Issue 36

Sz. Szávai et alii, Frattura ed Integrità Strutturale, 36 (2016) 36-45; DOI: 10.3221/IGF-ESIS.36.04 45 One should also note that any effects of phase variations are not yet seen by the neutron measurements, as no reference specimen could be measured so far. One remarkable observation from these results is that in no case the welding longitudinal direction exhibits the highest residual stresses, neither in tension nor in compression [2]. S UMMARY n this study, residual stress prediction was carried out for dissimilar metal welded mock-up. Three-dimensional model was utilized to predict stress fields after welding, especially the longitudinal residual stresses which are in general most harmful to the integrity of the structure among the stress components, in dissimilar steel butt-welded joints between ferritic and austenitic steels which are in essence have different thermal and mechanical properties. All results are presented considering temperature dependent material properties, phase change, and convection boundary. Also, experimental measurements employing neutron diffraction have been conducted to assess residual stresses within the welded samples. An acceptable agreement has been found between the predicted and the measured data that verifies the validity of the employed model. The simulation results suggest obtaining a highly precise prediction of final residual stress in the joint of the dissimilar metals. Furthermore, considering the important manufacturing processes and developing more reasonable material models are necessary. Both the numerical model and the experiment show that strain hardening consent to the final residual stresses. A CKNOWLEDGEMENT he presented work was carried out as a part of the MULTIMETAL project that has received funding from the European Community’s Seventh Framework Program (FP7/2012- 2015) under grant agreement n◦295968. R EFERENCES [1] Szavai, Sz., MULTIMETAL Deliverable D3.3 VVER type mock-up. Manufacturing report, BZF, (2012). [2] Ohms, C., Martin, O., Bezi, Z., Beleznai, R., Szavai, Sz., MULTIMETAL Deliverable D3.10, Residual Stress Measurements of Mockup-3. Technical report, JRC, BZF, (2015). [3] Goldak, J., Chakravarti, A., Bibby, M., A new finite element model for welding heat sources model. Metallurgical Transactions B., 15B (1984) 299-305. [4] Lindgren, L.-E., Runnemalm, H., Näsström, M., Simulation of multipass welding of a thick plate. International Journal for Numerical Methods in Engineering, 44(9) (1999) 1301-1316. [5] MSC.Marc 2013.1 Volume A: Theory and User Information. [6] Smith, M.C., Smith, A.C., Wimpory, R., A review of the NeT Task Group 1 residual stress measurement and analysis round robin on a single weld bead-on-plate specimen, International Journal of Pressure Vessels and Piping, (2014) 93–140. [7] Saunders, N., Guo, Z., Li, X., Miodownik, A.P., Schillé, J.P., The calculation of TTT and CCT diagrams for general steels, Internal report, Sente Software Ltd., U.K., (2004). I T