Wyniki wyszukiwania - Biblioteka Nauki

1

PIV measurements of flow separation over laminar airfoil at transonic speeds

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Stryczniewicz W. , Placek R. , Szczepaniak R.

Journal of KONES

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2016

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tom Vol. 23, No. 1

329--335

EN

The paper presents results of transonic flow field visualization over a laminar airfoil in high-speed wind tunnel. Quite recently, considerable attention has been paid to experimental investigations of an interaction between the shock and the boundary layer for aerodynamics applications. The purpose of the paper is to investigate development of the flow separation over laminar airfoil at transonic speeds. In a course of presented studies, the Particle Image Velocimetry (PIV) method was used for instantaneous velocity measurements of flow field in the test section of N-3 Institute of Aviation transonic wind tunnel. The object of the research was a laminar airfoil inclined at various angles. The effect of the varying angle of incidence on the flow filed was investigated. The freestream Mach number was 0.7. The results of the PIV measurements were analysed in order to identify the type of the separation from the measured velocity fields. Three forms of separation for low, medium and high angle of incidence was distinguished. The results are in good agreement with theoretical models reported in the literature. The study showed that application of quantitative flow visualisation technique allowed gaining new insights on the complex phenomenon of transonic flow over airfoil. The results of the presented research can be used for better understanding of the mechanism of the flow separation process in transonic flow over airfoils and fluid structure interactions.

2

Numeryczno doświadczalne badanie warstwy elastometrowej obciążonej falą uderzeniową

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Niezgoda T. , Barnat W. , Panowicz R. , Gieleta R.

Górnictwo Odkrywkowe

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2010

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tom R. 51, nr 3

65-70

PL

Przedmiotem przedstawionych badań była numeryczno-doświadczalna analiza energochłonnych elastomerowych warstw połączona weryfikacją eksperymentalną. Opracowane struktury elastomerowe stanowią perspektywiczne materiały i będą wykorzystywane do rozwiązywania problemów związanych ze zwiększeniem bezpieczeństwa pojazdów wojskowych oraz newral- gicznych konstrukcji rurociągów i gazociągów szczególnie w niebezpiecznych miejscach, takich jak przejścia nad rzekami itp.

EN

The subject of investigation was numerical and experimentał analysis of energy absorbing elastomeric layers in connection with experimental verification. The energy absorbed layers were subjected to pressure impulse simulating a blast. The elaborated structures will by applied to solve problems connected with increasing the security of military vehicles and crucial oil and gas pipeline structures, particularly in dangerous locations, such as crossings over rivers etc.

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Initiation of rotating detonation in experimental combustion chamber : practical realization

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Kawalec M. , Perkowski W. , Irzycki A. , Snopkiewicz K. , Wróblewski W. , Bilar A. , Łukasik B.

Journal of KONES

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2013

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tom Vol. 20, No. 4

163--168

EN

Since 2009 in the Institute of Aviation, Warsaw a project that aim is to develop combustion chamber with rotating detonation for turbine engine has been carried out. Desired fuel is aviation kerosene (Jet-A) detonated in air. One of the most important problems to be solved was the initiation of rotating detonation in combustible mixture, which requires the fulfilment of several conditions: 1) good mixing of combustible mixture components, 2) properly fast flow of combustible mixture in the cylinder-shaped channel, 3) the appropriate height of the flow channel, associated with detonation cell size for the combustible mixture, 4) use of a source of detonation initiation with an appropriate energy and power for a given combustible mixture. There were considered and tested, in practice several different types of initiators: a) spark electric discharge in air, b) plasma electric discharge (the so-called "exploding wire"), c) micro-explosive charges, d) blank ammunition, e) gas initiator (with detonation of acetylene-oxygen stoichiometric mixture induced by spark electric discharge). The paper summarizes the theoretical energy parameters of several types of initiators, and the results of their comparative research on the test bench. In the course of these researches, the pressures of the shock wave generated by the initiators and recorded by a fast pressure sensor located at a distance from the initiator were compared.

4

Passive Control of Shock Wave Applied to Helicopter Rotor High-Speed Impulsive Noise Reduction

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Doerffer P. , Szulc O.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2010

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tom Vol. 14, No 3

297-305

EN

A strong, normal shock wave, terminating a local supersonic area on an airfoil (or a helicopter blade), not only limits the aerodynamic performance, but also becomes a source of High-Speed Impulsive (HSI) noise. The application of a passive control system (a cavity covered by a perforated plate) on a rotor blade should reduce the noise created by the moving shock. This article describes numerical investigations focused on the application of a passive control device on a helicopter blade in high-speed transonic hover conditions to weaken the shock wave – the main source of HSI noise.

5

On the influence of a carbon solid on the properties of a helium plasma in a theta pinch discharge

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Freese W. , Kunze H.

Nukleonika

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2000

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tom Vol. 45, nr 3

173-177

EN

A helium plasma produced in a 82 kJ theta pinch discharge has been seeded with carbon ions by a carbon solid rod positioned on the axis. The first shock front of the discharge ablates carbon atoms from the solid surface which are ionized and interact with the plasma. Some shock front properties (namely thickness, compression velocity and its shape) were analyzed with an ICCD-camera system taking 2-dimensional photos of the plasma continuum emitted along the axis with a time duration of 100 ns. While the influence on the shape was not found, the temporal behaviour was drastically changed when the rod was added. The shock front occurs earlier and compresses faster. An explanation remains to be given. Furthermore, the influence of the carbon impurities on the plasma parameters has been investigated by measuring the electron temperature and density by means of plasma spectroscopy comparing these results with those obtained from discharges in helium without rod. We found a decrease in the electron density about 500 ns after the shocked plasma has started to interact with the rod surface. Simultaneously increasing continuum emission and decreasing intensity of the HeII Pa line indicates a regime of recombination. No influence was found on the electron temperature.

6

Measurements of pressure in front of shock wave : assessment of methodology influence on the measurement results on the basis of experiments with the shock tube

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Perkowski W. , Irzycki A. , Kawalec M. , Łukasik B. , Snopkiewicz K.

Journal of KONES

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2013

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tom Vol. 20, No. 4

333--340

EN

The experiments, described in the article, are related to research of a rotating detonation that has been conducted in the Institute of Aviation in Warsaw since 2009, under the OPIE project: “Turbine engine with detonation combustion chamber”. Measurements of the shock wave parameters, are among the most difficult in the art. This is due to high speed of the wave transition, and above all, a very small thickness of the shock wave. For the purposes of the mentioned project, a methodology for measuring pressure on the rotating detonation wave was developed. It included the type of sensors, their location and their protection from heat and flames. In order to determine the capabilities, limitations and accuracy of the method that was used, a series of experiments were planned and carried out. They enabled the assessment of the impact, on the measurement of pressure in the shock wave, of the following factors: the location of the sensor (frontal and lateral) relative to the shock wave front, protrusion or retraction of the sensor in its housing, the covering of the sensor with a protective layer (such as a high temperature silicon). This paper presents the results of the experiments that were carried out with use of a small shock tube of a simple design. The high-pressure part of the tube (so-called “driver”) was charged with the compressed nitrogen gas. The membrane was designed to be torn by pressure and pressure magnitude of the shock wave were measured by a “twin pair” of the Kistler 603B type piezoelectric sensors, one of which was always the reference sensor.

7

100%

Vishwakarama J. P. , Pathak P.

Journal of Theoretical and Applied Mechanics

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2012

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tom Vol. 50 nr 2

563-575

EN

Similarity solutions are obtained for an adiabatic flow behind a cylindrical shock wave propagating in a rotational axisymmetric flow of a perfect gas, in which initial velocity and density are functions of the distance from the axis of symmetry. The initial medium is considered to have a variable azimuthal velocity component in addition to the variable axial velocity. Initial velocities and density are assumed to obey power laws. Distributions of the fluid velocities, density, pressure and vorticity components are obtained in the flow-field behind the shock front. Effects of variable initial velocities and density and the variation of the shock-Mach number are investigated.

PL

W pracy przedstawiono rozwiązania automorficzne otrzymane dla adiabatycznego przepływu czynnika za cylindryczną fala uderzeniową rozchodzącą się w rotacyjnym, osiowo-symetrycznym opływie gazu doskonałego, którego prędkość początkowa oraz gęstość są funkcjami odległości od osi symetrii. W stanie początkowym, analizowany czynnik posiada oprócz zmiennej składowej osiowej prędkości dodatkowo zmienną składową azymutalną. Założono, że prędkości początkowe i gęstość opisują funkcje potęgowe. Rozkłady prędkości płynu, gęstość, ciśnienie oraz składowe wirowości otrzymano w polu przepływu za frontem fali uderzeniowej. Zbadano także wpływ prędkości początkowych oraz gęstości na zmiany wartości liczby Macha.

8

Experimental studies of a moveable wall to a shock wave

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Górniak A. , Kaźmierczak A.

Journal of KONES

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2013

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tom Vol. 20, No. 3

145--151

EN

This paper explains the experiment conducted in order to reveal the response of a movable wall on a shock wave generated by ignition of a pyrotechnic gas generator dedicated for the automotive industry. This same kind of a pyrotechnic gas generator was used in each test. The test station consists on a pyrotechnic actuator in which the movable wall is expressed as a piston. The pyrotechnic actuator was specially design for such type of an investigation. Its design allows withstanding numerous tests without affecting the accuracy, and it is prepared to pressure measurement in three locations on the cylinder. However, here only the pressures measured in the vicinity of a cylinder bottom are under deliberation. This paper focusses on a shape of the piston influence on its movement characteristics (i.e. stroke velocity and acceleration). The experiment has shown that there is an influence of the shape of the movable wall on its movement characteristic. Furthermore, the experiment explained here constitutes a comparison of a piston velocity and acceleration with a flat and concave front surface. The dynamic pressure measurement have proven that the reflected shock wave increases its speed affecting the piston movement.

9

Explosive charge impact on the openwork steel shield

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Sławiński G. , Świerczewski M.

Journal of KONES

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2016

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tom Vol. 23, No. 3

481--487

EN

The article presents the issue of increasing the passive safety of soldiers in a military vehicle, which is subject to loads resulting from an explosion IED or mine. Traditional methods of increasing security involve the application of additional layers, which are made using materials with high density. This approach contributes to the reduction of mobility and efficiency of a vehicle on the battlefield. For these reasons, it is necessary to search for a new structural design, which will benefit from a solution, which will not worsen the driving parameters of a vehicle in combat. Therefore, we propose a novel solution of openwork panel with dividers. The effectiveness of the system will be checked by verified on the bench traverse. The blast shock wave will be induced by detonation of HE charge at the central point over 430 mm from the top surface of the range stand. Experimental test will be used to validate the numerical model. After positive validation and verification, numerical model it can be used for other blast conditions or optimize protective shield. The problem considered in the study was solved numerically with the FEM using the following CAD-CAE systems: CATIA (to prepare a surface model), HyperMesh (division into finite elements), LS-Dyna (a solver), LS-PrePost (pre and post processor).

10

Impulse Action Of Underwater Shock Wave As A Cause Of Disabling The Ship Power Plant

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Powierża Z. , Wojciechowska B.

Journal of Polish CIMAC

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2009

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tom Vol. 4, no 1

123-128

EN

This paper presents action of shock wave resulting from an underwater non-contact explosion, exerted on ship hull plating. The impulse load was considered in the range of wave regular reflection and refraction at the boundary of two media: water and steel. In most cases the impulse action leads to failures or damages of elements of ship power plant as well as shipboard equipment, however without endangering ship’s floatability. Typical kinds of failures which recurred on ships of various tonnage, are presented, a.o., on the example of ships sailing in Red Sea waters during Iraq-Iran war.

11

Czynniki rażenia broni jądrowej. Cz. 4, Fala uderzeniowa

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Solarz J.

Zeszyty Naukowe AON

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2004

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tom nr 1(54)

110-128

EN

The shock wave is the most serious nuclear weapon destructive factor. Its energy usually makes up for the half of overall energy given off during a nuclear blast. Having an enormous destructive power, it may lead to substantial destruction of armament and equipment and also to mass radiation among troops and civilian population. The emergence and spread of the nuclear bomb shock wave differs very little from the phenomena that occur during conventional charges explosions. The scale, however, is entirely different, the amount of destruction and radiation in particular. Therefore it is of utmost importance to recognise in detail all aspects of the shock wave emerging and spreading and its influence on conducting combat operations. The article presents the principles of the shock wave emergence after surface, under and over surface explosions. It has been pointed out to the idea of the destructive action of the shock wave and the static overpressure and the wind gusts have been discussed in detail. Additionally the influence of the terrain and meteorological conditions on the shock wave effects has been analysed. In order to understand better the threats, which the shock wave poses after an atomic explosion, its influence of living organisms, combat equipment and armament has been presented. Moreover the basic principles of protection against the shock wave have been defined.

12

Charakterystyki burzącego oddziaływania podczas zlokalizowanego wybuchu

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Silnikow M. W. , Michajlin A. I. , Orłow A. W. , Sierdcew N. I. , Nozdraczew A. W.

Techniczne Wyroby Włókiennicze

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2002

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tom R. 10, nr 1/2

32-39

13

Influence of limiting walls on shock wave structure in single passage test section with compressor profile

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Piotrowicz M. , Flaszyński P. , Szwaba R.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2015

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tom Vol. 19, No 2

141--152

EN

The shock wave boundary layer interaction on the suction side of a transonic compressor blade is one of the main objectives of the TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). In order to look more closely into the flow structure on the suction side of the blade, a design of a turbine passage model in a rectilinear transonic wind tunnel was proposed. The model which could reproduce the flow structure, the shock wave location, the pressure distribution and the boundary layer development similar to the obtained in a reference cascade profile is the main objective of the design presented here. The design of the proposed test section is very challenging, because of the existence of a shock wave, its interaction with the boundary layer and its influence on the 3-D flow structure in the test section. The paper presents the influence of the test section geometry configuration on the flow structure as an effect of the shock wave boundary layer interaction.

14

An analysis of an explosive shock wave impact onto military vehicles of contemporary warfare

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Saska P. , Krzystała E. , Mężyk A.

Journal of KONES

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2011

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tom Vol. 18, No. 1

515-524

EN

Landmines and improvised explosive devices (IED) are the basic weapon used by the rebels against the Coalition forces in Afghanistan and Iraq. It is estimated that about 50% of the casualties (wounded and killed) among the soldiers from the US and other countries participating in both conflicts are caused by explosive charge. Introduction of vehicles providing proper protection of the crew against an explosive shock wave generated by a detonation of mines and improvised explosive devices into the arsenal has become one of the priorities of modernization of armed forceps. The parameters critical to the emerging of a hazard for the surrounding includes the overpressure impulse and the shock wave overpressure. The problem of defining the parameters of an explosive shock wave generated after detonation of charges of various mass, shape and physical-chemical properties is a subject of studies at much scientific institution. The gained quantitative data are not, however, published in public reports, thus a need of performing one’s own experimental and numeric research arise. The goal of these studies is to find solutions increasing soldier’s safety at the battlefield. The paper presents an analysis of impact of a shock wave onto structures of military vehicle. Furthermore, methods of experimental definition of explosion shock wave parameters were presented and conclusions for the needs of further experimental-numerical studies were formulated.

15

The numerical simulation of the pyrotechnic actuator for the active bumper

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Górniak A. , Kaźmierczak A. , Krakowian K. , Włostowski R. , Błasiński T.

Journal of KONES

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2012

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tom Vol. 19, No. 3

141-147

EN

The paper contains the description and classification of pyrotechnic actuators focusing on the automotive industry applications. This paper also explains the compatibility issues during frontal impact of a passenger car with a large truck. The construction of the pyrotechnic actuators for the "active bumper" is presented here. The processes occurring within the pyrotechnic actuators after ignition of a pyrotechnic propellants have been explained. The investigations are focused on the dependence of a shape of the actuator's combustion chamber and the piston stroke time. It appears that the appropriate design of the combustion chamber can decrease the time required for a piston stroke using this same type of a propellant. This also allows to reduce the amount of propellant when the more rapid stroke is not required. This is because of the characteristics of the detonation waves which are responsible for the piston movement. The visualization of the detonation waves occurring due to ignition of the propellant is crucial for understanding the dependence between the construction of the actuators interior and the piston stroke time. Therefore, the approach of simulating numerically the detonation waves aroused. This simulation was conducted with aid of ANSYS Workbench 13 environment using the AUTODYN module. The numerical tests consists on modelling the actuator without changing the overall dimensions as well as the parameters of the propellant. The only elements modified were piston and the bottom of the cylinder shape.

16

Maximum discharge pressure of supercritical two-phase steam injector

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Trela M. , Kwidziński R. , Buła M.

Archives of Thermodynamics

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2004

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tom Vol. 25, no. 1

41-52

EN

The paper aims at the determination of the maximum output pressure as one of the pertinent parameters describing the steam injector performance. Experimental and theoretical results of discharge pressure investigation from steam-water injector are presented. Experiments included measurements of output pressure dependence on varying inlet flow rates of both media and on the water nozzle gap. Maximum output pressure obtained reached 97% of the inlet vapour pressure. Performance of the steam injector is described mathematically using momentum balance in mixing chamber and shock wave region. Loss coefficient of the steam injector is also determined. Having the loss coefficient one can evaluate the maximum pressure for geometry similiar steam injectors. From the analysis of the balance equations, the ways of increasing the maximum discharge pressure are suggested.

17

Modification of the elementary Mach reflection theory of an oblique shock wave at a rigid wall

100%

Łęgowski Z.

Journal of Technical Physics

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1998

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tom Vol. 39, no 1

67-75

EN

A modified version of the local theory of an oblique shock wave reflection at a rigid surface is presented, known as the elementary theory of Mach reflection (ETMR). Modification concerns solutions for pressure acting on the wall in the region adjacent to the Mach stem front. A good agreement is obtained with Henrych's [11] and Glasstones's [12] data, and with Henderson's [13] measurements, in a wide range of the incident wave intensities as well as in the whole range of its irregular interaction. The theory enables to remove the wall known paradoks of Mach reflection observed so far in the range of weak shock waves reflections, according to the classification introduced by von Neumann [4].

18

Enhanced evaporation of the condensate droplets within the asymmetrical shock wave zone

100%

Kornet S. , Badur J.

Transactions of the Institute of Fluid-Flow Machinery

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2015

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tom nr 128

119--130

EN

The present work is concerned with investigation into coupled phenomena occurring in the supersonic section of the de Laval nozzle, characterized by the presence of shock the flow of condensing steam. The numerical simulations results were compared with the experiment carried out by Dykas et al. in 2013 on the half arc nozzles. The present work includes simulations results of oscillation frequency of the shock wave and conditions for the enhancement evaporation of condensate within the asymmetrical shock wave. Novelty of our approach lies on modeling both the moment of initiation of a phase transition, as well as the moment of its reverse progress – called here revaporization of the condensate phase.

19

Generator płaskiej fali uderzeniowej

100%

Cudziło S. , Trzciński W. A.

Problemy Techniki Uzbrojenia

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2001

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tom R. 30, z. 80

215--224

PL

W pracy przedstawiono układ do wytwarzania płaskiej fali uderzeniowej w obciążanej próbce. W roli generatora fali zastosowano metalową płytkę napędzaną produktami detonacji ślizgającej się po jej powierzchni. Za pomocą modelu teoretycznego wyznaczono kąt ustawienia płytki. Przewidywania teoretyczne zweryfikowano eksperymentalnie wykorzystując technikę rentgenografii impulsowej. Zarejestrowano położenie miotanej płytki tuż przed uderzeniem w próbkę. Wykazano, że zaproponowana procedura określania kąta ustawienia płytki i sam generator fali płaskiej mogą być wykorzystane w układach przeznaczonych do badania dynamicznych właściwości materiałów.

20

Modelling and numerical analysis of explosion under the wheel of light armoured military vehicle

100%

Świerczewski M. , Sławiński G.

Engineering Transactions

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2017

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tom Vol. 65, iss. 4

587--599

EN

The article presents a method for numerical modelling of a blast shock effect on unsprung parts of the military vehicle suspension. An explosive charge during the tests was placed under a vehicle wheel according to STANAG 4569 requirements. The mass of the charge is 10 kg of TNT, which corresponds to the highest level of safety – 4a. During the research, there was also tested an influence of application of Run Flat in the Tyre-Run Flat-Rim system on the propagation of a shock wave under the vehicle chassis. A model and numerical calculations were carried out with the use of the following programs: CATIA, HyperMesh, LS-PrePost, LS-Dyna. To describe an effect of a pressure wave on the structure, ALE approach was applied, which allowed mapping such processes as: detonation, wave propagation, interaction with a structure and ORFF system response.