Publications

On Thursday, August 25, 2016, the ATDM L2 milestone review panel met with the milestone team to conduct a final assessment of the completeness and quality of the work performed. First and foremost, the panel would like to congratulate and commend the milestone team for a job well done. The team completed a significant body of high-quality work toward very ambitious goals. Additionally, their persistence in working through the technical challenges associated with evolving technology, the nontechnical challenges associated with integrating across multiple software development teams, and the many demands on their time speaks volumes about their commitment to delivering the best work possible to advance the ATDM program. The panel’s comments on the individual completion criteria appear in the last section of this memo.

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In our development team at Sandia National Laboratories we have honed our Scrum processes to where we continually deliver high-performance engineering analysis software to our customers. We deliver despite non-ideal circumstances, including development work that can be categorized as exploratory research, regular use of part-time developers, team size that varies widely among Sprints, highly specialized technical skill sets and a broad range of deliverables. We believe our methodologies can be applied to many research-oriented environments such as those found in government laboratories, academic institutions and corporate research facilities. Our goal is to increase the adoption of Lean/Agile project management in these environments by sharing our experiences with those research-oriented development teams who are considering using Lean/Agile, or have started and are encountering problems. In this paper we discuss how we create and prioritize our product backlog, write our user stories, calculate our capacity, plan our Sprints, report our results and communicate our progress to customers. By providing guidance and evidence of success in these areas we hope to overcome real and perceived obstacles that may limit the adoption of Lean/Agile techniques in research-oriented development environments. © 2013 IEEE.

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Modal-based methods for structural health monitoring require the identification of characteristic frequencies associated with a structure's primary modes of failure. A major difficulty is the extraction of damage-related frequency shifts from the large set of often benign frequency shifts observed experimentally. In this study, we apply peridynamics in combination with modal analysis for the prediction of characteristic frequency shifts throughout the damage evolution process. Peridynamics, a nonlocal extension of continuum mechanics, is unique in its ability to capture progressive material damage. The application of modal analysis to peridynamic models enables the tracking of structural modes and characteristic frequencies over the course of a simulation. Shifts in characteristic frequencies resulting from evolving structural damage can then be isolated and utilized in the analysis of frequency responses observed experimentally. We present a methodology for quasi-static peridynamic analyses, including the solution of the eigenvalue problem for identification of structural modes. Repeated solution of the eigenvalue problem over the course of a transient simulation yields a data set from which critical shifts in modal frequencies can be isolated. The application of peridynamics to modal analysis is demonstrated on the benchmark problem of a simply-supported beam. The computed natural frequencies of an undamaged beam are found to agree well with the classical local solution. Analyses in the presence of cracks of various lengths are shown to reveal frequency shifts associated with structural damage. Copyright © 2012 by ASME.

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