• 제목/요약/키워드: Stress Raio

검색결과 3건 처리시간 0.014초

강용접부의 피로거동에 미치는 용접후열처리 및 응력비의 영향 (Effect of PWHT and stress ratio on fatigue behavior of welded joints in steel)

  • 김경수;임재규;정세희
    • Journal of Welding and Joining
    • /
    • 제5권3호
    • /
    • pp.53-61
    • /
    • 1987
  • Post weld heat treatment(PWHT) is usually carried out to remove the residual stress and to improve the microstructure and mechanical properties of welded joints. By the way, welding structure transformed owing to PWHT and reheating for repair loads the random cycles fatigue as offshore welding structure of constant low cycle fatigue as pressure vessel, and then, pre-existing flaws or cracks exist in a structural component and those cracks grow under cyclic loading. Therefore, the effects of PWHT and stress ratio on fatigue crack growth behaviors were studied on the three regions such as HAZ, sub-critical HAZ and deposit metal of welded joints in SM53 steel. Fatigue crack growth behavior of as-weld depended on microstructure and fatigue crack growth rate of HAZ was the lowest at eac region, but after PWHT it was somewhat higher than that of as-wel. In case of applying the stress($10kg/mm^2$) during PWHT, fatigue crack growth resistance tended to increase in the overall range of .DELTA.K.

  • PDF

확장된 Maxwell-Wagner 분극 모델에 의한 서로 크기가 다른 입자들로 구성된 이성분계 전기유변 유체의 전산 모사 (Simulation of Bi-dispersed Electrorheological Fluids of Different Particle Sizes by the Extended Maxwell-Wagner Polarization Model)

  • 김영대
    • Korean Chemical Engineering Research
    • /
    • 제60권4호
    • /
    • pp.613-619
    • /
    • 2022
  • 전도성 입자로 제조된 전기유변(Electrorheological) 유체에서 입자 크기 및 서로 다른 크기의 입자들의 혼합이 전기유변 현상에 어떤 영향을 미치는지 살펴보기 위해 Onsager 이론으로 확장된 Maxwell-Wagner 분극 모델을 이용하여 전산 모사를 수행하였다. 전산 모사 결과 입자의 부피 분율이 같은 경우 단일한 크기의 입자로 구성된 균일한 전기유변 유체의 동적 항복응력은 입자 크기에 무관하였고, 크기가 서로 다른 입자들로 혼합된 비균일 전기유변 유체의 동적 항복응력은 균일한 전기유변 유체에 비해 감소하였다. 입자 부피 분율이 같은 경우 ${\dot{\gamma}}^*$≧0.01인 범위에서 큰 입자로 구성된 균일한 전기유변 유체가 작은 입자로 구성된 균일한 전기유변 유체보다 전단응력이 큰 것으로 나타났으며, ${\dot{\gamma}}^*$≧1인 경우에는 전기유변 유체는 큰 입자의 비율이 증가할수록 전단응력이 증가함을 보였다. 모든 입자 크기 및 조성에 대해 전도성 입자로 제조된 전기유변 유체의 특성인 비제곱 전기유변 현상(∆𝛕 ∝ En, n ≈ 1.55)도 예측하였다.

회전하는 정사각단면 $90^{\circ}$곡관내 난류유동에 관한 수치해석적 연구 (Study on the Analysis of Turbulent Flow in a Rotating Square Sectioned $90^{\circ}$ Curved Duct)

  • 이건휘;최영돈
    • 대한기계학회논문집
    • /
    • 제19권9호
    • /
    • pp.2206-2222
    • /
    • 1995
  • In this study, the characteristics of the three-dimensional turbulence flow in a rotating square sectioned 90.deg. bend were investigated by numerical simulation. And a dimensionless number, Coriolis force ratio, primarily subjected to the feature of the flow in the rotating 90.deg. bend was obtained as a result of one-dimensional theory. In the simulation study, low Reynolds number ASM developed by Kim(1991) in the square sectioned 180.deg. bend flow was modified in order to consider the rotational effects in the testing flows. In the near wall region of low Reynolds number, four turbulence models were employed and compared in order to find the most appropriate model for the analysis of the rotating 90.deg. bend flow. By comparison of the results with the experimental data, it is shown that low Reynolds number Algebraic Stress Model with rotating terms reflects most correctly the rotational effects. As the results of this study, centrifugal forces associated with the curvature of the bend and Coriolis forces and centripetal forces associated with the rotation affect directly both the mean motion and the turbulent fluctuations. Their actions on the mean flow are to induce a secondary motion while their effects on turbulence are to modify the pressure strain.