Upper Saint Clair, PA, United States
Upper Saint Clair, PA, United States

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Woelke P.B.,Thornton Tomasetti | Hiriyur B.K.,Thornton Tomasetti | Nahshon K.,Naval Surface Warfare Center Carderock Division | Hutchinson J.W.,Harvard University
Engineering Fracture Mechanics | Year: 2017

This paper addresses the numerical simulation of plasticity and ductile fracture of large scale structures (e.g. ships, railcars, automobiles) fabricated with welds that exhibit appreciably lower strength than the plate material, often referred to as weld undermatching. It has been observed, both numerically and experimentally, that for such structures the weld undermatching often leads to plasticity and fracture being limited to the weld and heat affected zone (HAZ). While the large size of the structures of interest precludes the use of a refined three-dimensional element mesh capable of capturing the details of the weld/HAZ behavior, cohesive zones are ideal for capturing the overall effects of undermatched weld plasticity and fracture on a structural scale. This paper focuses on establishing a systematic calibration process for determining the cohesive zone constitutive behavior and examining the validity of this approach in the context of mode I tearing of a large welded two-layer AA6061-T6 sandwich panel. First, test data from a welded coupon is used to calibrate the cohesive law. Tearing fracture of this panel is examined using the established cohesive law to represent weld/HAZ along with elastic-plastic shell elements, with in-plane dimensions much greater than the layer thickness, to represent the parent metal. It was verified that, for this structure, plasticity was indeed confined to the welds and heat affected zones, and that the behavior of the panel was captured with reasonable fidelity. © 2017 Elsevier Ltd

Ginn H.L.,University of South Carolina | Hingorani N.,EPRI | Sullivan J.R.,Naval Surface Warfare Center Carderock Division | Wachal R.,Manitoba HVDC Research Center Inc. | Wachal R.,University of Winnipeg
Proceedings of the IEEE | Year: 2015

When the control functions of various types of power electronics systems are examined, a significant degree of common functionality emerges, irrespective of the target application. It is possible to define hierarchical control architectures for these systems using common interface definitions between control system divisions or layers. Such definitions enable the use of common designs for multiple applications and the use of commercially available electronics and communications modules allowing cost reduction in power electronics applications. This paper presents various partitioning strategies of a hierarchical control architecture for use in high power electronics control systems and defines various parameters/functions that need to be handled within each layer, and those that need to be communicated between the layers. Each layer has characteristic processing and communication speed requirements, irrespective of the final applications. © 1963-2012 IEEE.

Tran K.N.,Naval Surface Warfare Center Carderock Division | Salamanca-Riba L.,University of Maryland University College
Advanced Engineering Materials | Year: 2013

Sensitized aluminum 5456-H116 is characterized by a continuous network of β phase. The use of ultrasonic impact treatment refines the near surface microstructure to produce nanograins that vary in size from 2 to 200 nm in diameter. The deformation layer does not exhibit the presence of a continuous β phase indicating that the near surface microstructure undergoes recrystallization. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gibson B.T.,Vanderbilt University | Lammlein D.H.,Naval Surface Warfare Center Carderock Division | Prater T.J.,United Launch Alliance | Longhurst W.R.,Austin Peay State University | And 5 more authors.
Journal of Manufacturing Processes | Year: 2014

This article provides an introduction to the basic principles of friction stir welding (FSW) as well as a survey of the latest research and applications in the field. The basic principles covered include terminology, material flow, joint configurations, tool design, materials, and defects. Material flow is discussed from both an experimental and a modeling perspective. Process variants are discussed as well, which include self-reacting (SR-FSW), stationary shoulder, friction stir processing (FSP), friction stir spot welding (FSSW), assisted FSW, and pulsed FSW. Multiple aspects of robotic friction stir welding are covered, including sensing, control, and joint tracking. Methods of evaluating weld quality are surveyed as well. The latest applications are discussed, with an emphasis on recent advances in aerospace, automotive, and ship building. Finally, the direction of future research and potential applications are examined. © 2013 The Society of Manufacturing Engineers.

Costanzo F.A.,Naval Surface Warfare Center Carderock Division
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

Today, many underwater explosion (UNDEX) shock problems are solved using direct transient analysis methods applied to detailed finite element models. Solution methodologies are diverse and complex, and necessarily include detailed representations of both the dynamic loading and the structure. As a result of these computational complexities, it is imperative that all such solution strategies also employ simple tools to benchmark and "ground" the more complex solutions. This paper illustrates the use of simple bounding solutions in generating reliable estimates of the global dynamic response of surface ship and submarine structures subjected to underwater shock. Three well documented methodologies are presented, including the Taylor flat plate analogy for both air- and water-backed plates, the peak translational velocity (PTV) method, and the application of the conservation of momentum principle to estimating the vertical kickoff velocity of floating structures (spar buoy approach). Derivations of the governing equations associated with each of these solution strategies are presented, along with a description of the appropriate ranges of applicability. Finally, practical applications of these "bounding" methods are summarized.

Lang B.W.,Naval Surface Warfare Center Carderock Division
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

This paper presents an overview of a recently published American National Standard [1] to be used for testing equipment that will be subjected to shock. This standard provides shock test parameters for testing a broad range of equipment, which will ensure inherent levels of shock resistance. It defines test requirements and severity thresholds for a large range of shock environments, including but not limited to shipping, transport, and rugged operational environments. The severity thresholds herein can be associated with specific shock environments and should be chosen for a given application on a case-by-case basis. The intent of the standard's requirements is to outline those elements necessary for verification of a successful and accurate shock test, but not the specific test method. This standard will allow vendors to better market, and users to more easily identify, equipment that will operate or simply survive in rugged shock environments. ©2010 Society for Experimental Mechanics Inc.

Costanzo F.A.,Naval Surface Warfare Center Carderock Division
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

This paper presents a brief introduction to the basic fundamentals of underwater explosions, including discussion of the features of explosive charge detonation, the formation and characterization of the associated shock wave, bulk cavitation effects, gas bubble formation and dynamics, surface effects and shock wave refraction characteristics. Illustrations of each of these fundamental aspects of underwater explosion (UNDEX) loadings are made with a set of videos from a variety of experimental testing events. In addition, analyses of associated measured loading and dynamic response data, as well as descriptions of supporting numerical simulations of these events are presented. At the conclusion of this paper, each of these UNDEX effects are tied together with a summary discussion and illustration. ©2010 Society for Experimental Mechanics Inc.

Ostanek J.K.,Naval Surface Warfare Center Carderock Division
Journal of Turbomachinery | Year: 2014

In much of the public literature on pin-fin heat transfer, the Nusselt number is presented as a function of Reynolds number using a power-law correlation. Power-law correlations typically have an accuracy of 20% while the experimental uncertainty of such measurements is typically between 5% and 10%. Additionally, the use of power-law correlations may require many sets of empirical constants to fully characterize heat transfer for different geometrical arrangements. In the present work, artificial neural networks were used to predict heat transfer as a function of streamwise spacing, spanwise spacing, pin-fin height, Reynolds number, and row position. When predicting experimental heat transfer data, the neural network was able to predict 73% of array-averaged heat transfer data to within 10% accuracy while published power-law correlations predicted 48% of the data to within 10% accuracy. Similarly, the neural network predicted 81% of row-averaged data to within 10% accuracy while 52% of the data was predicted to within 10% accuracy using power-law correlations. The present work shows that first-order heat transfer predictions may be simplified by using a single neural network model rather than combining or interpolating between power-law correlations. Furthermore, the neural network may be expanded to include additional pin-fin features of interest such as fillets, duct rotation, pin shape, pin inclination angle, and more making neural networks expandable and adaptable models for predicting pin-fin heat transfer.

Costanzo F.A.,Naval Surface Warfare Center Carderock Division
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2012

Often times during the early stage design process associated with a new ship, the Navy conducts underwater explosion testing of ship hull panels. These tests typically accompany the introduction of either new materials and/or new structural design concepts associated with panel dimensioning and stiffening details. In the planning of such dynamic panel tests, it is of great value to have available tools that enable rapid estimation of panel peak responses to UNDEX loads such that parametric studies can be achieved. This paper documents the development of one such analysis tool, which involves an analytic solution of the early UNDEX response of an air-backed panel bay. This solution strategy applies a separation of variables technique to a classical two dimensional flat rectangular plate with a dynamic loading function applied as an enforced initial velocity field. This velocity field is determined by applying Taylor's theory for computing the UNDEX-induced initial kickoff velocity of an infinite air-backed flat plate. The resulting analytic solution provides accurate estimates of the stress, velocity and displacement fields of the idealized flat rectangular plate representing the ship panel bay. Verification comparisons are made with actual experimental data, and guidelines for the applicability of the method are provided. © The Society for Experimental Mechanics, Inc. 2012.

Talmy I.G.,Naval Surface Warfare Center Carderock Division | Zaykoski J.A.,Naval Surface Warfare Center Carderock Division | Opeka M.M.,Naval Surface Warfare Center Carderock Division
Journal of the European Ceramic Society | Year: 2010

Multi-phase ceramics in the TaC-TaB2-C system were prepared from TaC and B4C mixtures by reactive pressureless sintering at 1700-1900°C. The pressureless densification was promoted by the use of nano-TaC and by the presence of active carbon in the reaction products. The presence of TaB2 inhibited grain growth of TaC and increased the hardness compared to pure TaC. If a coarse TaC powder was used, the compositions did not densify. In contrast, pure nano-TaC was pressureless sintered at 1800°C by the addition of 2wt.% carbon introduced as carbon black or graphite. The introduction of carbon black resulted in fully dense TaC ceramics at temperatures as low as 1500°C. The grain size of nominally pure TaC ceramics was a strong function of carbon stoichiometry. Enhanced grain size in sub-stoichiometric TaC, compared to stoichiometric TaC, was observed. Additional work is necessary to optimize processing parameters and evaluate the properties of ceramics in the TaC-TaB2-C system. © 2010.

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