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TUP018 |
Non-Schmid Crystal Plasticity Modeling of Deformation of Niobium | |
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Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222. The response of niobium (Nb) to load changes when the direction of loading with respect to the crystal orientation changes. Large grain Nb sheets are less expensive but more anisotropic than fine grain sheets. Designing a manufacturing process for large grain Nb sheets is complex and impractical, unless one uses a modeling approach that considers crystal orientation and plastic anisotropy. This improves the performance and reduces costs of a SRF cavity. Designing more sophisticated manufacturing methods like tube hydroforming is also feasible with such a model. Crystal plasticity has been very successful for FCC materials; nevertheless, there is still no model that can accurately predict the deformation behavior of most BCC materials like Nb. The classical crystal plasticity model fails for BCC materials. To successfully model the deformation, one should account for the effect non-Schmid stresses have on the core structure and hence, the mobility of the screw dislocation. In this study the effect of core structure is implemented into a crystal plasticity model for Nb. This is a generalization to the classical crystal plasticity and substantially improves predictions of the model. |
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| TUP037 | Dynamic Hardening Rule; a Generalization of the Classical Hardening Rule for Crystal Plasticity | 499 |
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Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222. The mechanical properties of a niobium (Nb) specimen can change with the orientation of the sheet. This anisotropy causes inhomogeneity in manufactured SRF cavities. Large grain Nb sheets are more anisotropic and less expensive than fine grain sheets. Designing a manufacturing process for large grain Nb sheets, however, is extremely complex, and requires using advance modeling techniques. A model capable of accurately predicting the deformation behavior of Nb can help improve the performance and reduce costs of a SRF cavity. Optimal design of the manufacturing of cavities with tube hydroforming process is possible with such a model. Crystal plasticity modeling of FCC materials has been very successful; however, there is still no model that can accurately predict the deformation behavior of BCC materials like the large grain Nb sheet. In this study, authors have proposed a dynamic hardening rule for crystal plasticity that significantly improves predictions of the model for large grain Nb. This model is the generalization of the classical hardening rule, and gives better control over the hardening rate. It also increases the stability of the model. |
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