Efficient Numerical Calculation Of Welding Residual Stress In Large - Scale Thick - Walled Structures With Nuclear Power

This paper based on the analysis of domestic and foreign residual stress test andnumerical simulation, analysed the residual stress of large nuclear thick-walled structuresand core barrel shell combined experiments and numerical calculation, and studyed efficientnumerical calculation methods of this kind of large structure by experimental and numericalmethods. Firstly, a two-dimensional (2D) axisymmetric model was developed to simulatethe temperature fields and welding residual stresses, simplify the weld passes, optimize loadstep number and provide the basis for three-dimensional (3D) efficient calculation. Secondly,a3D model was developed to simulate the welding residual stresses efficiently, study theeffects of moving temperature heat source model, strip temperature heat source model, thelength of strip heat source and grid circumferential length on calculation accuracy, andresearch the impacts on the residual stress imposed by gravity, grinding weld and repairinglength and stress distribution in weld start/end location. Thirdly, axial and hoop residualstress were measured with the X-ray diffraction method (XRD) on the girth weld and thesimulation and actual test results were compared and analysed.The study of weld passes simplification and load step optimization show that thecomputations of2D28weld passes model are consistent with the actual measurementresults on distribution trends and values; computations of simplified model with13weldpasses are basically consistent with the28weld passes model without simplification. Thecomputing time of16load step program is decreased to0.28hours and is the shortest, thecomputational efficiency improves about14times and the results are also consistent withthe non-simplified results on value and trend.The study of heat source model shows that the temperature fields and welding residualstresses of moving temperature heat source model and strip temperature heat source modelare consistent; but the computing time of strip temperature heat source model drops75percent. The computed results of circumferential length of30mm model are consistent withcircumferential length of15mm model, and the computing time is37percent ofcircumferential length of15mm model; the residual stresses of different segments areconsistent, but the computing results of deformation are different. The calculative error ofdeformation is reduced with the increase of the number of segments.The computations of3D model are consistent with the actual measurement results on distribution trends and values with the usage of efficient heat source model and optimizationof load step load. There are varying degrees of stress fluctuations in arc start/end location.Gravity has little effect on residual stress. Polishing excess weld metal has little effect on thedistribution of residual stress. When polishing step by step, the stress distribution curvingalong the weld thickness direction shows a tendency of anti-clockwise direction rotation; thetrend of the stress distribution does not change, but the peak value increases with thedecrease of weld passes. With the increase of repairing length, the residual stressdistribution curve shows a tendency of clockwise direction rotation; the hoop residual stressdistribution curve becomes steep gradually; axial residual stress decreases, at both ends inparticular; equivalent residual stress changes little.