• Title/Summary/Keyword: thermal residual stress

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Numerical simulation of relation between interface topography and residual stress in thermal barrier coatings

  • Yao, Guo-Feng;Ma, Hong-Mei;Zhang, Lin-Wen
    • Structural Engineering and Mechanics
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    • v.29 no.4
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    • pp.423-431
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    • 2008
  • With respect to thermal barrier coating, the analysis of interface cohesion and residual stress is important to the life of TBC from mechanical view point. Up to now, there is not a model of describing interface cohesion. In the paper, we give a simple model of computing residual stress and study the residual stress of TBC with ANSYS. The distribution of the residual stress in different interface topography and the relationship between the residual stress and the interface topography dimension are presented.

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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    • 2000.11a
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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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N.M.for the Effect of P.T. on Resicual Stress Relaxation (잔류응력 완화에 미치는 상변태의 수치적 모델링)

  • 장경복;손금렬;강성수
    • Journal of Welding and Joining
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    • v.17 no.6
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    • pp.84-89
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    • 1999
  • Most of ferrous b.c.c weld materials may experience martensitic transformation during rapid cooling after welding. It is well known that volume expansion due to the phase transformation could influence on the relaxation of welding residual stress. To apply this effect practically, it is a prerequisite to establish a numerical model which is able to estimate the effect of phase transformation on residual stress relaxation quantitatively. For this purpose, the analysis is carried out in two regions. i.e., heating and cooling, because the variation of material properties following a phase transformation in cooling is different in comparison with the case in heating, even at the same temperature. The variation of material properties following phase transformation is considered by the adjustment of specific heat and thermal expansion coefficient, and the distribution of residual stress in analysis is compared with that of experiment by previous study. consequently, in this study, simplified numerical procedures considering phase transformation, which based on a commercial finite element package was established through comparing with the experimental data of residual stress distribution by other researcher. To consider the phase transformation effect on residual stress relaxation, the transition of mechanical and thermal property such as thermal expansion coefficient and specific heat capacity was found by try and error method in this analysis.

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Stress distribution of near the interface on high temperature fatigue in ceramic/metal bonded joints (세라믹/금속접합재의 고온피로에 따른 접합계면의 응력분포)

  • 박영철;허선철;윤두표;김광영
    • Journal of Ocean Engineering and Technology
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    • v.10 no.2
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    • pp.106-119
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    • 1996
  • The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low speciffic weight, low thermal expansibillity, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductillity in order to compensate the weakness of ceramic.The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strngth of joint to a large amount by forming a singular stress field. In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined. In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.

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Residual Stress Measurement of Sand Casting by ESPI Device and Thermal Stress Analysis (ESPI 장비를 활용한 사형 주조품의 잔류응력 측정 및 주조 열응력 해석)

  • Kwak, Si-Young;Nam, Jeong-Ho
    • Journal of Korea Foundry Society
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    • v.40 no.1
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    • pp.1-6
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    • 2020
  • Many studies involving a thermal stress analysis using computational methods have been conducted, though there have been relatively few experimental attempts to investigate thermal stress phenomena. Casting products undergo thermal stress variations during the casting process as the temperature drops from the melting temperature to room temperature, with gradient cooling also occurring from the surface to the core. It is difficult to examine thermal stress states continuously during the casting process. Therefore, only the final states of thermal stress and deformations can be detemined. In this study, specimens sensitive to thermal stress, were made by a casting process. After which the residual stress levels in the specimens were measured by a hole drilling method with Electron Speckle-Interferometry technique. Subsequently, we examined the thermal stresses in terms of deformation during the casting process by means of a numerical analysis. Finally, we compared the experimental and numerical analysis results. It was found that the numerical thermal stress analysis is an effective means of understanding the stress generation mechanism in casting products during the casting process.

A Numerical Estimation of Fatigue Strength of Welded Steel Structures with Residual Stresses (용접 잔류음력을 고려한 강구조물의 피로강도평가)

  • Chung, Heung-Jin;Yoo, Byoung-Chan
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.265-270
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    • 2007
  • According to previous research, welding-induced residual stresses in steel structures can significantly affect the fatigue behaviour. Usually, high tensile residual stresses up to the yield strength are conservatively assumed at the weld toes. This conservative assumption can result in misleading fatigue assessments. Thee welding-induced residual stresses need be known in advance for a reliable fatigue assessment, which becomes possible to an increasing extent by numerical welding simulation. In this study, a fatigue Analysis technique for steel structures with welding induced residual stress is presented. First, We calculate the history of temperature according with welding process. Secondly, residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis and lastly, fatigue strength is estimated with modified Goodman equation which can consider the effect of mean stress level.

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Residual DC characteristic on Twisted Nematic Liquid Display on the Polyimide Surface by the Thermal Stress (열적 stress에 의한 폴리이미드 표면에서의 TN-LCD의 잔류DC 특성)

  • Bae, Yu-Han;Hwang, Jeoung-Yeon;Kim, Jong-Hwan;Mun, Hyun-Chan;Han, Jung-Min;Kim, Young-Hwan;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.11a
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    • pp.498-501
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    • 2004
  • In this study, the threshold voltage and the response time of thermal stressed TN-LCDs showed the same performances on no thermal stressed TN-LCDs. There was little change of value in TN cells. Also, the transmittances of TN-LCDs on the rubbed PI surface were almost same while increasing thermal stress time. However, the thermal stability of TN cell was decreased by the high thermal stress for the long duration. Residual DC was decreased as the thermal stress increases. Especially, when TN cell was stressed more and more by heating, residual DC was changed a lot. As a result, the residual DC property of LCD in projection TV is affected very much by heating.

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Evaluation of Characteristic for SS400 and STS304 Steel by Weld Thermal Cycle Simulation - 3rd Report: Residual Stress and Ultrasonic Parameter (용접열사이클 재현에 의한 SS400강 및 STS304강의 특성 평가 - 제3보: 잔류응력과 초음파 파라미터)

  • Ahn, Seok-Hwan;Choi, Moon-Oh;Jeong, Jeong-Hwan;Kim, Sung-Kwang;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.22 no.6
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    • pp.27-34
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    • 2008
  • The temperature distribution in the weldment is not uniform because a weldment is locally heated. Thermal plastic deformation results from the local expansion and shrinkage by the heating and cooling of metal. Therefore, residual stresses and distortion occur in the weldment. In this study, we had conducted on the weld thermal cycle simulation that is supposed as the HAZ on SS400 steel and STS304 steel. The residual stresses that were obtained from the drawing and the weld thermal cycle simulation were estimated by X-ray diffraction. We also carried out ultrasonic test for the weld thermal cycle simulated specimens, and then conducted on nondestructive evaluation by the ultrasonic parameters obtained ultrasonic test. From the results, residual stresses of weld thermal cycle simulated specimens after the residual stress removal heat treatment are lower than that of the drawing.

Numerical Simulation of Effects of TGO Growth and Asperity Ratio on Residual Stress Distributions in TC-BC-TGO Interface Region for Thermal Barrier Coatings (열차폐 코팅의 TGO 성장과 형상비에 따른 TC-BC-TGO 계면에서의 잔류응력 변화에 대한 유한요소해석)

  • Jang, Jung-Chel;Choi, Sung-Churl
    • Journal of the Korean Ceramic Society
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    • v.43 no.7 s.290
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    • pp.415-420
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    • 2006
  • The residual stresses in the interface region of the Thermal Barrier Coating (TBC)/Thermally Grown Oxide (TGO)/Bond Coat (BC) were calculated on the TBC-coated superalloy samples using a Finite Element Method (FEM). It was found that the stress distribution of the interface boundary was dependent upon mainly the geometrical shape or its aspect ratio and the thickness of TGO layer, which was formed by growth and swelling behavior of oxide layer. Maximum compressive residual stress in the TBC/TGO interface is higher than that of the TGO/bond coat interface, and the tensile stress had nothing to do with change of an aspect ratio. The compressive residual stresses in the TBC/TGO and TGO/bond coat interface region increased gradually with the TGO growth.

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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