Infrastructure Engineering - Theses
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ItemDeformation of polyurea-coated steel plates under localised blast loading( 2013)This thesis presents the results of experimental and numerical studies to investigate the effect of polyurea coatings on the deformation of steel plates under localised blast loading. Exploratory experiments and numerical modelling were initially performed to develop an explosive test methodology and provide validation data for preliminary numerical modelling. Using the developed methodology, explosive testing was conducted on bare and polyurea-coated steel plates, where the plate configurations all had the same areal density. It was found that the polyurea-coated plates resulted in higher residual deformations compared to the uncoated plates, with the residual deformations increasing with coating thickness (and hence increasing with thinner steel). High speed video footage of the events revealed that the polyurea coatings debonded and hyper-extended during the events, before coming to rest back against the plate. This resulted in transient deformations of the polyurea coatings which were approximately twice that of the bare steel plates. Following the explosive experiments, numerical modelling of the polyurea-coated plates under blast loading was conducted using AUTODYN®. The dimensions of the numerical mesh were selected through a sensitivity study. De-bonding of the polyurea was reproduced by using a thin layer of elements which failed at a designated principal stress value, which was tuned to fit the experimental measurements. The polyurea was modelled using a two-parameter Mooney-Rivlin relationship, the constants for which were validated in the preliminary simulations. The initial models of the explosive experiments showed excellent agreement with the experimental residual deformations of the plates, but under-predicted the peak transient deformations of the polyurea. To improve the model accuracy, tensile tests were conducted on the polyurea at various strain rates and used to fit new Mooney-Rivlin material model constants. The new material model constants gave improved results for the transient deformations of the polyurea coatings. Parametric studies were conducted using the validated material models to investigate the effect of bond strength, polyurea stiffness, polyurea bulk modulus and the coating location. It was found that the greatest improvement could be achieved by changing the coating location to the front (blast side) face of the steel plate instead of the back face. The coating performance could also be improved by increasing the polyurea stiffness or bulk modulus, or increasing the strength of the bond between the polyurea and the plate. None of the polyurea-coated plates in the parametric studies performed as well as a mass-equivalent steel plate. However, polyurea-coated steel plates may still be preferable for other reasons, for example when the coating is to be applied as an appliqué (add-on) armour.