A Closed-Space Model was constructed using steel plates to examine the influence of afterburning energy load generated by explosive detonation products on the damage characteristics of confined space. Additionally, the quasi-static pressure in the confined space was simplified by applying the energy conservation law. Relying on the adiabatic index of the mixture of detonation products and air, as well as the complete afterburning degree of detonation products, a simulation method for the afterburning effect was proposed. This method was used to calculate the afterburning energy of detonation products and determine the beginning and ending times of the afterburning effect. The numerical simulation of implosion damage in a confined space was carried out by this method. The implosion simulation considering the afterburning energy load was performed by employing two simulation methods: constant reaction rate and linearly increasing reaction rate. The results were compared with the implosion simulation results without considering the afterburning effect. The influence and degree of change of the afterburning effect on the implosion damage characteristics were analyzed. It is found that the afterburning effect with different reaction rates has a significant influence on the detonation damage characteristics, except for the temperature, in confined spaces. Moreover, the enhancement effect of the constant reaction rate is the most significant. It increased the velocity and acceleration loads under implosion in the confined space by 42.67% and 71.21%, respectively. The overpressure and quasi-static pressure were increased by 74.42% and 74.95%, respectively, and the kinetic energy was increased by approximately 212%. The proposed simulation method for the afterburning effect can better simulate the dynamic response of implosion ruin in confined spaces and provides a more accurate simulation method of the afterburning effect for the design and evaluation of explosion-proof structures.
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To address the issue of assessing structural breach damage in ships under underwater explosion, a breach prediction method based on the PCA-BOA-KNN model is established.
First, finite element models for five-compartment and seven-compartment segments are constructed, and explosion simulation analysis is carried out for 21 sets of underwater explosion conditions. Subsequently, principal component analysis (PCA) is employed to reduce the dimensionality of the peak acceleration, peak velocity, peak displacement, peak stress and peak overpressure values, resulting in two principal features. Finally, the PCA results are integrated into a Bayesian optimization algorithm (BOA) K-Nearest Neighbors (KNN) model. The established breach prediction model is used to predict the breach conditions at different ship cross-sections under a set of conditions.
The results show that by using PCA to extract the first two factors, the cumulative contribution rate is 85.165%. Therefore, the first two factors can represent the primary information of the five features. The results obtained using the PCA-BOA-KNN breach prediction model are generally consistent with the simulation results.
The proposed prediction model approach is effective for predicting ship structural breaches and has reference value for predicting breachs in ship structures with different principal dimensions.
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