• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.314-318
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• 2006

The interest on the detonation in small tubes, which can be applied to the ignition devices of propulsion system, is increasing. However, the propagation dynamics of detonation waves in small tubes has not been investigated clearly yet. In the present experiments, propagations of detonation waves in stoichiometric propane-oxygen mixture through transparent tubes were recorded using a high speed camera and average velocities were measured as well. In terms of average velocity, there exists a transition regime where the waves show smooth transition from the normal Chapman-Jouguet(CJ) detonation to the low velocity detonation$(\sim0.5V_{CJ})$ along the decreasing initial pressure. In this transition regime, the detonation waves are highly unstable and show cyclic or intermittent longitudinal velocity fluctuation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.6
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• pp.803-812
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• 1998

In this study, testing equipment with which several kinds of valves can be tested was composed. Two kinds of tilting check valves and a swing check valve were tested to analyze their dynamic characteristics. The results of the experiment showed that the tilting check valves protected the pump but that the swing check valve could not protect the pump when the reverse flow rate was high. Also the dynamic equation of the tilting check valve was formulated and simulated using system characteristic constant t$_{c}$ and one method of predicting t$_{c}$ by comparing the results of the simulation with the results of the experiment was proposed.sed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.1
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• pp.25-40
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• 2004

The supersonic shock wave generated by fully coupled explosion will change into subsonic shock wave, plastic wave, and elastic wave consecutively as the wave propagates through rock mass. While the estimation of the blast-induced peak pressure was the main aim of the companion paper, this paper will concentrate on the estimation of the rise time of blast-induced pressure. The rise time can be expressed as a function of explosive density, isentropic exponent, detonation velocity, exponential coefficient of the peak pressure attenuation, dynamic yield stress, plastic wave velocity, elastic wave velocity, rock density, Hugoniot parameters, etc. Parametric analysis was performed to pinpoint the most influential parameter that affects the rise time and it was found that rock properties are more sensitive than explosive properties. The probabilistic distribution of the rise time is evaluated by the Rosenblueth'S point estimate method from the probabilistic distributions of explosive properties and rock properties. Numerical analysis was performed to figure out the effect of rock properties and explosive properties on the uncertainty of blast-induced vibration. Uncertainty analysis showed that uncertainty of rock properties constitutes the main portion of blast-induced vibration uncertainty rather than that of explosive properties. Numerical analysis also showed that the loading rate, which is the ratio of the peak blasting pressure to the rise time, is the main influential factor on blast-induced vibration. The loading rate is again more influenced by rock properties than by explosive properties.

• Explosives and Blasting
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• v.23 no.3
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• pp.27-42
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• 2005

An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). The stress wave propagation modeling was conducted by simulating the experimental approach based on the Hopkinson's effect combined with the spatting phenomenon that had previously been developed to determine the dynamic tensile strength of Inada granite. As a result, the stress wave velocity obtained by the proposed modeling technique was 4167 m/s, which is merely $3\%$ lower than the actual wave velocity of 4300 m/s for an Inada granite.