bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of processing on quality of injection‐compression‐molded disks
Authors: Yang S. Y. , Ke M. Z.
Published: May 2005

A modified injection molding machine with a compression mechanism, and a mold with a movable wall and shut‐off mechanism, were used to investigate the effects of processing parameters on the quality of injection‐compression‐molded polystyrene disks. The compression start‐up time, compression force, melt temperature, and part thickness were selected processing parameters. The disk moldings were evaluated based on dimensional accuracy and birefringence. It is found that the compression start‐up time affects packing time, and thus greatly affects the residual orientation. If the transition from packing to compression could start before peak cavity pressure, disks with low residual orientation could be obtained. High compression force improves part quality and reduces thickness. Since both compression‐induced reduction and cooling‐induced shrinkage are involved, the effects of temperature and thickness are not as straightforward as the trends in conventional injection molding.
Experimental and theoretical studies of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts
Authors: Chang R. Y. , Tsaur B. D.
Published: May 2005

An integrated theory and computer program were developed in this study for simulation of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts. The basic theory considers the following items: (1) mold cooling analysis; (2) analysis of the polymeric filling, packing, and cooling processes; (3) viscoelastic behavior of polymeric fluid; (4) influence of thermal and mechanical properties of polymer; (5) pressure‐volume‐temperature relationship of polymer; (6) crystallization kinetics of crystalline polymer; and (7) solid mechanics analysis. Considered are the origins of defects, e.g. nonuniform cooling process, nonuniform volume shrinkage, flow‐induced residual stress, thermal induced residual stress, and crystallization behavior. The boundary element and the finite difference method were applied toward calculating the mold cooling analysis for obtaining the temperature profile at the cavity surface as the boundary conditions in filling and packing analysis. A hybrid finite‐element and finite‐difference methods were employed for simulating the injection molding filling, packing, and cooling processes. A control volume method was applied towards both finding the melt front position and also calculating the temperature and pressure profile at any instant during the filling process. A modified Tait equation provided a description of the pressure‐volume‐temperature relationship of crystalline polymers. The Malkin's kinetics model was employed to describe the behavior of polymer crystallization. The flow‐induced and thermal induced‐residual stresses employed as the initial conditions in the solid mechanics analysis were obtained with the linear thermo‐viscoelastic model. The displacements, including the thickness direction of part, which could not be calculated by the traditional bending moment method, were solved by using the numerical solid mechanics analysis with the three dimensional finite element method. These methods were applied to predict the shrinkage, warpage, and sink marks of crystalline polypropylene and amorphous ABS for the plate cavity. Both the qualitative results for the theoretical prediction correlated sufficiently with the experimental data. The theoretical results were also correlated using the commercial software C‐MOLD.
Predicting mechanical properties of acrylonitrile‐butadiene‐styrene terpolymer in injection molded plaque and box
Authors: Kim B. H. , Hwang T. W. , Park Hern Jin
Published: May 2005

A methodology to predict mechanical properties in injection molded parts has been developed. Knowledge of part properties before actual molding and testing will be of immense help to part and mold designers in modification of design. This methodology involved the application of connectionist learning systems, injection molding computer simulation, and experimental evaluation of mechanical properties, to relate the thermomechanical history of injection molded parts to the resulting part properties of injection molded parts are dependent upon their thermomechanical history which in turn is greatly influenced by the processing conditions and part geometry. As the relationships between engineering properties and thermomechanical history are complex and highly nonlinear, the methodology developed was based on a backpropagation neural network algorithm that provided the means for a nonparametric mapping between the part properties and thermomechanical history. The proposed methodology has been successfully applied to two geometries, plaque and box. This methodology provides designers with the ability to predict mechanical properties in injection molded parts when significant thermomechanical history can be obtained from injection molding simulation.
Free radical polymerizations associated with the trommsdorff effect under semibatch reactor conditions. I: Modeling
Authors: Ray Asit B. , Saraf D. N. , Gupta Santosh K.
Published: May 2005

Several important polymerizations [e.g., poly(methyl methacrylate) (PMMA), polystyrene] exhibit gel and glass effects during polymerization. These are associated with the decrease of the diffusivities of the macroradicals and monomer molecules with increasing viscosities of the reaction mass. A new model has been developed to account for the gel and glass effects, both under batch and semibatch reactor operations. The free volume theory of Vrentas and Duda has been used to account for the changes in the diffusion coefficients. The model parameters are tuned using experimental data on the isothermal bulk and solution polymerizations of MMA in batch reactors. Conversion histories and molecular weights have been obtained for cases where solvent, initiator or monomer are added to (or removed from) the reaction mass after some reaction has taken place. In addition, studies involving step changes in temperature hav been carried out. It is found that the conversion vs. time behavior after such step changes depend upon a complex interplay of three factors: Polymer concentration, molecular weight, and the temperature at the point these changes are effected.
Novel diagnosis of thermal deterioration for organic insulating resins by optical loss analysis
Authors: Takezawa Yoshitaka , Akasaka Shin‐Ichi , Koyama Tohru , Miya Hisaichi , Shimodera Makoto
Published: May 2005

We propose an “optical loss analysis” as a novel nondestructive diagnosis for the thermal deterioration of insulating resins. Using an alkyd resin film, the optical absorptin loss per unit optical path length and the glass transition temperature (Tg, DMA) by dynamic mechanical analysis were measured during heating tests. At longer heating times, values of the optical absorption loss and the Tg, DMA increased concurrently. By rescaling the heating time as a reduced time as a reduced time, a master curve of the deterioration for the resin was obtained. Consequently, when thermal stress is the main cause of the deterioration, one can estimate the degree of deterioration and theoretically the residual lives of resins using this optical loss analysis.
On the measurement of residual stress in plastic pipes
Authors: Clutton E. Q. , Williams J. G.
Published: May 2005

Recent work on the determination of residual stress in drawn pipes has revealed an error in previous methods used. Such pipes have residual stresses very different from those induced by melt extrusin during conventional pipe processing. In particular, it appears that there are considerable compressive stresses at the bore, and the hoop and axial values are not equal. In an attempt to measure these values, tests were performed on slit rings of varying length, and a pronounced dependence of ring overlap on length was observed. This was contrary to previous assumptions, and a corrected version of the analysis has been developed, which enables the true hoop and axial stresses to be determined by testing rings of various lengths. For isotropic pipes, it has been shown that hoop and axial stresses are roughly equal. Previous results obtained on thin pipe rings can now be corrected by multiplying by the factor 1/(1‐v). For anisotropic drawn pipes, a combination of rings and thin axial strips is used to determine the residual stresses. These pipes can show remarkably low stresses at the bore, which may play a significant part in determining their performance.
Mechanism of flame retardant action of red phosphorus in polyacrylonitrile
Authors: Ballistreri A. , Montaudo G. , Puglisi C. , Scamporrino E. , Vitalini D. , Calgari S.
Published: May 2005

The mechanism of flame retardant (FR) action of red phosphorus in polyacrylonitrile combustion was investigated by thermogravimetry, flash‐pyrolysis GC‐MS, and combustion methods. Red phosphorus was found to increase the thermal stability in air of polyacrylonitrile and to induce a char residue increment on this substrate. Both these effects disappeared when pyrolysis was carried out under nitrogen flow. Flash‐pyrolysis GC‐MS experiments showed that red phosphorus does not alter the pyrolysis product distribution of polyacrylonitrile, which implies that there is no specific interaction between polyacrylonitrile and red phosphorus. These data also showed that polymeric red phosphorus decomposes to volatile white phosphorus (P4) during pyrolysis. These observations allow us to propose a simple model for the mechanism of FR action of red phosphorus on polyacry‐lonitrile at the molecular level. Combustion data for polyacrylonitrile‐red phosphorus mixtures are in agreement with the proposed mechanism of FR action.
Aging effects on fire‐retardant additives in polymers
Authors: Clough R. L.
Published: May 2005

Extensive thermal aging experiments have been conducted on (i) ethylene‐propylene rubber (EPR) formulations containing various commercial halogenated‐hydrocarbon fire‐retardant additives together with Sb2O3, and (ii) on chlorosulfonated polyethylene (CSPE) formulations with and without added Sb2O3. Significant losses of both chlorine and antimony are found on aging, dependent upon the ability of the particular halocarbon to undergo intramolecular dehydrohalogenation. The stoichiometry indicates antimony volatilization as SbCl3. Arrhenius treatment of the data for the EPR formulation which undergoes the most rapid loss gives an overall activation energy of 34 kcal/mol for antimony volatilization and indicates that fire‐retardant loss should become appreciable only at temperatures significantly above ambient (i.e., 70°C). Oxygen index flammability measurements showed moderately increased flammability for certain aged EPR samples, but showed significantly decreased flammability for aged CSPE which was correlated with the loss of other volatile components from the formulation.
Block copolymerization of 3,3‐dimethyl‐2‐oxetanone. II. Synthesis of polydimethylsiloxane‐containing copolymers
Authors: Lefebvre P. M. , Jérôme R. , Teyssié Ph.
Published: May 2005

Carboxy‐terminated polydimethylsiloxanes (PDMSs) have been prepared by anchoring the functional end group on the main chain via a hydrolytically stable SiC bond. The neutralized carboxy‐terminated PDMSs are effective initiators of the 3,3‐dimethyl‐2‐oxetanone (or pivalolactone) block copolymerization. The yield of block copolymers depends on the initiation efficiency of the carboxylate end groups, but this limit can be overcome by the use of more than one carboxylate group per end chain, and “palm‐tree” structures are obtained. The ability to crystallize of poly(3,3‐dimethyl‐2‐oxetanone) is significantly depressed when this polyester is engaged in PDMS‐rich block copolymers, but the observed heterophase morphologies (350 Å) are uniformly fine.
Properties of polyimide films doped with copper complexes
Authors: Ezzell S. A. , Furtsch T. A. , Khor E. , Taylor L. T.
Published: May 2005

Polyimide films based on either 3, 3′, 4, 4′‐benzophenone tetracarboxylic acid dianhydride or pyromellitic dianhydride with 4,4′‐oxydianiline have been doped with copper(I) and copper(II) complexes. High‐quality, flexible, glass‐cast films have been obtained which exhibit increased softening temperatures and lower polymer decomposition temperatures. The atmosphere and glass sides of the films are quite different. The copper(I) dopant is oxidized on the air side of the film, while the glass side contains predominantly copper (I). In the copper(II) case most of the copper appears on the air side as a silvery substance in the Cu(II) state. Chemical as well as ion etching can remove this material. Electrical resistivity of the copper(II)‐doped films is decreased by three to five orders of magnitude relative to the polymer alone.
Polyimides and polyamides with semiflexible spacers
Authors: Evans John R. , Orwoll Robert A. , Tang Stephen S.
Published: May 2005

Thirteen polyimides and three polyamides were synthesized with alternating rigid and semiflexible polymethylene units along the chain backbone. Derivatives of the pyromellitic species served as rigid segments in the polyimides and the sulfanilamide group was incorporated in the rigid segments of the polyamides. These systems were examined for a thermotropic liquid–crystalline phase. None was detected, probably because of the high crystalline melting temperatures of these polymers.
Heterogeneous grafting on polymers containing chlorine: Grafting of amide groups in water suspension and the reactivity of the new polymer towards epoxy resins
Authors: Levin G. , Nae H. N.
Published: May 2005

Heterogeneous grafting on polyvinylchloride suspended in water was carried out using N‐butyl‐3‐mercaptopropionamide as nucleophile. Over 50% graft was obtained by using a small amount of solvent as a swelling agent and tricapryl methyl ammonium chloride as a phase transfer catalyst. Elemental analysis of the grafted polymer shows that the chlorine displaced from the polymers is replaced by the thio‐amide group. The above conclusion is supported by NMR and IR analysis. The kinetics of the chlorine displacement from PVC by the thio amide group obeys the Shell progressive mechanism. The rate at which an individual spherical particle reacts depends on the diffusion through the reacted layer. The grafted polymer is soluble in tetrahydrofuran or nitrobenzene. The films obtained from the grafted material are brittle due to excessive internal hydrogen bonding. The electrostatic charge which is a characteristic surface phenomena in PVC is diminished in the grafted polymer which may be due to the existence of the amide group near the surface. The amide groups attached to the side chains on the polymer may participate in various reactions, e.g., with epoxy resins. IR analysis of the cured film indicates the disappearance of the oxiran band at 913 cm−1 and an increase in the hydroxyl band around 3300 cm−1. Thus, grafting of amide groups on PVC enables us to further modify PVC by epoxy resins.
The crosslinking of epoxy resins at interfaces. II. At an aromatic polyamide surface
Authors: Garton Andrew , Daly John H.
Published: May 2005

The first 200–400 nm of crosslinked epoxy resin adjacent to an aromatic polyamide (aramid) surface were characterized by internal reflection spectroscopy (IRS) using an aramid‐coated IRS element. The crosslinking kinetics and final crosslinked state of an anhydride‐cured epoxy resin were strongly affected by the aramid surface, which produced a localized increase in the rate of anhydride consumption and a decrease in the yield of ester products. An aromatic amine‐cured epoxy resin was less affected by the aramid surface. Unidirectional aramid fiber:epoxy composites were examined by dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). The chemical changes detected spectroscopically were shown to correlate with mechanical and thermal transition data obtained by DMA and DSC. These results are rationalized on the basis of the effect of absorbed moisture in the aramid on the crosslinking chemistry.
Polymerization of oriented monomers. VIII. Polymerization of allyl and diallyl vesicle‐forming quaternary ammonium salts
Authors: Babilis D. , Dais Photis , Margaritis L. H. , Paleos C. M.
Published: May 2005

The synthesis of two novel allyl and diallyl vesicle‐forming quaternary ammonium salts is reported. The topochemical polymerization of these monomeric vesicles to their polymerized counterparts was performed by γ‐ray irradiation and the observed differentiation in polymerization rates of allyl and diallyl monomers was attributed to different polymerization mechanisms. It was further established that only polymerized vesicles which result from diallyl monomer retain the structure of the monomeric vesicles and exhibit simultaneously higher stability.
Solid‐state thermal polymerization of the heterocyclic HC7N7 acid
Authors: Skarda V. , Ivkovich D.
Published: May 2005

The preparation of a new type of thermally stable (up to 385°C) heterocyclic polymer, containing a five‐membered fused ring system, is described. The ultraviolet, visible, and infrared spectra indicate that this solid‐state polymerization probably proceeds via formation of an azomethine‐type intermolecular crosslink, rather than via opening of the C4N4 ring system. The reaction is facilitated by the presence of reactive protons, which act as an efficient catalyst for this nucleophilic addition to the nitrile group. It is suggested that this type of solid‐state polymerization may possibly be carried out on a single HC7N7 crystal resulting in a fully ordered macroscopic polymer single crystal.
Dehydrochlorination of polyvinylidene chloride (PVDC) in the presence of crown ether as a phase transfer agent
Authors: Yie‐Shun Chiu , Jagur‐Grodzinski Joseph , Vofsi David
Published: May 2005

Films of polyvinylidene chloride (PVDC) were heterogeneously dehydrochlorinated by reacting them with KF‐crown and KOH‐crown complexes dissolved in benzene. Solutions were in contact with an excess of unhydrous salts. This three‐phase reaction was very fast at 80°C and the removal of one chlorine atom per monomer unit was completed within 1 h. Further dehydrochlorination leads to triple‐bond formation and to aromatization of the system due to the intramolecular 1,6 elimination. The former reaction is dominant when KOH‐crown is used as the dehydrochlorinating agent and the latter is dominant in KF‐crown/CaO systems. The apparent energy of activation of the initial dehydrochlorination process is estimated to be 6.7 kcal./mol.
Theoretical Prediction of Energy Consumption and Particle Size Distribution in grinding and drilling of brittle materials
Authors: Weichert Reiner
Published: May 2005

Based on physical assumptions, simple equations have been derived for the probability of breakage of particles, for the dependence of fragmentation energy on particle size and for the fragment size distributions as a function of mass‐specific energy. The particles were considered as spheres, and Hertz theory of the stress distribution at the contact between a sphere of brittle material and a flat surface was applied in combination with Weibull statistics of failure. The predicted dependence of the probability of breakage on particle size and mass‐specific energy agrees well with experimentally obtained data for single‐particle experiments, even if the particles were not spherical. The resulting fragment size distribution could be predicted by the application of fracture mechanics. The theory can also be applied to rock drilling, where the breaking material is considered as a flat surface and the drilling tool as being of spherical shape. In both comminution and drilling, the experimental results agree fairly well with the theory.
Influence of the Particle Size Distribution on the flow behaviour of fine powders
Authors: Köhler Thomas , Schubert Heinrich
Published: May 2005

Some results are presented of investigations on the flow behaviour of very fine α‐alumina powders having different particle size distributions. Shear tests were performed in a translation shear cell. The humidity was in the range 0.3 < pD/pSD < 0.6 in order to ensure the formation of adsorbed water layers only and to exclude capillary condensation. In the region of adsorbed layer bondings, the flow behaviour of very fine powders deteriorates in comparison with regions where no adsorption layers exist. An extrapolation of the unconfined yield strength for very low consolidation stresses results in an approximately constant value for different particle size distributions. In contrast, the slope of the linear function σc = f (σ1) increases with decreasing particle size up to a certain limit. For narrow particle size distributions, there is a pronounced decrease in the bulk density with decreasing particle size. Further, the bulk density is strongly influenced by the width of the distribution.
A Re‐Examination of Piper's Shape Analysis Technique
Authors: Pickett James , Clark Nigel , Shuker Stephanie
Published: May 2005

An image shape analysis technique which measured the angles between adjacent vectors on the image edge was previously proposed by Piper, but the accompanying data was scant. This method is shown to have great promise when applied to several images obtained using a video camera with a computer. Better data representation is obtained using a single plot of the average measured angle at each step length versus the step length. Both scale and degree of maximum roughness are immediately evident on this plot. The measured angles may be corrected to remove image circularity effects from the angles, in which case some macroscopic shape effect is also described by the plot. Similarity with the Richardson (fractal dimension) plot is discussed.
Particle Turbulent Dispersion in 3D Magnetic Fields by using a Lagrangian approach
Authors: Berlemont Alain , Desjonqueres Philippe , Gouesbet GéRard
Published: May 2005

A Lagrangian approach is presented for the prediction of 3D dispersion in turbulent flows. A brief description of the main characteristics of the code PALAS (Particle Lagrangian Simulation) is given and the different methods for the simulation of either a fluid particle trajectory or a discrete particle trajectory are outlined. Comparisons with experimental results for particle 3D dispersion in grid turbulence with a nonhomogeneous force field are presented and proved to be very satisfactory in most instances.
Monitoring the Coating of Powder Particles by the measurement of the low frequency impedance of the powders
Authors: Hawkins E. , Harnby Norman
Published: May 2005

Experiments with a purpose built cylindrical capacitor are used to determine the sensitivity of low frequency impedance measurements to changes in the coatings of four different industrial powders. It is demonstrated that the technique should be suitable for off‐line quality control.
Performance of Disposable Respirators
Authors: Fardi Behzad , Liu Benjamin Y. H.
Published: May 2005

An experimental study of the filtration performance of several commercially available, NIOSH‐approved, disposable respirators was conducted using monodisperse DOP and NaCl particles with diameters in the 0.035 to 4 μm range.

The aerosol penetration through the respirators were measured at flow rates of 16, 28 and 48 L/m using a condensation nucleus counter, an aerodynamic particle sizer, and a laser optical particle counter for purposes of comparison. The results obtained by these instruments were found to be in good agreement with each other in the overlapping region of particle size of the instruments.

The peak penetration through the respirator filters was found to range from approximately 1.2% to 30% at 16 L/m, 3.5% to 37% at 28 L/m, and 6% to 45% at 48 L/m. The most penetrating particle size was found to lie in the 0.1 to 0.4 μm diameter range. Further, no significant difference in penetration for NaCl and DOP particles was found, suggesting that the particlebounce effect was not important in the present study.
The Influence of Temperature in the Range from 77 k to 338 k on the Detonation Velocity of RDX/TNT 60/40
Authors: Hollenberg K.
Published: May 2005

The detonation velocity of rods made of RDX/TNT 60/40 was determined with high accuracy in the temperature range from 77 K to 338 K. It was found out that the detonation velocity decreases with increasing temperature. To explain this thermodynamically unusual behaviour it is assumed that the effect of the increase of the detonation velocity with increasing temperature is superposed on the decrease caused by the simultaneous decreasing density of the explosive.
Shock Initiation of PBX‐9404 by electrically driven flyer plates
Authors: Weingart R. C. , Jackson R. K. , Honodel C. A. , Lee R. S.
Published: May 2005

The shock initiation threshold of PBX‐9404 has been studied over the pressure range 3.1 GPa‐28 GPa with pulse lengths ranging from 0.007 μs‐0.63 μs. The short‐duration, high pressure pulses were produced by the impact of thin plastic flyer plates accelerated by electrically exploded metal foils. We performed the experiments on explosive pellets 25.4 mm in diameter with thicknesses of 6.0 mm, 10.1 mm and 19.1 mm. No dependence of the initiation threshold on pellet thickness was observed. The data are represented reasonably well by either the critical initiation energy or by the constant P2τ initiation criteria.
A Comparative Study on some Explosive Properties of cobalt picrate and cobalt picramate
Authors: Agarwal J. P. , Agrawal (late) S. P.
Published: May 2005

Cobalt picrate and cobalt picramate were prepared, their IR spectra were recorded in KBr. Explosion delay, explosion temperature, activation energy, and explosion pressure were measured. Cobalt picrate is thermally more stable than cobalt picramate.
The Dynamic Shear Storage Modulus of Plastic‐Bonded Explosives and its relationship to sensitivity
Authors: Matuszak M. L. , Upham D. L. , Hildner R. A. , Shaw M. T.
Published: May 2005

The linear dynamic mechanical properties of plastic‐bonded explosives (PBXs) were measured from −40 °C to +50 °C over the frequency range of 0.1 Hz to 4 Hz with a Rheometrics dynamic mechanical spectrometer. The purpose of the measurements was to develop correlations between the viscoelastic properties of composite high explosive systems and their impact sensitivities. Data from drop‐skid tests using the 45°‐angled target, as performed by the Los Alamos Scientific Laboratory (LASL), were used in the sensitivity measurements. The skid‐test drop height was inversely proportional to the shear storage modulus of the PBXs and the glass transition temperature (measured dynamically) of the PBXs tested.
Quantum Mechanics and Molecular Dynamics Calculations provide new evidence for a free‐radical shock initiation model
Authors: Walker F. E.
Published: May 2005

The contrast between a hydrodynamic model for shock initiation of explosives and a newer microscopic free‐radical model is presented. The primary considerations of the free‐radical model are that shock energy is very coherent and that it is strong enough to cause mechanical fracture of covalent bonds. The shock front on a microscopic scale is very narrow (∼5 Å to 15 Å) and thermal equilibrium does not exist in the front. The free atoms and radicals formed by the shear and acceleration forces in the shock front initiate the chemical reaction that leads to hot spots and the eventual decomposition of the explosive materials. Energy‐release rates and vibrational velocities of the covalently bound atoms are factors in establishing detonation velocities. A number of explosives phenomena are discussed as the new model provides explanations for them. New information from molecular dynamics and quantum mechanical calculations on shock waves in condensed systems and recent experimental data are shown to support the free‐radical model.
Removal of 2,4,6‐trinitrotoluene (TNT) and 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX) from aqueous solutions with surfactants
Authors: Okamoto Y. , Chou E. J. , Croce M. , Freeman D. , Roth M. , Colitti O.
Published: May 2005

2,4,6‐Trinitrotoluene (TNT) was found to react in aqueous solution with surfactants containing amino and quaternary ammonium groups at pH 10–11 at ambient temperature. The surfactants investigated included N‐tallow 1,3‐diaminopropane, trimethyl N‐tallow ammonium chloride and N,N,N′,N′,N′‐pentamethyl N‐tallow 1,3‐propane diammonium dichloride. The reaction products were insoluble in water and readily separated through filtration. The dried solids were not explosive and the solids burned without explosion. The results showed that TNT can be reduced to less than 0.1 ppm from the initial concentration of 110 ppm in 2–3 hours. The wastewater of Composition B contains TNT and 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX). Treatment of the wastewater with the ammonium cationic surfactants showed that TNT was removed quantitatively by precipitation and RDX was simultaneously hydrolyzed. The mechanism of this treatment is discussed.
Etude mécanique de chargements moulé‐collés en propergol doublebase composite par Une méthode viscoélastique non‐linéaire
Authors: Meili G. , Dubroca G. , Pasquier M. , Thépenier J.
Published: May 2005

L'article présente une méthode d'étude mécanique de chargements moulé‐collés en propergol double‐base composite (en abrégé DBC) soumis à des cycles thermiques. La méthode proposée pour déterminer les contraintes et le coefficient de sécurité est basée sur le comportement non‐linéaire et la compressibilité du propergol. Le comportement non‐linéaire est obtenu d'après des essais de traction. Les équations d'équilibre sont résolues numériquement en découpant l'épaisseur de propergol en plusieurs couches. Les non‐linéarités affectent essentiellement le module et on utilise un critère multiaxial et l'équivalence temps‐température. On calcule à chaque pas de temps et pour chaque couche la température, le temps réduit, le facteur non‐linéaire, le coefficient de Poisson, et le dommage (selon le concept de Farris). Différents types de chargements (bloc à canal central étoilé, à mamelles, finocyl) ont été soumis à différents types de cycles thermiques. La comparison entre prédiction et expérience est convenable même pour des enchaînements complexes d'allongement et de température.
Effect of Burning Rate Modifiers on Propellant Performance. A theoretical study
Authors: Madhavan N. S. , Thanki K. P.
Published: May 2005

The addition of burning rate enhancers or suppressers in solid propellant composition is seen to affect the energy level considerably. In the present paper, an attempt is made to quantify such effects. Even though the study is carried out over the theoretical values of the performance parameters, the trends in the variations and the corrections occurring therefrom for the inclusion of burning rate modifiers seem to be applicable to the delivered or the actual values also more or less equally.
New Procedures for Purifying TNT
Authors: Gilbert E. E. , Siele V. I. , Chandler C. D. , Mundy R. A. , Spencer J. R. , Gibson G. R. , Bolleter W. T.
Published: May 2005

Ammonium and magnesium sulfites were tested for purifying crude TNT in comparison with the conventional (“sellite”) process using sodium sulfite. The magnesium process easily gave an acceptable product in better yield, of higher quality, and at lower estimated cost. Magnesium values suitable for recycle were recovered from the waste water by calcination. The ammonium process gave an acceptable product only under specific reaction conditions, but the waste water can be recovered by mixing it with TNT process spent sulfuric acid, thereby eliminating a calcination step.
The Chemistry of Detonations. IX. Some observations regarding a computer based parametric study of detonation characteristics of CHNO explosives
Authors: Short J. M. , Eccleston H. F. , Baroody E. E. , Mueller K. F. , Kamlet M. J.
Published: May 2005

Swaminathan and Rajagopalan (S and R) have recently published a parameter study describing the dependence of important detonation characteristics of CHNO explosives on their densities and enthalpies of formation which is seriously inconsistent with earlier highly reliable calculations by Mader using the same equation of state and presumably the same input information. S and R's computer‐based conclusions are also not in accord with parametric relationships established over a decade ago by Johansson and Persson and Kamlet and Jacobs. S and R's calculated detonation pressures are significantly lower at high loading densities and higher at lower loading densities than Mader's corresponding calculations. Also out of line on the high side (compared with Mader's calculations or experimentally observed values) are S and R's calculated detonation velocities. The differences between S and R's parametric relationships and those of the other workers can have important and misleading implications to the planning of future explosives chemistry research. It is suggested to those interested in such parametric studies that the simplified method for detonation property calculation be used, since the input information is explicit and easily checked and the results are at least as reliable as those from complex computer programs.
Synthesis and Properties of 1,1,1,3,5,5,5‐Heptanitropentane
Authors: Klager K. , Smith R. M.
Published: May 2005

A nearly zero oxygen balance of organic compounds is characteristic for explosives and high performance solid rocket propellants. Because of its high oxygen content, the introduction of a trinitromethyl group into suitable organic compounds presents an attractive and simple way to produce new explosives. The reaction of 2‐nitro‐3‐acetoxy‐1‐propene with nitroform is described which yields 1,1,1,3,5,5,5‐heptanitropentane. The properties of this compound are described to assess the usefulness of this explosive in a comparison with known explosives of similar structure using theoretical calculations for the lead block, ballistic mortar and detonation properties. Although a possibility exists to introduce another nitro group in position 3 which would produce a compound with even higher oxygen balance, all attempts so far have not achieved this desirable goal.
Explosively Disseminated Colored Smokes
Authors: Webster H. A.
Published: May 2005

The use high decomposition temperature fluorescent dyes to produce explosively disseminated colored smoke puffs has been demonstrated. The dye material used was a commercially available pigment that was a solid solution of an organic fluorescer in a polyamide resin. Practice shells were loaded with the fluorescent dye and the payload ejected with a black powder charge. Large, highly colored smoke clouds were produced by this method. The fluorescence spectra of the dyes and calculations of increased acquisition range due to the added fluorescence are presented.
Approximate Method of Calculating Critical Shock Initiation conditions and run distance to detonation
Authors: Andersen W. H.
Published: May 2005

An approximate model for pressure buildup behind the front of an initiating shock wave is developed. This model leads to the widely used P2t initiation criterion, but the pressure index is not limited to a value of two. Expressions for wave run time and distance to detonation are also obtained. The use of the model is illustrated using explosives widely discussed in the literature. It is shown that critical shock initiation and run distance to detonation can be rapidly estimated to good approximation over a wide range of shock conditions from the results of one or two relatively simple experiments. The calculational method may be useful for various applications.
Auto‐inflammation de la nitrocellulose
Authors: Isler J.
Published: May 2005

Les résultats présentés dans cet article composent le premier volet d'une étude menée au GERPy sur l'auto‐inflammation des munitions chargées en poudre à base de nitrocellulose. Une corrélation entre la cinétique de décomposition et l'auto‐inflammation d'échantillons cylindriques homogènes a été établie après modélisation du phénomène. Le modèle décrit permet de déterminer les profils de température ainsi que la température critique.
The Double Pipe Test for Commercial Explosives II. Numerical modelling and interpretation
Authors: Lownds C. M. , Du Plessis M. P.
Published: May 2005

An approximate numerical model of the Double Pipe Test has been devised to examine the effects of properties of the top pipe, witness pipe and the explosive on the depth of dent generated in the witness pipe. The model is based on a static calibration of the strength of the witness pipe, with strain‐rate correction for high rates of loading. The inertia of all material accelerated by the explosive product gases is also considered. A comparison of predicted and measured dent depths for various peak explosive pressures shows that the model adequately describes dynamic behaviour during the test. Measured dent depths are expected to correlate with the ability of an explosive to generate a shock wave in rock.
Influence of Blast Wave on Hard Structure
Authors: Liehmann W.
Published: May 2005

In this paper the pressure‐time histories of bursting gas vessels in closed rooms are investigated and discussed on the basis of TNT‐nomograms.

Experimental data of TNT‐charges from 0.1 kg to 1.5 kg were measured on various points in a closed room. To describe the results a simplified linear wave model was applied and a good agreement with the experimental data observed.

Similar experiments with bursting gas storage vessel were performed and compared with the TNT‐results. A TNT‐blast equivalent was defined and established. In addition a computer code was created. By use of the input data, which are energy content of the vessel, geometry of the room and other physical parameters, pressure‐time histories are calculated. These can be directly used for predicting the loading factors of hard structures.
Sensitivity of nitromethane for low velocity detonation
Authors: Ijsselstein R. R.
Published: May 2005

Recently the occurrence of a low velocity detonation (LVD) in nitromethane has been demonstrated. In the present study this phenomenon has been further investigated by mapping the shock loading regime in which a stable LVD can develop. A confinement geometry has been chosen that earlier appeared to be able to sustain the LVD. A calibrated shock donor system has been used, so that loading shock strengths were known. The critical shock strengths for the occurrence of both high and low velocity detonation could thus be determined. Including LVDs, nitromethane appears to have a sensitivity comparable to that of relatively sensitive high explosives. The results also indicate that the geometries of some standard shock sensitivity tests are not fully adequate to detect an LVD in nitromethane.
2,4,6‐Triphenyl‐ thiazolo[3,2‐a]‐s‐Triazine as a Stabilizer for single base propellant
Authors: Soliman Adly A.‐W.
Published: May 2005

2,4,6‐Triphenyl‐2,3,4,7‐tetrahydro‐thiazolo[3,2‐a]‐s‐triazine is used as a stabilizer for single base propellant and gave good results with the stability tests. Comparing the results of the stability and storage tests at 80°C, 90°C and 100°C with the results of the same tests after using diphenylamine instead of the thiazolo compound gave the same results without difference between the two stabilizers.
Crack Initiation in Perforated Propellants under high strain rate impact conditions
Authors: Fong C. W.
Published: May 2005

The fracture behaviour of gun propellant grains during impact has been measured on a modified Hopkinson Bar which uses a projectile as the input bar. Evidence for the detection of initial minor crack formation in seven‐perforated cylindrical specimens of single base, double base and triple base propellant is presented. Under compressive load (pressurization rates of 100 GPa/s‐200 GPa/s), minor crack formation does not immediately result in large scale crack propagation or fragmentation of the specimens. The single base and triple base propellant are equally more resistant to crack initiation than the double base propellant when tested in either the end‐on or side‐on modes. Implications for munition survivability are discussed in terms of mechanical frictional effects caused during compressive loading of cracked propellant or compressive heating in propellant cracks during the ballistic cycle.
The Compressional Heating Hazard in the Pressing of Propellant Doughs
Authors: Hawkins S. J. , Privett G.
Published: May 2005

The compressional heating hazard encountered during propellant dough extrusion, is discussed. A mathematical model describing a “worst case” situation is derived, and solved using a mini computer. The results indicate that pressurization regimes commonly used may be unnecessarily slow for small press sizes.
Determination of Gaseous and Solid Decomposition Products of Nitroguanidine
Authors: Volk F.
Published: May 2005

In spite of many publications dealing with the thermal decomposition of the cyclic nitramines RDX and HMX, the decomposition behavior of nitroguanidine (nigu), especially in the low temperature range, has not been investigated fundamentally in the past. Because nitroguanidine is an important explosive component for triple base propellants, a better understanding of the thermal decomposition at low temperatures is of interest.

For example, aging studies of triple base propellants exhibited a different decomposition behavior from single and double base propellants. Therefore nigu is supposed to influence the safe life time of propellants containing nitric acid esters.

The investigations of the decomposition of nigu published in the past, have been performed at temperatures between 190°C and 240°C. The aim of this work was to study the decomposition behavior of nigu at temperatures as low as possible.

In this connection, temperatures between 110°C and 240°C have been used. In this temperature range, nitroguanidines with different grain sizes have been investigated by measuring the weight loss and analyzing the decomposition gases by mass spectrometry. Also solid residues, like ammeline and melamine, remaining after the degradation tests were analyzed quantitatively by using high performance liquid chromatography. The formation of melamine and ammeline was found to depend strongly on the amount of the weight loss of nigu. The better stability behavior of triple base propellants is possibly due to the formation of NH3 which is being formed in the decomposition process of nigu. Ammonia reacts with nitric oxides and behaves therefore similar as a stabilizer.
The effects of gas explosions in free and partially confined fuel/air mixtures
Authors: Pföurtner H.
Published: May 2005

To obtain a further insight into the complex flame acceleration process of deflagrating fuel/air mixtures experimental investigations were carried out in free and partially confined homogeneous clouds with hydrogen as a fuel. The results of the experiments in an unconfined hemispherical configuration show a distinct dependence of the flame velocity on the cloud size which does not exceed, however, an upper limiting value. The experiments under partially confined conditions without additional turbulence indicate that the flame velocity and consequently the pressure field is governed by the hemispherical flame front initially formed; i.e. the flame velocity is not affected by the partial confinement. To increase the turbulence effects further experiments were carried out with a fan and with jet ignition. In the case of fan induced turbulence the flame velocity was strongly influenced by the fan speed. At a certain fan capacity the transition of a deflagration into a detonation was observed. With jet ignition produced by venting an explosion chamber into the partially confined cloud the transition occured even with hydrogen concentrations in air as low as 22 vol%. The results which are discussed on the basis of turbulence models show that high damaging overpressures or the transition from a deflagration into a detonation are only generated by strong turbulences as a consequence of flow and/or obstacles.
Rheological Characterization of Fuming Nitric Acid Gel
Authors: Gupta B. L. , Varma M. , Goel S. B.
Published: May 2005

Rheological characterization of fuming nitric acid gel has been attempted in low and high shear rate ranges using Brookfield and capillary viscometers respectively. The gel has been found to behave as a pseudoplastic thixotrope.
Use of kinetic DTA and TG methods for compatibility tests on 2,4,6‐‐trinitrotoluene
Authors: Hemmilä M. , Nieminen I. , Kariniemi A. , Valkonen J.
Published: May 2005

We have investigated the suitability of thermoanalytical methods for compatibility tests on explosives and contact materials. DTA and TG curves of various materials were evaluated using two DTA and four TG methods and one DSC method. TNT was used as model substance. The contact materials were paraffin, polyethylene, an epoxy resin paint and an epoxy glue. In earlier tests the first two were found compatible and the latter two incompatible with TNT. None of the methods provides an absolute value for the activation energy. However, in compatibility tests only the relative change in the activation energy is of interest and, for this, three of the methods proved informative.
The Cutting of Steel Tubes by Explosives Techniques. Cutting performance and effects on environment
Authors: Schumann St. , Freund H. U. , Geiger W.
Published: May 2005

In the light of special applications, trials were carried out on the separation of steel tubes using commercially obtainable explosive cutting charges in an annular configuration in order to find out their cutting performance and the effects on the environment incurred during separation. Tubes made of St37 steel having a diameter of 220 mm and a wall thickness of 10 mm as well as tubes consisting of hightensile 15 Mo 3 steel with a diameter of 273 mm and a wall thickness of 12.5 mm were used for this purpose. It was possible to cut the tubes accurately and neatly with the charges used. However, the projectiles formed during the detonation process are not compact, for which reason the cutting performance of the commercial charges used is not optimal. There is here a considerable potential for improvement. Measurements of the environmental effects conducted during the trials (fragmentation, blast wave, projectile impact on tube line) show that the incidental effects of explosive tube cutting are controllable.
Sensitivity and Evaluation of Explosive Substances
Authors: Fukuyama I. , Ogawa T. , Miyake A.
Published: May 2005

Explosion sensitivity involves many complex factors. A theory for evaluating and a method for testing have to be established. We have proposed an explosion sensitivity theory for explosive substances and have also tested the evaluating method. The results of our research reveal a satisfactory mutual relation between both theoretical and experimental values.
Viscosity Prediction of Composite Solid Propellant Slurry
Authors: Ke‐Xi Yang , Ze‐Ming Tao , Guo‐Juan Wang
Published: May 2005

The viscosity of composite solid propellant slurry is an important parameter in charging technical performance of solid rocket motors. It is affected not only by the liquid phase ingredients of propellants, but also by the size, content, shape and surface properties of solid fillers in propellants. This paper will present a prediction formula of viscosity of composite solid propellant and will also give a method for calculating the maximum packing volume fraction of solid in the formula. One can predict the viscosity of propellant slurry with the formula if the composition of the propellant is known.