Collision Speed Research Articles

Prediction of Traffic Accident Severity Based on Random Forest

This paper used the data of automobile traffic accidents from 2018 to 2020 in the Chinese National Automobile Accident In-Depth Investigation System. The prediction features of traffic accident severity are innovated. Four accident features that did not participate in the importance ranking were added: accident location, accident form, road information, and collision speed. Eight accident features (engine capacity, hour of day, age of vehicle, month of year, day of week, age band of drivers, vehicle maneuver, and speed limit) have been used in previous studies. Random forest was used to rank the importance of 12 accident features, and 7 important accident features were finally adopted. By comparing the algorithms and optimizing the results, the prediction model of traffic accident degree with higher accuracy is finally obtained.

Production and Performance Evaluation of Sisal Fibre (Agave Sisalana) As Composite Material for Car Bumper

A bumper is one of the main automobile parts used as protection for the car and passengers against front and rear collision. The aim of this study is to carry out a research on sisal fibre as a suitable reinforcement material for production of a composite car bumper. The research also evaluated the properties of the composite bumper to ascertain its improvement on crash-worthiness during car collision. Sisal fibre is a material that has properties of low weight, high strength, and low density. Considering the fact that fuel economy and efficiency is necessary in modern automobiles, the best way to increase the vehicle efficiency without sacrificing safety is to employ the use of sisal-fibre reinforced composite in the production of less weight and high strength bumpers. The research was conducted through experiment, analysis and production processes. Hand lay-up technique method was employed in the production of the mould and the composite car bumper. The results obtained from the tests are; Tensile strength; 69.51 MPa, Impact strength; 32.79kJ/m2, Compression strength; 6.92MPa, and flexural strength: 86.81MPa. At the end of the research, better quality, light weight and high strength composite bumper was produced. The analysis of the produced car bumper showed that it conformed to National Highway Traffic Safety Administration (NHTSA), 1971 and Federal motor vehicles safety standards (FMVSS, No. 215), at 8km/hr collision speed.

Complex Polymer Nanoparticle Synthesis and Morphology Control Using an Inkjet Mixing System

Complex polymer nanoparticles were synthesized via a one-step antisolvent precipitation method using an inkjet mixing system. The effect of collision speed, impact parameter, and solution concentration on the product profiles was investigated. Taking advantage of the rapid mixing capability of an inkjet mixing system, the balance of the diffusion and stabilization rate was discussed, and the mechanism of morphology change in complex polymer nanoparticles was suggested. According to the suggested mechanism, it was demonstrated that the morphology was controllable by changing the mixing ratio of solvents and anti-solvents under rapid mixing. It was also demonstrated that the morphology and particle size of the complex polymer nanoparticles were controllable by changing the collision rate, impact parameter, and solution concentration, and Janus polymer nanoparticles were successfully synthesized with dav = 300 nm and CV = 0.2.

Investigation on AEB Key Parameters for Improving Car to Two-Wheeler Collision Safety Using In-Depth Traffic Accident Data

Automatic emergency braking (AEB) system play an essential role in avoiding traffic collisions and minimizing impact strengths, which contributes to improving road traffic safety. However, the present research of the AEB system is mainly concentrated on avoiding the car to car and car to pedestrian collisions. China has typical mixed traffic characteristics, especially the frequent car to two-wheeler collision accidents. Research on the AEB system to prevent car to two-wheeler collisions in complex multi-traffic scenarios is of great significance to further improve the comprehensive performance of the AEB system. In this article, based on the cases of the car to two-wheeler collisions from China In-Depth Accident Study (CIDAS) database, the effects of three key parameters of the AEB system, braking deceleration, braking advance time, and detection range, on the accident rate and severity are studied by accident reconstruction and virtual experiment. Results show that the theoretical optimal detection range of the AEB system is 180°–35 m for the car to two-wheeler collision prevention. Moreover, the current feasible optimal detection range is 120°–35 m due to the limitation of environmental awareness technology. When the braking advance time is 1 s, the detection angle is 120°, and the detection distance is 35 m, the installation of the AEB system can avoid 22.3% of the car to two-wheeler collision accidents. Meanwhile, in the inevitable accidents, the average collision speed of vehicles decreases from 33.93 to 21.34 km/h, which effectively reduces the collision strengths. Findings of this study could help car manufacturers and makers of AEB hardware select the appropriate detection radar. They can also provide ideas and data support for formulating relevant laws and regulations of the AEB system, future development of AEB system, or other driver assistance systems.

Towards the impact of GMC collisions on the star formation rate

ABSTRACT Collisions between giant molecular clouds (GMCs) are one of the pathways for massive star formation due to the high densities created. However, the enhancement of the star formation rate (SFR) is not well constrained. In this study, we perform a parameter study of cloud–cloud collisions and investigate how the resulting SFR depends on the details of set-up. Our parameter study explores variations in collision speed, magnetic field inclination (with respect to the collisional axis), and resolution, as defined by the number of cells per Jeans length. In all our collision simulations, we find a factor of 2–3 increase in the SFR compared to our no collision simulation, with star formation beginning sooner with (a) high collisional velocities, (b) parallel orientation between the magnetic field and collision axis, (c) and lower resolution. The mean virial parameter of high density (and thus possible star-forming) gas increases with collisional velocity, but has little variation with magnetic field inclination. The alignment of the velocity and magnetic field remains uniform in low-density environments but becomes more perpendicular with increasing density, indicating the compression of the magnetic field by collapsing gas. Comparing the trends in the SFR with other GMC collision studies, we find good agreement with studies that account for the gravitational boundedness of the gas in their star formation algorithm, but not with those that simply form stars above a prescribed density threshold. This suggests that the latter approach should be used with caution when modelling star formation on resolved cloud scales.

Left-turn-across-path-from-opposite-direction accidents in China: CIDAS accident study

Abstract Left-turn-across-path-from-opposite-direction (LTAP/OD) conflicts are one of the most common crash types at intersections. The research aims to reveal the general and dynamic information about the conflict for the most relevant street layouts for each conflict configuration of the LTAP/OD accidents involving passenger cars, motorcycles and Ebikes. The analysis was based on 276 LTAP/OD accidents collected by the China in-depth accident study (CIDAS 2011–2019). The LTAP/OD accidents include 44 car-to-car conflicts, 157 car-to-motorcycle conflicts and 75 car-to-Ebike conflicts. Most accidents belonging to the three types were observed at the W0 street layout without a green belt separating the oncoming lane and no offset lane between the turning car and the oncoming traffic, the main distance between both vehicles in the beginning of the critical situation being about four metres, occurring in the clear day with no rain and at junctions lighted either because of daylight or based on street lighting. In terms of the turning car initial speed, the range is 15–30 km/h for most car-to-car and car-to-motorcycle accidents, but 30–40 km/h for most car-to-Ebike accidents. As for the collision speed, this range is between 10 km/h and 20 km/h for car-to-car and car-to-Ebike accidents and between 10 km/h and 25 km/h for car-to-motorcycle crashes. Based on the distributions of objective motorcycles’ and Ebikes' positions in collisions with passenger cars, the maximum longitudinal distance is 60 m for both types of accidents and the maximum lateral distance ranges from −20 m to 20 m and from −15 m to 15 m, respectively.

OSSOS. XXVI. On the Lack of Catastrophic Collisions in the Present Kuiper Belt

We investigate different conditions, including the orbital and size–frequency distribution (SFD) of the early Kuiper Belt, that can trigger catastrophic planetesimal destruction. The goal of this study is to test if there is evidence for collisional grinding in the Kuiper Belt that has occurred since its formation. This analysis has important implications for whether the present-day SFD of the cold classical trans-Neptunian objects (TNOs) is a result of collisional equilibrium or if it reflects the primordial stage of planetesimal accretion. As an input to our modeling, we use the most up-to-date debiased OSSOS++ ensemble sample of the TNO population and orbital model based on the present-day architecture of the Kuiper Belt. We calculate the specific impact energies between impactor–target pairs from different TNO groups and compare our computed energies to catastrophic disruption results from smoothed particle hydrodynamics simulations. We explore different scenarios by considering different total primordial Kuiper Belt masses and power slopes of the SFD and allowing collisions to take place over different timescales. The collisional evolution of the Kuiper Belt is a strong function of the unknown initial mass in the trans-Neptunian region, where collisional grinding of planetesimals requires a total primordial Kuiper Belt mass of M > 5 M ⊕, collision speeds as high as 3 km s−1, and collisions over at least 0.5 Gyr. We conclude that presently, most of the collisions in the trans-Neptunian region are in the cratering rather than disruption regime. Given the low collision rates among the cold classical Kuiper Belt objects, their SFD most likely represents the primordial planetesimal accretion.

Providing a detailed estimate of mortality using a simulation-based collision risk model.

Marine renewables could form a significant part of the green energy mix. However, a potential environmental impact of tidal energy converters (TECs) is collision risk between a device and animal, which has been a significant barrier in the consenting process. While it is important to understand the number of collisions of an animal with the device, the relative speed at which an animal collides with the device, and the point on the animal where collision occurs, will determine whether a collision is fatal, which is important in understanding population-level impacts. Using a simulation-based collision risk model, this paper demonstrates a novel method for producing estimates of mortality. Extracting both the speed and the location of collisions between an animal and TEC, in this instance a seal and horizontal axis turbine, collision speed and location of collision are used to produce probabilities of mortality. To provide a hypothetical example we quantified the speed and position at which a collision occurs to estimate mortality and, using collision position, we determine all predicted collisions with the head of the animal as fatal, for example, whilst deeming other collisions non-fatal. This is the first collision risk model to incorporate speed at the point of contact and the location where the collision occurs on the animal, to estimate the probability of mortality resulting from a collision. The hypothetical scenarios outline how these important variables extracted from the model can be used to predict the proportion of fatal events. This model enables a comprehensive approach that ultimately provides advancements in collision risk modelling for use in the consenting process of TECs. Furthermore, these methods can easily be adapted to other renewable energy devices and receptors, such as wind and birds.

Safety Study of High-Speed Collisions between Trains and Live Intruder.

To investigate the safety of train collisions with live intruders under high-speed operation, a new 3D finite element laminated model of live intruder filling was constructed based on reconstruction using physical 3D scanning, with three outer layers of the model simulating the skin, three inner layers simulating bone, and internal filling simulating internal organs. The model was simulated in LS-DYNA with pendulum side collision, and the force-time and force-displacement curves of the collision between the pendulum and the living intruder were obtained, which were consistent with the curve trend of the results of the cadaver pendulum collision test by Viano in 1989, and the accuracy of the finite element model of the intruder was verified. Through the simulation calculation of high-speed collision between the train and two kinds of living intrusions, the maximum acceleration of the train body, the maximum lifting of the wheel pair, the deformation of the cowcatcher, and the maximum central load on the cowcatcher during the collision can be obtained. The results of the study show that at a collision speed of 110 km/h and different collision positions, the collision risk factor between the train and heavier organisms is relatively high, and the risk arising from frontal collisions is generally greater than that of offset collisions; despite this, all the indicators such as the maximum acceleration of the train, the maximum lift of the wheel pairs, the reduction in the length of the cowcatcher discharge per 5 m of space, and the maximum central load borne by the cowcatcher discharge are lower than the EN15227 standard. Additionally, the safety of the train is not affected and the components can work reliably.

Dynamic characteristics of moving droplets impacting sessile droplets with different Reynolds numbers

The collision of moving droplets with sessile droplets is a common occurrence in fields of industry, including power generation, chemical engineering, and aerospace, among others. In this paper, the collision of propylene glycol, glycerol, and de-ionized water droplets is studied for given collision speeds and different volume ratios of moving and sessile droplets using high-speed photography. It is found that droplet collision at a speed of about 0.25 m/s leads to compression deformation, whereas collision at about 1.10 m/s typically produces features, such as a non-splashing liquid crown and a central liquid jet. In this paper, the main characteristics of the above phenomena are quantified, the influence of the Reynolds number at different volume ratios is studied, and the main phenomena are explained from the perspective of an energy analysis. The findings reported here are significant for the solution of practical engineering problems and improving the stability of equipment operation.

Experimental and finite element analysis on the sound absorption performance of wedge-like knitted composite

Limited by the single mechanism of sound absorption, most current sound-absorbing materials exhibit difficulties in balancing weight and acoustic performance. In this work, a flexible wedge-like knitted composite (WKC) realized by knitting and coating technology with multiple sound-absorbing mechanisms including porous sound absorption mechanism and wedge-like structure resonant mechanism is proposed. To study the influence mechanisms of coating and wedge structure on the sound absorption performance, experiment and finite element analysis were both conducted. By improving the porosity distribution through the addition of viscoelastic layer, the sound absorption coefficient (SAC) is enhanced by 239%, which is originated from the infiltrated silica gel into the fabric pores, increasing the complexity of the penetration path. The wedge structure plays a necessary role on enhancing the sound absorption coefficient under low frequency because the concave–convex surface of wedge generates stronger resonance of rear air cavity. The size effect of wedge shape is analyzed in terms of acoustic vibration angle and acoustic energy dissipation density. The increase of the acoustic vibration angle increases the reflection collision path and speed of sound vibration, which further enhances the energy dissipation. Therefore, the combination of viscoelastic coating layer and wedge structure effectively promote the sound absorption, especially at low frequency. This work provides guidance for the structural design and realization of innovative flexible sound absorbing materials, which is promising in application prospect of indoor curtain interiors, wall coverings and automotive interiors.

Severity of Placental Abruption in Restrained Pregnant Vehicle Drivers: Correct Seat Belt Use Confirmed by Finite Element Model Analysis.

Despite wearing a seat belt, pregnant drivers often suffer from negative fetal outcomes in the event of motor accidents. In order to maintain the safety of pregnant drivers and their fetuses, we assessed the severity of placental abruption caused by motor vehicle collisions using computer simulations. We employed a validated pregnant finite element model to determine the area of placental abruption. We investigated frontal vehicle collisions with a speed of 40 km/h or less involving restrained pregnant drivers with a gestational age of 30 weeks. For a crash speed of 40 km/h, the placental abruption area was 7.0% with a correctly positioned lap belt across the lower abdomen; it was 36.3% with the belt positioned at the umbilicus. The area of placental abruption depended on collision speed, but we found that with a correctly positioned belt it likely would not lead to negative fetal outcomes. We examined the effects on placental abruptions of reconfiguring seat belt width and force limiter setting. A wider lap belt and lower force limiter setting reduced the area of placental abruption to 3.5% and 1.1%, respectively; however, they allowed more forward movement upon collision. A 2.5 kN force limiter setting may be appropriate with respect to both forward movement and reduced placental abruption area. This study confirmed the importance of correctly using seat belts for pregnant drivers. It provides valuable evidence about improving safety equipment settings.

Drone flocking optimization using NSGA-II and principal component analysis

Individual agents in natural systems like flocks of birds or schools of fish display a remarkable ability to coordinate and communicate in local groups and execute a variety of tasks efficiently. Emulating such natural systems into drone swarms to solve problems in defense, agriculture, industrial automation, and humanitarian relief is an emerging technology. However, flocking of aerial robots while maintaining multiple objectives, like collision avoidance, high speed etc., is still a challenge. This paper proposes optimized flocking of drones in a confined environment with multiple conflicting objectives. The considered objectives are collision avoidance (with each other and the wall), speed, correlation, and communication (connected and disconnected agents). Principal Component Analysis (PCA) is applied for dimensionality reduction and understanding of the collective dynamics of the swarm. The control model is characterized by 12 parameters which are then optimized using a multi-objective solver (NSGA-II). The obtained results are reported and compared with that of the CMA-ES algorithm. The study is particularly useful as the proposed optimizer outputs a Pareto Front representing different types of swarms that can be applied to different scenarios in the real world.

A method to predict particle collision speeds in fluidized beds

The target of this method is gas–solid fluidized beds, in which the particles progressively become coated with liquid or generally become sticky for any reason. Previous studies have shown that the restitution coefficient of wet particle collisions depends on the speed at which the particles collide. Moreover, below a critical collision speed, the particles fail to rebound at all. Therefore, predicting particle collision speeds is important. Current methods to predict collision speeds are computationally expensive. The present method provides an analytical expression for particle collision speed, making it convenient for evaluating the potential for agglomeration. Moreover, it provides a basis for understanding the speed of particle motion in fluidized beds—usually only accessible through time-consuming numerical simulations—by anticipating the outcome of what is largely a repetitive computation of particle–particle collision and re-acceleration by the gas flow. The method combines the mean free time between inelastic particle collisions (with provision for collective particle motion), which cause them to lose kinetic energy, and the drag force by the turbulent gas flow on the particles, which accelerates them prior to their next collision. To validate the method, the results are compared to corresponding computational fluid dynamics (CFD) - discrete element method (DEM) calculations.

50 percentile dummy movement analysis using TEMA Automotive software

The dynamic loads acting on passengers during road accidents depend not only on the vehicle structure, but also on the properties of the applied passenger and driver protection system. Two-point seat belts are the most frequently used personal protection system for adult passengers in bus vehicles. The paper investigates the thread of dynamic loads acting on the body of a 50 percentile dummy placed in an armchair equipped with two-point seat belts. In order to solve this problem, tests recorded with the Phantom v310 camera were used, the object of which was the Hybrid II 50th dummy, and the recording of the tests was carried out for three different collision speeds. The article presents the results of the crash tests obtained with the use of the TEMA Automotive program. Crash test analysis showing the displacement of the head and upper torso of the dummy located in the limited space between the bus-type seats indicates that standard seat belts do not provide sufficient protection. The article indicates the basis for further research and improvement of the personal protection system of passengers transported in minibuses and buses.

A computational study on the basis for a safe speed limit for bicycles on shared paths considering the severity of pedestrian head injuries in bicyclist-pedestrian collisions

Bicyclists and pedestrians are two large vulnerable groups of road users. Many cities have allowed cyclists to share space with pedestrians on footpaths and off-road paths to reduce conflict with motor vehicles. The risk of bicyclist-pedestrian accidents is also increasing accordingly. Therefore, there is a need to understand the factors that affect the risk of injury in such accidents, especially to pedestrians who are considered more vulnerable. This paper presents a detailed investigation of bicyclist-pedestrian collisions and possible injury outcomes. The study has considered five levels of collision speed ranging from 10 km/h to 30 km/h, three pedestrian profiles (adult, child, and elderly) differentiated by their weight and height, three bicycles with different masses, and five impact directions. The bicyclist-pedestrian collision simulations have been analyzed based on four metrics: throw distance, peak head velocity on impact with the ground, head injury criterion (HIC) value, and the probability of severe head injury. For each simulation, the throw distance and peak head velocity on impact with the ground are extracted. Following that, the HIC and the probability of severe head injury to pedestrians are computed. The results show a significant effect of collision speed (p < 0.05) on all four metrics. The analysis has been further extended to study the effect of height and weight profile, bicycle mass, and impact directions on bicyclist-pedestrian collisions. According to the results, the impact directions largely influence the outcome of bicycle-pedestrian collisions. In general, direct impacts on pedestrian body center have been found to yield higher HIC values and probability of severe head injury to pedestrians than off-center impacts. Also, video analysis of simulated collisions has suggested that the accident mechanism depends on weight and height profiles (correlated with different age groups) and impact directions. Finally, recommendations have been proposed based on the study, including a speed limit of not more than 12 km/h for bicyclists on narrow shared paths and footpaths where risks of collisions with pedestrians are high. The results and analysis presented could be helpful for developing legislation to minimize conflicts between bicyclists and pedestrians on shared paths and to reduce potential injury to pedestrians.

Head Kinematics in Youth Ice Hockey by Player Speed and Impact Direction

Hockey is a fast-paced sport known for body checking, or intentional collisions used to separate opponents from the puck. Exposure to these impacts is concerning, as evidence suggests head impact exposure (HIE), even if noninjurious, can cause long-term brain changes. Currently, there is limited understanding of the effect of impact direction and collision speed on HIE. Video analysis was used to determine speed and direction for 162 collisions from 13 youth athletes. These data were paired with head kinematic data collected with an instrumented mouthpiece. Relationships between peak resultant head kinematics and speeds were evaluated with linear regression. Mean athlete speeds and relative velocity between athletes ranged from 2.05 to 2.76m/s. Mean peak resultant linear acceleration, rotational velocity, and rotational acceleration were 13.1g, 10.5rad/s, and 1112rad/s2, respectively. Significant relationships between speeds and head kinematics emerged when stratified by contact characteristics. HIE also varied by direction of collision; most collisions occurred in the forward-oblique (ie,offset from center) direction; frontal collisions had the greatest magnitude peak kinematics. These findings indicate that HIE in youth hockey is influenced by speed and direction of impact. This study may inform future strategies to reduce the severity of HIE in hockey.

Universal Properties of Dense Clumps in Magnetized Molecular Clouds Formed through Shock Compression of Two-phase Atomic Gases

We investigate the formation of molecular clouds from atomic gas by using three-dimensional magnetohydrodynamical simulations, including nonequilibrium chemical reactions, heating/cooling processes, and self-gravity by changing the collision speed V 0 and the angle θ between the magnetic field and colliding flow. We found that the efficiency of the dense-gas formation depends on θ. For small θ, anisotropic super-Alfvénic turbulence delays the formation of gravitationally unstable clumps. An increase in θ develops shock-amplified magnetic fields along which the gas accumulates, creating prominent filamentary structures. We further investigate the statistical properties of dense clumps identified with different density thresholds. The statistical properties of the dense clumps with lower densities depend on V 0 and θ because their properties are inherited from the global turbulence structure of molecular clouds. By contrast, denser clumps appear to have asymptotic universal statistical properties, which do not significantly depend on the properties of the colliding flow. The internal velocity dispersions approach subsonic and plasma β becomes order of unity. We develop an analytic formula of the virial parameter that reproduces the simulation results reasonably well. This property may be one of the reasons for the universality of the initial mass function of stars.

Effect of solid rubber fenders on the structural damage due to collisions between a ship-shaped offshore installation and an offshore supply vessel

ABSTRACT The effect of solid rubber fenders on the structural damage due to collisions between a ship-shaped offshore installation and an offshore supply vessel was investigated. An LS-DYNA computational modelling technique was developed to simulate the kinetic energy absorption behaviour of solid rubber fenders. Physical crushing testing was performed on rubber fender models to validate the computational model under different collision speeds. Traditional LS-DYNA computational models to simulate the structural crashworthiness of ship-shaped offshore hull structures colliding with an offshore supply vessel were combined with the developed rubber fender model. The computational models were applied to a hypothetical very-large-crude-oil-carrier (VLCC) class floating production storage and offloading unit (FPSO) hull that collides with an offshore supply vessel equipped with rubber fenders in the forecastle deck area, and the effects of rubber fenders on the collision energy absorption characteristics were examined in association with the structural damage of both striking OSV and struck FPSO hull structures. The findings and insights derived from the study were summarised.

Grain growth during protostellar disc formation

ABSTRACT Recent observations indicate that mm/cm-sized grains may exist in the embedded protostellar discs. How such large grains grow from the micron size (or less) in the earliest phase of star formation remains relatively unexplored. In this study, we take a first step to model the grain growth in the protostellar environment, using 2D (axisymmetric) radiation hydrodynamic and grain growth simulations. We show that the grain growth calculations can be greatly simplified by the ‘terminal velocity approximation’, where the dust drift velocity relative to the gas is proportional to its stopping time, which is proportional to the grain size. We find that the grain–grain collision from size-dependent terminal velocity alone is too slow to convert a significant fraction of the initially micron-sized grains into mm/cm sizes during the deeply embedded Class 0 phase. Substantial grain growth is achieved when the grain–grain collision speed is enhanced by a factor of 4. The dust growth above and below the disc midplane enables the grains to settle faster towards the midplane, which increases the local dust-to-gas ratio, which, in turn, speeds up further growth there. How this needed enhancement can be achieved is unclear, although turbulence is a strong possibility that deserves further exploration.