scholarly journals Soft projectile impact forces measurement using Hopkinson bars: application to ice, artificial bird and rubber

2021 ◽  
Vol 250 ◽  
pp. 01008
Author(s):  
Ramón del Cuvillo ◽  
Jose Alfonso Artero-Guerrero ◽  
Jesús Pernas-Sánchez ◽  
Jorge López Puente
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Soft Materials ◽  
Peak Force ◽  
Video Cameras ◽  
Impact Forces ◽  
Compression Strain ◽  
Experimental Campaign ◽  
The Impact ◽  
Semiconductor Strain

This work presents an experimental campaign of impacts of soft projectiles to measure the induced force during the impact. Three different materials acting as soft impactors that could strike against a aeronautical structural component: ice, artificial bird and rubber have been impacted at several velocities against an aluminium Hopkinson bar. This device has been instrumented with semiconductor strain gauges that allow to obtain the induced compression strain. Additionally, all the impacts were recorded using high-speed video cameras, allowing the kinematic analysis of the projectile during the impact. After the results study, it has been concluded that there is a linear dependency between the kinetic energy and the peak force for all three materials. Added to that, it has been proved that the higher peak force corresponds to ice, despite the kinetic energy, followed by rubber and finally the artificial bird. In addition, while ice and artificial bird projectiles get radially dispersed after the impact, rubber spheres rebound due to its different behaviour. The obtained data is of great interest to design structures which could be subjected to impacts of soft materials such as aeronautic structures

Relationships Between Wheel/Rail Surface Impact Loadings and Correspondingly Transmitted Tie/Ballast Impact Pressures for Revenue Train Operations

2018 ◽  
Author(s):  
Travis J. Watts ◽  
Jerry G. Rose ◽  
Ethan J. Russell
Keyword(s):  
Test Section ◽  
Impact Load ◽  
Peak Force ◽  
Pressure Measurements ◽  
Track Geometry ◽  
Impact Forces ◽  
Interfacial Pressure ◽  
Degradation Rates ◽  
The Stability ◽  
The Impact

A series of specially designed granular material pressure cells were precisely positioned directly below the rail at the tie/ballast interface to measure typical interfacial pressures exerted by revenue freight trains. These vertical pressures were compared to the recorded wheel/rail nominal and peak forces for the same trains traversing nearby mainline wheel impact load detectors (WILDs). The cells were imbedded within the bottom of new wood ties so that the surfaces of the pressure cells were even with the bottoms of the ties and the underlying ballast. The cells were inserted below consecutive rail seats of one rail to record pressures for a complete wheel rotation. The stability and tightness of the ballast support influenced the magnitudes and consistencies of the recorded ballast pressures. Considerable effort was required to provide consistent ballast conditions for the instrumented ties and adjacent undisturbed transition ties. Norfolk Southern (NS) crews surfaced and tamped through the test section and adjacent approach ties. This effort along with normal accruing train traffic subsequently resulted in reasonably consistent pressure measurements throughout the test section. The impact ratio (impact factor) and peak force values recorded by the WILDs compared favorably with the resulting magnitudes of the transferred pressures at the tie/ballast interface. High peak force and high impact ratio WILD readings indicate the presence of wheel imperfections that increase nominal forces at the rail/wheel interface. The resulting increased dynamic impact forces can contribute to higher degradation rates for the track component materials and more rapid degradation rates of the track geometry. The paper contains comparative WILD force measurements and tie/ballast interfacial pressure measurements for loaded and empty trains. Typical tie/ballast pressures for locomotives and loaded freight cars ranges from 20 to 30 psi (140 to 210 kPa) for smooth wheels producing negligible impacts. The effect of increased wheel/rail impacts and peak force values on the correspondingly transmitted pressures at the tie/ballast interface is significant, with increased pressures of several orders of magnitude compared to nominal impact forces from wheels.

scholarly journals Effective Formula for Impact Damping Ratio for Simulation of Earthquake-induced Structural Pounding

Geosciences ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 347 ◽  
Author(s):  
Seyed Mohammad Khatami ◽  
Hosein Naderpour ◽  
Rui Carneiro Barros ◽  
Anna Jakubczyk-Gałczyńska ◽  
Robert Jankowski
Keyword(s):  
Kinetic Energy ◽  
Impact Force ◽  
Damping Ratio ◽  
Dissipated Energy ◽  
Force Model ◽  
Single Collision ◽  
Structural Pounding ◽  
Impact Forces ◽  
The Impact ◽  
Impact Damping

Structural pounding during earthquakes may cause substantial damage to colliding structures. The phenomenon is numerically studied using different models of collisions. The aim of the present paper is to propose an effective formula for the impact damping ratio, as a parameter of the impact force model used to study different problems of structural pounding under seismic excitations. Its accuracy has been verified by four various approaches. Firstly, for the case of collisions between two structural elements, the dissipated energy during impact has been compared to the loss of kinetic energy. In the second stage of verifications, the peak impact forces during single collision have been analyzed. Then, the accuracy of different equations have been verified by comparing the impact force time histories for the situation when a concrete ball is dropped on a rigid concrete surface. Finally, pounding between two structures during earthquakes has been studied. The results of the analysis focused on comparison between dissipated and kinetic energy show relatively low errors between calculated and assumed values of the coefficient of restitution when the proposed equation is used. In addition, the results of the comparison between experimentally and numerically determined peak impact forces during single collision confirm the effectiveness of the approach. The same conclusion has been obtained for the whole impact time history for collision between a ball and a rigid surface. Finally, the results of the comparative analysis, conducted for pounding between two structures during an earthquake, confirm the simulation accuracy when the proposed approach is used. The above conclusions indicate that the proposed formula for impact damping ratio, as a parameter of impact force model for simulation of earthquake-induced structural pounding, is very effective and accurate in numerical simulations in the case of different scenarios.

EVALUATION OF THE OPERATIONAL WEAR OF THE SANDVIK CV117 CENTRIFUGAL CRUSHER

Tribologia ◽  
2020 ◽  
Vol 289 (1) ◽  
pp. 31-39
Author(s):  
Dominika GRYGIER
Keyword(s):  
Kinetic Energy ◽  
Structural Properties ◽  
Direct Contact ◽  
Operating Time ◽  
Full Scale ◽  
Impact Forces ◽  
The Impact ◽  
Macroscopic Analysis

The purpose of the study described in the work was to evaluate the operating wear of the SANDVIK CV117 centrifugal crusher working in the Melaphyre mine in Grzędy. The research was carried out on work elements, such as the lining assembly, rotor tips, shredder hammers, the directional bushing, and the distributor divider. All components had direct contact with the aggregate, and their operating time was about 1150 hours. The studies included a mine full scale observation, macroscopic analysis of the elements, and an assessment of the impact of exploitation on selected structural properties of the elements material. On the basis of the carried out analyses, it was concluded that the major problem faced by all the tested components is the simultaneous interaction of high friction and impact forces resulting from the kinetic energy of the accelerated grains of the material acquired from the rotor during operation of the crusher.

Modeling a Viscoelastic Gymnastics Landing Mat during Impact

2006 ◽  
Vol 22 (2) ◽  
pp. 103-111 ◽  
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.

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

2021 ◽  
Vol 250 ◽  
pp. 01011
Author(s):  
Jorge López-Puente ◽  
Jesús Pernas-Sánchez ◽  
José Alfonso Artero-Guerrero ◽  
David Varas ◽  
Joseba Múgica ◽  
...  
Keyword(s):  
High Velocity ◽  
High Speed ◽  
Woven Composites ◽  
Residual Velocity ◽  
Video Cameras ◽  
High Speed Video ◽  
High Velocity Impacts ◽  
Deformable Structure ◽  
The Impact ◽  
Composite Blades

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.

scholarly journals Jumping with adhesion: landing surface incline alters impact force and body kinematics in crested geckos

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timothy E. Higham ◽  
Mara N. S. Hofmann ◽  
Michelle Modert ◽  
Marc Thielen ◽  
Thomas Speck
Keyword(s):  
High Speed ◽  
Impact Force ◽  
Three Dimensional ◽  
Adhesive System ◽  
Vertical Surface ◽  
High Impact ◽  
Body Movements ◽  
Impact Forces ◽  
Landing Platform ◽  
The Impact

AbstractArboreal habitats are characterized by a complex three-dimensional array of branches that vary in numerous characteristics, including incline, compliance, roughness, and diameter. Gaps must often be crossed, and this is frequently accomplished by leaping. Geckos bearing an adhesive system often jump in arboreal habitats, although few studies have examined their jumping biomechanics. We investigated the biomechanics of landing on smooth surfaces in crested geckos, Correlophus ciliatus, asking whether the incline of the landing platform alters impact forces and mid-air body movements. Using high-speed videography, we examined jumps from a horizontal take-off platform to horizontal, 45° and 90° landing platforms. Take-off velocity was greatest when geckos were jumping to a horizontal platform. Geckos did not modulate their body orientation in the air. Body curvature during landing, and landing duration, were greatest on the vertical platform. Together, these significantly reduced the impact force on the vertical platform. When landing on a smooth vertical surface, the geckos must engage the adhesive system to prevent slipping and falling. In contrast, landing on a horizontal surface requires no adhesion, but incurs high impact forces. Despite a lack of mid-air modulation, geckos appear robust to changing landing conditions.

scholarly journals The impact of raindrops on Salvinia molesta leaves: effects of trichomes and elasticity

2021 ◽  
Vol 18 (185) ◽  
Author(s):  
Wilfried Konrad ◽  
Anita Roth-Nebelsick ◽  
Benjamin Kessel ◽  
Tatiana Miranda ◽  
Martin Ebner ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Water Repellency ◽  
High Water ◽  
Rain Water ◽  
Residual Water ◽  
Intense Rainfall ◽  
Salvinia Molesta ◽  
Aquatic Fern ◽  
The Impact

The floating leaves of the aquatic fern Salvinia molesta are covered by superhydrophobic hairs (=trichomes) which are shaped like egg-beaters. These trichomes cause high water repellency and stable unwettability if the leaf is immersed. Whereas S. molesta hairs are technically interesting, there remains also the question concerning their biological relevance. S. molesta has its origin in Brazil within a region exposed to intense rainfall which easily penetrates the trichome cover. In this study, drop impact on leaves of S. molesta were analysed using a high-speed camera. The largest portion of the kinetic energy of a rain drop is absorbed by elastic responses of the trichomes and the leaf. Although rain water is mostly repelled, it turned out that the trichomes hamper swift shedding of rain water and some residual water can remain below the ‘egg-beaters’. Drops rolling over the trichomes can, however, ‘suck up’ water trapped beneath the egg-beaters because the energetic state of a drop on top of the trichomes is—on account of the superhydrophobicity of the hairs—much more favourable. The trichomes may therefore be beneficial during intense rainfall, because they absorb some kinetic energy and keep the leaf base mostly free from water.

scholarly journals Single-block rockfall dynamics inferred from seismic signal analysis

2017 ◽  
Author(s):  
Clément Hibert ◽  
Jean-Philippe Malet ◽  
Franck Bourrier ◽  
Floriane Provost ◽  
Frédéric Berger ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Scaling Laws ◽  
Scaling Law ◽  
Soft Rock ◽  
Signal Amplitude ◽  
Seismic Signal ◽  
Seismic Signals ◽  
Video Cameras ◽  
The Impact

Abstract. We conducted controlled releases of single blocks within a soft-rock (black marls) gully of the Rioux Bourdoux torrent (French Alps). 28 blocks, with masses ranging from 76 kg to 472 kg, were used for the experiment. An instrumentation combining video cameras and seismometers was deployed along the traveled path. The video cameras allow to reconstruct the trajectories of the blocks and to estimate their velocities at the time of the different impacts with the slope. These data are compared to the recorded seismic signals. As the distance between the falling block and the seismic sensors at the time of each impact is known, we were able to determine the associated seismic signal amplitude corrected from propagation and attenuation effects. We compared the velocity, the loss of potential energy, the kinetic energy and the momentum of the block at each impact to the true amplitude and the energy of the corresponding part of the seismic signal. Our results suggest that the amplitude of the seismic signal scales with the momentum of the block at the impact. We also found a scaling law between the potential energy lost, the kinetic energy and the energy of the seismic radiation generated by the impacts. By combining these scaling laws, we inferred the mass and the velocity before impact of each block directly from the seismic signal. Despite high uncertainties, the values found are close to the true values of the mass and the velocities of the blocks. These relationships also provide new insights to understand the source of high-frequency seismic signals generated by rockfalls.

scholarly journals Single-block rockfall dynamics inferred from seismic signal analysis

2017 ◽  
Vol 5 (2) ◽  
pp. 283-292 ◽  
Author(s):  
Clément Hibert ◽  
Jean-Philippe Malet ◽  
Franck Bourrier ◽  
Floriane Provost ◽  
Frédéric Berger ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Soft Rock ◽  
Seismic Energy ◽  
Signal Amplitude ◽  
Seismic Signal ◽  
Seismic Signals ◽  
Video Cameras ◽  
Radiated Seismic Energy ◽  
The Impact

Abstract. Seismic monitoring of mass movements can significantly help to mitigate the associated hazards; however, the link between event dynamics and the seismic signals generated is not completely understood. To better understand these relationships, we conducted controlled releases of single blocks within a soft-rock (black marls) gully of the Rioux-Bourdoux torrent (French Alps). A total of 28 blocks, with masses ranging from 76 to 472 kg, were used for the experiment. An instrumentation combining video cameras and seismometers was deployed along the travelled path. The video cameras allow reconstructing the trajectories of the blocks and estimating their velocities at the time of the different impacts with the slope. These data are compared to the recorded seismic signals. As the distance between the falling block and the seismic sensors at the time of each impact is known, we were able to determine the associated seismic signal amplitude corrected for propagation and attenuation effects. We compared the velocity, the potential energy lost, the kinetic energy and the momentum of the block at each impact to the true amplitude and the radiated seismic energy. Our results suggest that the amplitude of the seismic signal is correlated to the momentum of the block at the impact. We also found relationships between the potential energy lost, the kinetic energy and the seismic energy radiated by the impacts. Thanks to these relationships, we were able to retrieve the mass and the velocity before impact of each block directly from the seismic signal. Despite high uncertainties, the values found are close to the true values of the masses and the velocities of the blocks. These relationships allow for gaining a better understanding of the physical processes that control the source of high-frequency seismic signals generated by rockfalls.

The influence of aluminium, steel and polyurethane shoeing systems and of the unshod hoof on the injury risk of a horse kick

2017 ◽  
Vol 30 (05) ◽  
pp. 339-345 ◽  
Author(s):  
Miriam Sprick ◽  
Anton Fürst ◽  
Fabio Baschnagel ◽  
Silvain Michel ◽  
Gabor Piskoty ◽  
...  
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Injury Risk ◽  
Experimental Studies ◽  
Soft Materials ◽  
Physical Parameters ◽  
Hard Materials ◽  
Probability Of Fracture ◽  
The Impact ◽  
Impact Duration

SummaryObjectives: To evaluate the damage inflicted by an unshod hoof and by the various horseshoe materials (steel, aluminium and polyurethane) on the long bones of horses after a simulated kick.Methods: Sixty-four equine radii and tibiae were evaluated using a drop impact test setup. An impactor with a steel, aluminium, polyurethane, or hoof horn head was dropped onto prepared bones. An impactor velocity of 8 m/s was initially used with all four materials and then testing was repeated with a velocity of 12 m/s with the polyurethane and hoof horn heads. The impact process was analysed using a high-speed camera, and physical parameters, including peak contact force and impact duration, were calculated.Results: At 8 m/s, the probability of a fracture was 75% for steel and 81% for aluminium, whereas polyurethane and hoof horn did not damage the bones. At 12 m/s, the probability of a fracture was 25% for polyurethane and 12.5% for hoof horn. The peak contact force and impact duration differed significantly between ‘hard materials’ (aluminium and steel) and ‘soft materials’ (polyurethane and hoof horn).Clinical significance: The observed bone injuries were similar to those seen in analogous experimental studies carried out previously and comparable to clinical fracture cases suggesting that the simulated kick was realistic. The probability of fracture was significantly higher for steel and aluminium than for polyurethane and hoof horn, which suggests that the horseshoe material has a significant influence on the risk of injury for humans or horses kicked by a horse.Supplementary Material for this article is available online at https://doi.org/10.3415/VCOT-17-01-0003ORCID iD MAJ: http://orcid.org/0000-0003-2142-2942

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