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1. Rapid Learning and Knowledge-Gap Closure During the Conceptual Design Phase – Rapid R&D.

Author

Camarda, Charles J., Scotti, Stephen J., Kunttu, Iivari, and Perttula, Antti

Subjects
CONCEPTUAL design, NEW product development, CONCURRENT engineering, KNOWLEDGE gap theory, FAILURE mode & effects analysis
Abstract

New product development strategies, such as set-based concurrent engineering design (SBCED) or set-based design (SBD), have demonstrated improved ways to address knowledge gaps in alternate design concepts prior to the decision to select a single concept for development. Most of the corpus in this field addresses engineering product development that relies on systems and subsystems with years of prior experience in testing, development, and operation. These often have known or existing solutions, and use state-of-the-art (SOA), or near SOA technology. In addition, most papers do not dive into the details of how knowledge was attained to rapidly close critical knowledge gaps. This paper attempts to explain how a research-based method to construct knowledge can accelerate the knowledge capture critical for developing solutions to extremely challenging problems. This rapid R&D methodology enables a rapid acquisition of critical knowledge to understand potential failure modes of concepts in a set-based way. Thus, it enables intelligent decisions for the selection of the final concept as well as the continuous maturation of parallel concepts. The continuous, parallel maturation of multiple concepts enables effective off-ramps in the design process as requirements and new knowledge arise in the course of the development program, without incurring excessive rework, cost growth, and schedule creep. The goal of this paper is to describe a method that accelerates the generation of critical knowledge early in the conceptual design phase, as a way to close knowledge gaps quickly, and thus enable intelligent design decisions and concept selections early in the product development cycle. The methodological descriptions are illustrated with case examples from NASA technology development. [ABSTRACT FROM AUTHOR]

Published
2020
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2. Approximations in Optimization of Damage Tolerant Structures

Author

Garcelon, John H., Haftka, Raphael T., and Scotti, Stephen J.

Subjects
Structural optimization -- Analysis, Structural dynamics -- Analysis, Aerospace and defense industries, Business
Abstract

Approximations for structural response and design sensitivities significantly reduce the computational cost of structural optimization. To be useful, the approximation must be accurate and computationally efficient. Damage tolerant design puts even more stringent computational demands on optimization procedures and approximations due to the large structural changes inherent in damage. A robust approximation is evaluated and extended to include design sensitivities. It is implemented in an optimization procedure and tested. It is shown that this approximation is accurate and efficient for damage tolerant optimum design of complex structural models. Last, a qualitative measure is developed and tested that estimates the computational savings using these approximations.

Published
2000

3. Three-dimensional elastic constitutive relations of aligned carbon nanotube architectures

Author

Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Department of Mechanical Engineering, Stein, Itai Y., Handlin, Daniel, Guzman de Villoria, Roberto, Cebeci, Hulya Geyik, Parsons, Ethan M., Socrate, Simona, Wardle, Brian L., Scotti, Stephen, Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Department of Mechanical Engineering, Stein, Itai Y., Handlin, Daniel, Guzman de Villoria, Roberto, Cebeci, Hulya Geyik, Parsons, Ethan M., Socrate, Simona, Wardle, Brian L., and Scotti, Stephen

Abstract

Tailorable anisotropic intrinsic and scale-dependent properties of carbon nanotubes (CNTs) make them attractive elements in next-generation advanced materials. However, in order to model and predict the behavior of CNTs in macroscopic architectures, mechanical constitutive relations must be evaluated. This study presents the full stiffness tensor for aligned CNT-reinforced polymers as a function of the CNT packing (up to ∼20 vol. %), revealing noticeable anisotropy. Finite element models reveal that the usually neglected CNT waviness dictates the degree of anisotropy and packing dependence of the mechanical behavior, rather than any of the usually cited aggregation or polymer interphase mechanisms. Combined with extensive morphology characterization, this work enables the evaluation of structure-property relations for such materials, enabling design of aligned CNT material architectures., NECST Consortium, United States. Army Research Office (Contract No. W911NF- 07-D-0004), United States. Army Research Office (Contract No. W911NF-13-D-0001), United States. National Aeronautics and Space Administration (NASA Space Technology Research Fellowship Grant No. NNX11AN79H), National Science Foundation (U.S.) (Grant No. CMMI-1130437)

Published
2014

4. Testicular relapse of non-Hodgkin Lymphoma noted on FDG-PET

Author

Scotti, Stephen D, Laudadio, Jennifer, Scotti, Stephen D, and Laudadio, Jennifer

Abstract

Testicular relapse of leukemia and lymphoma is a well-recognized phenomenon, with testicular relapse of lymphoma being more common in the adult population and leukemia relapse being more common in the pediatric population. With the advent of F-18 fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in the evaluation of lymphoma it is possible to evaluate testicular uptake of FDG and to detect primary testicular lymphoma or testicular relapse on the FDG-PET examination. Testicular relapse of non-Hodgkin lymphoma (NHL) detected on FDG-PET has been reported previously. We report an additional case in which there was testicular activity at presentation, a response to therapy (orchiectomy not performed) and then testicular relapse followed by orchiectomy. We review the literature with regard to testicular recurrence and testicular uptake of FDG-PET. There have been studies that have examined normal standardized uptake value maximum (SUVmax) values in the testicle, with normal values ranging from 2.81 (30-39 years) to 2.18 (80-89 years), depending upon age. However, it should be noted that there could be considerable variability in SUVmax values depending upon the units used (e.g. normalized to lean body mass vs. body weight) and depending upon examination variables such as dietary conditions, muscle uptake or extravasation of FDG. Elevated activity or lateralizing activity should be viewed with suspicion, with etiologies including primary testicular tumor, primary or secondary testicular lymphoma and metastatic disease with other etiologies less likely.

Published
2009

8. Compression After Impact Experiments and Analysis on Honeycomb Core Sandwich Panels with Thin Facesheets

Author

McQuigg, Thomas Dale, Aerospace and Ocean Engineering, Kapania, Rakesh K., Patil, Mayuresh J., Scotti, Stephen J., Seidel, Gary D., and Walker, Sandra P.

Subjects
Damage Tolerance, Finite element method, Compression After Impact, Honeycomb Core Sandwich Panels, Multicontinuum Failure Theory
Abstract

A better understanding of the effect of impact damage on composite structures is necessary to give the engineer an ability to design safe, efficient structures. Current composite structures suffer severe strength reduction under compressive loading conditions, due to even light damage, such as from low velocity impact. A review is undertaken to access the current state-of-development in the areas of experimental testing, and analysis methods. A set of experiments on Nomex honeycomb core sandwich panels, with thin woven fiberglass cloth facesheets, is described, which includes detailed instrumentation and unique observation techniques. These techniques include high speed video photography of compression after impact (CAI) failure, as well as, digital image correlation (DIC) for full-field deformation measurements. The effect of nominal core density on the observed failure mode is described. A finite element model (FEM) is developed to simulate the experiments performed in the current study. The purpose of this simulation is to predict the experimental test results, and to conrm the experimental test conclusions. A newly-developed, commercial implementation of the Multicontinuum Failure Theory (MCT) for progressive failure analysis (PFA) in composite laminates, Helius:MCT, is included in this model. The inclusion of PFA in the present model gives it the new, unique ability to account for multiple failure modes. In addition, significant impact damage detail is included in the model as a result of a large amount of easily available experimental test data. A sensitivity study is used to assess the effect of each damage detail on overall analysis results. Mesh convergence of the new FEM is also discussed. Analysis results are compared to the experimental results for each of the 32 CAI sandwich panel specimens tested to failure. The failure of each specimen is accurately predicted in a high-fidelity, physics-based simulation and the results highlight key improvements in the understanding of honeycomb core sandwich panel CAI failure. Finally, a parametric study highlights the strength benefits compared to mass penalty for various core densities. Ph. D.

Published
2011

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