Download or read book Investigation of Active Slip Systems in High Purity Single Crystal Niobium written by Derek Baars and published by . This book was released on 2013 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigating Single Crystal Plasticity of Niobium with a Dislocation Mechanics based Model written by Eureka Pai Kulyadi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One suggested method to manufacture superconducting radio frequency (SRF) cavities, which are used as driving units in particle accelerators, is the deep-drawing of Niobium (Nb) disks that were cut from large-grained ingots. This is a promising and cost-effective alternative to the current industry standard of deep-drawing rolled poly-crystalline sheets. It is essential to understand the sources of the observed variability in the performance of cavities fabricated by either process in order to define the most suitable fabrication route.Cavity performance is hampered by material defects such as dislocations or crystallite boundaries that can arise and evolve during deformation processes involved in the mechanical shaping of the cavity (mostly by deep-drawing). Such defects can trap magnetic flux causing significant radio frequency (RF) losses leading to reduced performance. Understanding dislocation mechanics in Nb based on deformation experiments allows predictive modeling to enable informed design strategies for optimal cavity fabrication and improved performance.Crystal plasticity (CP) modeling is a powerful and well-established computational materials science tool to investigate mechanical structure-property relations in crystalline materials. A dislocation mechanics-based constitutive description of plastic deformation in body-centered cubic (BCC) metals is used to formulate a CP model for Nb. Uniaxial tension experiments on several Nb single crystals cut from a large-grained ingot disk were conducted at several different strain rates. The specific selection of grains and the in-plane orientation of deformation samples cut from those grains were based on the active slip systems anticipated from SCHMID factor calculations. The results from these specifically designed deformation experiments are used to validate the model.Simulations and corresponding deformation experiments exhibit notable discrepancies in terms of the stress-strain response and lattice reorientation. These discrepancies are rationalized by considering the effect of a distribution in pre-existing dislocation densities across the possible slip systems, which entails a significant variability in the resulting slip system activity and associated crystal reorientation and strain hardening behavior. An exhaustive numerical study probing thousands of initial dislocation density distributions could be condensed into inverse pole figure (IPF) maps that chart the range of crystallographic tensile directions for which stable outcomes can be expected despite a given variability in the pre-existing dislocation density distribution. Consequently, it becomes clear that while single-crystal experiments can be a useful guide toward the development and testing of dislocation mechanics-based models, care must be exercised as to not expect a one-to-one matching between any specific experiment and its corresponding simulation, since the exact values and distribution of pre-existing dislocations in the sample is generally unknown (and likely unknowable).
Download or read book Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2.3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (
Download or read book Effect of Substructure on the Plastic Deformation of High Purity Niobium Single Crystals written by Agrahar Chowdappa Raghurma and published by . This book was released on 1971 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kinetics and Mechanisms of Low Temperature Deformation in High Purity Niobium Single Crystals written by Nasser Hussein Karam and published by . This book was released on 1985 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Investigation of Low Energy Structure in Niobium Single Crystals by Tunneling written by John W. Hafstrom and published by . This book was released on 1969 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation of low energy superconductive tunneling into very pure single crystal niobium was performed. Lead and indium films, evaporated onto oxide barriers, were used as the probe. Evidence was found for a second energy gap in niobium at delta/10. The gap is temperature independent and agrees with various theoretical predictions. Additional new voltage structure is found in junctions formed with lead, indicative of tunneling processes occurring within the barrier. Various processes are proposed to explain the structure. (Author).
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 680 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deformation Induced Anistropy of the Critical Current in Single Crystal Niobium written by Jeremy A. Good and published by . This book was released on 1969 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anisotropy of the critical current in a (110) niobium single crystal of very high purity is observed to result from tensile deformation. The critical current exhibits local maxima when the magnetic field is directed along the (1,-1,0) and (001) directions. The height of the (1,-1,0) maximum increases with respect to the height of (001) maximum as the magnetic field is decreased. The (001) maximum is sensitive to the condition of the sample surface and exhibits rectification. There is a contribution to the anisotropy of the as-deformed crystal caused by anisotropic surface roughness, which can be removed by chemical polishing. The effect of the interaction at the surface is thought to be magnified by the decrease in the flux line lattice shear modulus C66 in that region.
Download or read book Single Crystal Large Grain Niobium Technology written by Ganapati Rao Myneni and published by AIP Conference Proceedings / H. This book was released on 2007-08-30 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: SRF Technology based accelerators, FEL’s, and ERL’s, are becoming common worldwide. Several new frontier technologies and applications are expected to be evolving in coming years as the cost of SRF technology comes. Terra Hertz (THz) Science could benefit from these advances, and many applications are likely to be developed in the fields of medical imaging, material science, pharmaceuticals, communications etc.
Download or read book Numerical and Experimental Investigation of Plasticity slip Evolution in Notched Single Crystal Superalloy Specimens written by Shadab Siddiqui and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results reveal that slip sector boundaries have complex curved shapes, rather than straight sector boundaries as predicted previously. Moreover, both the experimental and numerical results indicate that sector boundaries change with increasing load. A comparison between the isotropic and anisotropic results demonstrates that elastic anisotropy has a noticeable effect on the slip evolution near notches. The numerical model was further exploited to systematically evaluate the effects of crystallographic orientation, thickness and test temperature, on the evolution of plasticity in SCNBS. An analysis of the stresses as a function of thickness revealed that the activated slip systems and sector boundaries drastically change from the surface to the interior of the specimens. These numerical results suggest that experimental observation of slip lines on the surface is not representative of plasticity within the samples. Slip plane and sectors predicted near notches are found to be strong functions of the notch orientation, not only on the surface of the specimen but also at various thickness planes. Furthermore, results indicate that the slip fields are orientation dependent not only at low temperature (38°C), but also at high temperature (927°C). Based on the dominant slip system concept developed here, good correlation between numerical and experimental results was also found in copper single crystals subjected to four point bending load. This finding confirms that the dominant slip system concept not only works for single crystal superalloys, but is also applicable to other FCC single crystals, as well as for other loading modes.
Download or read book Yield Behavior of Niobuim Single Crystals written by D. C. Huffaker and published by . This book was released on 1964 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crystal Plasticity Finite Element Methods written by Franz Roters and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Download or read book An Investigation of Low Energy Structure in Niobium Single Crystals by Superconductive Tunneling written by John William Hafstrom and published by . This book was released on 1969 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Introduction to Composite Materials written by D. Hull and published by Cambridge University Press. This book was released on 1996-08-13 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: This edition has been greatly enlarged and updated to provide both scientists and engineers with a clear and comprehensive understanding of composite materials. In describing both theoretical and practical aspects of their production, properties and usage, the book crosses the borders of many disciplines. Topics covered include: fibres, matrices, laminates and interfaces; elastic deformation, stress and strain, strength, fatigue crack propagation and creep resistance; toughness and thermal properties; fatigue and deterioration under environmental conditions; fabrication and applications. Coverage has been increased to include polymeric, metallic and ceramic matrices and reinforcement in the form of long fibres, short fibres and particles. Designed primarily as a teaching text for final-year undergraduates in materials science and engineering, this book will also interest undergraduates and postgraduates in chemistry, physics, and mechanical engineering. In addition, it will be an excellent source book for academic and technological researchers on materials.
Download or read book Metals Abstracts Index written by and published by . This book was released on 1996 with total page 1622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interstitial Solutes and Deformation in Nb and Nb Single Crystals written by R. E. Ricker and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments were conducted on high purity single and polycrystalline niobium to determine the influence of low concentrations of interstitial impurities on mechanical properties and to evaluate the feasibility of using measurements of mechanical properties to detect, identify, and quantify the diffusible interstitial content.
