Zakoni raspodele mase parčadi razornih projektila

U radu je, prvenstveno sa statističkog aspekta, razmatrana raspodela mase parčadi razornih projektila. Prikazani su relevantni teorijski modeli raspodele broja, odnosno mase parčadi projektila: osnovni Mottov model, uopšteni Mottov model, modifikacija Stromsoe-Ingebrigtsena, eksponencijalna raspodela, uopštena eksponencijlna (Weibullova) raspodela i Heldov model raspodele. Korišćenjem dostupne baze eksperimentalnih podataka o fragmentaciji 26 različitih projektila, uz primenu metode najmanjih kvadrata, određene su optimalne vrednosti nepoznatih parametara u šest razmatranih modela raspodele parčadi za svaki od eksperimenata. Upoređivanjem teorijskih i eksperimentalnih rezultata pokazano je da svi teorijski modeli imaju visok stepen podudaranja sa rezultatima opita, kao i da analiza favorizuje tri dvoparametarska modela – uopštenu Mottovu, Weibullovu i Heldovu raspodelu. Daljim razmatranjem zaključeno je da Heldova raspodela predstavlja teorijski model koji je u najboljoj saglasnosti sa rezultatima eksperimenata

Zakoni raspodele mase parčadi razornih projektila

U radu je, prvenstveno sa statističkog aspekta, razmatrana raspodela mase parčadi razornih projektila. Prikazani su relevantni teorijski modeli raspodele broja, odnosno mase parčadi projektila: osnovni Mottov model, uopšteni Mottov model, modifikacija Stromsoe-Ingebrigtsena, eksponencijalna raspodela, uopštena eksponencijlna (Weibullova) raspodela i Heldov model raspodele. Korišćenjem dostupne baze eksperimentalnih podataka o fragmentaciji 26 različitih projektila, uz primenu metode najmanjih kvadrata, određene su optimalne vrednosti nepoznatih parametara u šest razmatranih modela raspodele parčadi za svaki od eksperimenata. Upoređivanjem teorijskih i eksperimentalnih rezultata pokazano je da svi teorijski modeli imaju visok stepen podudaranja sa rezultatima opita, kao i da analiza favorizuje tri dvoparametarska modela – uopštenu Mottovu, Weibullovu i Heldovu raspodelu. Daljim razmatranjem zaključeno je da Heldova raspodela predstavlja teorijski model koji je u najboljoj saglasnosti sa rezultatima eksperimenata

Modeling of fragmentation of rapidly expanding cylinders

U radu se razmatra proces fragmentacije košuljica projektila parčadnog dejstva, tj. generisanja parčadi rasprskavanjem metalnog cilindra koji je izložen visokim vrednostima unutrašnjeg pritiska usled detonacije eksploziva. Detaljno je razmotren klasični Mott-ov model fragmentacije metalnog prstena na osnovu koga je realizovan odgovarajući program za računar. Analiziran je zakon raspodele dužine (mase) fragmenata, kao i srednja dužina parčadi u funkciji osobina materijala prstena i karakteristika ekspanzije prstena. Razmotren je uticaj relevantnih parametara fragmentacionog procesa na karakter raspodele parčadi. Teorijska raspodela dužine fragmenata upoređena je sa dostupnim eksperimentalnim podacima pri čemu je dobijeno dobro podudaranje rezultata.The paper considers fragmentation process of high-explosive projectile casings, i.e. rapidly expanding cylinders loaded by extreme internal pressure generated by detonation of explosives. The classical, physically based, Mott model of the ring fragmentation is examined and the adequate computer program is realized. The fragment size (or mass) distribution is analyzed and the average fragment size is related to the characteristics of expansion and the casing material properties. The influence of the fragmentation process parameters on the nature of fragment length distribution is analyzed. The theoretical distributions are compared with experimental data and good correspondence is obtained

Modeling of fragmentation of rapidly expanding cylinders

U radu se razmatra proces fragmentacije košuljica projektila parčadnog dejstva, tj. generisanja parčadi rasprskavanjem metalnog cilindra koji je izložen visokim vrednostima unutrašnjeg pritiska usled detonacije eksploziva. Detaljno je razmotren klasični Mott-ov model fragmentacije metalnog prstena na osnovu koga je realizovan odgovarajući program za računar. Analiziran je zakon raspodele dužine (mase) fragmenata, kao i srednja dužina parčadi u funkciji osobina materijala prstena i karakteristika ekspanzije prstena. Razmotren je uticaj relevantnih parametara fragmentacionog procesa na karakter raspodele parčadi. Teorijska raspodela dužine fragmenata upoređena je sa dostupnim eksperimentalnim podacima pri čemu je dobijeno dobro podudaranje rezultata.The paper considers fragmentation process of high-explosive projectile casings, i.e. rapidly expanding cylinders loaded by extreme internal pressure generated by detonation of explosives. The classical, physically based, Mott model of the ring fragmentation is examined and the adequate computer program is realized. The fragment size (or mass) distribution is analyzed and the average fragment size is related to the characteristics of expansion and the casing material properties. The influence of the fragmentation process parameters on the nature of fragment length distribution is analyzed. The theoretical distributions are compared with experimental data and good correspondence is obtained

Fragment mass distribution of naturally fragmenting warheads

U radu se razmatraju statistički aspekti fragmentacije razornih bojnih glava. Modeliranje raspodele mase fragmenata je od velikog značaja pri određivanju efikasnosti razornih projektila. Dat je pregled sedam relevantnih teorijskih modela raspodele mase parčadi: Motov (Mott) model, generalizovani Motov model, Grejdijev (Grady) model, generalizovani Grejdijev model,lognormalna raspodela, Vajbulova (Weibull) i Heldova (Held) raspodela. Poređenje ovih modela sa reprezentativnom bazom podataka za 30 razornih projektila pokazalo je veoma dobro podudaranje teorijskih i eksperimentalnih rezultata. Analiza koeficijenata determinacije ukazala je da generalizovana Motova, generalizovana Grejdijeva i Vajbulova raspodela najbolje opisuju rezultate eksperimenata. Dalje poređenje ovih modela zasnovano na analizi medijane favorizuje generalizovanu Grejdijevu raspodelu čija se bimodalnost može fizički opravdati. Predloženi zakon raspodele mase fragmenata može se primeniti u složenom simulacionom modelu efikasnosti razornih projektila.The paper considers statistical aspects of high explosive warhead fragmentation. The modeling of fragment mass distribution is of great importance for determination of fragmenting warhead efficiency. Seven relevant theoretical fragment mass distribution models are reviewed: the Mott, the generalized Mott, the Grady, the generalized Grady, the lognormal, the Weibull and the Held distribution. Comparison of these models with representative experimental database of 30 fragmenting projectiles has shown, generally, a very good correspondence between theoretical models and experimental data. The goodness of fit analysis has indicated that the generalized Mott, the generalized Grady and the Weibull distribution enable the best description of experimental fragment mass distribution data. Further comparison of these models based on the median analysis prefers the generalized Grady distribution, and its bimodal characteristic can be physically justified. The suggested theoretical fragment mass distribution law can be applied in a complex fragmenting projectile efficiency simulation model

Fragment size distribution in dynamic fragmentation: Geometric probability approach

Dinamička fragmentacija je kompleksna pojava koja karakteriše brojne prirodne i tehničke sisteme. Određivanje zakona raspodele veličine (odnosno mase) generisanih fragmenata predstavlja jedan od najznačajnijih zadataka pri modeliranju dinamičke fragmentacije. U radu se razmatra uopšten pristup ovom problemu zasnovan na jednostavnoj pretpostavci o slučajnoj geometrijskoj segmentaciji tela. Polazeći od binomne raspodele mesta loma (tačaka, pravih ili ravni), izvedene su funkcije raspodele veličine fragmenata za 1D, 2D i 3D geometriju. Analizirani su modeli geometrijske fragmentacije zasnovani na pristupima Mott-a i Grady-Kipp-a. Takođe su razmatrani zakoni raspodele zasnovani na primeni Voronoi dijagrama. Rezultati razmatranih modela upoređeni su sa numeričkim simulacijama i eksperimentalnim rezultatima, pri čemu je pokazano da postoje značajna podudaranja, kao i izvesna ograničenja modela. Zaključeno je da preferirani teorijski model zavisi od dimenzionalnosti fragmentacionog procesa. .Dynamic fragmentation is a complex phenomenon inherent in numerous natural and engineering systems. Determination of the fragment size (or mass) distribution law is one of the most important objectives in dynamic fragmentation modeling. In the present paper, a general approach based on the simple assumption of random geometric partition of a body has been considered. Starting from the binomial distribution of fracture sites (points, lines or planes), size distribution laws are derived for 1D, 2D and 3D geometries. Geometric fragmentation models based on Mott's and Grady-Kipp's approaches are analyzed. The models originating from the Voronoi diagrams are also considered. The results of presented models are compared with numerical simulations and experimental data, showing significant compatibility as well as certain limitations. It has been concluded that preferred theoretical model depends on dimensionality of fragmentation process.

Fragment size distribution in dynamic fragmentation: Geometric probability approach

Dinamička fragmentacija je kompleksna pojava koja karakteriše brojne prirodne i tehničke sisteme. Određivanje zakona raspodele veličine (odnosno mase) generisanih fragmenata predstavlja jedan od najznačajnijih zadataka pri modeliranju dinamičke fragmentacije. U radu se razmatra uopšten pristup ovom problemu zasnovan na jednostavnoj pretpostavci o slučajnoj geometrijskoj segmentaciji tela. Polazeći od binomne raspodele mesta loma (tačaka, pravih ili ravni), izvedene su funkcije raspodele veličine fragmenata za 1D, 2D i 3D geometriju. Analizirani su modeli geometrijske fragmentacije zasnovani na pristupima Mott-a i Grady-Kipp-a. Takođe su razmatrani zakoni raspodele zasnovani na primeni Voronoi dijagrama. Rezultati razmatranih modela upoređeni su sa numeričkim simulacijama i eksperimentalnim rezultatima, pri čemu je pokazano da postoje značajna podudaranja, kao i izvesna ograničenja modela. Zaključeno je da preferirani teorijski model zavisi od dimenzionalnosti fragmentacionog procesa. .Dynamic fragmentation is a complex phenomenon inherent in numerous natural and engineering systems. Determination of the fragment size (or mass) distribution law is one of the most important objectives in dynamic fragmentation modeling. In the present paper, a general approach based on the simple assumption of random geometric partition of a body has been considered. Starting from the binomial distribution of fracture sites (points, lines or planes), size distribution laws are derived for 1D, 2D and 3D geometries. Geometric fragmentation models based on Mott's and Grady-Kipp's approaches are analyzed. The models originating from the Voronoi diagrams are also considered. The results of presented models are compared with numerical simulations and experimental data, showing significant compatibility as well as certain limitations. It has been concluded that preferred theoretical model depends on dimensionality of fragmentation process.

Two-component propellant grain for rocket motor combustion analysis and geometric optimization

The paper considers utilization of rocket motor propellant grains that consist of two propellants. The idea is to achieve approximately neutral burning using an outer surface inhibited cylindrical shape and complex contact surface between propellants. An existing propellant grain with complex geometry has been analytically modeled in terms of determination of evolution of corresponding burning surface areas. The analytical and experimental results' diagrams of this grain have been found to have a saw-tooth shape because of the segments that separate the two propellants, causing potential problems in the burning process during the relatively short active phase, showing an obvious need for further optimization. This has created an opportunity for development of improved propellant grain geometry and corresponding mathematical model for determination of main interior ballistic parameters. Comparison between calculation results based on both models and experimentally determined chamber pressure data shows very good agreement. Therefore, two-component propellant grains have significant application possibilities using the suggested modeling approaches

Numerical analysis of mine blast action on a vehicle

The main objective of the present research is development of a preliminary numerical model of dynamics and possible damage of a vehicle under the action of blast wave generated by the activation of a landmine. Such a model should provide a valuable insight into complex phenomena accompanied by detonation of a mine – pressure distribution in time, vehicle motion, damage, etc. Numerical simulation has been performed using Abaqus/Explicit, FEM-based software suitable for nonlinear processes with high strains, strain rates and energy densities, which is typical for explosion effects. A representative case study of an explosion of 8 kg explosive substance Composition B was analyzed. The explosion takes place under a vehicle with the mass of 8 tons, with specific V-shaped body consisted from 10 mm thick armor steel plates. The numerical model based on usage of Abaqus build-in CONWEP blast relations is described. The results obtained show the displacement, and stress-stain field in the loaded vehicle, on the basis of which the degree of damage to the target structure can be predicted. The guidelines for the further work and model improvement are suggested

Numerical Analysis of Initiation of Main Explosive Charge in an Artillery Projectile

The importance of investigation of main explosive charge initiation using booster charge stems directly from the objective to optimize the mass of booster charge needed to ensure steady state detonation of main explosive charge in order to achieve maximum projectile efficiency. Considered configuration consists of two explosives and three metal parts which represent elements of fuze and projectile. The main objective of this paper is to develop a numerical model of initiation of main explosive charge of an insensitive artillery ammunition. Through this research two variants of detonation point location were analyzed, ideal and stochastic one. The effects of the detonation transfer are analyzed using the Jones-Wilkins-Lee and Ignition and Growth equation of state models for explosives, applying the Coupled Eulerian-Lagrangian approach in the Abaqus/Explicit software. Analytical computation is introduced in this paper with a purpose to present P-u interaction between configuration elements and for comparison with results obtained by numerical method. The results of analytical and numerical approach are presented and discussed in detail. It is shown that suggested numerical model enables simulation and optimization of explosive train in fuzes of HE projectiles