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Department of Chemical Engineering
756
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Department of Electrical Engineering
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Department of Biological Sciences
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    ABSTRACT: In this article, we survey the developments in the generalised models of repairable systems reliability during 1990s, particularly the last five years. In this field, we notice the sharp fundamental problem that voluminous complex models were developed but there is an absence of sufficient data of interest for justifying the success in tackling the real engineering problems. Instead of following the myth of using simple models to face the complex reality, we select and review some practical models, particularly the stochastic processes behind them. The Models in three quick growth areas: age models, condition monitoring technique related models, say, proportional intensity and their extensions, and shock and wearing models, including the delay-time models are reviewed. With the belief that only those stochastic processes reflecting the instinct nature of the actual physical processes of repairable systems, without excessive assumptions, may have a better chance to meet the demands of engineers and managers.
    ORiON. 12/2014; 16(2).
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    ABSTRACT: This paper presents the results of an experimental and numerical investigation into the response of circular Domex-700 MC steel plates to repeated uniform blast loads. The Domex 700 steel tests plates of thickness either 2 or 3mm are mounted onto a ballistic pendulum and subjected to uniform blast load up to five times for repeated loading. In general, the plates show large inelastic global deformation with thinning occurring at the clamped boundary and in some cases tearing. A trend of increasing permanent mid-point deflection is observed for an increase in charge mass and number of witnessed blast loads. The results also show a decrease in the incremental mid-point deflection and an increase in the Vickers hardness of the plate at the boundary and central region with increasing number of witnessed blast loads. Numerical simulations are carried out to gain further insight into the deformation of plates subjected to repeated blast loading using ABAQUS/Explicit v6.10.1 in conjunction with the inbuilt blast function code, ConWep. A scaling factor is adopted to model the amplified blast wave resulting from the detonation of cylindrical charges at one end of a cylindrical tube. Very good correlation is obtained with regards to midpoint deflection and deformation profiles. The plastic strain obtained numerically shows good qualitative correlation with the experimental Vickers hardness tests.
    International Journal of Impact Engineering 12/2014;
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    ABSTRACT: This article presents the results of an experimental and numerical investigation into the response of partially confined right-circular stainless steel cylinders to air-blast loading. The blast loading was generated by detonating spheres of plastic explosive at two axial positions along the centre line of the cylinders. Partial confinement was created by closing one end of the cylinder and leaving the other end free to vent to air. Numerical simulations were performed to gain insight into the blast wave propagation and the transient response of the cylinders. As expected, the diametric deflection of the cylinders increased with increasing charge mass, and was a maximum in the same axial location as the charge. For the centrally located charges (L = 150 mm), the diametric deflections increased linearly with increasing charge mass. The numerical simulations showed that the reflected pressure from the closed end of the cylinder (that is, the axial component) interacted with the radially developed pressure reflected from the cylinder walls. This caused the pressure to be driven out of the open end of the cylinder when L = 150 mm, meaning that the expected quasi-static pressure accumulation had little effect on the deformation of the cylinder. When the charges were placed closer to the open end, at L = 225mm, the experimental diametric deflections increased exponentially with increasing charge mass, and were significantly higher than the deflections measured when L = 150 mm. The simulations predicted linear increases similar to those for L = 150 mm, but at slightly higher magnitudes. This eliminates the lower mechanical support at the open end from being the main cause of the higher experimentally observed deflections, as this would also have been observed in the numerical simulations. Since the numerical simulation results were unable to fully predict the response and pressure accumulation when L = 225mm, there must be some physical phenomena must be present in the experiments that did not affect the response when L = 150 mm (that was also not captured by the numerical simulations). One possible explanation is that afterburning of the explosive products was a significant factor when L = 225mm, but this requires further investigation to confirm.
    International Journal of Impact Engineering 11/2014;

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