15 research outputs found
Research of influence of different shaped charge liner materials on penetration depth using numerical simulations
No full textNumerical simulations, using the Ansys AUTODYN program, of Panzerfaust 30 (klein) anti-tank warhead, were performed to determine the influence of different liner materials on the penetration depth into a steel target. It has been shown that the choice of liner material can significantly affect the performance of the ammunition. Along with other methods of optimizing shaped charge ammunition (optimization of the shape, thickness and angle of the tip of the liner, use of more potent explosive and deviator, optimization of casing thickness and stand-off distance, etc.), the use of appropriate liner material is certainly one of the most im-portant parameters of shaped charge warheads to consider. Together with analytical calculations and experi-mental tests, simulations are a valuable tool. Using data obtained from numerical simulations, researchers can save both time and resources during the process of munition design and optimization
Review of the estimation methods for external blast loads on structures
No full textA review of external blast loads on structures modeling methods is presented in the paper. Also, numerical simulations of explosions in an urban scenario were done in software Ansys AUTODYN, and compared to experimental data.
Recommendations were given regarding the use of numerical simulations in blast wave parameter calculations for the urban environment, as well as suggestions for further research
Using numerical simulations for estimating the influence of different parameters of long rod kinetic energy penetrators
No full textSimulations were performed with long rod kinetic energy penetrators to characterize important parameters used. Hohler & Stilp\u27s experimental results served as the initial validation for the numerical model. Additionally, using numerical simulations, the impact of various (possible) penetrator materials on their penetration depth is illustrated. Additionally, the effects of using a steel jacket (sheath) over the penetrator and the penetrator fineness ratio (L/D) were examined. Research showed that the choice of penetrator material can significantly affect the penetrator\u27s effectiveness. With a penetrator of depleted uranium alloy (0.75% titanium), the maximum penetration depth was attained. It was shown that when increasing the penetrator fineness, the increase in penetrator length has a large influence on penetration depth. Decreasing the penetrator diameter the penetration depth is also decreased. Numerical simulations also showed that to minimize penetration degradation, the penetrator jacket must be relatively thin
The influence of projectile impact velocity and target characteristics on the terminal ballistics parameters of small-caliber projectile
No full textThe study examines the results of numerical simulations of the penetration of a 7,62mm x 63, AP, M2 projectile through a target. Model validation involved a numerical simulation of 7,62mm x 63, AP, M2 projectile penetration through an AA5083H116 target, for which experimental results were available in the literature. The results of the numerical simulation were used for regression analysis - to calibrate the Recht-Ipson model for the given projectile. Furthermore, penetration analyses of 7,62mm x 63, AP, M2 projectiles through various target materials were performed at consistent projectile velocities and mesh sizes. As expected, bainitic steels exhibited the highest resilience, demonstrating that increased material hardness and tensile strength correlate with enhanced projectile penetration resistance
Estimation of projected surface area of irregularly shaped fragments
No full textThe essence and the main contribution of this paper are consisted of the suggested novel method for estimation of a projected surface area of an irregularly shaped fragment, which represents a significant step toward a new method of an aerodynamic force estimation of a fragment motion through a resistive medium. The suggested method is to use a tri-axial ellipsoid that has a continuous surface (given as a mathematical function) to approximate an irregularly shaped fragment so that the fragment trajectory can be estimated faster taking into consideration that the aerodynamic force is proportional to a projected surface area of the fragment.During their motion, fragments can take any orientation relative to the velocity vector and aerodynamic force is proportional to a projected surface area of fragment perpendicular to the velocity vector, so it is necessary to have a method for correct estimation of the projected area in an arbitrary direction relatively to the fragment.The model was validated with analytical and CAD techniques, and verified using 3D model of a real fragment. The comparison of the projected surface area values for the fragment, obtained using the CAD tools and using our model, are generally in good agreement. This method represents a step toward modeling that does not require a CFD result for estimation of the aerodynamic force of irregularly shaped bodies. Keywords: Projected area, Fragments, Trajector
Trajectory estimation model for a solid body with an irregular shape undergoing extremely high aerodynamic forces
No full textA generalized (6DOF) model for evaluating fragment trajectory elements is defined, which incorporates a novel model for estimating the projected surface of the body and novel model for estimating aerodynamic force and moment. This 6DOF model is developed on the basis of differential equations of the center of mass motion and movement around the center of mass (currently no known model incorporates movement of the body around its center of mass), and can model the parameters that play an essential role in movement of the bodies with irregular shape through the atmosphere. In our model the basic parameters (i.e. body dimensions) can be arbitrarily changed in the initial part of the analysis, and based on their values and values of initial kinematic parameters (initial velocity, position, orientation), trajectories can be determined (as well as other parameters: velocities, orientation) in a relatively short amount of time.
The calculation of the complete trajectory of the fragments can be used in a number of applications: the analysis of the effects of the fragments (i.e. the safety analysis of the location of the ammunition depots, due to the potential explosion of the projectile) or in the estimation of a danger zones when demining larger quantities of the munition. Also, from the point of view of the parameters of the lethal zone of HE projectiles, it is generally important to estimate the trajectory of the fragments in the range up to 50m, so this model can be used to model such a scenario also. This model could also be potentially used wherever there is a need to calculate flight mechanics parameters of irregularly shaped bodies.
Generalized (6DOF) model for estimation of an irregularly shaped body trajectory is implemented in a computer program, written in MatLab. Based on the model, the trajectory calculations were performed for the complete trajectory and for shorter distances to the center of the explosion, with varied geometric-inertial parameters and initial kinematic conditions for the given fragment
Analysis of Optical Telescope Element (OTE) used in James Webb Space Telescope (JWST)
No full textThis paper presents an analysis of the James Webb Space Telescope (JWST) Optical Telescope Element (OTE) based on its published optical prescription and system architecture. Using modeling, key optical performance parameters were evaluated, including spot diagrams, footprint diagrams, wavefront error (WFE), point spread function (PSF), Strehl ratio, encircled energy (EE), and modulation transfer function (MTF). The segmented 6.6 m primary mirror was modeled using a User-Defined Aperture (UDA) approach to accurately reproduce the hexagonal pupil geometry and diffraction effects. Results confirm diffraction-limited performance across the evaluated field, with RMS wavefront error well below the Maréchal criterion, high Strehl ratios (≥0.87 off-axis and ≥0.97 on-axis at 1 µm), and encircled energy closely matching the diffraction limit. MTF curves demonstrate strong contrast transfer up to the cutoff spatial frequency with minimal field-dependent degradation.
Additional analyses were performed to assess the impact of individual segment piston and tilt misalignments. Controlled perturbations show that segment-level phase discontinuities significantly degrade WFE, emphasizing the importance of precise segment phasing and wavefront sensing and control (WFS&C)
Review of methods for prediction of internal blast loading
No full textA review of internal blast loads on structures modeling methods is presented in the paper. Also, numerical simulations of the internal explosion were done in numerical software Ansys Autodyn. Critical areas of confined spaces were identified for this type of explosion event.
Recommendations were given regarding the use of numerical simulations in blast wave parameter prediction, as well as suggestions for further research
Universal Media Strategy: Us vs. Them
No full textMit Media Representations of the Cultural Other in Turkey bietet Alparslan Nas eine Analyse neuester Medieninhalte (Werbung, Zeichentrickfilme, Filme und Fernsehserien) und versucht herauszuarbeiten, inwiefern das Verhältnis zwischen Zentrum und Peripherie in diesen zeitgenössischen Inhalten ausgenutzt wird. Trotz einiger grober Aussagen und schwachen Verbindungen zu vorhandenen Theorien beweist der Autor anhand narrativer Analyse deutlich die Interdependenz dieser zwei Kategorien. Diese kurze und überschaubare Studie enthüllt die Paradoxe einer turbulenten Zeit in der Türkei und beweist vielfach, dass die kulturelle Dichotomie zwischen Zentrum und Peripherie vielen Akteuren als strategisches Instrument dient, ihre Position in Medienrepräsentationen zu verstärken.Alparslan Nas’ Media Representations of the Cultural Other in Turkey offers up-to-date analysis of recent media content (advertisements, cartoons, films and TV shows) with the aim to answer whether a center-periphery binary is exploited in contemporary production. Despite some broad statements and weak ties with existing theoretical work, the author clearly demonstrates the interdependence of these two ‚imaginative categories’ through narrative analysis. By elucidating paradoxes of an incredibly turbulent period in Turkey, this short and comprehensible study brings a host of evidence that the center-periphery cultural dichotomy is a strategic instrument for different subjects to strengthen their position in media representations
Estimation of stresses on 155mm artillery projectiles during launch phase using numerical simulations
No full textThe paper provides an overview of research (analytical, numerical, and experimental methods) related to the stress state of artillery projectiles during movement through the barrel of the weapon. The characteristics of the 155mm HERA M549 and 155mm HE M795 projectiles, used in numerical simulations, are described. As a main goal of the research, numerical simulations were performed with the 155mm projectiles to determine the maximum equivalent stresses that occur during the launch of this ammunition. The obtained values were compared with the yield limit of the materials of the projectile components, in order to assess whether the plastic deformation would occur during the launch phase
