scholarly journals Perforation of Double-Spaced Aluminum Plates by Reactive Projectiles with Different Densities

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1229
Author(s):  
Hao Zhang ◽  
Haifu Wang ◽  
Qingbo Yu ◽  
Yuanfeng Zheng ◽  
Guancheng Lu ◽  
...  
Keyword(s):  
Theoretical Prediction ◽  
Initial Velocity ◽  
High Speed ◽  
Spray Angle ◽  
Video Sequences ◽  
Material Density ◽  
High Speed Video ◽  
Front Plate ◽  
Critical Velocities ◽  
Aluminum Plates

Perforation behavior of 3 mm/3 mm double-spaced aluminum plates by PTFE/Al/W (Polytetrafluoroethylene/Aluminum/Tungsten) reactive projectiles with densities ranging from 2.27 to 7.80 g/cm3 was studied experimentally and theoretically. Ballistic experiments show that the failure mode of the front plate transforms from petalling failure to plugging failure as projectile density increases. Theoretical prediction of the critical velocities for the reactive projectiles perforating the double-spaced plates is proposed, which is consistent with the experimental results and well represents the perforation performance of the projectiles. Dimensionless formulae for estimating the perforation diameter and deflection height of the front plates are obtained through dimensional analysis, indicating material density and strength are dominant factors to determine the perforation size. High-speed video sequences of the perforation process demonstrate that high-density reactive projectiles make greater damage to the rear plates because of the generation of projectile debris streams. Specifically, the maximum spray angle of the debris streams and the crater number in the debris concentration area of the rear plate both increase with the projectile density and initial velocity.

scholarly journals Standard of the Initial Ball Velocity for a Fly Ball in Baseball Hitting

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 137
Author(s):  
Hirotaka Nakashima ◽  
Gen Horiuchi ◽  
Shinji Sakurai
Keyword(s):  
Initial Velocity ◽  
High Speed ◽  
Baseball Players ◽  
Ball Impact ◽  
Video Cameras ◽  
High Speed Video ◽  
Before And After ◽  
Ball Velocity ◽  
Opposite Field ◽  
Measuring Tape

This study aimed to determine the minimum required initial velocity to hit a fly ball toward the same field (left-field for right-handed batters), center field, and opposite field (right field for right-handed batters). Six baseball players hit fastballs launched by a pitching machine. The movements of the balls before and after bat-to-ball impact were recorded using two high-speed video cameras. The flight distance was determined using a measuring tape. Seventy-nine trials were analyzed, and the minimum required initial velocities of batted balls were quantified to hit balls 60, 70, 80, 90, 100, 110, and 120 m in each direction through regression analysis. As a result, to hit a ball 120 m, initial velocities of 43.0, 43.9, and 46.0 m/s were required for the same field, center field, and opposite field, respectively. The result provides a useful index for batters to hit a fly ball in each of the directions.

Visual Tracking of Box Jellyfish

2015 ◽  
pp. 107-122 ◽  
Author(s):  
Magnus Oskarsson ◽  
Tobias Kjellberg ◽  
Tobias Palmér ◽  
Dan-Eric Nilsson ◽  
Kalle Åström
Keyword(s):  
High Speed ◽  
Motor Response ◽  
Building Blocks ◽  
Video Sequences ◽  
Special Test ◽  
Real Time System ◽  
Test Setup ◽  
Box Jellyfish ◽  
High Speed Video ◽  
Sensory Structures

In this chapter a system for tracking the motion of box jellyfish Tripedalia cystophora in a special test setup is investigated. The goal is to measure the motor response of the animal given certain visual stimuli. The approach is based on tracking the special sensory structures - the rhopalia - of the box jellyfish from high-speed video sequences. The focus has been on a real-time system with simple building blocks in the system. However, using a combination of simple intensity based detection and model based tracking promising tracking results with up to 95% accuracy are achieved.

scholarly journals Study of backspatter using high-speed video of experimental gunshots

2020 ◽  
Author(s):  
Christian Schyma ◽  
Fabienne Baumann ◽  
Burkhard Madea ◽  
Walther Gotsmy
Keyword(s):  
Biological Material ◽  
Initial Velocity ◽  
High Speed ◽  
Edge Length ◽  
Surface Material ◽  
Experimental Conditions ◽  
High Speed Video ◽  
Entry Wound ◽  
Close Range ◽  
Wound Ballistic

AbstractBackspatter is biological material that is ejected from the entry wound against the line of fire. This phenomenon was also observed in wound ballistic simulations using so called "reference cubes" (12 cm edge length, 10% gelatin, 4 °C, paint pad beneath the cover). High-speed video records from 102 experimental shots to these target models using full metal jacketed bullets in the calibers .32 auto, .38 special, 9 mm Luger and .357 Magnum were analyzed for chronology, morphological appearance and velocity of fluid ejection. Generally, a short tail splashing of surface material occurred when the bullet was penetrating the target. In 51 shots from distance (≥ 5 cm), regardless of caliber and shot range, a linear jet of fluid started in connection with the first collapse of the temporary cavity. The initial velocity of the jet was measured between 6 and 45 m/s. The jet was streaming on for about 60 to 100 ms with a stochastic deviation of ± 13° to the horizontal. Close range and contact shots showed earlier and faster (up to 330 m/s) backspatter depending on the cartridge and the gap between muzzle and target. Gaseous aerosol-like spray and cone-like spatter indicated an increasing influence of muzzle gases with decreasing shot range. Even under standardized experimental conditions, variations of backspatter were observed in near/contact shots.

scholarly journals Influence of liquid properties on ultrasonic atomization

2017 ◽  
Author(s):  
Antonio Lozano ◽  
Juan Antonio García ◽  
Javier Alconchel ◽  
Félix Barreras ◽  
Esteban Calvo ◽  
...  
Keyword(s):  
Surface Tension ◽  
Weight Loss ◽  
Vapor Pressure ◽  
High Speed ◽  
Liquid Surface ◽  
Video Sequences ◽  
Narrow Size Distribution ◽  
Piezoceramic Disk ◽  
Ultrasonic Atomization ◽  
High Speed Video

Ultrasonic atomization is very convenient because it can generate droplets with diameters of a few microns andwith very narrow size distribution. Besides, opposite to twin fluid nozzles, in ultrasonic atomization, dropletgeneration and transport are decoupled processes. Droplets are ejected from the liquid surface with very lowvelocities, so driving them is relatively simple. Although this atomization method is now common in some specificapplications, for example in household humidifiers, there are still some details about the physics of this processthat are not completely understood. Up to date, most of the published results have been limited to experimentswith water. However, it has been demonstrated that atomization rates quickly decrease as liquid viscosityincreases. This work analyzes the characteristics of ultrasonic atomization of some alternative fluids to determineif there is any influence of other physical properties such as surface tension or vapor pressure. Experiments areperformed using a commercial piezoceramic disk with a resonance frequency of 1.65 MHz. The disk is excitedwith a sinusoidal signal with voltage amplitudes that go up to 60 V. Sprays are visually characterized analyzinginstantaneous images and high speed video sequences. Besides atomization rates are calculated by measuringthe weight loss in a fixed time.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4588

Characteristics of Spatter in Micro-Drilling of Metal Sheet by Pulsed Nd:YAG Laser

2016 ◽  
Vol 10 (6) ◽  
pp. 874-881 ◽  
Author(s):  
Yasuhiro Okamoto ◽  
◽  
Hibiki Yamamoto ◽  
Akira Okada ◽  
Keyword(s):  
Initial Velocity ◽  
High Speed ◽  
Gas Flow ◽  
Thermal Damage ◽  
Drilling Process ◽  
3D Tracking ◽  
Workpiece Surface ◽  
Video Cameras ◽  
High Speed Video ◽  
Micro Drilling

In laser cutting and drilling process, molten material was scattered as spatter, which deteriorates the surface integrity of a workpiece because of the thermal damage. It is expected that the control of assist gas flow can reduce the adhesion of spatter. In order to investigate the improvement method of thermal damage due to the adhesion of spatter, it is required to clarify characteristics of spatter. Therefore, a method was developed to collect and analyze spatter based on the use of high-speed video cameras in the laser micro-drilling process, and the characteristics of spatter movement were numerically investigated by CFD analysis. The scattering velocity and angle of the spatter were investigated by recognizing and tracking spatter with the high-speed video observation. The movement of spatter was observed by using two high-speed video cameras, and analyzed by using a two-direction tracking method, in which the 3D tracking lines of spatter particles were reconstructed in the forward and backward frames, and the actual trajectory of individual spatter particle was obtained by averaging those tracking lines. These measurements revealed that the initial velocity of spatter was mainly distributed from 52 m/s to 200 m/s with an average velocity of 129 m/s. The initial angle of spatter was mainly distributed between 0 and 30 degrees from the workpiece surface in the upward direction. There was little correlation between the initial velocity and angle of spatter. The diameter of spatter was mainly distributed from 1μm to 4μm with an average diameter of 3.7μm. It is important to use the processing conditions achieving the smaller spatter diameter in order to reduce the thermal damage caused by spatter. Although coaxial assist gas flow has an influence on the spatter behavior, that time period is very short. Therefore, it is important to control the spatter behavior outside of the coaxial assist gas flow by using an additional gas flow to prevent the thermal damage to the workpiece surface.

Identification of Release Conditions and Aerodynamic Forces in Pitched-Baseball Trajectories

2001 ◽  
Vol 17 (1) ◽  
pp. 63-76 ◽  
Author(s):  
LeRoy W. Alaways ◽  
Sean P. Mish ◽  
Mont Hubbard
Keyword(s):  
Drag Coefficient ◽  
Initial Velocity ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Three Dimensions ◽  
Video Cameras ◽  
High Speed Video ◽  
Position Data ◽  
Estimation Scheme ◽  
The Mean

Pitched-baseball trajectories were measured in three dimensions during competitions at the 1996 Summer Olympic games using two high-speed video cameras and standard DLT techniques. A dynamic model of baseball flight including aerodynamic drag and Magnus lift forces was used to simulate trajectories. This simulation together with the measured trajectory position data constituted the components of an estimation scheme to determine 8 of the 9 release conditions (3 components each of velocity, position, and angular velocity) as well as the mean drag coefficient CD and terminal conditions at home plate. The average pitch loses 5% of its initial velocity during flight. The dependence of estimated drag coefficient on Reynolds number hints at the possibility of the drag crisis occurring in pitched baseballs. Such data may be used to quantify a pitcher’s performance (including fastball speed and amount of curve-ball break) and its improvement or degradation over time. It may also be used to understand the effects of release parameters on baseball trajectories.

APPLICATION OF THE EARLY DAMAGE DIAGNOSTICS TECHNIQUE TO EXAMINATION OF THE AVIATION PANEL

2019 ◽  
Vol 85 (6) ◽  
pp. 53-63 ◽  
Author(s):  
I. E. Vasil’ev ◽  
Yu. G. Matvienko ◽  
A. V. Pankov ◽  
A. G. Kalinin
Keyword(s):  
Acoustic Emission ◽  
Damage Detection ◽  
High Speed ◽  
Early Stage ◽  
Video Data ◽  
High Speed Video ◽  
Damage Diagnostics ◽  
Subsurface Defect ◽  
Sensitive Coating ◽  
Early Damage

The results of using early damage diagnostics technique (developed in the Mechanical Engineering Research Institute of the Russian Academy of Sciences (IMASH RAN) for detecting the latent damage of an aviation panel made of composite material upon bench tensile tests are presented. We have assessed the capabilities of the developed technique and software regarding damage detection at the early stage of panel loading in conditions of elastic strain of the material using brittle strain-sensitive coating and simultaneous crack detection in the coating with a high-speed video camera “Video-print” and acoustic emission system “A-Line 32D.” When revealing a subsurface defect (a notch of the middle stringer) of the aviation panel, the general concept of damage detection at the early stage of loading in conditions of elastic behavior of the material was also tested in the course of the experiment, as well as the software specially developed for cluster analysis and classification of detected location pulses along with the equipment and software for simultaneous recording of video data flows and arrays of acoustic emission (AE) data. Synchronous recording of video images and AE pulses ensured precise control of the cracking process in the brittle strain-sensitive coating (tensocoating)at all stages of the experiment, whereas the use of structural-phenomenological approach kept track of the main trends in damage accumulation at different structural levels and identify the sources of their origin when classifying recorded AE data arrays. The combined use of oxide tensocoatings and high-speed video recording synchronized with the AE control system, provide the possibility of definite determination of the subsurface defect, reveal the maximum principal strains in the area of crack formation, quantify them and identify the main sources of AE signals upon monitoring the state of the aviation panel under loading P = 90 kN, which is about 12% of the critical load.

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