The performance of detonation and underwater explosion (UNDEX) of a six-formula HMX-based aluminized explosive was examined by detonation and UNDEX experiments. The detonation pressures, detonation velocities, and detonation heat of HMX-based aluminized explosive were measured. The reliability between the experimental results and those calculated by an empirical formula and the KHT code was verfied. UNDEX experiments were carried out on the propagation of a shock wave and a bubble pulse of a 1 kg cylindrical HMX-based aluminized explosive under-water at a depth of 4.7 m. Based on the experimental results of the shock wave, the coefficients of similarity law equation for the peak pressure and attenuation time constant of shock wave were in acceptable agreement. The bubble motion during UNDEX was simulated using MSC.DYTRAN software, and the radiusÀtime curves of bubbles were determined. The effect of the aluminum/oxygen ratio on the performance of the detonation and UNDEX for an HMX-based aluminized explosive was discussed.

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Abstract:To understand the underwater explosion (UNDEX) performance of RDX/AP-based aluminized explosives, six formulations of the explosives were prepared, with Al content varying from 30% to 55% and ammonium perchlorate (AP) content from 45% to 20%. A series of UNDEX tests that used a 1 kg cylindrical charge was conducted underwater at a depth of 4.7 m. The pressure histories of the shock wave produced at different positions and the bubble periods were measured. The coefficients of the similarity law equation for the shock wave parameters were fitted with experimental data. The effect of the aluminum/ oxygen (Al/O) ratio on the performance of the energy output structure for RDX/AP-based aluminized explosives is discussed. The bubble motion during UNDEX was simulated using MSC.DYTRAN software, and the radius-time curves of the bubbles were determined. The results show that AP influences the detonation reaction mechanism of RDX/AP-based aluminized explosives, which causes different UNDEX performances. The bubble energy of the RDX/AP-based aluminized explosive was higher than that of RDX-based and HMX-based aluminized explosives.

Abstract:The detonation performances of TNT-, RDX-, HMX-, and RDX/AP-based aluminized explosives were examined through detonation experiments. The detonation pressure, velocity, and heat of detonation of the four groups of aluminized explosives were measured. Reliability verification was conducted for the experimental results and for those calculated with an empirical formula and the KHT code. The test results on detonation pressures and velocities were in good agreement with the predicted values when aluminum (Al) particles were considered inert. The experimental heat of detonation values exhibited good consistency with the predicted values when a certain proportion of Al particles was active. Ammonium perchlorate (AP) can effectively reduce the detonation pressure and improve the heat of detonation for the RDX/AP-based aluminized explosive. A comparison of the current test results and literature data shows that errors may exist in early test data. The test data presented in this study allow for an improved understanding of the detonation performance of the four groups of aluminized explosives.

The response of aluminium sandwich panels with three thicknesses’ core subjected to different underwater loading levels has been studied in the fluid-structure interaction (FSI) experiments. The transient response of the panels is measured using a three-dimensional (3D) Digital Image Correlation (DIC) system, along with high-speed photography. The full-field shape and displacement profiles of dry face sheets were recorded in real time compared with those of monolithic plate. The out-of-plane deflection and in-plane strain were quantified and analyzed. Three typical deformation modes of sandwich panel were identified. The results show that the core structure is crushed resulting in an initial large circular shape of deformation in the center area of panels. From this moment on, the panel is starting to act as a free vibration beam with initial velocities. The deformation modes consisted of homogeneous large deformation for both face sheets, obvious deformation border on wet face sheet, core node imprinting, remarkable wrinkled skin of deformation border, and a partial delamination and partial tear failure of the dry face. The blast-resistance of sandwich panel can be highly efficiently improved by increasing the thickness of core structure.

Space manipulator suffers from vibration problems mainly due to the flexibility of joints and links in a microgravity environment. This article presents a new optimization method of trajectory planning with minimum residual vibration for space manipulator system which is modeled by absolute coordinate-based method. First, absolute nodal coordinate formulation, which can describe large rotation and large deformation of flexible bodies precisely, is used to describe the deformation of flexible links, and natural coordinate formulation with nonlinear torsion stiffness function is used to model flexible joints. Then, joint rotation trajectory resulting from the planned end-effector trajectory by inverse kinematics theory is discrete through the proposed cosine-based function that has been validated to suppress the residual vibration. The particle swarm optimization algorithm is employed to achieve minimum residual vibration by optimizing redundant coefficients of movement derived from inverse kinematics theory. The effectiveness of the proposed method is illustrated via simulation of a planar three-link manipulator taking large deformation and large rotation into account. Results show that the optimized method can exhibit better features for the residual vibration suppression as compared to those of the original cosine-based trajectory.

This study proposes an effective method to measure centrosymmetric 3D static and dynamic deformations from the microscale to macroscale using grid method with a single camera. The camera was tilted at a particular angle and used to observe specimen grids in order to acquire coupling fields of both in-plane and out-of-plane displacement. This study also analyzes the decoupling methods of these two displacement types, and a systematic deduction of a theoretical equation for 3D deformation analysis was conducted based on the method. The sensitivity of morphology measurement was then evaluated and the elimination of noise and rotational errors was discussed. The efficiency and accuracy of this technique was verified through a microscale static feasibility test and a highspeed impact experiment that simulated an underwater explosion. The proposed approach uses minimal equipment, is simple and convenient, and can be used to measure centrosymmetric 3D deformation in multi-scale both statically and dynamically. In addition, this method avoids the nonsynchronization problem of a pair of high-speed cameras in high-speed 3D measurements.