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Published byBertram Williamson Modified over 9 years ago
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An Investigation into the use of FEA methods for the prediction of Thermal Stress Ratcheting
Huse, Stephen
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Abstract Calculate heat transfer for given initial conditions
Calculate thermal gradients and stresses Predict the onset of thermal stress ratcheting using FEA methods Compare to ASME code prediction
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Background (cont.) Thermal gradients occur due to changes in temperature of fluid flowing through piping T - Mean Temperature V - Linear Temperature Gradient, ∆T1 Peak Temperature Gradient, ∆T2
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Background Bree Diagram Regions σp – Primary Stress, PD/2t
E – Elastic S – Shakedown P - Plastic cyclic R - Ratcheting σp – Primary Stress, PD/2t P – Pressure D – diameter t – thickness σt – Secondary Stress, EαΔT1/2(1-v) E – Young’s modulus α – Mean coefficient of thermal expansion ∆T1 – Linear temperature gradient v – Poisson’s ratio σy – Yield Strength
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Problem Description Nuclear power plants have high thermal gradients and pressures resulting in sever primary and secondary stresses Severe primary and secondary stresses result in accumulating plastic strains known as thermal ratcheting Prevention of thermal ratcheting is performed by limiting the allowable stresses
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Methodology Convective heat transfer of turbulent flow inside a cylinder: Nu=0.023Re0.8Prn Nu=hd/k h – convective heat transfer coefficient d – inner diameter k – fluid thermal conductivity Re=vd/ν v – velocity ν – kinematic viscosity Pr – Prandtl number ABAQUS for solving heat transfer analysis and structural analysis Geometry Material properties Load conditions
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References Bree, J. (1967). Elastic-plastic behaviour of thin tubes subject to internal pressure and intermittent high-heat fluxes with application to fast nuclear reactor fuel elements.Journal of Strain Analysis, (2), 2010 ASME boiler & pressure vessel code an international code. (2010). New York, NY: American Society of Mechanical Engineers. ABAQUS (Version 6.13) [Software]. (2013). Providence, RI: Dassault Systèmes Simulia Corp.
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