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1

Verification of Impact Energy Delivered by a Drop Weight

Künzel Martin, Kucera Jindrich, Smid Jakub, Horkel Jan

Central European Journal of Energetic Materials

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2024

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Vol. 21, no. 2

171--187

EN

Impact sensitivity of energetic materials is an important parameter for their safe handling and storage. The drop height or equivalent potential energy that is required to reach a certain probability of initiation in repeated tests is determined using a drop-weight instrument. In this work, photonic Doppler velocimetry was used to measure the drop weight velocity profile during its fall and rebound. Numerical simulations were performed to correctly understand the velocity records and to find out the differences from the ideal behavior. The efficiency of the conversion from the potential to kinetic energy was revealed for various drop weight masses and drop heights. The measured velocities at the moment of impact followed the free-fall predictions to within 1%. The energy conversion efficiency decreased from 0.997 to 0.992 with the drop weight decrease from 10 to 0.5 kg. The relative energies of the rebound drop-weights decreased with decreasing mass from >0.75 at 2-10 kg down to <0.4 at 0.5 kg. The PDV instrumentation was found useful for validating the drop-weight velocity. The resting times and rebound velocity profiles of the drop-weights agreed with the numerical simulation results that assumed elastic behavior of the instrument.

2

Using thermochemical code EXPLO5 to predict the performance parameters of explosives

Suceska Muhamed, Stimac Tumara Barbara, Künzel Martin

Materiały Wysokoenergetyczne

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2021

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T. 13

17--27

EN

Thanks to the development of more powerful computers and efficient numerical techniques, numerical modelling has become a compulsory tool in solving various problems in the field of energetic materials. In cases where measuring techniques are still unable to measure a given parameter, numerical modelling may be the only option of obtaining a value. In addition, numerical modelling helps us to better understand some phenomena, particularly in understanding the influence of input parameters on output results, as well as saving time and money. The thermochemical equilibrium code EXPLO5 is such a tool which enables theoretical prediction of performance of high explosives, propellants and pyrotechnic compositions. The code is used by more than 80 research laboratories worldwide.

PL

Ciągły rozwój coraz bardziej wydajnych komputerów oraz technik obliczeń numerycznych powoduje, że stosowanie modelowania numerycznego staje się koniecznością przy rozwiązywaniu różnorodnych problemów w obszarze materiałów wysokoenergetycznych. Tendencja ta jest szczególnie wyraźna w przypadkach, w których metody pomiarowe nadal nie umożliwiają zmierzenia wartości badanego parametru, tzn. gdy tylko modelowanie numeryczne daje możliwość określenia jego wartości liczbowej. Ponadto, modelowanie numeryczne umożliwia nam lepsze poznanie niektórych zjawisk, np. lepsze zrozumienie wpływu warunków początkowych danego procesu na jego wyniki końcowe. Dodatkowym atutem stosowania modelowania numerycznego jest oszczędność czasu i pieniędzy. Tego typu narzędziem jest EXPLO5, program do opisu równowagi termochemicznej. Umożliwia on, na drodze analizy teoretycznej, dokonanie predykcji efektów działania materiałów wybuchowych kruszących, paliw rakietowych i mieszanin pirotechnicznych. Program ten jest używany w ponad 80 laboratoriach badawczych w całym świecie.

3

Scaled-down test arrangements for characterizing high explosives

Künzel Martin, Kučera Jindrich

Materiały Wysokoenergetyczne

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2021

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T. 13

28--33

EN

Newly formulated explosives and the optimization of explosive mixtures requires an experimental determination of detonation parameters, especially detonation velocity, pressure and metal accelerating ability. Increasing material and labour costs force researchers to reduce test quantities and therefore to develop smaller scale experiments which provide sufficient data to determine an explosive’s properties. Seven test set-ups found in literature are described and compared in this paper.

PL

Otrzymywanie nowych materiałów wybuchowych i optymalizacja mieszanin wybuchowych wymaga eksperymentalnej weryfikacji parametrów detonacyjnych, zwłaszcza prędkości detonacji, ciśnienia i zdolności do przyspieszania wyrobów metalowych. Rosnące koszty materiałów i pracy zmuszają badaczy do minimalizowania testowanych ilości, a tym samym do opracowywania eksperymentów na małą skalę, które dostarczają wystarczających danych do oceny właściwości materiałów wybuchowych. W artykule opisano i porównano pod tym kątem siedem przykładów literaturowych układów badawczych.

4

The Effect of Detonator Shell Materials on Detonation Calorimetry Results

Němec Ondřej, Musil Tomáš, Künzel Martin

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 4

552--565

EN

Detonation calorimetry is a method for the determination of the heat released by the detonation of an explosive charge. Compared to classical combustion calorimetry, detonation calorimetry requires an inert atmosphere, a large sample mass and a detonator for its initiation. This detonator releases some energy for which the results must be corrected. Four types of detonator have been tested in the calorimeter alone and also in combination with explosive charges of PETN. It was found that the aluminium shell of the detonator considerably increases the apparent heat of detonation of the PETN samples in a vacuum, while the presence of combustible (polymeric) components has the opposite effect. Pressurization of the calorimetric vessel with nitrogen gas only partially suppresses these effects. The preferred technique is to use copper or glass confinement in a high pressure inert atmosphere.

5

Detonation Parameters of PlSEM Plastic Explosive

Cardoso Aline Anastacio, Selesovsky Jakub, Künzel Martin, Kucera Jindrich, Pachman Jiri

Central European Journal of Energetic Materials

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2019

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Vol. 16, no. 4

487--503

EN

PlSEM is a plastic explosive based on RDX, PETN and a non-explosive binder, and is used in linear shaped charges for demolition purposes. Its experimentally obtained detonation parameters are presented in the present paper. The detonation velocity was measured for cylindrical charges of various diameters, with and without confinement. The detonation pressure and particle velocity were determined using an impedance window matching technique, and cylinder tests were used to obtain the parameters of the JWL equation of state of the detonation products. Detonation velocities from 7.75 to 8.05 km·s–1 were obtained for unconfined charges with diameters from 4 to 8 mm, and from 8.15 to 8.24 km·s–1 for charges with 25 mm diameter. The experimentally determined detonation pressure was found to be 24.6 GPa.