• Title, Summary, Keyword: thermal residual stress

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Effect of Thermal Cycle on Strength of Ceramic and Metal Joint (세라믹/금속접합재의 강도에 미치는 열사이클 영향)

  • 박영철;오세욱;김광영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1664-1673
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    • 1994
  • As a fundamental study on effects of thermal-cycles on residual stress of ceramics/metal joints, residual stresses in $Si_3N_4$/SUS304 joint specimens were measured before and single thermal-cycle by X-ray diffraction method and finite element method(FEM). The residual stress was found to increase after single thermal-cycle, which was agreeable with the results of residual stress measurement by X-ray diffraction method and residual stress analysis by finite element method. After the residual stress measurement, 4-point bending tests were performed. The relationship between the bending strength, the thermal-cycle temperature and hold time was examined. The bending strength was found to decrease with the increase of residual stress in linear relation.

Stress Analysis of the Micro-structure Considering the Residual Stress (잔류응력을 고려한 미세구조물의 강도해석)

  • 심재준;한근조;안성찬;한동섭
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.820-823
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    • 2002
  • MEMS structures Generally have been fabricated using surface-machining, but the interface failure between silicon substrate and evaporated thin film frequently takes place due to difference of linear coefficient of thermal expansion. Therefore this paper studied the effect of the residual stress caused by variable external loads. This study did not analyzed accurate quantity of the residual stress but trend for the effect of residual stress. Several specimens were fabricated using other material(Al, Au and Cu) and thermal load was applied. The residual stress was measured by nano-indentation using AFM. The results showed the existence of the residual stress due to thermal load. The indentation area of the thermal loaded thin film reduced about 3.5% comparing with the virgin thin film caused by residual stress. The finite element analysis results are similar to indentation test.

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Evaluation of High Temperature Strength Characteric in Joint Metal (접합재의 고온강도 특성 평가)

  • Huh, Sun-Chul;Park, Young-Chul;Yun, Han-Ki;Park, Won-Jo
    • Proceedings of the KSME Conference
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    • pp.103-108
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    • 2000
  • Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

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Research on residual stress in SiCf reinforced titanium matrix composites

  • Qu, Haitao;Hou, Hongliang;Zhao, Bing;Lin, Song
    • Steel and Composite Structures
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    • v.17 no.2
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    • pp.173-184
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    • 2014
  • This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

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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    • 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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Thermal Residual Stress Analysis of Fiber Reinforced Metal Laminate (섬유강화금속적층판(FRML)의 열응력 해석)

  • 김위대;양승희
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.61-64
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    • 2002
  • Fiber reinforced metal laminate(FRML) consists of alternations layers of metal and fiber reinforced composite. The difference in the coefficients of thermal expansion between metal and composite layer produces remarkable amount of thermal residual stresses between layers. Generally, FRML shows a tensile stress in metal layers, a compressive stress in composite layers after curing. In this study, the thermal residual stresses of several types of FRML are investigated to get the best combination of metal and composite which can reduce the thermal residual stresses. The residual stress level is compared with the strength of each layers to explain the fracture mechanism of FRML.

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Evaluation of the Residual Stress on the Multi-layer Thin Film made of Different Materials (이종재료를 사용한 다층 박막에서의 잔류응력 평가)

  • 심재준;한근조;김태형;안성찬;한동섭;이성욱
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.9
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    • pp.135-141
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    • 2003
  • MEMS structures generally have been fabricated using surface-machining method, but the interface failure between silicon substrate and evaporated thin film frequently takes place due to the residual stress inducing by the applied the various loads. And the very important physical property in the heated environment is the linear coefficient of thermal expansion. Therefore this paper studied the residual stress caused the thermal loads in the thin film and introduced the simple method to measure the trend of the residual stress by the indentation. Specimens were made of materials such as Al, Au and Cu and thermal load was applied repeatedly. The residual stress was measured by nano-indentation using AFM and FEA. The existence of the residual stress due to thermal load was verified by the experimental results. The indentation length of the thermal loaded specimens increased minimum 11.8% comparing with the virgin thin film caused by tensile residual stress. The finite element analysis results are similar to indentation test.

Characteristics of bending strength and residual stress distribution on high thermal cycle of ceramic and metal joint (세라믹/금속접합재의 고온 열사이클에 따른 잔류응력분포 및 굽힘강도 특성)

  • Park, Young-Chul;Hue, Sun-Chul;Boo, Myoung-Hwan;Kim, Hyun-Su;Kang, Jae-Wook
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1541-1550
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    • 1997
  • Since the ceramic/metal joint material is made at a high temperature, the residual stress develops when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of Si$_3$N$_4$STS304 joints quantitatively and to compare the strength of joints. The difference of residual stress is measured when repeated thermal cycl is loaded, under the conditions of the practical use of the ceramic/metal joint. The residual stress increases at 1 cycle of thermal load but decreases in 3 cycles to 10 cycles of thermal load. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a result, it is known that the stress of joint decreases as the number of thermal cycle increases.

Finite Element Analysis of Effect of Preheating on the Residual Stress in 304 Stainless Steel Weldment (304 스테인레스강 용접부 잔류응력에 미치는 예열 효과의 유한요속 해석)

  • 장경복;김하근;강성수
    • Journal of Welding and Joining
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    • v.16 no.5
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    • pp.67-75
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    • 1998
  • This study aimed at he experimental and finite element analytic investigation of the effect of preheating on he residual stress of weldment. In this study, an autogenous arc welding was used on type 304 stainless steel and MARC as F.E.M. common code was utilized in analysis The analyses include transient and moving heat source and thermal properties as function of temperature. During welding, the thermal cycles of four locations in the weldment were recorded to investigate of the behavior of thermal stress and residual stress. The experimental and analytic results had good coincidence and show that there are two factors influencing the formation of welding residual stress in preheat process. One is the elevation of welding equilibrium temperature and the other is the increase of amount of heat input. The former decrease welding residual stress and the latter increase welding residual stress. Therefore, the cumulative effects result in the welding residual stress not being improved significantly with preheating in 304 stainless steel.

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The Effect of W Particle Volume Percent on the Residual Stress of W Heavy Alloy (텅스텐계 중합금에서 텅스텐 입자의 부피비가 잔류응력에 미치는 영향)

  • 송홍섭
    • Journal of Korean Powder Metallurgy Institute
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    • v.1 no.1
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    • pp.52-59
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    • 1994
  • Since the coefficient of thermal expansion (CTE) of matrix phase is larger about 4 times than that of W particle in tungsten heavy alloy, the thermal stresses due to the CTE difference between the two phases are induced in the alloy during heating and cooling processes. In the present study, a series of W heavy alloy containing various W particle volumes of 0 to 90% is made to investigate the residual stress taking place during cooling process. The CTE and residual stress of the series of alloy are measured by dilatometer and X-ray diffractometer. The residual stress of W particle is in compressive stress irrespective of W particle vol% and tends to increase with decreasing W particle vol% while that of the matrix phase is in tensile stress. The measured residual stress of W particle is about a third of calculated thermal stress. The influence of W particle vol% on the residual stress of W heavy alloy is discussed in terms of the deformation behaviors of W particle and matrix phase.

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