Time filter

Source Type

Halifax, Canada

Ripley R.C.,University of Waterloo | Ripley R.C.,Martec Ltd. | Zhang F.,University of Waterloo | Lien F.-S.,University of Waterloo
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

For condensed explosives, containing metal particle additives, interaction of the detonation shock and reaction zone with solid inclusions leads to high rates of momentum and heat transfer that consequently introduce non-ideal detonation phenomena. During the time scale of the leading detonation shock crossing a particle, the acceleration and heating of metal particles are shown to depend on the volume fraction of particles, dense packing configuration, material density ratio of explosive to solid particles and ratio of particle diameter to detonation reaction-zone length. Dimensional analysis and physical parameter evaluation are used to formalize the factors affecting particle acceleration and heating. Three-dimensional mesoscale calculations are conducted for matrices of spherical metal particles immersed in a liquid explosive for various particle diameter and solid loading conditions, to determine the velocity and temperature transmission factors resulting from shock compression. Results are incorporated as interphase exchange source terms for macroscopic continuum models that can be applied to practical detonation problems involving multi-phase explosives or shock propagation in dense particle-fluid systems. © 2012 The Royal Society.

Ripley R.C.,Martec Ltd. | Zhang F.,Defence Research and Development Canada
Journal of Physics: Conference Series | Year: 2014

The formation of post-detonation 'particle' jets is widely observed in many problems associated with explosive dispersal of granular materials and liquids. Jets have been shown to form very early, however the mechanism controlling the number of jetting instabilities remains unresolved despite a number of active theories. Recent experiments involving cylindrical charges with a range of central explosive masses for dispersal of dry solid particles and pure liquid are used to formulate macroscopic numerical models for jet formation and growth. The number of jets is strongly related to the dominant perturbation during the shock interaction timescale that controls the initial fracturing of the particle bed and liquid bulk. Perturbations may originate at the interfaces between explosive, shock-dispersed media, and outer edge of the charge due to Richtmyer-Meshkov instabilities. The inner boundary controls the number of major structures, while the outer boundary may introduce additional overlapping structures and microjets that are overtaken by the major structures. In practice, each interface may feature a thin casing material that breaks up, thereby influencing or possibly dominating the instabilities. Hydrocode simulation is used to examine the role of each interface in conjunction with casing effects on the perturbation leading to jet initiation. The subsequent formation of coherent jet structures requires dense multiphase flow of particles and droplets that interact though inelastic collision, agglomeration, and turbulent flow. Macroscopic multiphase flow simulation shows dense particle clustering and major jet structures overtaking smaller instabilities. Late-time dispersal is controlled by particle drag and evaporation of droplets. Numerical results for dispersal and jetting evolution are compared with experiments. © Published under licence by IOP Publishing Ltd.

MacKay J.R.,Canadian Department of National Defence | MacKay J.R.,Technical University of Delft | Jiang L.,Martec Ltd. | Glas A.H.,TNO
Marine Structures | Year: 2011

Nonlinear finite element (FE) collapse pressure predictions are compared to experimental results for submarine pressure hull test specimens with and without artificial corrosion and tested to collapse under external hydrostatic pressure. The accuracy of FE models, and their sensitivity to modeling and solution procedures, are investigated by comparing FE simulations of the experiments using two different model generators and three solvers. The standard FE methodology includes the use of quadrilateral shell elements, nonlinear mapping of measured geometric imperfections, and quasi-static incremental analyses including nonlinear material and geometry. The FE models are found to be accurate to approximately 11%, with 95% confidence, regardless of the model generator and solver that is used. Collapse pressure predictions for identical FE models obtained using each of the three solvers agree within 2.8%, indicating that the choice of FE solver does not significantly affect the predicted collapse pressure. The FE predictions are found to be more accurate for corroded than for undamaged models, and neglecting the shell eccentricity that arises due to one-sided shell thinning is found to significantly decrease the resulting accuracy of the FE model. © 2011.

Martec Ltd. | Date: 2011-06-24

A ceiling fan comprising an electric motor that drives a circular plate, the circular plate has three or four equally spaced quadrants positioned adjacent its periphery each quadrant is secured to the plate to be pivotal thereto to provide limited acuate movement about the pivot axis, each quadrant having a fan blade secured thereto, the acuate movement of each quadrant being confined from a first position where the blades are within the periphery of the plate to a second position where the blades extend radially outwardly at the plate, each quadrant being attached to the plate by a coil spring which urges the quadrant into the first position, each quadrant being directly joined to the adjacent quadrant by a rigid tie bar so that any movement of one quadrant causes the same movement of all the other quadrants.

Agency: GTR | Branch: Innovate UK | Program: | Phase: Innovation Voucher | Award Amount: 5.00K | Year: 2015

Martec of Whitwell Ltd project engaging specialist knowledge of elastomer materials through the Innovation Voucher scheme of Innovate UK to help further develop their Marplug hygienic pig.

Discover hidden collaborations