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Daykin, Edward

Publications and source records attributed to Daykin, Edward.

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Modeling of Hypervelocity Impact Experiments Using Gamma-SPH Technique

Hypervelocity impact research has been conducted using light gas guns to characterize materials under shock conditions. Hypervelocity impact produces high pressure and temperature states during the projectile-target interaction. Projectile and target materials both experience severe localized deformation under these conditions, which creates stretching, bending, and complete perforation in thin target plates. Relatively thick target plates show several failure modes, such as spalling, petalling, discing, and plugging. These failure modes are mostly controlled by several factors such as impact velocity, material properties, loading geometry, etc. Gas gun experiments were performed to measure the plastic deformation of steel plates during hypervelocity impact. The MPDV system was used to measure free surface velocity during these experiments. Simulation models developed in the IMPETUS AFEA Gamma SPH solver show that the physical measurements of impact cratering and bulge are in reasonable agreement with simulation results. Velocity profiles are in general agreement with the experiments capturing all the major features observed experimentally.

36 MATERIALS SCIENCE↗
DOE OSTI2017

An Overview of Broadband Laser Ranging (BLR) Architecture and Measurement Considerations

Broadband Laser Ranging (BLR) is a developmental diagnostic intended to measure the position of rapidly moving surfaces in combination with optical velocimetry. Design and employment of a BLR diagnostic on dynamic experiments requires consideration for both the inherent measurement system tradeoffs as well as architectural choices appropriate to the nature of investigation. The diagnostic uses spectral interferometry to measure distance by mapping femtosecond laser pulses to the time domain via chromatic dispersion within the fiber-optic architecture. The system parameters and governing equations that describe measurement range, resolution, and Doppler sensitivity will be discussed. We will also briefly review the impact of diagnostic architectural choices including: nature of interferometer, Interferometric dispersion matching, optical amplification, integration of optical velocimetry, BLR calibration, and field operability. To summarize we will present the architectural and operational approach currently being pursued by NSTec within an on-going collaboration between NSTec, Lawrence Livermore and Los Alamos National Labs.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Failure Mechanisms in Fored, Layered, and Additive Manufactured Titanium due to Hypervelocity Impact: Experiments and Simulations

This article presents a study of dynamic failure events in forged, layered, and additive manufactured (AM) titanium alloy subject to hypervelocity impact. Experiments were conducted using a two stage light-gas gun, 0.22-caliber Lexan projectiles, and different types of titanium target plates. A four-channel Photonic Doppler Velocimetry (PDV) system was used to study the free surface velocities to provide an understanding of the different failure mechanisms in these materials. The experimental measurements were used to validate computational simulations, which describe the behavior of these materials under shock. It was determined that AM, forged titanium, and multi-layered stacks produce similar velocity profiles during the early stage of impact, with the AM targets exhibiting spall at lower velocities and the multi-layered stacks exhibiting vibrations between plates. Simulations of solid and layered forged materials provide a good match to experimental data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Single-Crystal Copper Research

Presentation on the use of single-crystal copper to examine whether texture in polycrystalline metals is important, and when.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Comparison of Failure Mechanisms Due to Shock Propagation in Forged, Layered, and Additive Manufactured Titanium

This chapter for the Stewardship Science Academic Programs Annual Report describes a project focused on characterizing the shock propagation and failure mechanisms in forged, layered, and additive manufactured (AM) materials. The AM process fabricates a part layer by layer, which provides opportunities to tailor geometry and optimize structural performance in addition to minimizing the amount of material waste for odd shaped parts.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Grain-Selective MPDV Experiments NLV-04-14, Year 2 of 2

Presentation describes project to better understand shocked material properties through application of multi-point Doppler velocimetry (MPDV) and to develop diagnostic techniques to further leverage MPDV for gas gun experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Characterization of Shock Propagation and Failure Mechanisms in Composite and Additive Manufactured Materials NLV-16-15, Year 1 of 3

Presentation describes effort to introduce experimental and simulation techniques for understanding the behavior of additive manufactured titanium under shock loading by conducting a series of ballistic impact experiments with two-stage light gas gun on titanium targets and using Photonic Doppler Velocimetry (PDV) techniques to measure free surface velocity.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Dynamic-range studies and improvements for multiplexed photonic Doppler velocimetry

This paper presents studies of the dynamic range achievable with multiplexed photonic Doppler velocimetry (MPDV) measurements, and demonstrates techniques to extend the dynamic range. Improved dynamic range for MPDV measurements is needed in order to track the velocity of the free surface behind a cloud of ejecta. Therefore, the authors have undertaken theoretical and experimental studies of factors affecting dynamic range, particularly in cases where the large number of MPDV probe points precludes high illumination power on each channel. To quantify the potential dynamic range of a given MPDV configuration, they introduce a metric called the frequency-domain number of bits, FNOB, which is less stringent than the formally defined equivalent number of bits (ENOB). This new metric is simple to compute in the lab, and it is well suited to conventional PDV analysis, which does not require digitizer phase coherence beyond tens of nanoseconds.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Use of a Multiplexed Photonic Doppler Velocimetry (MPDV) System to Study Plastic Deformation of Metallic Steel Plates in High Velocity Impact

High-velocity impact experiments with a gas gun pose unique challenges, in terms of experimental setup and computational simulation, since the projectile-target interaction creates extreme pressure and temperature within few micro seconds. The objective of this study is to accurately measure the plastic deformation of plates under projectile impact that does not lead to full penetration. In this work, free surface velocities at the back side of target plates are measured using the newly developed Multiplexed Photonic Doppler Velocimetry (MPDV) system, which is an interferometric fiber-optic technique which can measure velocity from the Doppler shift of the light reflected from the moving back surface of the target. The MPDV system allows measurements of velocity from different locations on the target plate using multiple optical fiber probes oriented in specific directions and patterns. Data are reduced using a Fast Fourier transformation (FFT) technique to obtain the free surface velocity profiles. These velocity profiles can present insights into the dynamic behavior of impacted materials under shock loading conditions.

MPDV, multiplexing, high-velocity impact, velocime↗
DOE OSTI2015

Modeling Plastic Deformation of Steel Plates in Hypervelocity Impact Experiments

Hypervelocity impact experiments were done with a two-stage light gas gun to study the plastic deformation of metallic plates. Cylindrical Lexan projectiles were fired at A36 steel target plates with a velocity range of 4.5-6.0 km/s. Experiments were designed to produce a front side impact crater and a permanent bulging deformation on the back surface of the target while preventing complete perforation. Free surface velocities from the back surface of target plate were acquired using the newly developed Multiplexed Photonic Doppler Velocimetry (MPDV) system. Two different computational techniques were developed to simulate this type of experiment: Lagrangian-based smooth particle hydrodynamics (SPH) in LS-DYNA and the Eulerian-based hydrocode CTH. Parameters for material models including equation of state, compressive strength, and spall model were selected to obtain highest fidelity numerical results to compare with experiment.

36 MATERIALS SCIENCE↗