A5036009808- High-Velocity Impact and Material Behavior
- High-pressure geophysics and materials
- Energetic Materials and Combustion
- Laser-Plasma Interactions and Diagnostics
- Electromagnetic Launch and Propulsion Technology
- Astro and Planetary Science
- Planetary Science and Exploration
- Nuclear Physics and Applications
- Microstructure and mechanical properties
- Diamond and Carbon-based Materials Research
- Nuclear Materials and Properties
- Advanced X-ray Imaging Techniques
- Metal and Thin Film Mechanics
- Intermetallics and Advanced Alloy Properties
- Surface Treatment and Residual Stress
- Solid State Laser Technologies
- Metallic Glasses and Amorphous Alloys
- Laser-induced spectroscopy and plasma
- Advanced X-ray and CT Imaging
- Medical Imaging Techniques and Applications
- Granular flow and fluidized beds
- Additive Manufacturing Materials and Processes
- Structural Response to Dynamic Loads
- Ion-surface interactions and analysis
- Photorefractive and Nonlinear Optics
University of Oxford
2018-2024
Science Oxford
2019-2024
Imperial College London
2013-2023
European Synchrotron Radiation Facility
2020
Science and Technology Facilities Council
2016
Daresbury Laboratory
2016
Sci-Tech Daresbury
2016
Diamond Light Source
2016
Imperial Valley College
2015
Los Alamos National Laboratory
2009-2011
We present the free surface response of 2, 5, and 8 μm aluminum films to shocks generated from chirped ultrafast lasers. find two distinct steps measured velocity that indicate a separation faster elastic wave slower plastic wave. resolve waves times as short 20 ps. peak velocities high 1.4 km/s corresponding stresses 12 GPa. The rapidly decay with increasing sample thickness. magnitude both temporal between them was strongly dependent on incident laser drive energy.
This study demonstrates the improvement in fatigue strength of additive manufacturing (AM) metals such as laser-based powder bed fusion by post-processing. Titanium alloy samples manufactured fused (PBF) Ti6Al4V produced through laser sintering (LS), treated submerged peening (SLP), cavitation (CP), and shot accelerated via a water jet (SPwj), were subjected to torsional testing compared with as-built specimen. At SLP, ablation (LA) (LC) which was developed following LA. A cavitating used...
Abstract<title/>The shock compression of reactive powder mixtures can yield varied chemical behaviour with occurrence mechanochemical reactions in the timescale high pressure state, or thermochemical temperature equilibration, simply creation dense packed highly state material. The principal challenge has been to understand processes that distinguish between (shock induced) and assisted) reactions, which broad implications for synthesis novel metastable non-equilibrium materials, design...
This article offers a comprehensive experimental and theoretical study of the causes thermal hardening in FCC Al BCC Fe at high strain rates, with aim to shed light on important mechanisms governing deformation failures materials subjected shocks impacts very rates. Experimental evidence regarding temperature dependence dynamic yield point shock loaded 107 s−1 is provided. The increases range 125K–795K; for same loading temperate range, remains largely insensitive. A Multiscale Discrete...
When a metal is subjected to extremely rapid compression, shock wave launched that generates dislocations as it propagates. The evolves into characteristic two-wave structure, with an elastic preceding plastic front. It has been known for more than six decades the amplitude of decays farther travels metal: this "the decay precursor." precursor dynamic yield point because marks transition from behavior. In Letter we provide full explanation attenuation using first method dislocation dynamics...
Adiabatic shear band (ASB) formation in textured HCP polycrystals has been investigated under regimes of high rate compression and loading using dynamic thermo-mechanically coupled, dislocation-based crystal plasticity modelling. The balance between plastic dissipation leading to internal heat generation versus thermal diffusion at a crystallographic length scale shown be pivotal for the or otherwise ASBs. Micro-texture found have key role both advancing inhibiting growth, its control offers...
Betatron radiation from laser wakefield accelerators is an ultrashort pulsed source of hard, synchrotron-like x-ray radiation. It emanates a centimetre scale plasma accelerator producing GeV level electron beams. In recent years betatron has been developed as unique capable high resolution images in compact geometries. However, until now, the short pulse nature this not exploited. This report details first experiment to utilize image rapidly evolving phenomenon by using it radiograph driven...
The present study demonstrates experimental evidence of subsurface mesoscale damage initiation and evolution in angle-ply CFRP laminates under high strain-rate loading at low temperatures using synchrotron-based X-ray MHz radiography. A bespoke set loading, temperature control in-situ imaging systems were applied to simultaneously correlate mechanical response with observed a time-resolved manner. results demonstrate that independent temperature, evolved following specific sequence; firstly...
Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal situ caries models. The aim this study was determine the effect incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation 1.56% w/w GIC significantly increased microtensile bond strength (33%) compressive (23%) enhanced release calcium, phosphate, fluoride ions at neutral acidic pH....
In this article, it is demonstrated that current methods of modelling plasticity as the collective motion discrete dislocations, such two-dimensional dislocation (DDP), are unsuitable for simulation very high strain rate processes (10 6 s −1 or more) plastic relaxation during shock loading. Current DDP models treat dislocations quasi-statically, ignoring time-dependent nature elastic fields dislocations. It shown assumption introduces unphysical artefacts into system when simulating...
Abstract Understanding Warm Dense Matter (WDM), the state of planetary interiors, is a new frontier in scientific research. There exists very little experimental data probing WDM states at atomic level to test current models and those performed up now are limited quality. Here, we report proof-of-principle experiment that makes microscopic investigations materials under dynamic compression easily accessible users with quality close achievable ambient. Using single 100 ps synchrotron x-ray...
Numerical simulations of shock wave propagation through discretely represented powder mixtures were performed to investigate the characteristics deformation and mixing in Ni+Al system. The initial particle arrangements morphologies imported from experimentally obtained micrographs pressed at densities range 45%–80% theoretical maximum density (TMD). Simulations using these for each compact subjected driver velocities (Up) 0.5, 0.75, 1km∕s, resulting velocity (Us) was used construct Us-Up...
The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range transient deformation processes in materials under extreme conditions. In this paper, the challenges high-resolution time-resolved indirect X-ray detection are reviewed context dynamic experiments. particular, discussion targeted at two-dimensional integrating detector methods, such as those focused on radiography diffraction response scintillator to...
A new generation of cameras has made ultra-high-speed x-ray imaging at synchrotron light sources a reality, revealing never-before-seen details sub-surface transient phenomena. We introduce versatile indirect system capable capturing-for the first time-hundreds sequential pulses in 16-bunch mode European Synchrotron Radiation Facility, recording 5.68 Mfps over dozens microseconds, with an effective exposure 100 ps. The multiplex camera construction allows for various arrangements, including...
Abstract Extraordinary states of highly localised pressure and temperature can be generated upon the collapse impulsively driven cavities. Direct observation this phenomenon in solids has proved challenging, but recent advances high-speed synchrotron radiography now permit study transient, subsurface events real time. We present a on shock-induced spherical cavities solid polymethyl methacrylate medium, to shock between 0.49 16.60 GPa. Utilising multi-MHz phase contrast radiography, extended...
Abstract The effects of cold work on dynamic flow strength is studied through measurements dislocation density and elastic precursor attenuation in shocked aluminium. High-purity aluminium Al 6082 alloy samples are subjected to up three passes rotary swaging, a severe plastic deformation (SPD) technique, order produce large variations starting material conditions. Detailed characterisation performed using electron backscatter diffraction (EBSD) transmission microscopy (TEM) determine the...
Mixtures of flake-shaped nickel and spherical aluminum powders have been subjected to shock-loading up 6 GPa investigate the occurrence shock-induced chemical reactions. The high-pressure Hugoniot state is determined through time-resolved measurements input stress shock transit time specimen. An increase in velocity observed above levels 3.5 GPa, suggesting initiation an ultrafast reaction formation Ni-Al compound(s) occurring scale state.
Porous materials are of great interest because improved energy absorption over their solid counterparts. Their properties, however, have been difficult to optimize. Additive manufacturing has emerged as a potential technique closely define the structure and properties porous components, i.e. density, strut width pore size; behaviour these at very high impact energies remains largely unexplored. We describe an initial study dynamic compression response lattice fabricated through additive...
Abstract Chondritic meteorites are fragments of asteroids, the building blocks planets, that retain a record primordial processes. Important in their early evolution was impact-driven lithification, where porous mixture millimetre-scale chondrule inclusions and sub-micrometre dust compacted into rock. In this Article, shock compression analogue precursor chondrite material probed using state art dynamic X-ray radiography. Spatially-resolved particle velocities, front thicknesses were...
In this paper, we present the dynamic response of commercially pure copper subjected to combined tension-torsion loads representative real case impact scenarios. Experiments were conducted both quasi statically, at a strain rate equal 10−3 s−1, and dynamically rates in region between 500 s−1 1000 s−1. All high experiments using novel Split Hopkinson Tension-Torsion Bar instrumented with high-speed photographic equipment. The loading demonstrate capability apparatus generate longitudinal...