual stress occurred during cooling process. Residual stress in coating layer varies with sprayed conditions and is influenced greatly by the coating layer thickness. Surface residual stress due to coating layer thickness is measured by X-ray diffraction method and the residual stress in coating layer is estimated by the deflection of coating layer when the restraint force in substrate was removed. When zirconia was coated on the substrate, tensile residual stress remains on zirconia coated surface layer. The tensile stress is increased to 0.35mm thickness and after 0.45mm thickness it is decreased abrouptly. A thick bond and composite coating reduce the zirconia surface stress and composite coating controls effectively the thick zirconia surface stress.

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