Experimental analysis of high velocity impacts of composite fragments on aluminium plates

The improvement of engines is one of the ways to diminish the fuel consumption in civil aircrafts, and Open Rotors engines are one of the best promises in order to achieve a sensible efficiency increment. These engines have large composite blades that could, in the event of failure, impact against the fuselage, totally or partially. In this case, composite fragments could behave as impactors. In order to design fuselages for this event and adopt these new engines in the future, it is necessary to understand the impact behaviour of a composite fragment against a deformable structure. To this end, unidirectional and woven composites fragments were impacted at high velocity (up to 150 m/s) against aluminium panels at different impact velocities. The composite fragments were made using AS4/8552 (UD) and AGP-193PW (woven) prepregs manufactured by Hexcel Composites, both using AS4 fibres and 8552 epoxy matrix. High speed video cameras were used to record the impact process and to measure both the impact and the residual velocity and hence the energy absorbed.

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High-Velocity Impacts of Pyrophoric Alloy Fragments on Thin Armour Steel Plates

Materials ◽

10.3390/ma14164649 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4649

Author(s):

Evaristo Santamaria Ferraro ◽

Marina Seidl ◽

Tom De Vuyst ◽

Norbert Faderl

Keyword(s):

High Velocity ◽

High Speed ◽

Failure Modes ◽

Threshold Value ◽

Steel Plates ◽

Terminal Ballistics ◽

High Velocity Impacts ◽

Modern Warfare ◽

The Impact ◽

Armour Steel

The terminal ballistics effects of Intermetallic Reactive Materials (IRM) fragments have been the object of intense research in recent years. IRM fragments flying at velocities up to 2000 m/s represent a realistic threat in modern warfare scenarios as these materials are substituting conventional solutions in defense applications. The IRM add Impact Induced Energy Release (IIER) to the mechanical interaction with a target. Therefore, the necessity of investigations on IIER to quantify potential threats to existing protection systems. In this study, Mixed Rare Earths (MRE) fragments were used due to the mechanical and pyrophoric affinity with IRM, the commercial availability and cost-effectiveness. High-Velocity Impacts (HVI) of MRE were performed at velocities ranging from 800 to 1600 m/s and recorded using a high-speed camera. 70 MREs cylindrical fragments and 24 steel fragments were shot on armour steel plates with thicknesses ranging from 2 mm to 3 mm. The influence of the impact pitch angle (α) on HVI outcomes was assessed, defining a threshold value at α of 20°. The influence of the failure modes of MRE and steel fragments on the critical impact velocities (CIV) and critical kinetic energy (Ekin crit) was evaluated. An energy-based model was developed and fitted with sufficient accuracy the Normalised EKin crit (E˜kincrit) determined from the experiments. IIER was observed in all the experiments involving MRE. From the analyses, it was observed that the IIER spreads behind the targets with velocities comparable to the residual velocities of plugs and shattered fragment.

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Measurement of forced convection subcooled boiling flow through a vertical annular channel with high-speed video cameras and image reconstruction

Journal of Nuclear Science and Technology ◽

10.1080/00223131.2021.1954561 ◽

2021 ◽

pp. 1-15

Author(s):

Atsushi Ui ◽

Masahiro Furuya ◽

Takahiro Arai ◽

Kenetsu Shirakawa

Keyword(s):

Image Reconstruction ◽

Forced Convection ◽

High Speed ◽

Annular Channel ◽

Subcooled Boiling ◽

Video Cameras ◽

High Speed Video ◽

Boiling Flow ◽

Flow Through

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Newly Developed Two-Tip Optical-Fiber Probe for Accurate Measurement of High-Speed Micro-Droplets: Simultaneous Measurement of Their Velocities and Diameters

Volume 3: Thermal Hydraulics; Current Advanced Reactors: Plant Design, Construction, Workforce and Public Acceptance ◽

10.1115/icone17-75358 ◽

2009 ◽

Author(s):

Keisuke Matsuda ◽

Yusuke Ozawa ◽

Takayuki Saito

Keyword(s):

Optical Fiber ◽

High Velocity ◽

High Speed ◽

Video Camera ◽

Medium Size ◽

Fiber Probe ◽

Optical Fiber Probe ◽

High Speed Video ◽

Ultra High Speed ◽

High Speed Video Camera

Optical fiber probing is very useful and reliable for bubbles/droplets measurement particularly in the gas-liquid two-phase flows that have dense dispersed phase and are impossible to be measured via usual visualization techniques. For the practical purpose of small- or medium-size bubbles/droplets measurement, one of the authors successfully developed a Four-Tip Optical-fiber Probe (F-TOP) and reported their excellent performance in industrial uses. Recently, particular demands for measuring properties of micro bubbles/droplets have increased in researches on multi-phase flows. However, no one succeeded in simultaneously measuring diameters and velocities of high-speed micro-droplets (velocity > 50 m/s; 50 μm < diameter < 500 μm). We made a challenge of measuring such tiny droplets via newly developed optical fiber probe equipped with two tips (Two-Tip Optical-fiber Probe: T-TOP). We have succeeded in this difficult measurement with it. Each optical fiber probe composing the T-TOP is made of a silica optical fiber (125 μm in external diameter, 50 μm in core diameter, 37.5 μm in clad thickness). The optical fiber was fine-drawn using a micro pipette puller, and this yielded a sub-μm-scale tip. The interval of the fiber axes and the gap of the tips were arranged depending on the droplets diameter range. In this paper, we demonstrate the performance of the T-TOP. First, we confirm its practicality in industrial use. The strength of the T-TOP is confirmed by exposure test of high-velocity and high-temperature steam flows. Second, we consider the influence of the flow on the measurement of T-TOP; the optical noise due to probe vibration by the high-velocity gas flow around the T-TOP is considered. Next, we confirm its performance using an orifice-type nozzle (300 μm < droplets diameter < 500 μm; droplets velocities < 40 m/s). We confirm the performance of the T-TOP; the results of T-TOP are compared with those of the visualization of the droplets by using an ultra-high-speed video camera. At the same time, we consider the process of droplet contact with the T-TOP via visualization of ultra-high-speed video camera.

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

Proceedings ◽

10.3390/proceedings2020049137 ◽

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.

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The brittle fracture of solids by liquid impact, by solid impact, and by shock

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1964.0236 ◽

1964 ◽

Vol 282 (1390) ◽

pp. 331-352 ◽

Cited By ~ 150

Keyword(s):

Surface Wave ◽

High Velocity ◽

High Speed ◽

Turbine Blades ◽

Explosive Loading ◽

Back Surface ◽

High Speed Photography ◽

Liquid Mass ◽

Liquid Impact ◽

The Impact

The type of stress pulse produced when a liquid mass strikes a solid at high velocity is first examined. Compressible behaviour, giving rise to a sharp peak of pressure, is found to occur in the initial stages of the impact. The duration of this peak depends on the dimensions and impact velocity of the liquid mass, and also on the compressible wave velocity for the liquid. A comparison is made with pulses produced by solid/solid impact and by the detonation of small quantities of explosive. Both the high-speed liquid impact and the explosive loading give intense pulses of duration only a few microseconds. A solid/solid impact has, by comparison, a much longer impact time of the order of hundreds of microseconds. The fracture of glasses and hard polymers using these three types of loading is described. The development of fracture is followed by high-speed photography. Differences in the modes of fracture are attributed to variations in the shape and duration of the applied stress pulses. Short circumferential fractures produced around the loaded area in liquid impact and explosive loading are shown to be initiated by the Rayleigh surface wave at points where flaws existed. More complex fracture patterns on the front surfaces of plates are due to the reinforcement of the surface wave with components of stress waves reflected from the back surface. A combination of impact loading and etching makes it possible to investigate the distribution and depths of flaws, their role in the fracture process, and the effect which etching has upon them. The observation on the deformation produced in solids by liquid impact has practical significance in the problem of supersonic aircraft flying through rain and in the erosion of turbine blades moving at high velocity through wet steam.

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Kinematics Characteristic of Exoskeleton Walking Robot for Older People

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.644-650.167 ◽

2014 ◽

Vol 644-650 ◽

pp. 167-170 ◽

Cited By ~ 1

Author(s):

Yong Chen ◽

Sheng Lin ◽

Rong Hua Li ◽

Lian Dong Zhang

Keyword(s):

Older People ◽

High Speed ◽

Video Camera ◽

Step Length ◽

Walking Robot ◽

Step Frequency ◽

High Speed Video ◽

High Speed Video Camera ◽

Gait Parameters ◽

The Impact

The movement processes of the older people during walking on level ground were captured by the high-speed video camera with the speed of 500 frames per second. The gait parameters of the older people during walking on level ground were obtained by the quantitative analysis of the successive photographs captured by the high-speed video camera. Kinematics features of the older people during walking on level ground were discussed. Along with the growth of the age, step velocity, step frequency and step length were reduced, and gait cycle was rising. According to the morphology of the older people during walking on level ground, a mechanical model was put forward to aid the design of the exoskeleton walking robot. The couple walking characteristics between the older wearer and the exoskeleton walking robot was studied. In the single support phase of the exoskeleton walking robot, the change of the hip joint was gradually decreased to provide the driving force for the stable walk, the change of the knee joint was increased and following decreased and then increased to forward the older people's body center of gravity, and the change of the ankle joint was gradually increased to reduce the impact force of the ground. The results would provide the basic theory to bionic references for improving the reasonable properties of the exoskeleton walking robot. This work would provide certain theoretical and practical base in developing the exoskeleton walking robot on bionic structural design.

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Experimental Study on the Response Characteristics of Oilcans under High-Velocity Fragment Impact

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.510.500 ◽

2012 ◽

Vol 510 ◽

pp. 500-506

Author(s):

Chang Hai Chen ◽

Xi Zhu ◽

Hai Liang Hou ◽

Li Jun Zhang ◽

Ting Tang

Keyword(s):

Experimental Study ◽

High Velocity ◽

High Speed ◽

Room Temperature ◽

Experimental Results ◽

Fuel Oil ◽

High Speed Camera ◽

Response Characteristics ◽

Fuel Oils ◽

The Impact

To explore the deflagration possibility of the warship cabin filled with fuel oil under impact of high-speed fragments in the condition of room temperature, experiments were carried out employing the small aluminium oilcans filled with fuel oil. Response processes of the oilcans were observed with the help of a high-speed camera. The disintegration as well as flying scattering of the oilcans were analyzed. The reasons for atomization of the fuel oils were presented. Finally, the deflagration possibility of warship oil cabin was analyzed. Results show that the pressure inside the oilcan is quite great under the impact of the high-speed fragment, which makes the oilcan disintegration and flying scattering. Simultaneously, fuel oils inside the oilcans are atomized quickly followed by ejected in front and back directions. Under the same condition as in present tests, deflagration will not occur for fuel oils used by warships. Experimental results will provide valuable references for the deflagration analysis of warship fuel oil cabins subjected to the impact of high-velocity fragments.

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Modeling a Viscoelastic Gymnastics Landing Mat during Impact

Journal of Applied Biomechanics ◽

10.1123/jab.22.2.103 ◽

2006 ◽

Vol 22 (2) ◽

pp. 103-111 ◽

Cited By ~ 6

Author(s):

Chris Mills ◽

Matthew T.G. Pain ◽

Maurice R. Yeadon

Keyword(s):

High Speed ◽

Force Plate ◽

System Model ◽

Video Cameras ◽

Key Characteristics ◽

Single Mass ◽

Force Time ◽

Mass Spring ◽

The Impact ◽

Landing Mat

Landing mats that can undergo a large amount of area deformation are now essential for the safe completion of landings in gymnastics. The objective of this study was to develop an analytical model of a landing mat that reproduces the key characteristics of the mat-ground force during impact with minimal simulation run time. A force plate and two high-speed video cameras were used to record the mat deformation during vertical drop testing of a 24-kg impactor. Four increasingly complex point mass spring-damper models, from a single mass spring-damper system, Model 1, to a 3-layer mass spring-damper system, Model 4, were constructed using Matlab to model the mat's behavior during impact. A fifth model composed of a 3-layer mass spring-damper system was developed using visual Nastran 4D. The results showed that Models 4 and 5 were able to match the loading phase of the impact with simulation times of less than 1 second for Model 4 and 28 seconds for Model 5. Both Models 4 and 5 successfully reproduced the key force-time characteristics of the mat-ground interface, such as peak forces, time of peak forces, interpeak minima and initial rates of loading, and could be incorporated into a gymnast-mat model.

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