Marcin Konarzewski

Introduction to numerical analysis of directed fragmentation warheads

The aim of the paper is to presents one of the possible approaches to the numerical analysis of the behaviour of directed fragmentation war heads. These kinds of warheads consists of: metallic or composite cover, explosive material and a driven and fragmentation liner. The explosives are initiated by a booster causes driving the liner in a few milliseconds up to about 900 m/s. The liner fragments into many parts during this intensive and dynamic load. The fragments move in a cone which dimensions depend on the warheads shape and mechanical parameters of others warheads parts. All of the warheads elements are selected to meet the assumed parameters. The fragments velocity, their mass or geometric dimensions and cone angle are the most important parameters of the warheads fragments. Such a warhead, in the initial phase of the liner driving can be numerically modelled in the field of the continuum damage mechanics. Such a description is presented in other papers. This approach in a further phase of driving cause the increases of inaccuracies. Therefore, this paper proposes the use of ALE and FSI approach to describe the behaviour of the fragmentation warheads. A three-dimensional numerical model of the directed fragmentation warheads was made in the MSC Patran, and the dynamic phenomena analysis used a nonlinear finite element method implemented in the LS-Dyna program.

HYBRID LOCOMOTIVES OVERVIEW OF CONSTRUCTION SOLUTIONS

Nowadays, transportation becomes a significant source, apart from factories and power plants, of air pollution. Therefore, due to legal restrictions on the emission of noxious gases, other power sources for vehicles are necessary. Some of these power sources allow replacement of the internal combustion engine completely, whereas the other ones only support the engine operation. Hence, a hybrid powertrain – alternative to the drivetrain equipped with an internal combustion engine only – is increasingly being used. The hybrid powertrain was mostly applied in cars and buses but recently it has been also used in railway vehicles such as locomotives and multiple units. The paper presents a shortened and brief overview of construction solutions of selected hybrid locomotives. A list of the applied hybrid drive systems as well as the basic data and properties are provided. The most important variants of vehicles are compared. The presented material allows identification of the development trends in the considered area. The hybrid locomotive usually uses an onboard rechargeable energy storage system, placed between the power source and the traction transmission system connected to the wheelsets. Modification of a classic diesel-electric locomotives is a relatively simple procedure since they have all the components of a series hybrid transmission except the storage battery. Therefore, the existing and operated diesel-electric locomotives can be modified to increase their efficiency and reduce operating costs and emissions.

NUMERICAL ANALYSIS OF THE FRONT IMPACT BETWEEN TWO SHUNTING LOCOMOTIVES

The main aim of this study is to carry out dynamic finite element analysis of a crash between two identical shunting locomotives. Numerical simulations include front-end impact of the running locomotive with a stationary one situated on the track. The first design collision scenario includes such obstacle for railway vehicles operated on national and regional networks. A considered locomotive based on a popular Polish shunting locomotive – SM42. However, the tested locomotive was slightly modernized in comparison with the original one. Finite element model of the locomotive was developed by the authors. FE analyses were carried out according to the PN-EN 15227 standard, which provides crashworthiness requirements for railway vehicle bodies. LESS-DYNA computer code was used for the simulations. The energy balance was initially checked in order to confirm the accuracy of analysis. The paper presents selected results of analyses focused on the locomotive frame behaviour. Contours of effective stress for selected moments of time are presented. Time histories of selected parameters are also depicted. The current study is a part of the project focused on modernization of the SM42 locomotive. Therefore, it is required to evaluate the locomotive behaviour during the impact test. Dynamic numerical simulation is acceptable since the experimental tests on the complete objects under consideration are impractical and impossible at the moment.

NUMERICAL ANALYSIS OF THE INFLUENCE OF THE DEFLECTOR STIFFNESS AND GEOMETRY ON ITS EFFECTIVENESS

The aim of the paper is to present the results of numerical analyses of designed classical system for measuring impact of the pressure wave originating from the detonation of explosive charge. In the paper, authors present classical ballistic pendulum in the form of the 1-meter length, HEB220, double T beam, which was suspended on the four parallel steel cables. On the front part of the pendulum, steel deflector was attached, whose aim was to disperse the energy. A few variants of used deflector were prepared, differing in the deflector geometry and thickness of the used material. In the next step, presented system was loaded with use of pressure wave, originating from detonation of 50 grams explosive charge. In order to properly describe the detonation process ConWep method was used. In this method, on the basis of preset geometric and mass parameters, together with TNT equivalent, the pressure pulse is determined. A three dimensional model of classical ballistic pendulum was prepared in MSC Patran software and numerical analyses were performed using LS-Dyna software. As the result of numerical analyses, the maximum deflection of the pendulum was determined for each case. Based on obtained results the influence of deflector geometry and stiffness on energy absorbing was identified and presented in the form of graphs.

Experimental and numerical studies of selected types of batteries - state-of-the-art

The purpose of this article is to provide—on the basis of the literature review—the current state of knowledge concerning the experimental and numerical studies of selected types of batteries. The authors focused their actions on batteries that could to be the base for an energy storage system possible to apply in hybrid shunting locomotive. Following standards, e.g. IEEE 1625, IEEE 1725, UL 1973 and UL 2271 were taken into consideration within the context of the experimental research. Numerical analysis based mostly on the original solutions proposed by research teams. In recent times, the significant growth of interest in hybrid vehicles can be observed. Therefore, appropriate design of the energy storage system for each case is necessary. Moreover, the battery working process in hybrid vehicles is very specific, hence determination of their working conditions depending on the vehicle application is required. Very often, the experimental studies related with the batteries are based on the parameters recorded during the test conducted during the regular operation of the vehicle. Furthermore, research teams also carry out numerical analysis based on e.g. the finite element method (FEM). Such analyses can be focused on the thermal analyses of single cell or cells, analyses of the electrochemical effects as well as a coupled electro-thermal analyses.

Crushing Behaviour of the PVC Foam Loaded with Beaters of Various Shapes

Abstract Statistically, at least 50% of all injuries experienced by police officers in the line of duty are due to assaults with blunt objects. Therefore, vests used by the police should provide not only good ballistic resistance, but also good protection against such threats. Foamed materials are possible to be used for body protectors or inserts of protective clothes. The effects of dynamic impact with beaters of different shapes onto behaviour of polymeric foamed material were determined. There were used four types of beaters: flat, cylindrical, edgy and cornered. Strikes with blunt objects such as a flat board, baseball bat, edgy brick, pavement brick or a sharp stone, to which a protective ware can be subjected, were simulated. The impact load was applied to the rectangular specimens, made of polyvinyl chloride foam, with a usage of a drop hammer. Plots of force versus compression for all the tested samples were obtained and analysed. The effects of impacts with beaters of different shapes onto foamed material samples were presented. A shape of the blunt object significantly influences crushing behaviour of the foamed material. The impact energy of a flat beater is absorbed effectively on a short distance, since it is spread on a relatively large surface. The cylindrical and edgy beaters did not cause fragmentation of the samples, however, on the upper surfaces of the samples, permanent deformations mapping the beaters shapes as well as some cracks occurred. An impact with a sharp object, for example, a cornered beater is very difficult to be neutralized by the foam material, because it is cumulated on a small area.

Numerical analyses of the V-shaped deflector effectiveness

One of the most effective ways to protect mobile objects from the effects of the pressure wave originating from the detonation of a landmine or an explosive charge is to use a special design of the bottom of the protected vehicle. Such structure, called the deflector, in most cases has the shape of the V letter. Article presents the study of effectiveness of the V-shaped deflector. Authors prepared numerical model of a ballistic pendulum consisting of the 1 meter long HEB220 H-beam, suspended using four parallel steel ropes. In the front part of the beam, deflector was mounted. The test component was loaded with pressure wave coming from the detonation of an explosive charge. The article presents an analysis of the ability of the deflector to disperse and/or absorption of energy, depending on the type of the used explosive material and its mass. Studies have been done on the basis of numerical analysis performed with use of the finite element method with explicit integration over time scheme, implemented in the LS-Dyna software. For generation of the pressure wave originating from the detonation of explosive charge ConWep algorithm was used. It uses the predefined by the user geometric and mass parameters, and TNT equivalent to the generation of a pressure pulses.

INFLUENCE OF DIMENSIONAL PROPORTIONS OF CYLINDRICAL EXPLOSIVE ON RESULTING BLAST WAVE

Explosives are broadly used today in many applications, both civilian and military. Many experiments involving explosives use either ball or cylinder charges. However, there can be raised a question whether an exact shape influences the resulting blast wave, and, additionally, if the length to diameter ratio of the cylinder influences the wave. To answer the question, numerical analysis was conducted. A 3D model of the charge was constructed in LS-Prepost software and calculated with use of an explicit FEM method in LS-DYNA software. To determine the change of character of the blast wave, the dimensions of the charge change, whereas the mass and distance from the centre of the charge are constant. Several length to diameter ratios was tested, starting from 0.25, to 2, in 0.25 increments. Two explosives, HMX and TNT, were used. As expected, the resulting Blast wave was different in each case, with 100% difference in pressure values between 0.25 and 2 L to D ratios, especially along the length axis of the cylinder. The results show that the exact diameters of the charges need to be taken into consideration while determining a type of charge to be used as well as determining the goal to be achieved during a particular conducted experiment.

Analysis of the detonation initiation point position influence on the cylindrical fragmentation warhead effectiveness

The article presents results of the numerical analyses of the fragmentation warhead, which is one of the key elements of the missile used to combat anti-tank missiles. The fragmentation warhead is composed of such elements as outer casing, inner casing, explosive material and fragmentation liner. The fragmentation liner is built from steel spheres or cylinders embedded in epoxy resin. As a result of the explosive material detonation the pressure wave is generated, which affects the liner, causes its fragmentation, and drives each splinter. In order to perform numerical analyses the model of the cylindrical fragmentation warhead with a diameter of 80 millimetres and a length of 100 mm was prepared. The fragmentation liner consists of steel spheres with a diameter of 5 mm. It was assumed in simulation that the detonating material is the plastic explosive C4. The influence of the position of the explosive charge detonation initiation point of the fragmentation warhead on its effectiveness was studied. Effectiveness was evaluated by measuring the maximum speed obtained by the fragments and their spatial distribution. A threedimensional model of the studied system has been prepared using the MSC Patran software and the numerical analyses were performed using the finite element method with explicit scheme of the time integration implemented in the LS-Dyna solver. To model gas domain Arbitrary Lagrangian-Eulerian (ALE) method was used and interaction between gas and solid body was modelled with FSI coupling.

Influence of destructor case type on behaviour of fragments in military vehicles active protection system

Military vehicles active protection systems against cumulative missiles are designed to destroy the attacking missile before it hits the vehicle armour. The article presents the results of numerical studies of one of the elements of active protection system, which is the fragmentation destructor. A typical directed fragmentation warhead consists of a few parts: metallic or composite case, explosive material and fragmentation elements in the form of spheres, cylinders. The authors of this study evaluated the influence of the destructor case type – in particular material – on the effectiveness of the destructor. The effectiveness was evaluated on the basis of the maximum speed of balls. Evaluation was performed for the selected balls from each layer. Numerical calculations were performed for two materials of the case: steel and aluminum. It was assumed in simulation that the detonating material is the plastic explosive C4. The numerical analyses were based on the finite element method with the explicit time integration method implemented in the Ls-Dyna program. The interaction of solid and gaseous medium has been modelled using ALE coupling. Mechanical properties of the case were described using a simplified Johnson-Cook type material. The detonation process was described using programmed burn model approximations, and the behaviour of detonation products was described with the JWL (John, Wilkins, Lee) equation.