Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 23: Mechanical Properties I
MM 23.1: Vortrag
Mittwoch, 29. März 2006, 14:00–14:15, IFW B
Deformation of laminated niobium and alumina: constraints from the interfaces — •Yonghe Liu1,2 and Dieter Brunner1 — 1Max-Planck-Institut für Metallforschung, 70569 Stuttgart, Germany — 2Institut für Physik und Zentrum für Mikro- und Nanotechnologien, Technische Universität Ilmenau, 98693 Ilmenau, Germany
The forming of thin metal sheets is highly constrained by interfaces between workpiece and dies. Constraints are usually treated as friction in a form of stiction, or coulomb friction depending upon lubrication. Our study of the deformation behavior of thin niobium sheets focus on the effects of constraints from interfaces. Polycrystalline niobium and sapphire joints were prepared by diffusion bonding in ultra high vacuum chamber to simulate the stiction, while the coulomb friction was simulated by stacking the niobium/sapphire pieces, or niobium/niobium pieces. We applied an optical full field strain mapping method to determine the strains on the side faces of the metal layers in in-situ deformations. In the case of stiction, the detected strain patterns are coupled with strain localization at interfaces and along the maximum shear directions. Once friction changes from stiction to coulomb friction through interface debonding, the strain localization at interface disappears. A ductile fracture model considering stress triaxiality was employed to understand the results. The results obtained by strain mapping can be directly compared with that obtained by finite element method.