Papers by Keyword: PBX

Abstract: Split Hopkinson bar technique was often used to measure the dynamic mechanical properties of engineering materials. In this paper, the dynamic tensile and compression mechanical properties of polymer explosive bonded (PBX) under different strain rates were obtained by using split Hopkinson pressure/tension bar. The thickness of the specimen and the shape of the incident wave are designed to ensure the rationality of the experimental results. By comparing the experimental results, it was found that the PBX had different dynamic tensile and compression properties. The PBXs have been tested and shown tensile and compressive strengths ratios that range between 5 and 7. A constitutive relation is developed for modeling the dynamic mechanical response of PBX-I by using the Boltzmann superposition principle with a Prony series representation. The parameters of the PBX-I were fitted by using least square method. A finite element model was used to simulate the dynamic compressive and tensile behavior of PBX-I, and the numerical simulation results were in good agreement with the experimental results, which proved that the linear viscoelastic constitutive relation can be applied to the PBX-I.

Abstract: Perforated structure is the mechanical weak link of polymer-bonded explosive (PBX). Improving its mechanical property may promote the reliability and effectiveness of weapon system. In this study, strengthening of the perforated PBX plate is conducted by employing surface coating. Digital image correlation (DIC) analysis results suggest that the regional applied epoxy coating layer is able to improve the mechanical properties of the plate. By confining the deformation and releasing the stress concentration around the perforation, the coating layer enhances the load carrying ability and energy dissipation capacity of the plate significantly. This investigation may provide a convenient and effective structure modification method for energetic material, and at the same time, lay foundation to the performance optimization of weapon system.

Abstract: This paper focuses on the ignition of polymer-bonded explosives (PBXs) under conditions of non-shock loading. The analysis uses a recently developed ignition criterion [ which is based on the quantification of the distributions of the sizes and temperatures of hotspots in loading events. This quantification is achieved by using a cohesive finite element method (CFEM) developed recently and the characterization by Tarver et al. [ of the critical size-temperature threshold of hotspots required for chemical ignition of solid explosives. Calculations are performed on PBXs having monomodal grain size distributions with grain volume fractions varying between 0.72 and 0.90. The impact velocities considered vary between 100 and 200 ms^-1. Results show that the average distance between the hotspots is dependent on the grain volume fraction. As the grain volume fraction increases, the time to criticality (t_c) decreases, signifying increases in the ignition sensitivity of PBX to impact loading. The microstructure-performance relations obtained can be used to design PBXs with tailored performance characteristics and safety envelopes.

Abstract: In order to integrate the telecommunications network and IP network, providing companies with a unified voice services, a design of IP PBX phone system is proposed. On the basis of VoIP, this design implements most of the traditional PBX functions. It provides function-code functionality allows user to directly control phone; provides user-trunk-LLDC configurations to manage user’s privilege; provides a powerful and flexible IVR system; provides SIP phone and SIP trunk support. It also supports most call features such as black list, speed dial code, forward, transfer, pick-up, can meet most companies’ requirements.

Abstract: A framework for quantifying the thermomechanical response of polymer bonded explosives (PBX) at the microstructural level is developed using a cohesive finite element method (CFEM). This framework allows the contributions of individual constituents, fracture and frictional contact along failed crack surfaces to heating to be analyzed and tracked. Digitized micrographs of actual PBX materials and idealized microstructures with various distributions of grain sizes are used in the analysis. The analysis concerns impact loading of HMX/Estane with strain rates on the order of 104 – 105 s-1. Issues studied include large deformation, thermomechanical coupling, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, and frictional heating. The Estane matrix is described by a thermo-elasto-viscoelastic constitutive formulation, accounting for temperature dependence, strain rate sensitivity and strain hardening. The HMX crystals are assumed to be elastic under the conditions analyzed. Energy localization leading to formation of local hot spots as potential ignition sites is primarily due to the viscoelastic dissipation in the matrix in early stages of deformation and frictional heating along crack surfaces in later stages of deformation. Microstructure-response relations that can be used in the design of soft energetic composites are established.