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Numerical simulation of residual stresses due to cladding process

: Siegele, D.; Brand, M.

Lidbury, D. ; American Society of Mechanical Engineers -ASME-, Pressure Vessels and Piping Division:
ASME Pressure Vessels and Piping Conference 2007. Proceedings. Vol.6: Materials and fabrication : Presented at 2007 ASME Pressure Vessels and Piping Conference, July 22 - 26, 2007, San Antonio, Texas, USA
New York/NY.: ASME, 2008
ISBN: 0-7918-4284-3
ISBN: 978-0-7918-4284-3
Pressure Vessels and Piping Conference (PVP) <2007, San Antonio/Tex.>
Fraunhofer IWM ()

The inner surface of reactor pressure vessels is protected against corrosion by an austenitic cladding. Generally, the cladding is welded on the ferritic base metal with two layers to avoid sub-clad cracks and to improve the microstructure of the cladding material. On the other hand, due to the cladding process and the difference of the thermal expansion coefficient of the austenitic cladding and the ferritic base material residual stresses act in the component. This residual stress field is important for assessing crack postulates in the cladding or subclad flaws in the base metal. For the determination of the residual stress field, plates of RPV steel were cladded and heat treated representative to the RPV relevant conditions. During the cladding process the temperature and distortion were measured as basis for the validation of the finite element simulations. The numerical simulation was performed with the finite element code SYSWELD. The heat source of the model was calibrated on the measured temperature profile. In the analysis, the temperature dependent material properties as well as the transformation behavior of the ferritic base metal were taken into account. The calculated residual stresses show tensile stresses in the cladding followed by compressive stresses in the base metal that are in agreement with measurements with X-ray diffraction technique.