Shelf-life estimation of gun propellant stockpile

Gun propellant stability is an important consideration when assessing the safety of gun ammunition. In order to predict deteriorating stability of propellant stockpiles over lifetime, the master sample surveillance program has long been used by U.S. military laboratories. In this paper, we utilize the information obtained from the Navy's master sample surveillance program and employ a random effects linear model to estimate the safe shelf-life of gun propellant stockpiles. Estimation methods are discussed and applied to 5-inch 54-caliber Navy Cool (NACO) propellants. Several recommendations are made to improve the current practice of the surveillance program and subsequent data analyses.     

Numerical simulation of impact breakage of gun propellant charge

Fragmentation of gun charge bed is the basic reason of bore burst. Fragmentation dynamics of charge bed is the kernel content of launch safety. In order to simulate fragmentation of propellant bed, there is a need to obtain the packing structure of propellant bed at first. In this paper, the packing process of propellant bed under gravity is simulated, and the close-grained structure of propellant bed is achieved. Then, the 3D discrete element model of propellant bed is presented and the numerical analysis code, which can simulate impact fragmentation behavior of propellant grains, is developed. The fragmentation process of propellant bed under an impact load is calculated by the code, and the entire failure process of propellant grains is presented. Furthermore, the results obtained from simulations are in acceptable agreements with experiment observations, which indicates the accuracy of the computational model.     

Role of inorganic additives on the ballistic performance of gun propellant formulations

This paper explores the possibility of increasing the ballistic performance of gun propellant with the addition of inorganic additives viz. aluminium and ammonium perchlorate. Compositions based on propellant NQ containing additional aluminium and ammonium perchlorate in different parts were studied theoretically and experimentally. Performance in respect of ballistic parameters, sensitivity, thermal characteristics, thermal stability and mechanical properties are evaluated and compared with that of the conventional triple base propellant NQ. Experimental data on comparative study indicate that the compositions containing aluminium and ammonium perchlorate are superior to propellant NQ in respect of energy.     

A uniaxial nonlinear viscoelastic constitutive model with damage for M30 gun propellant

The nonlinear viscoelastic mechanical response of a conventional tank gun propellant, M30, is modeled using a “modified superposition integral” that incorporates the effects of microstructural fracture damage. Specifically, a linear, time-dependent kernel is convolved with the first-time derivative of a power-law function of stress and a damage “softening” that accounts for damage evolution by a microcrack growth mechanism. The microcrack damage function is a master curve formed from shifted isothermal, compressive, uniaxial constant strain rate (0.01 s⁻¹ to 420 s⁻¹) data on solid, right-circular cylinders of M30 gun propellant. An attractive feature of the model is its ability to predict work-softening behavior under conditions of monotonically increasing deformation. Time-dependent predictions of stress versus time, failure stress versus failure time, and failure stress versus strain rate, quantitatively agree with experimental results from constant strain rate tests on the propellant. Theoretical predictions of time-dependent stresses for Heaviside and “ballistic-like” strain histories are also provided.     

Process development of a nitramine propellant for the GAU-8 30 mm gun system

The Air Force is actively pursuing an alternative to the double-base propellant used in the 30 mm GAU-8 system on the A-10 aircraft. To suppress the seThe Naval Ordnance Station has just completed the manufacture of a 2268-kg (5000-lb) sample lot for the Air Force to be used for actual flight test and     

Tensile fracture of HTPB based propellant specimens

Abstract

Small addition of titanium (～0·01 wt-%) to low carbon (～0·04 wt-%) aluminium killed extra deep drawing quality steel resulted in a decrease in strain aging as well as a decrease in plastic anisotropy after cold rolling and annealing. The extent of decrease in both the strain aging and plastic anisotropy was found to be a function of Ti/N ratio. It was found that at a Ti/N ratio of 2·4, the aluminium killed low carbon steel was completely non-aging after cold rolling and annealing. However, there was also a concomitant decrease in the plastic anisotropy with the increase in Ti/N ratio. The average plastic anisotropy ratio r _avg decreased from a value of 1·8 in steels with no titanium (Ti/N=0), to a value of 1·4 in steels with Ti/N=2·4.     

Plasmon enhanced solar-to-fuel energy conversion

Future generations of photoelectrodes for solar fuel generation must employ inexpensive, earth-abundant absorber materials in order to provide a large-scale source of clean energy. These materials tend to have poor electrical transport properties and exhibit carrier diffusion lengths which are significantly shorter than the absorption depth of light. As a result, many photoexcited carriers are generated too far from a reactive surface and recombine instead of participating in solar-to-fuel conversion. We demonstrate that plasmonic resonances in metallic nanostructures and multilayer interference effects can be engineered to strongly concentrate sunlight close to the electrode/liquid interface, precisely where the relevant reactions take place. On comparison of spectral features in the enhanced photocurrent spectra to full-field electromagnetic simulations, the contribution of surface plasmon excitations is verified. These results open the door to the optimization of a wide variety of photochemical processes by leveraging the rapid advances in the field of plasmonics.     

Gas gun accelerator based on passive magnetodynamic suspension

A gas gun accelerator (GGA) based on magnetodynamic suspension (MDS) can repeatedly launch heavy objects. An object is stably suspended in the magnetic field and flies inside the launch tube without any support and friction, keeping a small gap (<0.01 m) from the tube's inner surface. The launch tube is cut into two parts, joined on each side by special cameras with slits between the upper and lower parts. Steel cores of the MDS stator are installed inside each camera. Two holders with levitator magnets are attached to the object on both sides. To start launching, an object is inserted into the tube and is accelerated by pressure of combustive gases burning behind the object.     

某外能源转管机枪击发机构参数优化设计

运用多刚体动力学理论,利用动力学分析软件ADAMS对某转管机枪的击发机构进行参数化建模并进行优化,对多个重要的参数进行了敏感度分析,得到各参数最优设计值组合,为武器的改进设计起到指导作用。该方法对武器的其他机构的优化分析也具有一定参考价值。     

Teager能量算子增强倒阶次谱提取轴承微弱故障特征

针对变速器加速过程下轴承故障特征易于暴露难以提取问题,提出一种Teager能量算子增强倒阶次谱方法。计算加速过程等角度重采样信号的Teager能量算子,对Teager能量算子输出进行倒谱分析,获得Teager能量算子增强倒阶次谱。对加速过程滚动轴承外圈、内圈剥落故障信号进行分析,结果表明,Teager能量算子能有效增强冲击成分,抑制非冲击成分;倒阶次谱能从干扰中准确识别被增强的故障冲击特征,提取轴承微弱故障特征。     

Minimizing life-cycle costs of gun propellant selection through model-based decision making: a case study in environmental screening and performance testing

 The work presented here demonstrates the first phases of a newly-proposed gun propellant formulation process that will minimize life-cycle costs through science-based design. This new approach to gun propellant formulation proposes maximal use of modeling and simulation in the earliest phases of the developmental cycle to screen candidate formulations, resulting in the elimination of probable poor performers and the identification of the most promising candidates for further study and testing. The screening and identification of promising candidate formulations is demonstrated in the study presented here under the assumption of a specific weapon platform and user requirements. The process of selecting a propellant for the assumed gun system application has been distilled into a series of measurable steps leading from a set of candidate materials, through logical and numerical filters, to a shorter list of energetic materials demonstrated as viable choices for the weapon platform. Environmental filtering and performance modeling are used to screen propellants through a well-defined sequence of tests designed to weed out materials that do not meet standards in terms of safety, energy, or manufacturability. Because much of the testing is performed by computer modeling, the gun systems and energetic materials need not be present (nor even existent) in order to be described and matched against performance requirements for future applications. The calculations presented here demonstrate that utilizing computer models in the early developmental stages of the formulation process rather than physical testing produces enormous savings in labor, material, and environmental costs, along with a tremendous reduction in the time required to select a "best candidate" propellant. Received: 3 August 1999 / Accepted: 9 November 1999     

Experimental investigation of fracture surface energy of a solid propellant under different loading rates

Fracture tests on solid propellants have been performed under three ranges of loading rate leading to fracture toughness results in terms of J_IC and (Andrews' parameter). Using two different specimen shapes, finite size effects have been pointed out (considering SENT sample) when dealing with Andrews' theory and a modified equation, taking into account the specimen compliance, is proposed. Significant influence of loading rate on J_IC is observed leading to few conclusions concerning fracture process of solid propellants.     

Concepts for enhanced energy absorption using hollow micro-lattices

We present a basic analysis that establishes the metrics affecting the energy absorbed by multilayer cellular media during irreversible compaction on either a mass or volume basis. The behaviors at low and high impulse levels are distinguished through the energy dissipated in the shock. The overall mass of an energy absorbing system (comprising a cellular medium and a buffer) is minimized by maximizing the non-dimensional dissipation per unit mass parameter for the cellular medium, Λ≡Umρs/σY$\Lambda \equiv U_{\text{m}}{\rho }_{\text{s}}/{\sigma }_{\text{Y}}$, where U_m is the dissipation per unit mass of the cellular medium, ascertained from the area under the quasi-static compressive stress/strain curve, σ_Y the yield strength of the constituent material and ρ_s the density of the material used in the medium. Plots of Λ$\Lambda$ against the non-dimensional stress transmitted through the medium, σtr/σY${\sigma }_{\text{tr}}/{\sigma }_{\text{Y}}$ demonstrate the relative energy absorbing characteristics of foams and prismatic media, such as honeycombs. Comparisons with these benchmark systems are used to demonstrate the superior performance of micro-lattices, especially those with hollow truss members. Numerical calculations demonstrate the relative densities and geometric configurations wherein the lattices offer benefit. Experimental results obtained for a Ni micro-lattice with hollow members not only affirm the benefits, but also demonstrate energy absorption levels substantially exceeding those predicted by analysis. This assessment highlights the new opportunities that tailored micro-lattices provide for unprecedented levels of energy absorption for protection from impulsive loads.     

A homogeneous and noncompetitive immunoassay based on the enhanced fluorescence resonance energy transfer by leucine zipper interaction

Fluorescence resonance energy transfer (FRET) between two GFP variants is a powerful technique to describe protein-protein interaction in a biological system. However, it has a limitation that the two variants tethered to the respective proteins have to be in sufficient proximity upon binding, which is often difficult to attain by simple N- or C-terminal fusions. Here we describe a novel method to significantly enhance FRET between GFP variant-tagged proteins with the use of leucine zippers. For the homogeneous sandwich immunoassay of a high molecular weight antigen human serum albumin (HSA), two separate single-chain Fvs recognizing distant epitopes of HSA were respectively fused with fluorescence donor ECFP or acceptor EYFP, and FRET between the two was analyzed by fluorescence spectrometry. Because these two proteins did not give any detectable FRET uponantigen addition, we tethered each protein with a leucine zipper motif (c-Jun or FosB) at the C-terminus to help the neighborhood of the GFP variants. Upon antigen addition, the new pairs showed significant antigen-dependent FRET. By exchanging the binding domains, the method will find a range of applications for the assay of other proteins and their interactions in vitro or in vivo.     

基于模态试验的某火炮身管有限元模型修正

针对某火炮刚柔耦合发射动力学中柔性身管有限元模型精度低的问题,提出一种基于支持向量机响应面模型修正理论和模态试验的身管组件有限元模型修正方法。应用ANSYS有限元分析软件对某火炮身管与支架装配体进行模态分析,提取前6阶模态的固有频率和振型,为验证模型,设计了模态试验方案,实测了火炮身管与支架装配体的模态信息。基于有限元模型数据与实测数据的相对误差,采用支持向量机响应面模型修正方法对身管与支架装配体弹性模量和密度进行修正。MAC模型确认结果和动力学模型应用结果表明：修正后的身管组件有限元模型精度有了大幅度提高,能更加真实地反映身管组件的结构特征,为射击精度分析提供了更加准确的模型基础。     

Industrial oven improvement for energy reduction and enhanced process performance

Industrial ovens consume a considerable amount of energy and have a significant impact on product quality; therefore, improving ovens should be an important objective for manufacturers. This paper presents a novel and practical approach to oven improvement that emphasises both energy reduction and enhanced process performance. The three-phased approach incorporates product understanding, process improvement and process parameter optimisation. Cure understanding is developed using Dynamic Mechanical Analysis (DMA) and CIE-Lch colour tests, which together highlight the impact of temperature variation on cure conversion and resulting product quality. Process improvement encompasses thermodynamic modelling of the oven air to evaluate the impact of insulation on temperature uniformity and system responsiveness. Finally, process parameters, such as temperature, pressure negativity and air flow, are optimised to reduce energy consumption. The methodology has been effectively demonstrated for a 1 MW festoon oven, resulting in an 87.5 % reduction in cooling time, saving 202 h of annual downtime and a reduction in gas consumption by 20–30 %.     

An enhanced energy conserving time stepping algorithm for frictionless particle contacts

An Enhanced Energy Conserving Algorithm (EECA) formulation for time integration of frictionless contact–impact problems is presented. In it the energy, linear and angular momentum are conserved for every contact using an enhanced Penalty method. Previous formulations for these problems have shown that the total bodies' energy decreases for contact due to an artificial energy transfer between the penalty spring and the contacting bodies. Consequently, they are not able to reproduce a physical response after a single contact, introducing errors in trajectories and velocities. Through the conserving balance equations, EECA computes a physical response by inserting for every contact an additional amount of linear momentum and contact force. The structure of these equations defines the additional linear momentum to restore the energy and the enhanced Penalty method based on a spring and a dashpot. This method approximately enforces the first and second Kuhn–Tucker conditions. The new algorithm has been applied to several frictionless rigid problems using the Discrete Element Method. The first two problems consist of the simulation and analytical comparison of the Newton's Cradle and Carom problems (billiard pool problem). The last two are the hopper filling process and the breaking of a pool ball's triangular arrangement, both of which involve a medium number of contacts. Application of this formulation will be straightforward to elastic and general‐shaped bodies using the Finite Element Method. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel geopolymer based composites with enhanced ductility

Geopolymer materials have been proposed for various applications due to their excellent fire resistance and low processing cost. One requirement that geopolymer composites need to meet for structural applications is graceful failure, as catastrophic failure during service can result in significant loss of life. In this paper, the properties of novel low cost composites made by infiltrating stainless steel mesh with geopolymer resin are reported. Four point flexure tests on these composites showed metal-like yielding behavior instead of catastrophic failure and the “yield strength” was significantly higher than the flexure strength of the geopolymer matrix. Exposure to high temperatures, 800 and 1,050°C, resulted in the “yield strength” decreasing to ∼59 and ∼44% level respectively compared to the strength of as-processed samples. However, the good ductility was still retained after the high temperature treatment, which makes this novel composite a strong candidate for the applications where catastrophic failure upon fire/high temperature exposure needs to be avoided.     

基于BP神经网络的舰炮武器系统综合保障性能评价

通过对舰炮武器系统的分析，建立舰炮武器系统综合保障性能评价的指标体系。把神经网络的相关知识应用到舰炮武器系统综合保障性能评价中，得到了相应的BP神经网络评价模型。通过一些舰炮武器系统的实例计算，验证了模型的正确性，为舰炮武器系统的研制和改进提供了一定的参考依据。