No abstract available

No abstract available

[en] SYNROC was synthesized using simulated inert matrix fuels (IMFs) and the resulting materials characterized using Ti K-edge, Zr K-edge, and Nd L₃-edge x-ray absorption near edge spectroscopy (XANES). Based on the fitting results of Ti K-edge XANES it was determined that SYNROC has had significant alterations to the zirconolite (CaZrTi₂O₇) phase, with respect to the chemical environment of Ti. However, results from both the Zr K-edge and Nd L₃-edge XANES support the continued existence of a zirconolite phase in the SYNROC synthesized using the IMFs as starting reagents. (author)

[en] This work presents a mechanism of deformation-twin-induced grain boundary failure, and demonstrates the mechanism using molecular dynamics simulations. Deformation twinning is observed as the dominant mechanism during tensile deformation of columnar nanocrystalline body-centered cubic Mo. As a twin approaches a grain boundary, local stress concentration develops due to the incompatible plastic deformations in the two neighboring grains. The magnitude of the stress concentration increases as the twin widens, leading to grain boundary cracking by nucleation and coalescence of microcracks/voids.

[en] A least-squares minimization approach has been developed to determine depth from magnetic data. The approach is based on fitting a simple dike model convolved with the same horizontal gradient filter as applied to the observed magnetic data. The problem of depth determination from magnetic data has been transformed into a solution to a nonlinear equation of the form f (z) =0. Procedures are also formulated to estimate the effective magnetization inclination and the effective magnetization intensity. The method is applied to synthetic data with and without random errors. Finally, the method is applied to field example from Canada. In all cases determined, the depth parameter is found to be in good agreement with the actual depth. (author)

[en] The new developments summarized in this work represent both theoretical and experimental investigations of the effects of plastic strain generation in shape memory alloys (SMAs). Based on the results of SMA experimental characterization described in the literature and additional testing described in this work, a new 3D constitutive model is proposed. This phenomenological model captures both the conventional shape memory effects of pseudoelasticity and thermal strain recovery, and additionally considers the initiation and evolution of plastic strains. The model is numerically implemented in a finite element framework using a return mapping algorithm to solve the constitutive equations at each material point. This combination of theory and implementation is unique in its ability to capture the simultaneous evolution of recoverable transformation strains and irrecoverable plastic strains. The consideration of isotropic and kinematic plastic hardening allows the derivation of a theoretical framework capturing the interactions between irrecoverable plastic strain and recoverable strain due to martensitic transformation. Further, the numerical integration of the constitutive equations is formulated such that objectivity is maintained for SMA structures undergoing moderate strains and large displacements. The implemented model has been used to perform 3D analysis of SMA structural components under uniaxial and bending loads, including a case of local buckling behavior. Experimentally validated results considering simultaneous transformation and plasticity in a bending member are provided, illustrating the predictive accuracy of the model and its implementation

[en] A method is developed for predicting and formulating realistic synthetic post-detonation debris relevant to a nuclear surface detonation in arbitrary urban settings. Using these methods guides the development of synthetic debris that serves as a tool for developing and validating novel rapid forensic analysis methods. In order to accurately fabricate realistic homogenous surrogate material, the method incorporates regional soil compositions, land use data, and vehicle contributions to the urban environment. (author)

[en] A Kolsky apparatus with numerous modifications has been designed for mechanical characterization of materials at high strain rates. These modifications include employing a highly precise optical table, pillow blocks with Frelon®-coated linear bearings as bar supports and a laser system for better precision bar alignment, etc. In addition, the striker bars were coated with Teflon® to minimize the friction with the gun barrel after removal of the conventional plastic sabots. This new design significantly simplifies the alignment process, improving the final alignment and calibration in the bar system; both are critical for validity and accuracy of the resulting data. An example of a dynamic experiment on a 6061 aluminum specimen by using this newly designed Kolsky bar is also presented

No abstract available

[en] We study the general phenomenon of plastic depinning using a vortex system confined in a Corbino-disc superconductor. For an ordered initial vortex configuration, the vortices driven by a suddenly applied dc current (force) are gradually pinned to random pinning centers, indicating dynamic disordering. This is detected from the decaying of voltage V (t) (mean velocity) toward a steady-state value V^∞. On the other hand, when the initial configuration is disordered, a gradual increase of V (t) toward V^∞ is observed, reflecting dynamic ordering. In both cases, relaxation times to reach the steady state exhibit a power-law divergence at the depinning current. Our results clearly show that the transient response depends on the initial vortex configurations: however, the transient time as well as the final mean vortex velocity only depends on the applied current, and the critical behaviors of the depinning transition are identical. To the best of our knowledge, this work is the first to demonstrate this fact predicted by numerical simulations and other more indirect experiments (e.g. Pérez Daroca et al 2011 Phys. Rev. B 84 012508). (paper)