P. Frankl

Qinetiq (United Kingdom)

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Peter Gould

Qinetiq (United Kingdom)

P. Church

Qinetiq (United Kingdom)

Ian Cullis

Halstead Hospital

Paul F. Greenwood

University of Western Australia

Nikolaos Nikiforakis

University of Cambridge

Philip Blakely

University of Cambridge

R. Cornish

Halstead Hospital

I. Lewtas

Qinetiq (United Kingdom)

Paul Bennett

University of Cambridge

Cooperative Institutions

Qinetiq (United Kingdom)

University of Cambridge

Halstead Hospital

Schlumberger (British Virgin Islands)

Sevenoaks Hospital

Syracuse University

University of New England

University of Alberta

Ministry of Defence

University of Washington

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On the problem of symmetrical flow past a given symmetrical profile with subsonic velocity at infinity and local supersonic velocities

Journal of Applied Mathematics and Mechanics (1959)

P. Frankl

Infinity

Discontinuity (linguistics)

Choked flow

10.1016/0021-8928(59)90044-9

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Predictive model for segmented poly(urea)

EPJ Web of Conferences (2012)

Peter Gould R. Cornish P. Frankl I. Lewtas

Segmented poly(urea) has been shown to be of significant benefit in protecting vehicles from blast and impact and there have been several experimental studies to determine the mechanisms by which this protective function might occur. One suggested route is by mechanical activation of the glass transition. In order to enable design of protective structures using this material a constitutive model and equation of state are needed for numerical simulation hydrocodes. Determination of such a predictive model may also help elucidate the beneficial mechanisms that occur in polyurea during high rate loading. The tool deployed to do this has been Group Interaction Modelling (GIM) – a mean field technique that has been shown to predict the mechanical and physical properties of polymers from their structure alone. The structure of polyurea has been used to characterise the parameters in the GIM scheme without recourse to experimental data and the equation of state and constitutive model predicts response over a wide range of temperatures and strain rates. The shock Hugoniot has been predicted and validated against existing data. Mechanical response in tensile tests has also been predicted and validated.

Polyurea

10.1051/epjconf/20122604007

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Simulating geometrically complex blast scenarios

Defence Technology (2016)

Ian Cullis Nikolaos Nikiforakis P. Frankl Philip Blakely Paul Bennett

The effects of blast waves generated by energetic and non-energetic sources are of continuing interest to the ballistics research community. Modern conflicts are increasingly characterised by asymmetric urban warfare, with improvised explosive devices (IEDs) often playing a dominant role on the one hand and an armed forces requirement for minimal collateral effects from their weapons on the other. These problems are characterised by disparate length- and time-scales and may also be governed by complex physics. There is thus an increasing need to be able to rapidly assess and accurately predict the effects of energetic blast in topologically complex scenarios. To this end, this paper presents a new QinetiQ-developed advanced computational package called EAGLE-Blast, which is capable of accurately resolving the generation, propagation and interaction of blast waves around geometrically complex shapes such as vehicles and buildings. After a brief description of the numerical methodology, various blast scenario simulations are described and the results compared with experimental data to demonstrate the validation of the scheme and its ability to describe these complex scenarios accurately and efficiently. The paper concludes with a brief discussion on the use of the code in supporting the development of algorithms for fast running engineering models.

Ballistics

Blast wave

10.1016/j.dt.2016.01.005

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Assessment of Ductile Fracture Model in Pipe Fracture Scenario

Procedia Engineering (2017)

P. Frankl P. Church Peter Gould

QinetiQ has a major and long standing interest in the dynamic deformation and fracture response of materials and has been very active in developing constitutive and fracture models. These models have been validated across a number of different tests, triaxial stress states and strain rates [1]. The models have also been used on a range of Defence and commercial applications where the material characterisation has been controlled by QinetiQ. However, they have not been exercised extensively on industrial applications using available data in the literature. The constitutive models are based on interrupted tensile testing to separate the strain hardening, strain rate and thermal softening and for body centred cubic (BCC) steels give rise to the modified Armstrong-Zerilli model [1]. The ductile fracture model is based on a path dependent approach linking the damage to the stress-state resulting in the Goldthorpe Path Dependent Fracture (PDF) model [2]. Essentially the Goldthorpe PDF model gives a single value of critical damage (Void Fracture Number – VFN) applicable to all stress states and strain rates. This paper describes the application of the QinetiQ constitutive and fracture models in the simulation of an industrial application and assesses their ability to capture the main deformation and fracture mechanisms. The application was an anchor dropping onto a pipe both dynamically and statically to determine whether the pipe is fractured [3]. The DYNA3D hydrocode was used to simulate the dynamic impact and the subsequent deformation and fracture of the pipe. The material constants for the model were estimated for the actual materials by using the testing published in the literature [3] and comparing them with 'similar' materials within the QinetiQ materials database. Given there is some subjectivity in this process, the likeliness of failure was investigated, particularly regarding the VFN relating to the fracture process. The results are discussed with respect to the degree of deformation and fracture within the pipe and the sensitivity of these features to the input conditions. The results are also discussed in the context of whether the predictive accuracy of the simulations is such that they could ultimately be used to design a pipe that is more resistant to the impact loading, for example by increasing the yield strength through processing.

Hardening (computing)

Void (composites)

10.1016/j.proeng.2017.08.086

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