THE EFFECT OF DEEP CRYOGENIC ON TENSILE STRENGTH AND IMPACT TOUGHNESS IN QUENCH TEMPERED STEEL PLATE AS A CANDIDATE FOR BALLISTIC RESISTANCE MATERIAL

Ballistic resistant materials are materials containing right combination of hardness, strength, and toughness. The quench process produces high hardness and tensile strength but decreases toughness. The hardening process has been performed using an induction machine and a tempering process on a medium carbon steel plate. This work aimed to determine and analyze the effect of deep cryogenic treatment (DCT) on steel plates that have been quenched tempered. This research utilized steel plates of 130 x 130 x 8 mm size which has been quenched and then immersed in liquid nitrogen at a temperature of -196°C for 1, 5, 10, and 20 days. The micro Vickers hardness test specimen, tensile test and charpy impact test were made to determine the effect of immersion time. The test results and analysis showed that DCT had the ability to change microstructure, improve the hardness, tensile strength, and impact toughness. Furthermore, the maximum hardness was obtained during the immersion treatment of 20 days, which was 449.45 VHN and 1107.53 MPa, respectively. However, the highest toughness was obtained during the immersion of 10 days, which was 1,001 J/mm2. In order to get the optimal combination of ballistic characters, further ballistic testing is needed, both in simulation using the finite element method and ballistic experiment test.

Experimental Comparison between Event and Global Shutter Cameras

We compare event-cameras with fast (global shutter) frame-cameras experimentally, asking: “What is the application domain, in which an event-camera surpasses a fast frame-camera?” Surprisingly, finding the answer has been difficult. Our methodology was to test event- and frame-cameras on generic computer vision tasks where event-camera advantages should manifest. We used two methods: (1) a controlled, cheap, and easily reproducible experiment (observing a marker on a rotating disk at varying speeds); (2) selecting one challenging practical ballistic experiment (observing a flying bullet having a ground truth provided by an ultra-high-speed expensive frame-camera). The experimental results include sampling/detection rates and position estimation errors as functions of illuminance and motion speed; and the minimum pixel latency of two commercial state-of-the-art event-cameras (ATIS, DVS240). Event-cameras respond more slowly to positive than to negative large and sudden contrast changes. They outperformed a frame-camera in bandwidth efficiency in all our experiments. Both camera types provide comparable position estimation accuracy. The better event-camera was limited by pixel latency when tracking small objects, resulting in motion blur effects. Sensor bandwidth limited the event-camera in object recognition. However, future generations of event-cameras might alleviate bandwidth limitations.

Setting up Experiments for Analyzing Disturbances of the Head Shock Wave Due to the Presence of Particles in the Supersonic Flow

The research in the field of devices and methods of experimental physics includes, in particular, the creation of installations for conducting experiments in the physics of multiphase nonequilibrium flows. Multiphase flow around bodies is of significant importance in various fields of technology, for example, in power engineering, contact visualization methods, aerosol technologies, in the application of various coatings, etc. In the high-speed two-phase flow around bodies, the physics of particle collisions with the surface and the interaction of flying particles with the head shock wave play an important role. Most of the experiments in this area, including the passage of the model through the zone of rain, snow, dust, cooled clouds, etc., are carried out in the reverse setting. In this case, the model is fixed, and the flow is made by one or another high-enthalpy aerodynamic installation. This approach does not correspond to the initial stage of the interaction formed before the entrance to the zone of the two-phase medium, between the head shock and the incident particle. Nevertheless, for some approaches, it is of interest to visually confirm the possibility of an oncoming particle being ejected at a supersonic speed by the front of the head shock wave and to see the deceleration of the model from the shadow pattern with a change in the Mach line. The paper considers a direct ballistic experiment which by shadow visualization tests the possibility of cavern formation near a body crossing the trajectory of the atmosphere saturated with dust particles

Динамика капель, подброшенных над испаряющейся поверхностью воды

The data of a ballistic experiment are analyzed, in which an intense capillary wave injects up microdroplets formed and levitated above a heated region of water due to an ascending convective steam-air flow. The drag force resisting the movement of a droplet is estimated. Using various theoretical approaches, the flow parameters (velocity at different heights, the rate of change of velocity) are estimated. The maximum size of droplets that can levitate freely has been determined. The impossibility of the stationary droplet levitation in a linearly inhomogeneous flow is shown.

Characterization of Crater Area in a Target Penetrated by a Wf/Zr-Based Amorphous Matrix Composite Projectile

Tungsten fiber-reinforced Zr41.25Ti13.75Cu12.5Ni10Be22.5 amorphous matrix composites (hereinafter referred to as Wf/Zr-based amorphous matrix composites) are considered as a potential new generation of projectile material, while the penetration behavior of Wf/Zr-based amorphous matrix composites is not fully clear yet. In order to better understand the penetration behavior of this composite material and study its armor-piercing performance, a ballistic experiment was performed and the hardness and microstructure around the crater of a target material were studied. A ballistic experiment was performed with a projectile of Wf/Zr-based amorphous matrix composite and a target of 4043 steel. After the ballistic experiment, the target was cut through the crater using a wire cutting machine into a sample with size 150 mm × 40 mm × 20 mm, which was later polished by different types of sandpaper. The micro-hardness was analyzed in a micro-hardness tester, and the microstructure was observed by SEM. According to this study, three layers were identified in the direction lateral to the crater, consisting of a martensite layer, a deformation strengthening layer, and the original structure layer. Moreover, the martensite layer initially thickened and then thinned in the direction longitudinal to the crater.

Experimental Investigation on the Failure Mechanism of Grooved Steel Plate Impacted by Projectile with Different Nose Shapes

In order to study the penetration performance of the tandem warhead composed of a front circular shaped charge and a rear penetration projectile, a grooved steel plate was processed to simulate the effect of circular shaped jets on metal plate, then the failure mechanism of the grooved steel plate impacted by rear projectile was investigated by ballistic experiment, meanwhile, the effect of projectile nose shape on the failure mechanism was also analyzed. The results show that the main failure mechanism of grooved steel plate is ductile tensile deformation or damage when the projectile impacted on the inner plate body and the depth of the pre-splitting groove is not big enough (usually more than 4mm), on the other hand, the circumferential sheared fracture of the bottom of the groove occurred when the depth of the pre-splitting groove is not less than 4mm. The oval projectile body has much greater erosion damage than rod-shaped projectile during the penetration process.

AN EXPERIMENTAL STUDY OF THE PENETRATION OF CYLINDRICAL PROJECTILES INTO DRY SAND

For the most complete study of the laws of shock interaction of solids with soil barriers, further development of experimental techniques for recording the parameters of the interaction process in direct and inverse experiments is necessary. In this work, to determine the parameters of the movement of the projectile (displacement and speed) in a direct experiment, a millimeter-wave radio interferometer is used. This method allows continuous recording of the movement of the rear end of the striker with high accuracy over a wide range of movements. Using the proposed technique, experiments were carried out to record the motion parameters of cylindrical impactors made of steel and aluminum alloy when interacting with an obstacle made of dry sand. At the same time, the movement of the rear end of the striker was also controlled using high-speed filming until the full immersion of the striker. The experiments showed that the measurement results obtained using two methods coincide within the measurement error. Based on the experiments, it can be concluded that the methodology for determining the displacement and velocity of a projectile in a ballistic experiment using a millimeter-wave radio interferometer allows continuous measurement of large displacements (100 mm or more), including when completely immersed in a target with sufficient practical goals accuracy. Based on the results of the experiments, the dependences of the movement of the projectile and its speed on time are constructed. A change in the penetration law was found with a decrease in the penetration velocity to values less than 100 m/s.

MEASURING DISPLACEMENT AND VELOCITY OF A STRIKER USING A RADIO-INTERFEROMETER

Investigating impact interaction of solid and deformed bodies with obstacles of various physical natures requires developing experimental methodologies of registering the parameters of the interaction process. In experimental investigations of impact interaction of solids, it is common practice to measure displacement of strikers as a function of time, as well as their velocity and deceleration. To determine the displacement and velocity of a striker, a radio-interferometric methodology of registering the displacement of its rear end is proposed. In contrast with the registration methods based on high-speed filming and pulsed X-ray photography, the method using a millimeter-range radio-interferometer provides continuous high-accuracy registering of the displacement of the rear end of a striker in a wide range of displacement values. To test the effectiveness of the methodology, a series of experiments have been conducted on registering the motion of a cylindrical striker of an aluminum alloy, fired from a 20mm-dia gas gun. The displacement of the striker was also monitored using high-speed filming. The results of measuring using the two methodologies differ within the limits of the error of measurement. Based on the results of the above experiments, it has been concluded that the methodology of determining the displacement and velocity of strikers in a ballistic experiment using a mm-range radio-interferometer makes it possible to measure practically continuously large displacements (100 mm and larger) to a safe accuracy. The present methodology can be used for measuring the displacement and velocity of the rear end of a striker interacting with obstacles of various physical natures (metals, ceramics, soils, concretes, etc.).

Experimental simulation in the modern wound ballistics

The main medical and biological aspects of conducting experiments in wound ballistics are considered. It is established, that currently in the studies devoted to the study of wound ballistics of firearms ammunition, the method of experimental modeling using simulators of various origins is widely used. A detailed description of the main simulators used by the leading domestic researchers is given now with a reflection of their positive and negative properties. The question of choice of an optimal laboratory animal for the solution of certain problems of ballistic experiment is considered. The world practice of studying the problems of wound ballistics has shown that the organs and tissues of a pig are the closest, of all known animals, to organs and tissues of man in a whole series of morphofunctional properties. The similarity in the structure of organs with a human can in some respects be quite striking, which is used in experimental surgery, especially for studying cardiovascular diseases and in organ transplantation studies. To transfer experimental data from a model (simulator) to a human, it is necessary to observe the main condition of modeling, namely, the principle of similarity of the experimental model to the process that should be reproduced. The problem of use of human corpses and corpse material is reflected, and also attention is paid to a need of observance of ethical rules and norms at carrying out this kind of experiments. It is concluded that despite the extensive list of available materials of non-biological origin, it is not possible to completely abandon the use of laboratory animals and corpse material at this stage of development of science, and their use should be carried out with mandatory compliance with certain norms of ethical and legal nature.