Reduction of global effects on vehicles after IED detonations

Global effects caused by the detonation of an IED near a military vehicle induce subsequent severe acceleration effects on the vehicle occupants. Two concepts to minimize these global effects were developed, with the help of a combined method based on a scaled experimental technology and numerical simulations. The first concept consists in the optimization of the vehicle shape to reduce the momentum transfer and thus the occupant loading. Three scaled V-shaped vehicles with different ground clearances were built and compared to a reference vehicle equipped with a flat floor. The second concept, called dynamic impulse compensation （DIC）, is based on a momentum compensation technique. The principal possibility of this concept was demonstrated on a scaled vehicle. In addition, the numerical simulations have been performed with generic full size vehicles including dummy models, proving the capability of the DIC technoloey to reduce the occuoant loading.     

Nitrogen analogs of TEX e A computational studyLemi

TEX, a well-known nitramine type explosive, has been subjected to centric perturbations by replacing its etheric （acetal） oxygens withnitrogen atoms one by one. The structural features, stabilities and IR and UV-VIS spectra of new structures formed are investigated. For thispurpose, density functional theory has been employed at the B3LYP/6-31G （d,p） and B3LYP/6-311G（d） levels. In general the calculationsrevealed that the oxygenenitrogen replacement resulted in more energetic but less sensitive structures than TEX.Copyright . 2014, China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.     

Reliability sensitivity analysis based on multi-hyperplane combination method

For a nonlinear limit state function, the first-order reliability method （FORM） may cause large errors in the computation of not only the reliability index or failure probability but also the reliability sensitivity. In order to obtain more the accurate results of the reliability sensitivity analysis, a number of hyperplanes are built near the design point by first-order Tayler series expansion, which replace the known nonlinear limit state hypersurface, and an equivalent computational method is utilized to construct an equivalent hyperplane of the obtained hyperplanes. And the reliability sensitivities can be estimated more accurately by the derived equations based on the equivalent hyperplane. An example shows that the method is effective and feasible.     

Influence of A1203 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing

The influence of three factors, such as volume percentage of reinforcement particles （i.e. A1203）, tool tilt angle and concave angle of shoulder, on the mechanical properties of Cu-A1203 surface composites fabricated via friction stir processing was studied. Taguchi method was used to optimize these factors for maximizing the mechanical properties of surface composites. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. It was found that A1203 particles are uniformly dispersed in the stir zone. The tensile properties of the surface composites increased with the increase in the volume percentage of the A1203 reinforcement particles. This is due to the addition of the reinforcement particles which increases the temperature of recrystallization by pinning the grain boundaries of the copper matrix and blocking the movement of the dislocations. The observed mechanical properties are correlated with microstructure and fracture features.     

On the continued acceleration of bomb casing fragments following casing fracture

It has been said that, once a bomb casing has fractured, ＂detonation gases will then stream around the fragments or bypass them, and the acceleration process stops there.＂ However, while apparently copious gas flow through casing fractures indicates some pressure release, it is also an indication of significant gas drive pressure, post casing fracture. This paper shows two approaches to the problem of calculating the actual loss of drive. One presents first-order analytical calculations, in cylindrical geometry, of pressure loss to the inside surface of a fractured casing. The second shows the modelling of a selected example in the CTH code. Both approaches reveal that gas escape, while occurring at its own sound- speed relative to the adjacent casing fragments, has to compete with rapid radial expansion of the casing. Together with some historic ex- periments now publicly available, our calculations indicate that post-fracture casing fragment acceleration is, for most systems, unlikely to be reduced significantly.     

Long-rod penetration： the transition zone between rigid and hydrodynamic penetration modes

Long-rod penetration in a wide range of velocity means that the initial impact velocity varies in a range from tens of meters per second to several kilometers per second. The long rods maintain rigid state when the impact velocity is low, the nose of rod deforms and even is blunted when the velocity gets higher, and the nose erodes and fails to lead to the consumption of long projectile when the velocity is very high due to instantaneous high pressure. That is, from low velocity to high velocity, the projectile undergoes rigid rods, deforming non-erosive rods, and erosive rods. Because of the complicated changes of the projectile, no well-established theoretical model and numerical simulation have been used to study the transition zone. Based on the analysis of penetration behavior in the transition zone, a phenomenological model to describe target resistance and a formula to calculate penetration depth in transition zone are proposed, and a method to obtain the boundary velocity of transition zone is determined. A combined theoretical analysis model for three response regions is built by analyzing the characteristics in these regions. The penetration depth predicted by this combined model is in good agreement with experimental result.     

Study of nano-nitramine explosives： preparation,sensitivity and application

Nano-nitramine explosives （RDX, HMX, CL-20） are produced on a bi-directional grinding mill. The scanning electron microscope （SEM） observations show that the prepared particles are semi-spherical, and the narrow size distributions are characterized using the laser particle size analyzer. Compared with the micron-sized samples, the nano-products show obvious decrease in friction and impact sensitivities. In the case of shock sensitivities, nano-products have lower values by 59.9% （RDX）, 56.4% （HMX）, and 58.1% （CL-20）, respectively. When nano-RDX and nano-HMX are used in plastic bonded explosives （PBX） as alternative materials of micron-sized particles, their shock sensitivities are significantly decreased by 24.5% （RDX） and 22.9% （HMX）, and their detonation velocities are increased by about 1.7%. Therefore, it is ex- pected to promote the application of nano-nitramine explosives in PBXs and composite modified double-based propellants （CMDBs） so that some of their properties would be improved.     

Conversion of Torpedo＇s Lake and Sea Test Data Based on Grey System Theory

As only a little information can be obtained from torpedo＇s lake and sea tests, and the torpedo＇s life does not distribute typically. If conventional methods are used to convert the environment factor for torpedo＇s lake and sea tests, their results can not reflect the actual conditions. A conversion model of the environment factor for torpedo＇s lake and sea tests is set up based on the GM（1,2） model of the grey system theory. For the merit of the grey system, the problem of uncertain life distributions and few samples can be solved. The calculation results show that the method is easy, realistic and high precise.     

Neural network modeling to evaluate the dynamic flow stress of highstrength armor steels under high strain rate compression

An artificial neural network （ANN） constitutive model is developed for high strength armor steel tempered at 500
C, 600
C and 650
Cbased on high strain rate data generated from split Hopkinson pressure bar （SHPB） experiments. A new neural network configuration consistingof both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered asinputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook （JeC） model and neural networkmodel is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and temperingtemperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of temperingtemperatures （500e650
C）, strains （0.05e0.2） and strain rates （1000e5500/s） are employed to formulate JeC model to predict the high strainrate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the highstrain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient （R） andaverage absolute relative error （AARE）. R and AARE for the JeC model are found to be 0.7461 and 27.624%, respectively, while R and AAREfor the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with theexperimental data for all tempering temperatures.Copyright . 2014, China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.     

Scale-up synthesis and characterization of 2,6-diamino-3,5-dinitropyrazine- 1-oxide

2,6-diamino-3,5-dinitropyrazine-1-oxide （ANPZO）, as an insensitive high explosive, with a high yield and excellent purity has been prepared at pilot plant scale by an improved method. The synthesized ANPZO is characterized by IR, laser granularity measurement, SEM and HPLC. The particle analysis revealed that the improved method could offer desired product with average particle size of 40 gm and high purity （〉98.45%）. The experimental parameters exhibited that the detonation velocity of the formulation based on ANPZO was higher than that of the corresponding TATB formulation. The DSC curve showed that the exothermic decomposition of the product occurred at the temperature between 300.5℃ and 360.4℃. Furthermore, the sensitivity test suggests its safe nature towards mechanical stimulus.     

Torpedo＇s Search Trajectory Design Based on Acquisition and Hit Probability Calculation

Taking aim at light torpedo search trajectory characteristic of warship, by analyzing common used torpedo search trajectory, a better torpedo search trajectory is designed, a mathematic model is built up, and the simulation calculation taking MK46 torpedo for example is carried out. The calculation results testify that this method can increase acquisition probability and hit probability by about 10 % - 30 % at some situations and becomes feasible for the torpedo trajectory design. The research is of great reference value for the acoustic homing torpedo trajectory design and the torpedo combat efficiency research.     

Research on the fracture behavior of PBX under static tension

The fracture behavior of polymer-bonded explosive （PBX） seriously affects the safety and reliability of weapon system. The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method. A two- dimensional representative volume element （RVE） is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed. A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed. The results show that the simulated strain-stress relation is coincident with experiment data. It is found that interface debonding leads to the nucleation and propagation of meso-cracks, and a main crack approximately perpendicular to the loading direction is generated finally. The interface debonding tends to occur in the interface perpendicular to the loading direction. There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve. It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress, and the main crack tends to propagate toward the initial meso-cracks.     

Experiment and simulation of launching process of a small-diameter steel cartridge case

In order to explore the rules of the deformation force during the launching of a small-diameter steel cartridge, the semi-closed bomb test method is used to test the greatest strains on chamber outer wall under the different chamber pressures. The pressure curves of cartridge chamber are measured in experiment, and the tensile test data of cartridge are loaded into the numerical calculation to compare with the experimental data. The conclusion was obtained that the calculated results match better with the experimental results by considering strain rate bilinear kinematic hardening material constitutive model. The forces on the various parts of the cartridge during launching and their deformation rules are achieved, in which the equivalent plastic strain decreases and the cylinder ring withstands the maximum equivalent stress when the cartridge case clings to the bore from the mouth to the bottom.     

Problem of the reference height of the projectile trajectory as a reduced meteo-ballistic weighting factor

This paper deals with the issue of preparation of the aiming angles with the use of tabular firing tables and needed determination of the ballistic elements μB （ballistic wind wB Wxm WzB, ballistic （virtual） temperature τB, ballistic density ρB） from the standardized met messages. The weighting factors are used for the calculation of ballistic elementsμB that are incorporated into the trajectory calculations characteristics of weapon and ammunition. Two different methodologies practically used in the praxis are analysed and compared. For the comparison of the two methodologies the reference height of trajectory determined from the weighting factor functions is employed. On the basis of the analyses conducted, the potential for further increase in accuracy of these aiming angles preparation methods is pointed out.     

Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~ 1 MPa to ~ 5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy- acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral prim- ing section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve （near Friedlander waveform）. The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy- acetylene, results in a peak pressure increasing to 1.70 MPa.     

Numerical simulation of the natural fragmentation of explosively loaded thick walled cylinders

The ability to predict the natural fragmentation of an explosively loaded metal casing would represent a significant achievement. Physically- based material models permit the use of small scale laboratory tests to characterise and validate their parameters. The model can then be directly employed to understand and design the system of interest and identify the experiments required for validation of the predictions across a wide area of the performance space. This is fundamentally different to the use of phenomenologically based material algorithms which require a much wider range of characterisation and validation tests to be able to predict a reduced area of the performance space. Eulerians numerical simulation methods are used to describe the fragmentation of thick walled EN24 steel cylinders filled with PBXN-109 explosive. The methodology to characterise the constitutive response of the material using the physically based Armstrong-Zerilli constitutive model and the Goldthorpe path dependent fracture model is described, and the results are presented. The ability of an Eulerian hydrocode to describe the fragmentation process and reproduce the experimentally observed fragment mass and velocity distributions is presented and discussed. Finally the suitability of the current experimental analysis methodology for simulation validation is addressed.     

Numerical Analysis of 3 mm Ferrite Dielectric Waveguide Through Galerkin＇s Method

With the development of long range missile early warning radar, MMW phased array antenna is strongly needed. The phase shifter （PS） with high power capability and low insertion loss is a key technology in this kind of radar. Ferrite dielectric waveguide is introduced in this paper to manufacture PS, the cross section can be enlarged to 4 times of that of the conventional PS, which facilitates the engineering realization with reduced insertion loss. A novel vector base function of Galerkin method is proposed in calculating the eigenvalue of ferrite dielectric waveguide. The field distribution of main mode, power density and efficiency of 94 GHz difference phase shifter are also given.     

Deconsolidation and combustion performance of thermally consolidated propellants deterred by multi-layers coating

Both heating and solvent-spray methods are used to consolidate the standard grains of double-base oblate sphere propellants plasticized with triethyleneglycol dinitrate （TEGDN） （TEGDN propellants） to high density propellants. The obtained consolidated propellants are deterred and coated with the slow burning multi-layer coating. The maximum compaction density of deterred and coated consolidated propellants can reach up to 1.39 g/cm3. Their mechanic, deconsolidation and combustion performances are tested by the materials test machine, interrupted burning set-up and closed vessel, respectively. The static compression strength of consolidated propellants deterred by multi-layer coating increases significantly to 18 MPa, indicating that they can be applied in most circumstances of charge service. And the samples are easy to deconsolidate in the interrupted burning test. Furthermore, the closed bomb burning curves of the samples indicate a two-stage combustion phenomenon under the condition of certain thickness of coated multi-layers. After the outer deterred multi-layer coating of consolidated samples is finished burning, the inner consolidated propellants continue to burn and breakup into aggregates and grains. The high burning progressivity can be carefully obtained by the smart control of deconsolidation process and duration of consolidated propellants. The preliminary results of consolidated propellants show that a rapid deconsolidation process at higher deconsolidation pressure is presented in the dynamic vivacity curves of closed bomb test. Higher density and higher macro progressivity of consolidated propellants can be obtained by the techniques in this paper.     

Quantification of projection angle in fragment generator warhead

Tactical Ballistic Missile （TBM） class target neutralization by the fragment spray of a Fragment Generator Warhead （FGW） calls for quantification of fragment projection angle scatter to finalize the end game engagement logic. For conventional axi-symmetric warhead, dispersion is assumed to be normal with a standard deviation of 30. However, such information is not available in case of FGW. Hence, a set of experiments are conducted to determine the dispersion of fragments. The experiments are conducted with a specific configuration of FGW in an identical arena to quantify the scatter and then verified its applicability to other configurations having a range of L/D and C/M ratios, and contoured fragmenting discs. From the experimental study, it is concluded that the scatter in projection angle follows normal distribution with a standard deviation of 0.75° at Chi-square significance level of 0.01（χ2 0.99）.     

Research on modeling of nonlinear vibration isolation system based on Bouc-Wen model

A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouc-Wen dif- ferential model. It not only reflects the hysteresis force characteristics of the Bouc-Wen model, but also determines its corresponding pa- rameters. The simulation results show that restoring force-displacement curve hysteresis loop is very close to the real curve. The model trained can accurately predict the time response of system. The model is checked under the noise level. The result shows that the model has higher modeling precision, good generalization capability and a certain anti-interference ability.