• Title/Summary/Keyword: Temperature stress

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A Study on the Fatigue Crack Propagation Threshold Characteristic in Steel of Pressure Vessel at Low Temperature (압력용기용 강의 저온 피로크랙전파 하한계 특성에 관한 연구)

  • 박경동;박상오
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.05a
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    • pp.326-331
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    • 2001
  • In this study. CT specimens were prepared from ASME SA5l6 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ in the range of stress ratio of 0.1 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ΔKsub/th/ in the early stage of fatigue crack growth ( Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth ( Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da.dN -ΔK in RegionII, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate da/dN is rapid in proportion to descend temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

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Relaxation of Singular Stress in Adhesively Bonded Joint at High Temperature

  • Lee, Sang Soon
    • Journal of the Semiconductor & Display Technology
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    • v.17 no.1
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    • pp.35-39
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    • 2018
  • This paper deals with the relaxation of singular stresses developed in an epoxy adhesive at high temperature. The interface stresses are analyzed using BEM. The adhesive employed in this study is an epoxy which can be cured at room temperature. The adhesive is assumed to be linearly viscoelastic. First, the distribution of the interface stresses developed in the adhesive layer under the uniform tensile stress has been calculated. The singular stress has been observed near the interface corner. Such singular stresses near the interface corner may cause epoxy layer separated from adherent. Second, the interfacial thermal stress has been investigated. The uniform temperature rise can relieve the stress level developed in the adhesive layer under the external loading, which can be viewed as an advantage of thermal loading. It is also obvious that temperature rise reduces the bonding strength of the adhesive layer. Experimental evaluation is required to assess a trade-off between the advantageous and deleterious effects of temperature.

Effect of two temperature and energy dissipation in an axisymmetric modified couple stress isotropic thermoelastic solid

  • Lata, Parveen;Kaur, Harpreet
    • Coupled systems mechanics
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    • v.11 no.3
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    • pp.199-215
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    • 2022
  • The present paper deals with the axisymmetric deformation in homogeneousisotropic thermoelastic solid with two temperatures, with and without energy dissipation using modified couple stresstheory. The effect of energy dissipation and two temperature isstudied due to the concentrated normalforce, normalforce overthe circularregion, thermal pointsource and thermalsource over the circular region. The Laplace and Hankel transform techniques have been used to find the solution to the problem. The displacement components, conductive temperature distribution, stress components and couple stress are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. Effects of two temperature and energy dissipation on the conductive temperature,stress components and couple stress are depicted graphically.

Unsteady heat transfer and thermal stress analysis of a gasoline engine cylinder head (실린더 헤드의 비정상 열전달 및 열응력 해석)

  • 박진무;임영훈;김병탁
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.3
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    • pp.41-52
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    • 1990
  • In this study are determined the unsteady temperature and thermal stress fields for a domestic 4-cylinder, 4-cycle gasoline engine cylinder head by the three-dimensional finite element method. A representative part of the cylinder head is modelled as a combination of hexahedron isoparametric elements, and the time-dependent temperature and the heat transfer coefficient of the gas are imposed as the thermal boundary conditions for the engine speeds of 500 rpm and 2000 rpm. The obtained results, which are represented graphically, indicate that the amplitudes of temperature fluctuation during a cycle are about 10.deg. C and 3.deg. C respectively on the surface of combustion chamber, and the maximum temperature fields occur at 30.deg. , 10.deg. respectively before the initiation of the exhaust stroke. Thermal stress fields due to non-uniform temperature distributions show that compressive stress is much larger than tensile stress throughout a cycle. It is also found that the compressive stress varies with substantial amplitude between the exhaust port and ignition plug hole, and the high tensile stress with small fluctuation occurs between exhaust port and the adjacent head bolt hole.

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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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    • 2000.04a
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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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A Study on the Characteristics of High Temperature and Mechanisms for Creep Deformation of AZ31 Mg Alloy (AZ31마그네슘 합금의 고온특성 및 크리이프 변형기구에 관한연구)

  • Kang, D.M.;An, J.O.
    • Journal of Power System Engineering
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    • v.9 no.4
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    • pp.96-101
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    • 2005
  • Magnesium alloys have been widely used for many structural components of automobiles and aircraft because of high specific strength and good cast ability in spite of hexagonal closed-packed crystal structure of pure magnesium. In this study, uniaxial tension tests at high temperature and creep tests are done in order to investigate the characteristics of high temperature and mechanisms for creep deformation of AZ31 Mg alloy. Yield stress and ultimate tensile stress decreased with increasing temperature, but elongation increased from results of uniaxial tension test at high temperature. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined during creep of AZ31 Mg alloy over the temperature range of 473K to 573K and stress range of 23.42 MPa to 93.59 MPa, respectively, in order to investigate the creep behavior. Constant load creep tests were carried out in the equipment including automatic temperature controller, whose data are sent to computer. At around the temperature of $473K{\sim}493K$ and under the stress level of $62.43{\sim}93.59%MPa$, and again at around the temperature of $553K{\sim}573K$ and under the stress level of $23.42{\sim}39.00MPa$, the creep behavior obeyed a simple power-law relating steady state creep rate to applied stress and the activation energy for the creep deformation was nearly equal, respectively, and a little low to that of the self diffusion of Mg alloy including aluminum. Also rupture surfaces at high temperature have had bigger dimples than those at lower temperature by SEM.

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A Study on the Fatigue Behaviors of Cr-Mo-V Alloy for Steam Turbine at High Temperature Difference (터빈용 Cr-Mo-V강의 고온 환경변화에 따른 피로거동에 관한 연구)

  • Song, Sam-Hong;Kang, Myung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.1
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    • pp.173-179
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    • 1997
  • The high temperature fatigue tests were performed using the specimens taken from Cr-Mo-V steel, widely used as thermal power plant turbine materials for examination fatigue behavior of materials in power plants which have been operated for long periods. The fatigue tests at high temperature were performed at the various temperature and applied stress. The results obtained are summarized as follows : The fatigue crack length increases and the fatigue life decreases with temperature and applied stress according to the same number of stress cycle. The fatigue crack propagation and the fatigue life were much influenced by temperature and applied stress.

A Study of Shot Peened Spring Steel(SUP9) for Fatigue Life Improvement and Compressive Residual Stress Disappearance on the High Temperature (SUP9 스프링강의 숏피닝가공에 의한 피로수명향상과 고온환경에서의 압축잔류응력 소멸현상에 관한 연구)

  • Park, Kyoung-Dong;Son, Myoung-Koon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.2 no.1
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    • pp.22-31
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    • 2003
  • The compressive residual stress, which is induced by shot peening process, seems to be an Important factor in increasing the fatigue strength. And then it was showed that residual stress was disappearenced at the high temperature. The fatigue charateristic investigation of a SUP9 spring steel processed shot peening is performed by considering the high temperature service conditions in the range of room temperature through $180^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. The fatigue resistance characteristics and fracture strength at high temperature is considerable lower than that of room temperature in the early stage and stable of fatigue crack growth region.

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A Study of Shot peened Spring Steel for Fatigue Life Improvement and Compressive Residual Stress Disappearance on the High Temperature (SUP9 스프링강의 쇼트피닝가공에 의한 피로수명향상과 고온환경에서의 압축잔류응력 소멸현상에 관한 연구)

  • Park, Keyoung-Dong;Son, Myung-Koon
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2002.10a
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    • pp.347-353
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    • 2002
  • The compressive residual stress, which is induced by shot peening process, seems to be an important factor of increasing the fatigue strength. And then it was showed that residual stress was disappearenced at the high temperature. The fatigue characteristic study of a SUP9 spring steel processed shot peening is performed by considering the high temperature service conditions in the range of room temperature through $180^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. The fatigue resistance characteristics and fracture strength at high temperature is considerable lower than that of room temperature in the early stage and stable of fatigue crack growth region.

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Effect of Cr Addition on the High Temperature Deformation Behavior of Fe-Al Intermetallics (Fe-Al 금속간 화합물의 고온변형거동에 미치는 Cr 첨가의 효과)

  • Bang W.;Lim H. T.;Ha T. K.;Song J. H.;Chang Y. W.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2001.05a
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    • pp.167-171
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    • 2001
  • High temperature deformation behavior of Fe-28Al-5Cr alloy has been investigated known to show anomalous temperature dependence of yield strength. Specifically, the effect of Cr addition has been examined. A series of tensile and load relaxation tests have been carried out to obtain the flow behavior of Fe-28Al-5Cr alloy at the elevated temperatures. The flow curves have then been analyzed using the inelastic deformation theory recently proposed. Firstly, high temperature flow stress of iron aluminides can be resolved into internal stress and frictional stress. Secondly, the temperature corresponding to peak strength gets higher level at faster strain rate, which presumably due to the increased contribution of internal stress in observed flow stress. And thirdly, the alloying of Cr seems to cause solid-solution strengthening of frictional stress level and the elevation of 2nd order transition temperature. In this analogy, Fe-28Al-5Cr exhibits better strength especially at relatively higher temperature and lower strain rate than Fe-28Al.

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