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TY - CONF AU - Mapar, A. AU - Bieler, T.R. AU - Murphy, J.E. AU - Pourboghrat, F. ED - Schaa, Volker RW ED - He, Yuan ED - Li, Lu ED - Zhao, Ning TI - Modeling the Hydroforming of a Large Grain Niobium Tube With Crystal Plasticity J2 - Proc. of SRF2017, Lanzhou, China, July 17-21, 2017 C1 - Lanzhou, China T2 - International Conference on RF Superconductivity T3 - 18 LA - english AB - Current SRF cavities are made from fine grained polycrystalline niobium half-cells welded together. Hot spots are commonly found in the heat-affected zone, making seamless hydroformed cavities attractive. Large grain cavities usually perform as well as fine grain cavities, often having a higher Q, presumably due to fewer grain boundaries. Large grain Nb forms non-uniformly, which introduces problems in manufacturing. A model that could realistically predict the deformation response of large grain Nb could facilitate the design of large grain hydroformed tubes. To this end, a crystal plasticity model was developed and calibrated with tensile stress-strain data of Nb single crystals. A seamless large grain tube was made from rolling a fine grain sheet into a tube, welded, and heat treated to grow large grains. The heat treatment resulted in a large grain tube with a single grain orientation in the center. The tube was hydroformed until it cracked. The hydroforming process was simulated with the crystal plasticity model, which was able to predict the deformed shape of the tube, the location of the crack and other localized areas with heterogeneous strain. PB - JACoW CP - Geneva, Switzerland SP - 616 EP - 619 KW - ion KW - cavity KW - niobium KW - experiment KW - SRF DA - 2018/01 PY - 2018 SN - 978-3-95450-191-5 DO - 10.18429/JACoW-SRF2017-TUPB095 UR - http://jacow.org/srf2017/papers/tupb095.pdf ER -