Dr Trevor Cloete

Senior Lecturer

Trevor was born in Cape Town and completed his primary schooling at various schools in the Cape Town area. He attended Hottentots Holland High School for his secondary education where he Matriculated in 1989. In 1990 he entered the University of Stellenbosch to study engineering, obtaining a B.Ing (Meganies) in 1993 and a M.Ing (Meganies) in 1996 (these degrees are the equivalent of a B.Sc. and M.Sc. in Mechanical Engineering). His masters dissertation concerned the numerical simulation of fibre composite production techniques involving viscous fluid flow and heat transfer through anisotropic porous media. He is currently reading for a PhD in Structural Impact under the supervision of Prof. G. Nurick.

Provisional Ph.D. Title: The Deformation and Fracture of Blast Loaded Plates

 

Current Research

The response of structures, such as an armoured personal carrier (APC), to fluid shock waves produced by high explosives, such as a landmine, is a complex and multi-faceted problem. In particular, the hull must be able to isolate the passengers from the landmine blast while not exceeding the weight and space constraints that would make the vehicle impractical. This implies that both penetration (i.e. large plastic deformation) of the hull into the passenger space and/or loss of hull integrity (i.e. tearing or shear failure) must be prevented.

Numerical simulations are playing an increasing role in the analysis of hull designs. The numerical problem is challenging on several fronts, in particular the simulation of various deformation mechanisms at differing scales. For instance, large plastic deformation occurs at the scale of the vehicle while tearing and shear failure occur at he scale of a plate thickness. A practical analysis methodology that can capture both these phenomena along with the total vehicle response is required.

A related problem is that the experimental results of blast tests reported in the open literature do not provide data with the same level of detail as obtained from numerical simulations. In other words, sufficient data for code validation to the required level of detail is not easily available.

The primary research objective of this Ph.D. is the design and development of a precision blast test rig that can provide high fidelity experimental data for the validation of numerical simulation methodologies. In particular the rig can measure reaction forces at a plate boundary so as to capture the timing and magnitude of boundary failure events. The rig can also be configured to measure the blast pressure history. This work includes developing analytical models of the blast rig and specimen configuration. Ultimately, this rig will be used to investigate the degree of detail and sophistication required in both material testing and numerical modelling to predict the behaviour of blast loaded plates to within the bounds of experimental accuracy.

Other Research Interest

  • Dynamic material testing techniques
    • Intermediate strain rates
    • Combined shear and tension/compression
  • Dynamic ductile damage
  • Dynamic properties of cortical and cancellous bone

 

Publications

Journal Papers

  • 2007, Hartley R. S., Cloete T. J. and Nurick G. N., “An Experimental Assessment of Friction Effects in the Split Hopkinson Pressure Bar using the Ring Compression Test”, International Journal of Impact Engineering, Vol. 34, pp. 1705-1728.
  • 2006, Govender R. A., Cloete T. J., and Nurick G. N., “A Numerical Investigation of Dispersion in Hopkinson Pressure Bar Experiments”, J. Phys. IV France, Vol. 134, pp. 521-526.
  • 2006, Cloete T. J., Hartley R. S. and Nurick G. N., “A Microstructural Investigation of ‘Machining Rings’ and Deformation Uniformity for Dynamic Ring Compression Tests”, J. Phys. IV France, Vol. 134, pp. 591-596.
  • 2005, Cloete T. J., Nurick G. N. and Palmer R. N., “The Deformation and Shear Failure of Peripherally Clamped Centrally Supported Blast Loaded Circular Plates”, International Journal of Impact Engineering, Vol. 32, pp. 92-117.
  • 2004, McBride A. T., Govender I., Powell M. S. and Cloete T. J., “Contributions to the Experimental Validation of the Discrete Element Method Applied to Tumbling Mills”, Engineering Computations, Vol. 21, No. 2-4, pp. 119-136.
  • 2004, Marais S. T., Tait R. B., Cloete T. J. and Nurick G. N., “Material Testing at High Strain Rate using the Split Hopkinson Pressure Bar”, Latin American Journal of Solids and Structures, Vol. 1, pp. 319-339.
  • 2003, Cloete, T. J., Ahmed, R. and Nurick G. N., "Peripherally Clamped Centrally Supported Blast Loaded Circular Plates: A Precision Test for Code Validation", J. Phys. IV France, Vol. 110, pp. 507-512.

Published Conferences Proceedings

  • 2009, Cloete, T.J. and Oxtoby, S., "A new technique for compression tests at intermediate strain rates: Prototype results", In G. Dyckmans (ed.), Proceedings of the 9th International DYMAT conference on the mechanical and physical behaviour of materials under dynamic loading, 7-11 September 2009, Royal Military Academy, Brussels, Belgium. France: Edp Sciences S.A. ISBN 9782759804733.
  • 2009, Cloete, T.J., Van der Westhuizen, A., Kok, S. and Nurick, G.N., "A tapered striker pulse shaping technique for uniform strain rate dynamic compression of bovine bone", In G. Dyckmans (ed.), Proceedings of the 9th International DYMAT conference on the mechanical and physical behaviour of materials under dynamic loading, 7-11 September 2009, Royal Military Academy, Brussels, Belgium. France: EDP Sciences S.A. ISBN 9782759804733.
  • 2007, Van der Westhuizen A., Cloete T. J., Kok S. and Nurick G. N., “Strain rate dependent mechanical properties of bovine bone in axial compression”, In H. Mackay (ed.), Proceedings of the 2007 International IRCOBI Conference on the Biomechanics of Injury, 19-21 September 2007, pp. 377-384, Maastricht, The Netherlands. AGU Zurich Winkelriedstrasse, Switzerland: IRCOBI. ISBN 2-9514210-8-7
  • 2004, Cloete T. J., Palmer R. N. and Nurick G. N., “The Deformation and Shear Failure of Peripherally Clamped Centrally Supported Blast Loaded Circular Plates”, 5th International Symposium on Impact Engineering (ISIE 5), Cambridge, United Kingdom.
  • 2000, Cloete, T. J. and; Nurick, G. N.,"A Strain Hardening Law Based on a Composite Mechanics Approach to Dislocation Substructure Formation", Proceedings of the 3rd South African Conference on Applied Mechanics, (SACAM 2000), Durban, South Africa, pp. 691-696.
  • 2000, Marais S. T., Tait R. B. and Cloete T. J., “Evaluation of Pochhammer-Chree dispersion curves in an Unsplit Hopkinson Bar”, 3rd Solid Mechanics, Materials and Manufacturing Conference (M3), Cape Town, South Africa.
  • 2000, Cloete T. J., Daykin L. and Nurick G. N., “A Numerical Assessment of the Accuracy of Data Processing Procedures for the Split Hopkinson Bar”, 3rd Solid Mechanics, Materials and Manufacturing Conference (M3), Cape Town, South Africa.
  • 1996, Cloete, T. J. and; van der Westhuizen, J. "An Alternative Approach to Volume Flux Prediction During FEM Modelling of RTM", Proceedings of the 1st South African Conference on Applied Mechanics, Midrand, South Africa, pp. 53-60.