Effects Of Impact Speed Research Articles

Head and neck injury risk resulting from impact with small unmanned aerial vehicles: effect of impact speed, angle, and location

It is necessary to analyse the injury risk caused by UAV to establish management standards. A lightweight quadrotor UAV was used to assess the risk of human head and neck injury, taking the impact speed, UAV position, and impact angle into account. First, the MAVIC2 UAV- Hybrid III dummy impacting FE model was developed and verified against the UAV impact tests. Second, lots of simulations were conducted under different impact scenarios to analyse the head and neck injury. Under vertical impact condition, HIC and Nij grew exponentially as the impact speed increased. While under the horizontal impact condition, HIC increased in the form of the power function and Nij increased exponentially. Under vertical impact condition at 20 m/s (maximum flight speed, corresponding to the impact energy of 181.4 J), the HIC was 54% of the threshold, while the Nij was 88% of the threshold, which illustrated that the injury risk of the neck was high, while that of the head was low. Under horizontal impact condition at 20 m/s (181.4 J), the HIC was 51% of the threshold, and the Nij was 24% of the threshold, which illustrated that the injury risk of both the head and neck was low. HIC declined exponentially as the impact angle increased, whereas Nij increased in the form of the power function. Among all the impact positions, the UAV’s arm caused the least injury risk, while the transverse falling attitude between the two arms and the reverse vertical falling attitude generated higher injury risks.

Effect of Impact Speed and Position of Pedestrian on Lower Extremity Injuries Caused by a Pickup Truck in Traffic Accidents

Pedestrians often suffer severe injuries in road traffic accidents. Therefore, pedestrian safety and, more precisely, analysis of injuries of the knee joint and lower limb bones were the focus of this research. A Vietnamese-sized human body model (HBM), named V-THUMS, scaled from the Total Human Model for Safety (THUMS) representing a walking pedestrian, was utilized in a numerical simulation. A pickup truck model was used to simulate pedestrian collisions with impact speeds from 20 km/h to 50 km/h. To reduce the computational time, the pickup truck model was simplified. In addition, the collision angle was varied from 0o, 30o, 60o, 90o, -30o, -60o to -90o to explore the effect of angle position on the injury mechanisms of the leg. The results illustrate that in some cases at low speeds there is a relationship between bone fracture and ligament rupture that does not exist at high speeds. The femur is very difficult to fracture because the bone is very hard and thick. It was found that at 20 km/h impact speed, the lower limbs are unharmed.

A novel test rig for the investigation of roller–cage impacts of a needle roller bearing

Collisions between a roller and its cage result in crack initiation and propagation, leading to the fracture of the cage bridge. The impact forces applied to a needle roller-bearing cage bridge can change the cage’s strain distribution, which is related to the relative speed of the roller and cage. In this work, a needle roller-bearing roller–cage impact test rig was built to quantify cage strain and investigate the effects of speed on roller–cage impact forces. On the cage bridge, three crack sizes were machined and put on the needle roller-bearing roller–cage impact test rig. The strain was measured by a strain gauge positioned on the cage. An encoder measured the shaft speed. The effects of impact speed and crack size on roller–cage impact force and cage deformation were investigated.

Analysis of the impact hulling behaviour of paddy grains

Rice hulling is the process of separating rice husks from the grain. Impact hulling is the norm for paddy grain processing because it produces higher quality hulled brown rice. However, high breakage fractions and low one-time hulling percentages can directly affect the quality of subsequent rice processing and restrict the development of paddy grain processing. Understanding the mechanism of paddy grain impact hulling is key to improving the performance of centrifugal rice hullers. In this paper, a single-seed impact test and the discrete element method (DEM) were used to simulate the paddy grain impact hulling. The effects of impact speed and angle on hulling percentage, breakage percentage and hulling pattern were investigated. The results showed that the effectiveness of paddy grain hulling after impact was due to the relative motion between rice husk and its kernel. The combined effect of impact and friction produces a relative motion between the husk and the kernel and increasing the relative motion improves hulling. Optimal impact parameters were obtained using a weighting method. The results of the study could improve the hulling performance of centrifugal rice hulling providing the basis improving the design. • Impact hulling relies on the relative motion between rice husk and brown rice. • The effect of impact velocity and angle on hulling performance was investigated. • The combined effect of impact and friction is key to the relative motion. • The combined weighted scoring method was used to evaluate the hulling performance. • Impact velocity of 35–40 m s −1 , impact angle of 60°, are the optimum.

A Study of the Effect of Impact Speed on the Dynamics of Mechanical Interactions of Bodies

The mechanorheological viscoelastic plastic model was used to study the effect of impact speed on the dynamics of mechanical interaction of a spherical body with the surface. An analysis of the impact process made it possible to draw some conclusions. The impact interaction time depends on the impact speed and mechanical properties of the material. The impact time decreases with an increase in the impact speed, a decrease in plasticity, and an increase in elasticity. With an increase in the impact speed, the impact time decreases. During the experiment, the initial impact speed increased 10 times. During the impact interaction, the body deformation increased 6-7 times. According to the calculations, the average body deformation speed also increased 10 times. As a result, the time for travelling a distance equal to the elastic and plastic deformation when loading bodies and the elastic deformation when unloading bodies decreased. The total deformation is composed of elastic and plastic components. With an increase in the impact speed, the plastic component increases, which decreases the unloading time due to a decrease in the elastic component. The impact time is an important characteristic of the dynamic process of interaction. Therefore, when identifying theoretical models to the real processes, these parameters should be congruent. To improve the modeling accuracy and reliability for various technological processes under dynamic loads, it is necessary to take into account various factors.

Analysis on the Difference of Impact Response between Single Coal‐Rock Particle and the Box Structure‐Based Tail Beam

In the process of coal caving, the basis of identifying coal and rock by the vibration signal is the difference of the tail beam response when coal‐rock impacts the tail beam, and the tail beam in the hydraulic support is a complex box structure with multiplate transverse and longitudinal welding, and the response difference of the box structure‐based tail beam under the impact of coal‐rock is not clear. Therefore, this paper studies the response difference of box structure‐based tail beam when coal‐rock particle impacts on the box structure‐based tail beam. Firstly, through the construction and analysis of the impact theoretical model of the coal‐rock particle and metal plate, it is found that the complex box structure of the tail beam makes it extremely difficult to establish the impact theoretical model of the coal‐rock and box structure‐based tail beam, so it is impossible to directly study the response of the box structure‐based tail beam when the coal‐rock impacts on the box structure‐based tail beam by the theoretical method. Therefore, the impact simulation model of coal‐rock particle and box structure‐based tail beam is further established. Through the changes of kinetic energy and internal energy of the box structure‐based tail beam system, the contact response of collision contact zone, and noncollision contact zone of the box structure‐based tail beam, the response difference of box structure‐based tail beam when coal‐rock particle impacts on the box structure‐based tail beam is analyzed. Then, by changing the impact speed and contact mode of the coal‐rock particle, the effects of impact speed and the contact mode on the response difference of the box structure‐based tail beam are studied separately. The conclusion shows that the response difference of the box structure‐based tail beam under the impact of the coal particle and rock particle is obvious, and the difference increases as the impact speed increases, and the difference increases as the contact range increases.

Effects of strain rate and bond preparation for dissimilar materials in energy dispersive applications

Composite materials, typically consisting of two or more dissimilar materials adhered together in layers, are frequently used for energy absorption applications. The interface and material characteristics strongly influence the global energy absorptive capability of the composite. This research focuses on ceramic-polymer interfaces and, in particular, links between the properties of the composite, the interface and the separate materials. After characterisation of the materials, the effects of impact speed and bond condition were considered for a polymer-ceramic bond in a threepoint bend configuration. Specimens were loaded in a screw-driven machine at 0.05 mm s-1 and through projectile impact at speeds of approximately 50 m s-1. Screw-driven experiments were performed at ambient and sub ambient conditions, with the temperature chosen to simulate the expected polymer performance in the gas gun experiment, making use of the equivalence of rate and temperature for polymers.

Shock responses of nanoporous gold subjected to dynamic loadings: Energy absorption

Using the finite element analysis, we investigate the shock response, deformation behavior and energy–absorbing characteristics of stochastic bicontinuous nanoporous gold computationally, considering the effects of impact speed and relative density of materials. Three deformation modes during shocking, quasi–static compression, transition state and dynamic compression, are observed with the increasing impact speeds and the corresponding internal deformation mechanisms are demonstrated. The shock response under low–speed loading is similar to the R–LHP–L materials model, and it is more inclined to the R–S–H model as the impact speed rises. The peak stress, plateau stress, densification strain, energy, specific energy absorption (per unit volume) are assessed quantitatively. The peak stress shows a monotonous increase with impact speed, due to the enhanced inertial effect. The plateau stress and energy–absorbing efficiency are insensitive to low impact velocity, but significantly enhanced under high–speed loading. Remarkably, the results show that the energy absorption efficiency of nanoporous gold is better than conventional foam materials and nanofluidic energy absorption and dissipation system. The research not only further clarifies the shock responses and associated mechanisms of NPG, but also promotes its industrial application as an energy–absorbing material.

Multi-crack propagation in PMMA plates under dynamic out-of-plane impact

In this paper, the multi-crack propagation within polymethyl methacrylate (PMMA) plates under out-of-plane impact is experimentally investigated. First, the dynamic propagation behaviors of in-plane radial and circular cracks are directly recorded using a non-contact optical measurement platform in which a high-speed imaging system is combined with a low-speed impact loading device. Second, the dynamic energy release rates and crack velocities of multiple cracks are studied using caustics, and the effects of impact speed and plate thickness are studied. Finally, a mathematical model of dynamic energy release rate which is related to the radial crack length is established based on the principle of energy conservation. The fracture mechanism of multi-crack propagation in PMMA plates is quantitatively analyzed.

Atomistic modeling of pileup process in metal deposition manufacture

Abstract In present work, molecular dynamics (MD) simulation was employed to model the impact of single and double molten aluminum drops onto to an aluminum substrate. The study was related to the pileup process in metal deposition manufacture. Most previous investigations used the continuum scale Volume-of-Fluid (VOF) method to model this phenomenon. Here, the underlying mechanism of pileup process was examined in more details. The effect of impact speed on the height and width of the solidified drops was studied. The penetration depth of molten drops into the solid substrate was also investigated. The present model would be useful for future investigations as the process could now be studied at the atomic scale and the final solidified structure could also be assessed in terms of its defect and crystallinity.

Real-Time Contact Sensory Feedback for Upper Limb Robotic Prostheses

Lack of sense of touch is a fundamental problem for today's robotic prostheses. Considering that touch feedback plays a significant role in identifying contacted objects, the aim of this study is to use acceleration signals, which occur due to physical contact of a prosthetic hand with objects, as sensory feedback. These contact signals are applied on the clavicle bone using a tactor. First, a library of accelerations occurring as a result of tapping on different materials is prepared. The effect of impact speed is studied and used as a scaler for real-time applications. A stochastic signal model is developed for the contact accelerations. Due to the distinct waveform characteristics of different materials, the rate of change of acceleration is used to identify hardness of the objects. In a psychophysical study, the whole procedure of recording, identifying, and replaying the signals is investigated. Results of this study showed the ability of the designed tactor to provide distinguishable hardness sensations of different materials in real time. Furthermore, considering the results of the position control test with and without vision, it can be concluded that the proposed contact sensory feedback method could be enough to substitute for vision during simple grasping tasks.

Analysis of impact phenomenon on superhydrophobic surfaces based on molecular dynamics simulation

The dynamic behavior of hydrophobic material directly effects its application. The impact phenomenon of droplets on hydrophobic materials is an important indicator to characterize the dynamic properties of hydrophobic materials. At present, the study on impact phenomenon mainly focuses on macroscopic experiments and theoretical analysis. This paper adopts molecular dynamics simulation to systematically investigate the impact phenomenon of a nano-sized water droplets on pillared graphite surface on the nano-scale. The effects of impact speed and angles of nanodroplets on impact phenomenon of droplets was quantitatively analyzed by a variety of impact simulations. Results showed that the droplets experience Cassie, Cassie-Jumping, Wenzel-Jumping, Wenzel-Cassie and Wenzel state successively with the increase of the collision angle and velocity. A rebounce occurs easily at an intermediate collision angle and bigger velocity. By changing the gap, height and area of the pillars on substrate, the influence of the hydrophobic property on impact phenomenon is analyzed. Studies illustrates that the dimensions of the gaps and height of pillars on graphite substrate have a more significant effect on the impact phenomenon when compared with the area of pillars. This research can provide a theoretical reference for the study of dynamic wetting behavior of hydrophobic material.

A causal model of crash test pulses: effect of impact speed on deformation and other variables

Consider crash tests in which a car strikes a solid block. Suppose there is a particular differential equation (that includes a term in deformation to the power n) relating acceleration at any instant to deformation and velocity at that moment. If that is the case, the dependencies on impact speed of maximum acceleration, duration of impact and deformation are interconnected: the relationships are power functions, and the exponents are all determined by the exponent n in the differential equation. Data from both tests and real crashes suggest that n is about 0.5 for front wheel drive cars.

Numerical modelling of shock-induced chemical reactions (SICR) in reactive powder mixtures using smoothed particle hydrodynamics (SPH)

Shock compaction of reactive powder mixtures to synthesize new materials is one of the oldest material processing techniques and has been studied extensively by several researchers over the past few decades. The quantitative connection between the shock energy imparted and the extent of reaction that can be completed in the small time window associated with the passage of the shock wave is complicated and depends on a large variety of parameters. In particular, our understanding of the complex interplay between the thermo-elasto-viscoplastic behaviour of the granular constituents and their temperature dependent, diffusion-limited reaction mechanism may be enriched through careful numerical simulations. A robust numerical model should be able to handle extremely large deformations coupled with diffusion mediated fast reaction kinetics. In this work, a meshfree discrete particle numerical method based on smoothed particle hydrodynamics (SPH) to simulate shock-induced chemical reactions (SICR) in reactive powder mixtures is proposed. We present a numerical strategy to carry out reactions between reactant powder particles and partition the obtained products between the particles in a manner that accounts for the requirement that the total mass of the entire system remains constant as the reactions occur. Instead of solving the reaction–diffusion problem, we propose a ‘pseudo-diffusion’ model in which a distance dependent reaction rate constant is defined to carry out chemical reaction kinetics. This approach mimics the actual reaction–diffusion process at short times. Our numerical model is demonstrated for the well-studied reaction system Nb + 2Si NbSi2. The predicted mass fractions of the product obtained from the simulations are in agreement with experimental observations. Finally, the effects of impact speed, particle arrangement and mixing ratio on the predicted product mass fractions are discussed.

The effect of impact speed on the HIC obtained in pedestrian headform tests

Pedestrian headform impact tests are generally carried out at a fixed impact speed, which varies depending on the test protocol in use. Thus, it may be desirable to extrapolate a single test result to higher and lower test speeds. This paper investigates the influence of impact speed on the Head Injury Criterion (HIC) and the peak dynamic displacement. The relationship between impact speed and these test measurements is first considered analytically using a linear spring model, and then empirically using the results of 29 headform tests on seven different locations. The results indicate that power functions can be used to predict the effect of impact speed, with exponents of approximately 2.5 for HIC and 0.8 for peak displacement. These relationships might be used for assessing head impact performance over a wider range of speeds than are presently tested.

Ejecta from impact craters

An important feature of impacts into Solar System bodies is the fate of crater ejecta, the near-surface material launched during the highly dynamic crater formation process. Laboratory measurements of impact crater ejecta from 18 studies are summarized. The data are examined and used to assess our understanding of how the ejecta velocity and mass distributions depend on the conditions of an impact event. The effects of impact speed on the ejecta are reasonably well understood, but the dependences on target properties such as strength and porosity are only poorly constrained. A point-source scaling model for the ejecta mass and velocity distributions is developed and fit to the data for several classes of materials distinguished by porosity.

Modelling hypervelocity impact fracture of ceramic panels using a mesh-free method

This paper studies the application of Smoothed Particle Hydrodynamics (SPH) for modelling hyper-velocity impact fracture and fragmentation in ceramic panels. Numerical modelling of complex fracture processes is important to understand the fundamental failure mechanisms in a variety of systems. Finite Element Method (FEM) is the mesh-based method conventionally applied to numerical simulation of fracture and fragmentation. However, the mesh generation and manipulation do not often provide the desired accuracy of the solutions, especially in problems with extreme deformations and discontinuities. To overcome this, here we use a mesh-free method called Smoothed Particle Hydrodynamic (SPH) to investigate the three-dimensional fracture of ceramic panels. The effect of impact speed on the fracture pattern and energy transfer is analysed. The SPH simulations are found to be robust in understanding the fracture mechanisms and in providing crucial design parameters.

OS0902 金属長柱の動的座屈現象に及ぼす負荷速度,断面性状と長さの効果(OS09-01 材料・構造の衝撃問題1,OS09材料・構造の衝撃問題(1))

OS0902 金属長柱の動的座屈現象に及ぼす負荷速度,断面性状と長さの効果(OS09-01 材料・構造の衝撃問題1,OS09材料・構造の衝撃問題(1))

Neck injuries in low speed frontal collisions

Since large bus or locomotive accidents are not frequently reported, the cause of bus or train occupant injuries is not clearly defined. For the large public transportation system that is considered much safer than passenger vehicles, most countries have only the roller-over protection safety rule. This paper uses a dynamic sled test approach to understand the effects of impact speed on the risk of cervical injury. The sled impact test simulates lower speed frontal accidents of occupant impact speed in the range 2.9 m/s to 8.0 m/s. From the series of sled test, relative occupant velocity with respect to struck vehicle is considered one of the main factors to investigate the neck injury mechanism. From the results, higher than 7 m/sec of relative occupant impact speed may cause a severe neck injury. It is also found that compressive shear force and extensional neck moment NCE is the dominated factor for neck injuries.

Hydrocode simulation of the Chicxulub impact event and the production of climatically active gases

We constructed a numerical model of the Chicxulub impact event using the Chart‐D Squared (CSQ) code coupled with the ANalytic Equation Of State (ANEOS) package. In the simulations we utilized a target stratigraphy based on borehole data and employed newly developed equations of state for the materials that are believed to play a crucial role in the impact‐related extinction hypothesis: carbonates (calcite) and evaporites (anhydrite). Simulations explored the effects of different projectile sizes (10 to 30 km in diameter) and porosity (0 to 50%). The effect of impact speed is addressed by doing simulations of asteroid impacts (vi = 20 km/s) and comet impacts (vi = 50 km/s). The masses of climatically important species injected into the upper atmosphere by the impact increase with the energy of the impact event, ranging from 350 to 3500 Gt for CO2, from 40 to 560 Gt for S, and from 200 to 1400 Gt for water vapor. While our results are in good agreement with those of Ivanov et al. [1996], our estimated CO2 production is 1 to 2 orders of magnitude lower than the results of Takata and Ahrens [1994], indicating that the impact event enhanced the end‐Cretaceous atmospheric CO2 inventory by, at most, 40%. Consequently, sulfur may have been the most important climatically active gas injected into the stratosphere. The amount of S released by the impact is several orders of magnitude higher than any known volcanic eruption and, with H2O, is high enough to produce a sudden and significant perturbation of Earth's climate.