Pressure, Energy, Temperature and Extreme Rates (PETER) … · 2019-09-01 · Pressure, Energy,...

7–9 April 2014Grand Connaught Rooms, London, UK

http://peter14.iopconfs.org

Organised by the IOP Shock Wave and Extreme Conditions Group

Pressure, Energy, Temperature and Extreme Rates (PETER)

Conference 2014

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Pressure, Energy, Temperature and Extreme Rates (PETER) Conference 2014

Contents Oral programme………………………………………………………………………………………….2-5

Oral abstracts…………………………………………………………………………………………..6-25

Poster programme………………………………………………………………………………………...26

Poster abstracts……………………………………………………………………………………....27-32

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Programme

Monday 7 April 2014 09:15 Registration and welcome refreshments

Cambria Suite

10:00 Welcome address W G Proud, Institute of Shock Physics, Imperial College London, UK Ampthill Suite

10:25 Chairman: W G Proud, Institute of Shock Physics, Imperial College London, UK (Invited) Orion: A new ultra-high power laser facility for High Energy Density Physics C Danson, AWE, UK

11:10 Experimental research on the cleanness of indirectly laser-driven multimegabar shocks W Zhebin, Laser Fusion Research Center, China Academy of Engineering Physics, People's Republic of China

11:30 The effect of temperature and microstructure on the dynamic strength properties in

shocked metals L Chen, Imperial College London, UK

11:50 Morning refreshment break Cambria Suite

12:10 The microstructural and mechanical response of Tantalum single crystals to one-dimensional shock loading G Whiteman, AWE, UK

12:30 Study on evolution dynamics for the dynamic tensile failure (Spallation) of OFHC X Pei, Institute of Fluid Physics, People's Republic of China

12:50 CTH simulations of impact loaded cellular structures formed by selective laser melting R Winter, AWE, UK

13:10 Lunch Cambria Suite

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Tuesday 8 April 2014 09:30 Registration and refreshments

Cambria Suite

10:00 Chairman: K Brown, University of Cambridge, UK (Invited) Effects of blast on the human J Clasper, CBIS, UK Ampthill Suite

10:45 Experimental platforms for studying dynamic responses of tissue to blast-type pressures B Butler, University of Cambridge, UK

11:05 Time-resolved diagnostics in blast, shock and impact studies W G Proud, Imperial, College London, UK / Royal British Legion Centre for Blast Injury Studies, UK


14:10 Chairman: G Appelby Thomas, Cranfield University, UK (Invited) Shock-temperature measurements with emissive layer technique: Application to the polymorphic transition of tin C Chauvin, Comissariat à l’Energie Atomique, France

14:55 The molecular dynamics study on the micro-spallation of metal under shock loading J Chen, Institute of Applied Physics and Computational Mathematics, People's Republic of China

15:15 Deconstruction of a polymer bonded composite Hugoniot D Williamson, University of Cambridge, UK

15:35 Afternoon refreshment break Cambria Suite

15:55 Mechanical failure behaviors of the poled PZT 95/5 under shock compression F Zhang, National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P R China

16:15 High pressure and temperature hydrogenation of graphene D Smith, University of Salford, UK

16:35 Close of day one

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11:45

Dynamic fragmentation of lake quarry granite S S Kirk, The Cavendish Laboratory, Cambridge, UK

12:05 CALCITE: Anisotropy in shock physics G Tear, Institute of Shock Physics, UK

12:25 Age hardening and it’s effects on the shock response of materials J C F Millett, AWE, UK

12:45 Poster session and lunch break Cambria Suite

14:15 Chairman: N Abdul-Karim, University College London, UK (Invited) The effect of boundary conditions on the response of structures when subjected to a blast load – An overview G Nurick, University of Cape Town, South Africa

15:00 Morphology and chemical composition of undetonated post-blast explosive residues N Abdul-Karim, Christopher Ingold Laboratories, University College London, UK

15:20 Dynamic x-ray imaging of subsurface dynamics in high-Z materials at the Diamond Light Source D Eakins, Imperial College London, UK

15:40 Afternoon refreshment break Cambria Suite

16:00 Lecture on the activities of the IOP Shock Wave and Extreme Conditions Group W Proud, Institute of Shock Physics, Imperial College London, UK

16:40

Close of day two

Wednesday 9 April 2014 09:30 Registration and refreshments

Cambria Suite

10:00 Chairman: G Whiteman, AWE, UK (Invited) Hypervelocity shock transformation of natural superhard materials: Crystalline diamond A P Jones, University College London, UK Ampthill Suite

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10:45

Examining the devolatilisation of minerals from impacts using Raman spectroscopy N K Ramkissoon, University of Kent, UK

11:05 Using Raman mapping to determine hypervelocity impact peak shock pressures in

high purity silicon, germanium, gallium arsenide and peridot targets M C Price, University of Kent, UK


11:45 Ballistic response of comminuted ceramics G J Appleby-Thomas, Cranfield University, UK

12:05 Temperature effects on the mechanical behaviour of PZT 95/5 A Khan, Institute of Shock Physics, Imperial College London, UK

12:25 The importance of oxygen and water on the ageing behaviour of a polyethylene glycol based propellant R Tunnell, Imperial College London, UK

12:45 Closing remarks W Proud, Institute of Shock Physics, Imperial College London, UK

13:00 Close of day three and conference

13:00 – 14:00 Lunch Cambria Suite

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(Invited) Orion: A new ultra-high power laser facility for High Energy Density Physics

C Danson

AWE plc., UK

Orion is a high power laser interaction facility designed to meet the requirements of AWE’s technical programme in high energy density physics. The facility consists of ten ‘long’ pulse beamlines (each providing 500J in a 1ns pulse @ 351nm) and two synchronized ultra-short Petawatt beamlines (each providing 500J in a 500fs @ 1053nm). These Petawatt beamlines use adaptive optics within the beamline which allow them to be focused on target with a focused intensity of >1021Wcm-2. One of these Petawatt beamlines can be operated in an ultra-high contrast mode where a sub-aperture (300mm) is frequency doubled generating 200TW to target with a contrast of >1014.

Orion also boasts a comprehensive suite of plasma diagnostics; these include a broad range of optical, particle and X-ray diagnostics. The configuration of many of these key diagnostics is flexible due to the adoption of Ten Inch Manipulator (TIM) interface.

The first experimental campaign to commission Orion, which required heating of aluminium to greater that 500eV at twice solid density, was successfully concluded. The campaigns used one of the short-pulse beams of Orion in high-contrast mode, 100J at 0.53 micron. The emission of aluminium tracer layers buried in either plastic or diamond indicated that temperatures in excess of 600eV (>6 million degrees Celsius) were achieved. When using plastic targets these temperatures were recorded to a depth of ~ 30 microns.

The laser facility has now just completed its first year of

operations and I will report on the initial results of the first experimental campaigns. This will include a discussion of the academic access programme where six weeks of the first year’s operations were made available to the academic community. These first two academic campaigns were both led by the University of Oxford: the first investigates shock/ramp compression of materials generating megabar pressures in solid matter; and the second studying astrophysical phenomena associated with accretion shocks in binary stars.

Experimental research on the cleanness of indirectly laser-driven multimegabar shocks

W Zhebin, Z Chen, D Xiaoxi, W Feng, P Xiaoshi, G Liang, L Zhichao, Z Huan, J Shaoen, Y Jiamin and D Yongkun

Laser Fusion Research Center, China Academy of Engineering Physics, P R China

Shock waves are routinely used to study the behavior of materials at high pressure. Knowledge of the equation of state (EOS) of the material above megabar is critical to the study of inertial confinement fusion(ICF), astrophysics and other high-energy-density physics. High-power lasers can shock material to as high as Gbar Pressures. Different from the direct laser-driven approach, the indirectly laser-driven approach, where the powered pulsed laser energy is first transferred to the thermal x-ray flux by a high-Z cavity(hohlraum) before irradiating on shock sample, has potential to keep shock more spatially uniform(i.e. planarity) and more temporally stable(stability) which seems much valuable to meet the rigid requirement of EOS data accuracy. The cleanness of shock, which means the sample state must be kept

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to unchanged before shock arrive, is very difficult to be kept in environments of laser-driven shock EOS experiment, while its influence on accuracy of EOS data is hard to be quantified and has always been ignored which aroused suspicion of reliability of laser-driven shock EOS data.

An experimental research on the cleanness of indirectly laser-driven multimegabar shock has been performed on SG-Ⅲ prototype laser facility. The quantitative diagnostic of cleanness of shock has been developed which is based on detecting the expansion of rear surface of sample with VISAR. The quantitative diagnostic of preheating source has also been developed which is based on detecting the angular distribution of gold M-band X-ray with MXRD(M-band x-ray diode) array. With aid of those techniques, three types of ways to improve the cleanness of shock can be quantitatively studied: one type is changing target geometry, the second type is applying laser smoothing technique and the third type is to use gas-filled hohlraum. Analysis shows that the laser smoothing technique is surprisingly effective than target geometry to improve the cleanness. Based on the developed techniques, we will improve the shock cleanness of EOS platform on SG-Ⅲ prototype laser facility further and quantitatively evaluate its effect on accuracy of EOS data.

[1] John D. Lindl, The physics basis for ignition using indirect-drive targets on the National Ignition Facility, Phys. Plasmas 11, 339 (2004)

[2] Ron Davidson, Frontiers in High Energy Density Physics: The X-Games of Contemporary Science, The National Academies Press:Washington D.C (2002)

[3] Olson R. E. et al., Shock propagation, preheat, and x-ray burnthrough in indirect-drive inertial confinement fusion ablator materials, Phys. Plasmas, 11, 2778 (2004)

[4] Rothman, S. D., A. M. Evans, et al., Impedance match equation of state experiments using indirectly laser-driven multimegabar shocks, Phys. Plasmas 9,1721 (2002)

The effect of temperature and microstructure on the dynamic strength properties in shocked metals

L Chen1, D Eakins1, D Swift2, M Kumar2, J Florando2, A Lazicki2 and J Hawreliak2 1Imperial College London, UK, 2Livermore National Lab, USA

Dynamic strength properties of materials depend largely on microstructure and can vary with temperature. Much work has previously been done to explore temperature effects on metals at high strain rates, specifically seeking to understand the transition from thermal activation to phonon drag as the rate-controlling mechanism. Recent efforts have been made to explore further in strain-rate and temperature for various metals. In this talk, we describe experiments performed at Los Alamos National Laboratory’s (LANL) Trident Laser Facility which focused on correlating strength properties of BCC and FCC metals at temperatures extending from 120 K to 800 K. Line-imaging VISAR was employed to reveal distinct features related to dynamic strength, such as the transition from elastic to plastic deformation during the first stages of compression. Initial findings indicate that most FCC materials exhibit a dependency of strength on temperatures. In the future, these results will be molecular dynamic simulations and used to develop improved models of material strength and gain insight into the physics at play.

The microstructural and mechanical response of Tantalum single crystals to one-dimensional shock loading

G Whiteman1, J C F Millett1, B Pang2 and I P Jones2 1AWE, UK, 2University of Birmingham, UK

In this work, we present a series of plate impact experiments on single crystal tantalum, of orientations [100], [110] and [111]. At low (ca. 6 GPa) pressures, results show that the HEL is highest in the [100] orientation whilst [110] the lowest. Strong variations in shock speed have also been observed, with [100] being the slowest, and both [110] and [111] being comparable to that of a polycrystalline tantalum at higher (23 GPa) stresses. Microstructural

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examination of samples recovered from a 6 GPa loading showed that dislocation density increased from [100], [110] to [111] respectively. The activated slip systems were as expected in the [1-00] and [111] crystals, but in the [110] crystal, Burgers vectors perpendicular to the loading axis were also observed, although at present, the reasons for this are not clear. Some degree of twinning was also noted, with area fractions of 5% in [100], 2% in [110] and 1% in [111]. It is suspected that this is due to lateral release effects, as the samples were potted in epoxy during target assembly, and thus can only be considered to be partially confined.

Study on evolution dynamics for the dynamic tensile failure (Spallation) of OFHC

X Pei, H He, P Li and H Peng

Institute of Fluid Physics, People’s Republic of China

Plate impact experiments have been carried out to examine the influence of tensile duration on dynamically induced damage evolution of OFHC. A new double-layer-sample target experimental technique, tentatively termed as damage-frozen technique, is presented in this paper, with which the tensile duration can be controlled by varying the thickness of the first sample with the total thickness of the double-layer sample fixed. The experimental configuration used in this work permits real-time (VISAR) measurements of the second sample free surface velocity histories, soft recovery, and post experiment metallurgical analysis of the soft recovered samples. The relationship between wave profiles and damage evolution with different tensile duration time is established. The properties of damage evolution dynamics in the spall fracture of ductile metals are studied by theoretical model and simulation. Based on three damage degree, a model of damage evolution dynamics was established in which the process of damage evolution are divided into four stages: nucleation of void, elastic-plastic growth of voids, complete plastic growth of voids and coalescence of voids. Based on the present model, the experiments were simulated, and the factors that affect the damage evolution dynamics and the parameters in the model were discussed.

CTH simulations of impact loaded cellular structures formed by selective laser melting

R Winter1, M Cotton1, E Harris1, D Chapman2, D Eakins2, J Maw1 and G McShane3 1AWE, UK, 2Imperial College London, UK, 3University of Cambridge, UK

Lattices consisting of an array of intersecting stainless steel rods were fabricated into discs using selective laser melting (SLM). Optical metallography showed the average grain size to be ~5µm. Tensile tests on specimens manufactured by the same method as the cellular specimens revealed the yield strength of the SLM 316L to be ~ 0.64 GPa, a value consistent with the observed small grain size. The discs of cellular steel were impacted against solid stainless steel targets at velocities ranging from 300-700 m/s using a gas gun. The waves transmitted to the back surface of the target plates were measured using the Het-V technique. Each of the traces exhibited an elastic wave, followed by a plateau on which was superimposed oscillations of wavelength ~ 1µs. The velocity then rose to a second plateau as a result of a wave reflected from the back surface of the flyer. The elastic and crush pressures (PE and PC) of the cellular material were estimated from the measured yields strength to be 0.44 GPa and 1.9 GPa respectively. These values enabled the experiments to be modeled using the P(α) model in CTH. It was found that a good match to the average levels and timing of the observed velocity plateaus were obtained by CTH. The experimentally observed oscillations were, of course, not reproduced by the P(α) model. Three dimensional “structural” CTH calculations were run in which stl files used to manufacture the cellular samples were imported into CTH. In this case the detailed, dimensioned, structure of the lattice was modeled. These simulations gave a reasonable match to all of the features observed in the experiments including the oscillations which were superimposed on the first and second velocity plateaus at the back surface of the solid steel target. It is anticipated that the validated computer models will now be used to provide an understanding of the deformation processes in the cellular samples and, thereby, to optimise both SLM and other cellular structures for application as energy absorbers.

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(Invited) Shock-temperature measurements with emissive layer technique: Application to the polymorphic transition of tin

C Chauvin, J Petit and F Sinatti

Comissariat à l’Energie Atomique, France

Reliable low temperature measurements of a material under dynamic loadings are of fundamental importance to understand its behavior, to investigate its phase-diagram and to differentiate its EOS. Promising results at material/LiF interface below 15 GPa have been obtained with an emissive layer: the mechanical, thermal and optical properties of this layer are satisfying to reduce uncertainties of the interface temperature and so to deduce the temperature of the material to be compared with the calculations. An application of the temperature measurements around the polymorphic transition in tin are investigated.

However, the technical challenge of this measurement is to deduce, from the collected radiance, an accurate interface temperature depending on the evaluation of the dynamic emissivity. Because the measurement of the emissivity of the thermally radiating shocked surface is still difficult to determine, a way to overcome the lack of knowledge of the emissivity consists in artificially increasing the dynamic emissivity of the material up to an apparent value as close as possible to 1 (the blackbody emissivity). The detected radiance is then amplified, the range of dynamic emissivity is restricted and so the interface temperature becomes accurate (fig. 2).

Besides the difficulty in deducing an accurate temperature measurement, assessing the material temperature needs to understand the heat transfer phenomena at this complex interface. Between two adjacent materials under dynamic loading, only thermal conduction provides heat transfer. Thanks to the Fourier’s law, interface and material temperatures can be linked depending on the thermal properties of each material (fig. 3). At a complex interface and particularly with the presence of an emissive layer (EL) and a glue layer, the thermal conductivity of the EL must be enough important and its thickness enough thin to enable an efficient heat exchange and to obtain the temperature of

1. Temperature measurement theory

High-speed multi-wavelength infrared optical pyrometry is the most effective diagnostic to achieve temperature measurement below 1000 K. Although the method to collect radiance is well known, measurement at these low temperatures is still difficult due to the low amplitude of the radiated energy: any potential background lights must be avoided or at least under control. Thermal radiation emitted at the material/LiF interface was collected by a parabolic mirror then transmitted to the pyrometer.

The original feature allows not to use optical fiber which significantly increases the loss of the collected flux and prevents from detecting low temperature. The pyrometer is designed to provide electrical signals proportional to the collected flux at different wavelength ranges.

The lower blackbody-temperature threshold of the pyrometer is 323 K and its time resolution is 70 ns (fig. 1).

Figure 1: Drawing of the experiment and of the pyrometer.

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the emissive layer as close as possible to that of the material. In order to investigate the influence of the EL, different configurations of plate impact experiments were tested. The use of a graphite layer gives promising results: the thermal-mechanical properties of this layer are determined, the emissivity and opacity are verified. Thanks to a 1-D lagrangian code Unidim including thermal conduction modelling under shock-wave compression, experiments can be simulated to obtain material temperature.

2. Analysis of the polymorphic transition β-γ of tin

The multiphase EOS developed by Mabire has been successfully applied to the restitution of phase change in tin. However, the capabilities and limitations of this kind of model remain partially unknown, in particular due to the lack of reliable temperature data.

Plate impact experiments (fig. 4.)were performed to observe the behaviour of tin under shock wave compression (from 8 to 15 GPa) and under release to investigate its β-γ and γ-β polymorphic transitions at different impact velocities.

For the first time, both velocity and temperature measurements have been performed at the interface allowing to improve our understanding of mixture phenomenon to investigate the phase diagram.

Velocity profiles display the direct and reverse transitions showing coherent singularities. The temperature profiles without EL show additional distinct features function of the impact strain consistent with the compressive path which could indicate a mixture of the two phases: it needs to be confirmed by another experimental diagnostic such as X-ray diffraction. Temperature measurements with an EL have been achieved with sufficient precision to be compared to our phase transition model of metals under shock loading. These experimental results reveal the existence of an hysteresis for the transition during the loading and the release already studied by Mabire.

The Mabire EOS provides an overall good estimate of the velocity profiles and their singularities. However, its prediction of the temperature profiles may be less satisfactory around the direct and inverse β- transitions. This underlines the limit of a model of a simple hysteresis, and the need for future improvements in terms of phase kinetics description.

[1] Mabire, C., Héreil, P.-L., J. Phys. IV France 10, pp.9-749-9-754, 2000

Figure 2: Method to infer the interface temperature with upper and lower bounds for emissivity for each wavelength with and without emissive layer.

Figure 3: Link between material Trel and interface Tint temperatures.

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The molecular dynamics study on the micro-spallation of metal under shock loading

J Chen and M Xiang

Institute of Applied Physics and Computational Mathematics, People’s Republic of China

The mechanisms of micro-spalling and melting in nanocrystalline Pb under shock loading are studied by the molecular dynamics simulations. A wide range of shock intensity is conducted with the lowest one just above the threshold of solid spallation, and the highest one higher than the threshold of compression melting. The spallation mechanism is dominated by cavitation, i.e., nucleation, growth, and coalescence of voids. Our results also show that grain boundaries have significant influences on cavitation behaviors in cases of classical spallation and micro-spallation. In these cases, cavitation and melting both start on grain boundaries, and they display mutual promotion: melting makes the voids nucleate at smaller tensile stress, and void growth speeds melting. Influences of microstructure, strain rate, and temperature on spall strength are qualitatively discussed. Due to grain boundary effects, the spall strength of nanocrystalline Pb varies slowly with the shock intensity in cases of classical spallation. In cases of releasing melting and compression melting, spall strength of both single-crystalline and nanocrystalline Pb drops dramatically as shock intensity increases.

Deconstruction of a polymer bonded composite Hugoniot

D Williamson and A Jardine

University of Cambridge, UK

The utility of experimental data is increased if one has a framework for understanding the underlying physical basis for the results. Group Interaction Modelling (GIM) represents one such framework [1]. GIM can be used to describe fundamental properties such as density, expansivity, heat capacity, modulus and shock parameters. It also tells us how these properties are related to each other. Taken holistically, it follows that the results of one experiment can be used to constrain those of another through the building of a material model which can be tested on many levels. Here we demonstrate that the shock Hugoniot of a composite material can be described by the volume weighted response of its constituents and that GIM can be used to describe each of them. The goodness of fit can be viewed in light of the predictions of other thermophysical properties which, for the particular composite under consideration at least, is relatively extensive.

[1] D. Porter, Group Interaction Modelling of Polymer Properties, Marcel Dekker, New York, 1995

Mechanical failure behaviors of the poled PZT 95/5 under shock compression

F Zhang, H He, G Liu and Y Liu

National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, People’s Republic of China

PZT 95/5 ferroelectric ceramics has been utilized for the use in shock driven pulsed power supplies for many years. In our previous studying, the low impendence failure layer had been confirmed in unpoled PZT 95/5 when the shock stress is up to 2.4 GPa. But to the shock compresson of the poled PZT 95/5, the failure behaviors of this material need further study. In this paper, the failure behaviors of axially poled PZT 95/5 have been tested by measuring the particle velocity of the rear free surface at different stress. Results indicate that the failure layer exists in poled PZT 95/5 when the shock stress reaches 2.4 GPa. Through analyzing the velocity profile of free surface, which show that the velocity of this failure layer is the same as shock-wave speed and the delay time decreases with increasing the shock stress. Comparing the failure behaviors of unpoled PZT 95/5 with poled PZT 95/5, it reveals the delay time in poled state is

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slight higher than that in unpoled state. The ferroelectric to antiferroelectric phase transition has been introduced to explain the increasing of the delay time in the poled PZT 95/5.

High pressure and temperature hydrogenation of graphene

D Smith1, I Crowe2, M P Halsall2, E Gregoryanz3 and J E Proctor1 1University of Salford, UK, 2University of Manchester, UK, 3University of Edinburgh, UK

The interaction between graphene and hydrogen (H) and deuterium (D) is of great interest to development of graphene-based technologies, including hydrogen storage, high-performance composite materials and especially electronics – where graphene’s extremely high carrier mobility remains unexploited due to the lack of intrinsic band gap in the material. By chemical functionalisation with H, there is potential to open a bandgap in graphene with control over its properties.

Partial hydrogenation of graphene has been achieved by direct exposure to atomic H at ambient conditions [1, 2], but it is believed that this technique only yields 10% at. H coverage [3]. Electron diffraction studies of hydrogenated graphene [1] show contraction in the lattice parameter, suggesting that in-plane compressive strain in graphene might facilitate the reaction.

We present a new technique for activating the reaction of H/D with graphene using combined high pressures and temperatures. Graphene samples on copper foil have been subjected to pressures of 7 GPa and temperatures up of 200°C in H2 and D2 atmospheres in a diamond anvil cell. The Raman spectrum of the graphene was observed before and after the process to monitor the exent of the hydrogenation and changes characteristic of a change in bonding from sp2 (planar as in graphene) to sp3 (diamond-like) hybridisation are observed. Figure 1 shows the appearance of the carbon D peak after 2pz orbitals in graphene have formed covalent bonds with hydrogen or deuterium atoms during high-pressure heating.

A variety of pressure and temperature combinations have been employed in an attempt to find the necessary conditions for activating hydrogenation/deuteration and to maximise the extent of the reaction and it has been shown that the reaction will not take place at ambient temperature, even under pressures up to 9 GPa.

Figure 1: D peak enhancement in graphene following hydrogen (left) and deuterium (right) treatment at 7 GPa pressure and 200°C temperature.

[1] Elias, D et al., Science 323 p. 610–613 (2009) [2] Sessi, P et al., Nano Lett. 9(12) p. 4343–4347 (2009) [3] Pumera, M. & Wong, C. H. A., Chem. Soc. Rev. 42(14) p. 5987–95 (2013)

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(Invited) Effects of blast on the human

J Clasper

CBIS, UK

Medical advances have led to unprecedented survival rates in the current conflict in Afghanistan, and have resulted in survivors with both severe and unique injury patterns. Improvised Explosive Devices were the most common weapons used against the Coalition Forces in Afghanistan and Iraq, both against dismounted troops as well as those protected by vehicles. In addition suicide bombers remain a frequently deployed weapon of terrorism. The specific weapon deployed, and the environment in which it is used has also influenced the wounding pattern. The intensive experience of the last decade has resulted in an increased understanding of the effects of blast on the human.

This talk with describe the medical classification, by mechanism of blast injury, and discuss the specific effects on different systems and organs. The engineering or scientific explanation for the injuries will be introduced, together with the unique multi-disciplinary approach to the investigation, and mitigation of the injuries.

Experimental platforms for studying dynamic responses of tissue to blast-type pressures

B Butler1, C Bo2, D Tucker1, A Jardine1, W Proud2, T-T Nguyen2, R Curry3, A Williams1 and K Brown2 1University of Cambridge, UK, 2Imperial College London, UK, 3University of Cape Town, South Africa

To investigate the molecular and cellular changes that occur as a result of blast injury, we aim to develop protocols to mimic this type of insult in the laboratory. With this goal in mind, we have used an ex vivo organ culture (EVOC) of porcine trachea tissue, originally designed to investigate respiratory infection, in studies that simulate blast injury. We have constructed an adaptor that enables us to subject EVOCs to overpressures using the shock tube platform constructed at the Imperial College London Centre for Blast Injury Studies. We observe a dose-response based upon comparison of tissue pathologies with applied peak pressures ranging from ~40 – 150 kPa. Future studies will build on this data to explore underlying molecular changes that occur in our EVOC model using conditions that are representative of those that create known pathologies in human blast injuries.

Time-resolved diagnostics in blast, shock and impact studies

W G Proud1,2, D J Chapman1, D Eakins1 and S Masouros1,2 1Imperial, College London, UK, 2Royal British Legion Centre for Blast Injury Studies, UK

Given the complex loading situations associated with blast and the heterogeneous structure and materials in the human body, predicting the medical outcome of blast injury represents a considerable challenge. This paper will outline some of the approaches being adopted and address in particular the range of experimental diagnostic tools available.

Experimental and computational models of human injury and of mitigation technologies are useful tools for elucidating the physical mechanisms involved in a blast scenario. Experiments involving individual components of the system (e.g., the combat boot, the vehicle, the human leg) give an understanding of the whole, complex ‘structure’ under fairly controlled, repeatable conditions. However, these experiments can be expensive, time consuming and labour intensive, albeit invaluable. Individual-component experiments (e.g., testing of combat boot components, of vehicle components, of soft and skeletal human components) are well controlled and repeatable and allow us to understand individual

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material behaviour. Alternatively, computational models that can predict the behaviour of the whole ‘structure’, based upon interactions of component parts, are also useful. The basic research paradigm is illustrated in figure 1.

In particular, A number of high-speed techniques (figure 2) are being developed which allow greater insight into blast, shock and impact processes. In the field of high-strain rate studies materials, in general, show increased flow stress with increasing strain rate. Some of this effect is due to inertial effects while some to the activation energy and kinetics of the deformation and failure processes. Blast and impact scenarios are complex for a wide variety of reasons, not the least of which is the large range of strain rates present in the deformation processes. Shock wave studies require nanosecond time resolution in order to understand which processes are initiated at these high dynamic pressures. This talk will describe a number of optical and image analysis techniques which allow point, line and full-field measurements to be made. The talk will be illustrated by experimental results across a range of materials types and comparison with more established techniques made.

Figure 1: Multi-faceted (or interdisciplinary) modelling approach to understand materials and blast injury.

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Figure 2. (a)The stress/pressure- time regimes of various experimental techniques. (b) Schematic of a shock tube, showing high and low pressure sections (c) A typical output. (d) Sample holders for loading of cells and tissues on an SHPB system. (e) Experimental voltage output from strain gauges for liquid and tissue samples compressed using an SHPB system. (f) A traumatic injury simulator (AnUBIS) to simulate the loading environment transferred to the lower limb from the floor of a vehicle when attacked by a mine. (g) Strain seen in the hind foot of cadaveric legs tested in different orientations. Dynamic fragmentation of lake quarry granite

S S Kirk, C H Braithwaite and A P Jardine

The Cavendish Laboratory, Cambridge, UK

Understanding the dynamic fragmentation of geological materials is important for many applications, and is particularly significant to the blast mining industry. Laboratory scale expanding ring experiments provide a convenient

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method of studying tensile fragmentation, under well-defined conditions. Here, we report a series of explosively-driven expanding ring experiments, which investigate the dynamic fragmentation of ‘Lake Quarry Granite’, a well characterised Australian granite. Ring fragments were soft captured and sieved to measure the fragment size distribution for each experiment. Heterodyne laser velocimetry was used to monitor the outer ring surface, enabling the strain rate to be determined. Fragment size distributions were then compared with predictions from dynamic fragmentation theory. High speed photography was used to monitor the experiments and showed the formation and growth of cracks, while fractographic analysis identified an inter-granular failure mechanism. Over the range studied, the reduction in fragment size with increasing strain rate was shown to be limited by the grain size of the material, and demonstrates the importance of relating microstructure to dynamic fragmentation models of granular materials.

CALCITE: Anisotropy in shock physics

G Tear

Institute of Shock Physics, UK

Calcite is an anisotropic material exhibiting orientation dependent mechanical properties and optical birefringence. When loaded by a uniaxial shock this directionality becomes very significant, leading to widely differing responses. In this study calcite has been impacted along the <10-10> direction using a light gas gun to pressures in the range 2 GPa to 5 GPa. Changes to the birefringence were measured using a polarimeter and related to the state of strain.

Age hardening and it’s effects on the shock response of materials

J C F Millett

AWE, UK

Age or precipitation hardening is an important industrial process that allows the optimisation of mechanical properties of materials for the required application. Whilst the process has been studied extensively and understood at quasi-static strain-rates, its affects on the shock loading regime is less well known. In this presentation, we examine the response of the aluminium alloys 6061 and 7017, and a copper 2% beryllium alloy; the former due to its wide spread use in industry and the latter due to the large increases in strength (ca. x5) when comparing solution treated to fully aged at low strain-rates. Results are discussed in terms of the Hugoniot Elastic Limit (yield), shear and spall (tensile) strengths, and in the case of 6061, shocked and recovered microstructures. In the case of the aluminium alloys, ageing appears to be largely ineffective, whilst in the copper-beryllium alloy, ageing increases strength by only a factor of ca. x 2, rather than x 5 as seen in the quasi-static response. Microstructural examination has shown that the presence of fine precipitates hinders the motion of dislocations, which we believe reduces the overall strain-rate sensitivity. Therefore it would seem that under shock loading conditions, the response of materials in the solution and fully aged conditions effectively converge.

(Invited) The effect of boundary conditions on the response of structures when subjected to a blast load – An overview

G Nurick

University of Cape Town, South Africa

Over the years there have been many studies on the response of plates subjected to blast loads. The plates have different boundary conditions - fully clamped; fully built-in (integral); or welded around the boundary. In addition the plates could have supporting stiffeners. These different conditions affect the response of the plate in terms of mid-point

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deflection, plate profile and plate failure. This presentation will provide an overview of these conditions.

Due to the simplicity and cost the early reported test results were mainly performed on plates clamped around the periphery of a circular or quadrangular plate [1-7]. Later tests were reported on plates that were machined from a block of steel [8 - 17]; and in recent years there have been publications which show the response of plates that have been welded on all sides of a rectangular plate [18 -19]. More recent studies [20] discuss the effect of a cube subjected to a confined blast – the sides of the cube have different boundary conditions – one side is fully welded, one side is fully clamped and four sides are partially welded around the relevant peripheries.

[1] Nurick GN, Martin JB. Deformation of thin plates subjected to impulsive loads – a review. Part I: theoretical considerations. Int J Impact Engng; 1989; 8: 159-69

[2] Nurick GN, Martin JB. Deformation of thin plates subjected to impulsive loads – a review. Part II: experimental studies. Int J Impact Engng: 1989;8: 171-86

[3] Teeling-Smith RG, Nurick GN. The deformation and tearing of thin circular plates subjected to impulsive loads. Int J Impact Engng: 1991; 11(1): 77-91

[4] Nurick GN, Shave GC. The deformation and tearing of thin square plates subjected to impulsive loads an experimental study. Int J Impact Engng: 1996; 18: 99-116

[5] Jones N. Structural Impact. Cambridge University Press; 1989 and 1997 [6] Nurick GN, Gelman ME, Marshall NS.Tearing of blast loaded plates with clamped boundary conditions. Int. J Impact Engng 1996;18: 803-827 [7] Jacob N, Chung Kim Yuen S, Nurick GN,Bonorchis D, Desai SA, Tait D. Quadrangular plates subjected to localised

blast loads – an insight into scaling. Int.J of Impact Engng. 2004;30,1179-1208 [8] Chung Kim Yuen,Nurick GN. Experimental and numerical studies on the response of quadrangular stiffened plates – Part I: uniform blast loading. Int J Impact Engng. 2005; 31; 55-83 [9] Langdon GS, Chung Kim Yuen S, Nurick GN. Experimental and numerical studies on the response of

quadrangular stiffened plates – Part II: localised blast loading. Int J Impact Engng.2005; 31, 85-111 [10] Chung Kim Yuen S, Nurick GN. Modelling the deformation and tearing of thin and thick plates subjected to localised blast loads. Plasticity and Impact Mechanics. IMPLAST 2003. (Ed. Gupta, NK.) Phoenix Publishing House, New Delhi.2003; 729 – 739 [11] Langdon GS, Chung Kim Yuen S, Nurick GN. The response of stiffened square plates subjected to localised blast loading. Structures Under Shock and Impact (SUSI) VII May, 2002. Montreal,Canada.pp 3-12 [12] Chung Kim Yuen S, Nurick GN. Deformation and tearing of uniformly blast-loaded quadrangular stiffened plates”. International Conference on Structural Engineering, Mechanics and Computation, (SEMC), 2-4 April 2001. Cape Town, South Africa: 1029-1036 [13] Nurick GN, Lumpp DM. Deflection and tearing of clamped stiffened circular plates subjected to uniform impulsive blast loads. (Eds. Jones, N, Brebbia, CA & Watson, AJ ). Structures under Shock and Impact IV: 393-404, Computational Mechanics Publications, Southampton, Boston, 1996 [14] Thomas BM, Nurick GN. The Effect of Boundary Conditions on Thin Plates Subjected to Impulsive Loads. Plasticity

1995-The 5th Int Symp on Plasticity and its Current Application.Osaka, Japan, 85-88,July 1995 [15] Nurick GN, Olson MD Fagnan JR, Levin A. Deformation and Tearing of Blast Loaded Stiffened Square Plates Int.J.

Impact Engng. 1995; 16: 273-292 [16] Olson MD, Nurick GN, Fagnan JR. Deformation and Rupture of Blast Loaded Square Plates-Predictions and

Experiments. Int.J. Impact Engng. 1993; 13 : 279-291 [17] Chung Kim Yuen S, Nurick GN. The effect of plate thickness on localised blast loads – an experimental study.

Proc 16th Int Symp Military Aspects of Blast and Shock (MABS16) Oxford, UK: 2000; 491-499 [18] Bonorchis D, Nurick GN. The effect of welded boundaries on the response of rectangular hot-rolled mild steel

plates subjected to localised blast loading. Int J Impact Enging; 2007; 34; 1729-1738 [19] Bonorchis D, Nurick GN. The influence of boundary conditions on the loading of rectangular plates subjected to

localised blast loading – importance in numerical simulations. Int J Impact Engng;2009;36,;40-52

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[20] Gerreto C, Chung Kim Yuen S, Nurick G. An Experimental study of the effects of degrees of confinement on the reponse of square mild steel plates subjected to blast loading. Int j Impact Engng. 2014 (In Press)

Morphology and chemical composition of undetonated post-blast explosive residues

N Abdul-Karim

Christopher Ingold Laboratories, University College London, UK

The survival of undetonated explosive residues from high order detonations is not an uncommon finding, yet the mechanism for their formation, morphology, dispersal and deposition is unknown and untested to date. What is happening to these particles during the detonation? How are they able to survive and how do the temperatures and pressures of a detonation affect them?

This project involves the controlled detonations of various energetic materials in order to assess the physical morphology and chemical characteristics of the post-blast residues. Residues were collected directly onto sample stubs and analysed using SEM-EDX, Raman spectroscopy and MeV/SIMS. The findings demonstrate the variations in particle morphology based on the explosive used and the chemical signatures produced by these residues.

Free field detonations of larger amounts of explosive have also been conducted; these trials incorporated the use of high speed imaging, piezoelectric gauges and chemical techniques, including Ion Chromatography and Ultra Performance Liquid Chromatography/Mass Spectrometry, to analyse the residue samples collected from ‘witness’ materials surrounding the detonation centre. Contour maps of residue distribution were produced based on the chemical analyses and the information generated by the high speed imaging and pressure data were incorporated into the interpretation in order to develop a holistic explanation of the dispersal and deposition of undetonated residues.

Dynamic x-ray imaging of subsurface dynamics in high-Z materials at the Diamond Light Source

D E Eakins, D J Chapman, M Rutherford, M Collinson, D Jones, J Music, S Stafford, G Tear, T White and J Winters

Institute of Shock Physics, Imperial College London, UK

The bulk mechanical response of materials subjected to dynamic loading has its origins in physical processes occurring at the underlying mesoscale. Our standard time-resolved diagnostics, however, are almost exclusively based upon visible radiation, and thus suffer limited penetration into high-Z materials. One possible solution is the use of synchrotron X-rays, as demonstrated recently at the Advanced Photon Source. Extending these studies to the intermediate stages of damage evolution, and the correspondingly larger samples, requires working with high-energy X-rays (> 50 keV), which in turn present additional challenges for beam shuttering/synchronisation and scintillator light yield.

In this talk, we describe recent efforts to develop a dynamic X-ray imaging capability at the Diamond Light Source. Using a portable purpose-built small-bore launcher, dynamic loading experiments were performed on the I12 high-energy beamline, synchronised to a custom hybrid bunch mode. A combination of pre-shot tomography and simultaneous line VISAR, HetV and dynamic X-ray imaging was used to study a range of dynamic damage phenomena. Preliminary results on the compression of SiC powders, collapse of additively-manufactured steel lattices, and spall formation in a magnesium alloy will be highlighted. Planned improvements to event jitter, light collection and framing, including areas of continued challenge, will be discussed.

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(Invited) Hypervelocity shock transformation of natural superhard materials: Crystalline diamond

A P Jones1, P McMillan1, R Hazael1, J Milledge1, P DeCarli*1, R Wylie1, D Dobson1, M Moore2, F Nestola3 and M Alvaro3 1University College London, UK, 2Royal Holloway, UK, 3Padua University, Italy

*[Deceased August 2013 while the project was active: Stanford Research Institute]

Elemental carbon in the form of diamond is familiar both as jewellery derived from natural cubic symmetry crystals, and as an industrial material due to its premier hardness, thermal conductivity and electronic properties. Diamond has exceptional thermal and pressure stability exceeding the ambient conditions at the centre of planets even larger than the Earth (super Earth’s), such that its indestructible survival of galactic catastrophes may help to explain its widespread occurrence as nanodiamond in many meteorites. Although extreme conditions for the phase diagram of carbon are attracting attention, surprising degrees of uncertainty characterize the less extreme, low temperature region, where hexagonal diamond (lonsdaleite) occurs both in nature and experiment, but is difficult to identify. Lonsdaleite has been identified in a wide range of natural impact deposits, assumed to have formed after hexagonal graphite. We describe an extraordinary set of experiments using shock techniques and materials unlikely to easily be reproduced, whose products have finally been unlocked after 50 years by technological advances in synchrotron Xray analysis. Our findings provide the first unequivocal evidence for long-lived shock transformation of cubic to hexagonal diamond with no precursor graphite. Hexagonal diamond (lonsdaleite) shares many diagnostic characteristics with cubic diamond, but is anisotropic both optically and physically. It may be harder than cubic diamond. In addition to presenting our technical data for hexagonal diamond in the carbon PT phase diagram, we discuss the likely formation conditions for lonsdaleite in a range of primarily natural materials.

Examining the devolatilisation of minerals from impacts using Raman spectroscopy

N K Ramkissoon1, M C Price1, A T Kearsley2, M J Cole1, P Wozniakiewicz1,2 and M J Burchell1

1University of Kent, UK, 2The Natural History Museum, UK

Introduction: Impacts played a major part in the early development of the Solar system [1]. They may also have had an equally important role in subsequent planetary evolution, including the formation and evolution of atmospheres and hydrospheres around the terrestrial planets and their satellites [1, 2]. Previous studies [3, 4, 5] have demonstrated that hypervelocity impacts can result in the release of volatiles from hydrated, carbonate and sulphate mineral targets. It is important to understand the conditions and mechanisms of impact induced devolatilisation in specific important mineral species, especially those abundant on the surfaces of planetary bodies. With this understanding, we may be able to use remote-sensing, or rover-based instruments, to recognise, and quantify, any devolatilisation that may have occurred. For example, [6] has shown that Raman spectroscopy is capable of quantifying the loss of volatiles from impacts, and this instrument is beginning to be seen as a useful tool for in situ planetary surface analysis [7], evident by the inclusion of a Raman spectrometer onboard ESA’s ExoMars rover [8]. Here we present results of laboratory impact experiments using two minerals believed to be relevant in the evolution of Mars: goethite and gypsum (in the form of plaster-of-paris (PoP)).

Experiments: To date, two experimental programmes (Table 1) have been carried using the University of Kent’s two stage light gas gun [9]. The first series of experiments used a Goethiteprojectile(1.5 × 1.5 × 2 mm) that was fired onto Aluminium plates at velocities between 1 – 5 km s-1. The second set of experiments used PoP in its hydrous or semi-hydrous phase as either the projectile or target. Both sets of experiments were analysed using a LabRam-HR Raman spectrometer at the University.

Table 1. Shot program for devolatilisation experiments.

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Results: Goethite. Analysis of the residue within craters resulting from impacts showed the loss of OH from goethite, producing hematite, through the reaction:

2 FeO (OH) Fe2O3 +H2O

The experiments show at impact velocities of ~3 km s-1 almost complete dehydration of goethite occurs, as indicated by the doublet peak at 607 and 658 cm-1 and the formation of a broad peak at 1315 cm-1. Whereas a lower impact velocity of 1.3 km s-1 shows almost no sign of devolatilisation as a result of impact.

Hydrated plaster of paris.Raman spectra taken from inside craters showed a slight indication of dehydration of the PoP target, via the following reaction:

CaSO4·2H2O CaSO4·0.5H2O + 1.5H2O

The appearance of a small feature at 3553 cm-1, next to the H2O features at 3405 and 3493 cm-1, suggests the formation of semi-hydrated material in the crater; although this still requires confirmation.

Semi-hydrated plaster of paris. Analysis of crater residue from a buckshot of semi-hydrated PoP powder, showed there has been a loss of the remaining volatiles (H2O, O and S) within the PoP, as signified by a change in the spectra from the semi-hydrated phase to a phase that closely resembles that of CaCO3. This may reflect creation of fine-grained CaO, rapid hydration of this strongly hygroscopic phase by atmospheric moisture, and uptake of CO2. However, a peak present in the impact residue at 507.1 cm-1 is not present in pure CaCO3. There is a difference of a few wavenumbers between the positions of comparable peaks between the residue material and CaCO3, which may be the result of shock from the impact. Further analysis is being conducted to determine the exact composition of the residue material, and whether this might includehigh pressure mineral polymorphs.

A sample of hydrous PoP was heated to a temperature of 1400 °C (in 50 °C increments) in air using the Raman spectrometer’s variable temperature stage. Heating PoP showed there was a loss of the hydration between 100 and 150 °C, indicated by the loss of the lose H2O peaks at 3401 and 3495 cm-1. EDX analysis of the remaining material after heating shows a detectable loss of sulphur between the heated sample and a control sample. However, the Raman spectra taken of heated PoP sample does not resemble the spectra from impact residue made from the particles of the semi-hydrous phase or CaCO3. It may be possible that what is being seen in the impact residue, and heated PoP samples, are intermediate stages of the complete devolatilisation of PoP.

Conclusions: Initial experiments show hypervelocity impacts induce devolatilistion of goethite and both semi-hydrous and hydrous PoP. The impacts lead to a distinctive change in the Raman signatures of both of these minerals. These early results indicate the degree of devolatilisation is dependent on both the velocity and the size of the projectile. Continued investigation (including modelling to determine the peak pressures/temperatures associated with the impacts) is underway in order to confidently quantify the degree of impact induced devolatilisation of minerals using Raman spectrometry.

[1] Tyburczy J. A. et al. (2001) Earth and Planet. Sci. Let, 192, 23-30 [2] Kurosawa K. et al. (2012) Earth and Planet. Sci. Let., 337-338, 68-76 [3] Lange M. A. and Aherns T. J. (1982) Jour. Geophy. Res.87, A451-A456

Shot I.D. Target (mm = plate thickness) Projectile v (km s-1)

G111013#1 PoP (PS250913#1) 1 mm diameter stainless steel sphere 6.15 G141113#2 1 × 3.0 mm Al plate Semi- hydrous PoP (buckshot) 4.26 G281113#1 2 × 1.5 mm Al plate Semi- hydrous PoP 3.72

G111013#2 2 × 3.0 mm Al plates Goethite cuboid 4.11 G241013#1 2 × 1.5 mm and 1× 3.0 mm Al plates Goethite cuboid 5.13

G061113#2 2 × 3.0 mm Al plates Goethite cuboid 3.25 G121213#2 2 × 1.5 mm Al plates Goethite cuboid 1.36

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[4] Chen G. et al. (1994) Earth and Planet. Sci. Let, 128, 615-628 [5] Kawaragi K. et al. (2009) Earth and Planet. Sci. Let, 282, 56-64 [6] Miliković K. et al. (2013) 44th LPSC, Abstract #1940 [7] Tercea N. et al (2008) Space Sci. Rev. 135, 281-292 [8] Perez C. et al. (2013) EPSC2013,Abstract #935 [9] Burchell M. J. et al. (1999) Meas. Sci. and Tech, 10, 41-50 [10] Liu Y. et al (2009) 40th LPSC, Abstract #2128

Using Raman mapping to determine hypervelocity impact peak shock pressures in high purity silicon, germanium, gallium arsenide and peridot targets

M C Price1, R Hibbert1, D C Arnold1, P J Wozniakiewicz2, M J Cole1 and M J Burchell1 1University of Kent, UK, 2Natural History Museum, UK

Introduction: Impacts are ubiquitous throughout the Solar System and occur at all scales and at a range of speeds. However, on Earth, the only evidence we have of such events is through direct observation of impact flashes [1 - 3], or by looking at materials that fall onto the Earth as a result of such events (such as meteorites). Knowing the shock history of these meteorites would enable us to infer the impact energy of the event. However, although shocks are known to cause changes to minerals (such as phase changes, melting etc.) there has been (to date) very little work done to quantify such changes.

Impact Experiments: To help redress this lack of knowledge, impacts were performed using the two stage light gas gun (LGG) at Kent [4]. In these experiments monodisperse molybdenum spheres with a diameter of 50 microns were fired at speeds between 0.3km s-1– 4.5km s-1 onto high purity wafers of silicon, germanium and (in one case) gallium-arsenide. Although these materials are not exactly relevant to Solar System impacts, they are extremely useful as they can be obtained with very high purities, known crystal orientations, and have a very clean, very strong Raman spectrum (indeed, silicon is a standard calibrator for Raman spectrometers). When stressed, the position of the distinctive Raman peak of each of these materials shifts in wavenumber due to the deformation of the crystal lattice. The amount of this shift (typically a few wavenumbers) is detectable with a high sensitivity Raman spectrometer, and thus the degree of impact induced stress within the material can be measured. For example, for silicon, the relationship between Raman shift, Δω (cm-1), and stress, σ (MPa), is σ = -476 Δω (using the average of the two expressions given in [5] and [6]). Similar expressions exist for pure germanium [7].

Table 1: Details of shock experiments performed to date.

Shot ID Velocity (km s-1) Target(s) E090114#1 0.362 Si E191213#1 0.382 Si S290114#1 0.612 Si, Peridot G221113#1 1.209 GaAs, Ge G150114#1 1.569 Si, Peridot G061113#1 2.090 Si G131213#2 2.705 Si, Ge G150114#2 3.030 Si, Peridot G160114#1 4.170 Si, Peridot

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Low speed gun: Although the Kent gun is a two stage LGG, we have recently developed the capability to fire at speeds significantly below 1 km s-1 (our lowest speed to date is 362 m s-1). This is achieved by replacing our aluminium burst disk with a Mylar disc with a thickness of 250 µm, or an aluminium foil with a thickness of 50 µm. The launch tube is then pressurised until the burst disk ruptures, which then launches the sabot and projectile. The speed is tuneable by changing the gas that is used to pressurise the tube: N2 (to get ~380 m s-1), He (to get ~600 m s-1), H2 (to get ~1000 m s-1). This means that we can fire onto brittle targets (such as silicon) at speeds that do not totally destroy the target. Indeed, our lowest speed shots at 362 m s-1 caused minimal damage to the surface of the silicon, merely circular ‘bruises’ with no visible damage to the surface, Figure 2 (A).

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Results: After impact, the targets were removed from the target chamber, and then placed in a scanning electron microscope to get high resolution images (and stereo-pair) images of some of the impact craters (Fig. 1). These craters were then mapped using a Horiba LabRam-HR Raman spectrometer with a high power (500 mW) 532 nm laser. This spectrometer has a resolution of better than 1 cm-1, using an 1800 lines per mm grating and a 532nm wavelength laser. Using this system, very high resolution (100 × 100 pixel) maps could be obtained of a crater in approximately 10 hours (Figure 2). The maps were then processed, and contour maps produced to show the degree of stressing within the target.

Hydrocode modelling: Complimentary hydrocode modelling is being carried out (using Ansys’ AUTDOYN software) to compare the peak pressures modelled by the code to the measured stresses within the target’s lattice. This work is currently underway.

Figure 1 (left): 10 kV secondary electron anaglyph (red: left, cyan: right) SEM image of an impact crater on a [100] oriented silicon wafer impacted with a 50 µm diameter molybdenum sphere at 2.08 km s-1. The crater is 60 µm in diameter. Figure 2 (below): (A) Optical image of a low speed (0.362 km s-1) ‘bruise’ on the surface of a silicon wafer. (B) Compression map showing the negative shift of the characteristic 520.6 cm-1 Si line. (C) Tension map showing the positive shift of the 520.6 cm-1 Si line. Higher intensity equates to greater shift, and thus higher tension or compression. The max. shift here is approx. ±4 cm-1, equivalent to a stress of ±1.9 GPa.

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Conclusions and on-going work: High resolution, high speed Raman mapping of silicon, germanium and gallium-arsenide wafers and gem quality olivine (peridots) that have been shocked by impact with high velocity metal spheres may provide a novel way of determining the peak shock pressure experienced by a material during an impact event. The shock deforms the lattice, and leaves a ‘fingerprint’ of the event. This lattice deformity causes a change in the Raman signature of the target from which the degree of strain that the lattice has experienced can be deduced. The shot programme has been finished (Table 1), and mapping of the craters, detailed analyses and hydrocode modelling are on-going and will be presented.

[1] D. W. Dunham et al., 2000, 31st LPSC, #1547 [2] B. M. Cudnik et al. 2003. Earth, Moon and Planets, 93, 145 [3] M. Delcroix & R. Hueso. 2013. EPSC, #EPSC2013-812-1 [4] M. J. Burchell et al. 1999. Meas. Sci. Tech. 44, 10 [5] E. Anastassakis et al. 1970. Solid State Comms., 8, 133 [6] E. Anastassakis et al. 1971. J. Phys. Chem. Solids, 32, 563 [7] C. Y. Peng. 2009. J. Applied Physics, 105, 083537

Ballistic response of comminuted ceramics

G J Appleby-Thomas, D C Wood and A Hameed

Cranfield University, UK

Strong evidence that the ballistic-resistance of fragmented (comminuted) ceramics is similar, independent of the original strength of the material, has emerged from recent studies. Experimental investigations focused on the ballistic response of such materials have suggested that ballistic response is strongly linked to shattered material morphology. Consequently, it is postulated that post-impact ballistic performance could be maximised via careful control of control of ceramic fragmentation on impact. Essentially, such an approach should allow control of multi-hit capabilities. In this study, ballistic tests into pre-formed ‘fragmented-ceramic’ analogues based around two morphologically differing (but chemically identical) alumina feedstock materials compacted into target ‘pucks’ were conducted. Analysis of impacted targets has provided strong hints of a morphology-based contribution to ballistic response. However, this contribution cannot yet be quantified due to insufficient fidelity in the experimental data set.

Temperature effects on the mechanical behaviour of PZT 95/5

A Khan, J E Balzer, J M Wilgeroth and W G Proud

Institute of Shock Physics, Imperial College London, UK

This research is to develop a better understanding of the piezoelectric ceramic lead zirconate titanate (PZT) 95/5 with varying temperatures, porosities and strain rates. Here, unpoled PZT samples of two different porosities were subjected to a range of compression rates, using quasi-static loading equipment, drop-weight towers and Split Hopkinson Pressure Bars (SHPBs). Varying temperatures were achieved using purpose-made environmental chambers. The resulting stress-strain relationships are compared. The samples were square tiles, 7.5 x 7.5 mm and 3 mm thickness. The density of the standard PZT used here was 7.75 g cm^-3 (henceforth described as PZT), whilst the density of the higher porosity PZT was 7.38 g cm^-3 (henceforth described as PPZT). This research is part of a wider study.

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The importance of oxygen and water on the ageing behaviour of a polyethylene glycol based propellant

R Tunnell, R Cook, D Tod and W Proud

Imperial College London, UK

High energy propellants containing polyethylene glycol (PEG) are susceptible to degradation in a humid environment. It has been established that PEG readily oxidises and the by-products of this include water and formic acid. It was not known if it was possible for a PEG based propellant to produce water in the bulk of a sample affecting the ageing processes in a confined environment where any water and acid could not readily escape. As a result, the impact of ageing a PEG based propellant in the presence of differing concentrations of atmospheric oxygen both with and without humidifying agents has been considered. The results indicate the key ageing mechanism is oxidation which causes softening of the material. However, even when extensive degradation has occurred, water does not accumulate as it either evaporates or takes part in further reactions.

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Poster Programme

P:01 Thermoelectric properties of SbNCa3 and BiNCa3 for thermoelectric devices and alternative energy

applications M Bilal, University of Malakand, Pakistan

P.02 Hybrid MMCs at varying strain rates R Davenport, Brunel BCAST, UK

P.03 Compatibility of W-Re thermocouple materials for use at high temperatures C J Elliott, National Physical Laboratory, UK

P.04 Impact Europa – Or how does a water filled ice shell withstand hypervelocity impacts? K Landers, University of Kent, UK

P.05 In-situ X-ray studies of mesoscopic phenomena during dynamic loading M Rutherford, Institute of Shock Physics, Imperial College London, UK

P.06 Phase stability and elastic properties of titanium alloys D Smith, Joule Physics Laboratory, University of Salford, UK

P.07 Solubility of hydrogen in Zircaloy-4 nuclear fuel cladding D Smith, Joule Physics Laboratory, University of Salford, UK

P.08 On the importance of the 7.62 mm FFV bullet jacket during penetration G J Appleby-Thomas, Cranfield University UK

P.09 Can fossils survive hypervelocity impact? L Yolland, University of Kent, UK

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Poster abstracts

P.01 Thermoelectric properties of SbNCa3 and BiNCa3 for thermoelectric devices and alternative energy applications

M Bilal1, B Khan1, H A Rahnamaye Aliabad2, M Maqbool3,4, S Jalai Asadabadi5 and I Ahmad1

1University of Malakand, Chakdara, Pakistan, 2Hakim Sabzevari University, Sabzevar, Iran, 3Qatar University, Qatar, 4Ball State University, USA, 5University of Isfahan, Iran

Thermoelectric properties of two antiperovskites SbNCa3 and BiNCa3 are calculated using first principles calculations. High values of Seebeck coefficients are observed for these materials. Electrical and thermal conductivities are also calculated. Increase in thermal conductivity and decrease in electrical conductivity is found with increasing temperature. Maximum value of thermal conductivity was 92 x 1014 W/mKs and 88 x1014 W/mKs for SbNCa3 and BiNCa3 respectively at a temperature of 900 K. The peak values of 5×1020 /Ωms and 5.2×1020 /Ωms for electrical conductivity are achieved for n-type SbNCa3 and BiNCa3 respectively at a temperature of 300 K. Figure of merit is achieved for these materials at room temperature which shows that these materials can be useful for thermoelectric devices and alternative energy sources.

P.02 Hybrid MMCs at varying strain rates

R Davenport and H B Nadendla

Brunel BCAST, UK

Metal-reinforced metal matrix composites (Hybrid MMCs) are a comparatively unexplored area of composite development. It is hoped that these will offer beneficial strength-to-weight ratios, similar to ceramic-reinforced composites whilst retaining higher ductility.

Composite materials also offer a challenging study of material behaviour across strain rate regimes, as rate-dependant deformation mechanisms may be active in the matrix, the reinforcement and the interface between the two. Microstructural study of composite samples deformed at a variety of strain rates is intended to reveal which deformation mechanisms are active in the different strain rate regimes, and indicate where any deformation mechanism transitions may be seen.

P.03 Compatibility of W-Re thermocouple materials for use at high temperatures

C J Elliott1, M Large2, J V Pearce1 and G Machin1 1National Physical Laboratory, UK, 2University of Surrey, UK

Industrial demands for high temperature measurement and process control mean that thermocouples are now being used for increasingly higher temperature measurements. At high temperatures (>2000 °C), chemical reactions between the constituent parts of the thermocouple and its environment are commonplace and lead to large and uncontrollable drift of the thermocouple output.

Methods of self-validation have been developed to determine and counter the impact of the drift, but very little is understood about the processes which lead to the drift occurring. To address this issue, NPL has performed controlled tests to shed some light onto the chemical reactions which occur when a typical high temperature thermocouple (Type C; W-5%Re vs. W-26%Re thermoelements) is exposed to temperatures up to 2300 °C. This work has been completed within the framework of the European Metrology Research Project IND01 “HiTeMS”

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In addition to the internal reactions which may be occurring at high temperatures, the working environment external to the thermocouple may also introduce additional complications: for example, where a high-temperature fixed point cell is placed in-situ over the thermocouple measurement junction (such as in self-validation procedures), the sheath will be in direct contact with carbon. For this reason, the presence and impact of carbon is also considered.

Controlled exposure between pure samples of W-Re thermocouple grade wires, thermoelement insulators (boron nitride, hafnia, silicon carbide and zirconia), sheath materials (tantalum and molybdenum) and graphite have been made. Each test sample was exposed for 24 h at high temperature – of either 1700 °C, 2000 °C or 2300 °C. Detailed visual results are presented and supported with elemental surface analysis, allowing conclusions on the suitability of contact between these individual materials to be drawn, and considerations for changes in the design of the thermocouple to be made.

[Please note that a full paper on this work has also been presented at TempMeko 2013 (an international temperature metrology community conference), and is due to be published within the proceedings in International Journal of Thermophysics this year.

P.04 Impact Europa – Or how does a water filled ice shell withstand Hypervelocity impacts?

K Landers, K H McDermott, M J Cole, M C Price and M J Burchell

University of Kent, UK

Introduction: In the outer solar system, some of the icy satellites of the giant planets have sub-surface oceans. Europa is a good example of this. Bodies throughout the Solar System are impacted in high speed impacts, and normally a crater results. If the impact energy density is great enough the body may undergo catastrophic disruption. Impacts are often studied in the laboratory via experiments on ice targets in two-stage light gas guns. A typical such study is [1] where solid ice targets were used to study catastrophic disruption. However, it is important to ask how these impacts will change when the ice is only a surface layer and there is a subsurface ocean.

Method: Accordingly, we have constructed hollow ice spheres (ice thickness typically 4 cm, sphere diameter 18 cm) which we then fill with water. Unlike the real case of Europa, there is no solid (rocky) core in the centre of these targets, but they serve to study the case of ice over water on a spherical body. These are placed in the Kent light gas gun and projectiles fired at them at speeds above 1 km s-1. The impacts are video’d, which is important as the flow of water out of a broken target can be destructive in its own right and we need to see how the target responds to the impacts.

Results: A typical impact is shown in Fig. 1. By varying the impact speed we are currently determining the energy density needed to just catastrophically disrupt a water-filled ice sphere and will compare this to the energy to disrupt a solid ice sphere of the same size.

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Figure 1. Impact on a 18.1 cm ice sphere at 3.01 km s-1. The impact was from the right, and the water and ice is exploding back along the impact direction. The main bulk of the ice sphere is also starting to break apart.

[1] Impact Cratering and Break-up of the Small Bodies of the Solar System. Leliwa-Kopystynski J., Burchell M.J. and Lowen D. Icarus 195, 817 – 826, 2008

P.05 In-situ X-ray studies of mesoscopic phenomena during dynamic loading

M Rutherford

Institute of Shock Physics, Imperial College London

A rigorous understanding of the behaviour of condensed matter under the extreme conditions induced by dynamic loading necessitates an appreciation of material behaviour across length scales spanning the mesoscale (sub-μm to mm) to the continuum. For many years though, the existence and kinetics of fundamental processes responsible for bulk material behaviour have often been inferred from either time-resolved continuum-level measurements or microstructural analysis of material recovered post-shock. Ultimately, real-time, in-situ, spatially and time-resolved studies of the mesoscale are required to understand the evolution of processes such as defect generation, localised plasticity, and phase transformation in compressed materials.

This poster will present an overview of the ISP’s dynamic x-ray imaging programme at the Diamond Light Source synchrotron alongside recent results in which in-situ x-ray imaging was complimented by heterodyne-velocimetry and line-VISAR measurements. Future directions for work at the Diamond Light Source and the Central Laser Facility will be touched upon.

P.06 Phase stability and elastic properties of titanium alloys

D Smith1, A Sankaran2, H Weekes2, JE Proctor1* and D Dye2 1Joule Physics Laboratory, University of Salford, UK, 2Imperial College London, UK

The desirable mechanical properties of titanium and our ability to precisely vary these properties through alloying with different elements are responsible for the wide range of industrial applications of titanium alloys. What is particularly important is our ability to stabilize different phases of titanium at ambient conditions by alloying with different elements. However, surprisingly little data is available that directly observes the stabilizing effect of alloying with different elements by observing its effect on the high pressure phase transition pressures in titanium. In this work we have studied the phase stability of a wide range of β-titanium alloys.

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We find surprisingly good phase stability of these alloys in the β-phase even at pressures up to 40 GPa, well into the ω-phase region on the pure titanium phase diagram. We found that Ti-7Mo, Ti-7Mo-1O, Ti-24Nb-4Zr-8Sn (Ti-2448) and Ti-36Nb-2Ta-0.3O (“gum metal”) all remained stable in the β phase at high pressure up to 40 GPa. Ti-36Nb-2Ta-0.3O was pressurized to much higher pressure (70GPa), and a transformation into a mixture of α and ω phases was observed commencing at 50 GPa.

We also conducted a study of a sample of the α-titanium Ti-6Al-4V (Ti64) alloy with ultra-low interstitial oxygen content. We compressed this alloy up to 50 GPa under non-hydrostatic conditions to compare to our previous work on this alloy with normal interstitial oxygen content. We found that the α→ω transition pressure was reduced slightly by the absence of interstitial oxygen.

P.07 Solubility of hydrogen in Zircaloy-4 nuclear fuel cladding

D Smith1, H Weekes2*, SC Lumley2, JE Proctor1*, E Gregoryanz3, M Wenman2 and D Dye2 1Joule Physics Laboratory, University of Salford, UK, 2Imperial College London, UK,3School of Physics and Centre for Science at Extreme Conditions, University of Edinburgh, UK

A key issue with water cooled nuclear reactor fuel is hydrogen pickup by the zircaloy fuel pin cladding. This has many consequences regarding safety and economics of the fuel, particularly due to the low solubility of hydrogen in zirconium alloys (~60 ppm at 300°C)1 and the resulting precipitation of a brittle hydride phase which appears as a needle-like precipitate2. These hydrides are an issue during any reactivity initiated accident where a sudden increase in temperature and pressure within the fuel pin can rupture the cladding.

In the literature 2 very different models of the mechanism for DHC have been proposed. The precipitate first model (PFM) suggests that hydrogen in supersaturation within the zirconium matrix will precipitate out in the presence of a hydrostatic tensile stress at a flaw such as a crack tip. The precipitation of the hydride phase removes hydrogen from solution and sets up a hydrogen concentration gradient from the bulk (high concentration) to the crack tip (low concentration), causing flow of hydrogen to the crack tip meaning the hydride grows until a critical hydride size causes it to crack.

The opposing model is known as diffusion first model (DFM). DFM suggests that the introduction of a flaw producing a tensile hydrostatic stress field will reduce the chemical potential of hydrogen in this region. The chemical potential gradient set up between the crack tip and the bulk causes hydrogen to flow to the crack tip until it exceeds the solubility limit and causes the precipitation of a hydride. Provided the stress remains tensile and there is a much greater amount of hydrogen in the bulk than can be consumed, this process continues allowing hydrides to grow until they reach a critical size for fracture.

Previous studies have studied the behaviour of the system only under tensile stress. Here we study the behaviour of the system under compressive stress, allowing much higher stress to be applied to the system than previously achieved. We have performed a series of X-ray diffraction experiments on both pure and electrochemically hydrided zircaloy-4 under compression of up to 10 GPa pressure in a diamond anvil high-pressure cell, both in an inert atmosphere and in a hydrogen atmosphere. Using this technique, we estimate the solubility of hydrogen in zircaloy as a function of pressure by observing a lattice expansion of the zircaloy upon absorption of hydrogen, and also observe the precipitation of hydrogen out of solution on pressure decrease through the observation of separate X-ray diffraction peaks originating from a hydride phase.

Our results give strong support to the PFM model: that hydrostatic compressive stress increases hydrogen solubility in zircaloy and hydrostatic tensile stress decreases it.

[1] H Okamoto, J. Phase Equilib. Diff. 27, 548 (2006) [2] GJC Carpenter et al., J. Nucl. Mat. 48, 267 (1973)

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P.08 On the importance of the 7.62 mm FFV bullet jacket during penetration

A Roberts, G J Appleby-Thomas, P J Hazell, A Hameed and M Gibson

Cranfield University, UK

There is a paucity of information apparent in the literature on the effects of the jacket during penetration, despite its role as a critical component of ammunition. Recent studies have strongly suggested that for a 7.62 mm FFV projectile there is a measurable affects due to the jacket on penetration into ceramic-faced targets. Here, reverse ballistics shots employing 7.62 mm FFV rounds impacting ceramic ‘targets’ accelerated to c.a. 830 m/s were undertaken. By varying the degree of jacket modification about the ‘projectile’ tip while monitoring the penetration event a multi-channel flash X-ray system, the contribution of the jacket to penetration was dynamically illustrated.

P.09 Can fossils survive hypervelocity impact?

L J Yolland, K H McDermott, M C Price and M J Burchell

University of Kent, UK

Introduction: Panspermia is the idea that life comes from space. These days, litho-panspermia [1] is a more common idea, namely that a rock is ejected from a planetary surface as ejecta after a nearly giant impact, drifts through space and impacts another planet. And if it carries life it can “seed” the new planet. There is a variant on this, namely that rocks may also carry fossils and these can then be found in meteorites. Hunting for fossils in meteorites has gone on for many years, e.g., [2], but no one has shown if fossils in projectiles can indeed survive the shock pressures involved in this process of ejection and subsequent impact. Therefore, we have carried out experiments with fossil laden projectiles to look for fossil survival.

Method: We use diatom fossils frozen into a projectile in this study. The projectiles were fired using a two-stage light gas gun at Kent. We fired at water, and then filter the water to look for fossils or their fragments. We use a SEM to image the recovered material after an impact. Impact speeds have ranged from 0.388 to 5.34 km s-1. We model the impacts using the Autodyn hydrocode to understand the shock history of the samples.

Results: We find that below 1 km s-1, we can readily find fossils after the impact. However, at higher speeds the mean fragment size falls and the number of intact fossils we recover falls as well. The mean size after impact, along with the largest fragment found in each shot is shown in Fig. 1 a vs impact speed, and Fig. 1 b vs. peak shock pressure. However, we do still find some small intact fossils in impacts at 5 km s-1.

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[1] Melosh HJ. 1988 The rocky road to Panspermia. Nature 332, 687 – 688 [2] McKay DS, Gibson EK, Thomas Keprta KL, Vali H, Romanek CS, Clemett SJ, Chillier XDF, Maechling CR, Zare

RN. 1996 Search for past life on Mars: Possible relic biogenic activity in Martian meteorite ALH84001. Science 273, 924 – 930

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