Collision Speed Research Articles

Mental models of driving and speed: biases, choices and reality

ABSTRACTThis paper provides a review of research performed by Svenson with colleagues and others work on mental models and their practical implications. Mental models describe how people perceive and think about the world including covariances and relationships between different variables, such as driving speed and time. Research on mental models has detected the time-saving bias [Svenson, O. (1970). A functional measurement approach to intuitive estimation as exemplified by estimated time savings. Journal of Experimental Psychology, 86, 204–210]. It means that drivers relatively overestimate the time that can be saved by increasing speed from an already high speed, for example, 90–130 km/h, and underestimate the time that can be saved by increasing speed from a low speed, for example, 30–45 km/h. In congruence with this finding, mean speed judgments and perceptions of mean speeds are also biased and higher speeds given too much weight and low speeds too little weight in comparison with objective reality. Replacing or adding a new speedometer in the car showing min per km eliminated or weakened the time-saving bias. Information about braking distances at different speeds did not improve overoptimistic judgments of braking capacity, but information about collision speed with an object suddenly appearing on the road did improve judgments of braking capacity. This is relevant to drivers, politicians and traffic regulators.

The Physics of Protoplanetesimal Dust Agglomerates. VIII. Microgravity Collisions between Porous SiO2 Aggregates and Loosely Bound Agglomerates

Abstract We performed laboratory experiments colliding 0.8–1.0 mm and 1.0–1.6 mm SiO2 dust aggregates with loosely bound centimeter-sized agglomerates of those aggregates in microgravity. This work builds on previous microgravity laboratory experiments examining the collisional properties of porous loosely bound dust aggregates. In centimeter-sized aggregates, surface forces dominate self-gravity and may play a large role in aggregate growth beyond this size range. We characterize the properties of protoplanetary aggregate analogs to help place constraints on initial formation mechanisms and environments. We determined several important physical characteristics of these aggregates in a large number of low-velocity collisions. We observed low coefficients of restitution and fragmentation thresholds near 1 m s−1 for 1–2 cm agglomerates, which are in good agreement with previous findings in the literature. We find the accretion efficiency for agglomerates of loosely bound aggregates to be higher than that for just aggregates themselves. We find sticking thresholds of 6.6 ± 2 cm s−1, somewhat higher than those in similar studies, which have observed few aggregates stick at speeds of under 3 cm s−1. Even with highly dissipative collisions, loosely bound agglomerates have difficulty accreting beyond centimeter-sized bodies at typical collision speeds in the disk. Our results indicate agglomerates of porous aggregates have slightly higher sticking thresholds than previously thought, allowing possible growth to decimeter-sized bodies if velocities are low enough.

Assessment of bicycle-car accidents under four different types of collision.

Bicycle riders are among the highest risk group in traffic. A cyclist simulation study captured kinematics and injuries to legs, pelvis, neck, and head for one human body size. We analyzed the number of parameters (forces acting on left and right tibia, head injury criterion, neck tensile force, neck shear force, and pelvic acceleration) for each of the four different cases: bicyclist ride out-residential driveway, motorist overtaking-undetected bicyclist, bicyclist left turn-same direction, and bicyclist right turn-opposite direction. The comparison of simulation outcomes for leg injuries with official hospital records has shown a very good correlation in terms of injury severity prediction. This study concludes that if countermeasures to prevent fatal cyclist injury in car impacts were to be concentrated on mitigating head and neck impact to the windscreen of the car, a dominant share of fatal cyclist crashes and severe traumatic head injury cases at collision speeds exceeding 40 km/h could be prevented.

A DOWNWARD HEAD POSTURE LEADS TO HIGHER CERVICAL SPINE LOADING DURING HEAD-FIRST IMPACTS IN SIMULATED RUGBY TACKLES

BackgroundA rugby tackle is an open and unpredictable event, which can lead to intentional or unintentional head-first impacts rather than the preferred ‘shoulder first’ technique.ObjectiveTo identify the effect of head-neck...

Simulation study of the formation of a non-relativistic pair shock

We examine with a particle-in-cell (PIC) simulation the collision of two equally dense clouds of cold pair plasma. The clouds interpenetrate until instabilities set in, which heat up the plasma and trigger the formation of a pair of shocks. The fastest-growing waves at the collision speed $c/5$, where $c$ is the speed of light in vacuum, and low temperature are the electrostatic two-stream mode and the quasi-electrostatic oblique mode. Both waves grow and saturate via the formation of phase space vortices. The strong electric fields of these nonlinear plasma structures provide an efficient means of heating up and compressing the inflowing upstream leptons. The interaction of the hot leptons, which leak back into the upstream region, with the inflowing cool upstream leptons continuously drives electrostatic waves that mediate the shock. These waves heat up the inflowing upstream leptons primarily along the shock normal, which results in an anisotropic velocity distribution in the post-shock region. This distribution gives rise to the Weibel instability. Our simulation shows that even if the shock is mediated by quasi-electrostatic waves, strong magnetowaves will still develop in its downstream region.

THE ROLE OF PEBBLE FRAGMENTATION IN PLANETESIMAL FORMATION. II. NUMERICAL SIMULATIONS

ABSTRACT Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of millimeter- to centimeter-size pebbles. Such clouds can form, for example, through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1000 km. During the collapse, pebbles collide, and depending on their relative speeds, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model collision outcomes. We find that the internal structure of a planetesimal is strongly dependent on both its mass and the applied fragmentation model. Low-mass planetesimals have no/few fragmenting pebble collisions in the collapse phase and end up as porous pebble piles. The number of fragmenting collisions increases with increasing cloud mass, resulting in wider particle size distributions and higher density. The collapse is nevertheless “cold” in the sense that collision speeds are damped by the high collision frequency. This ensures that a significant fraction of large pebbles survive the collapse in all but the most massive clouds. Our results are in broad agreement with the observed increase in density of Kuiper Belt objects with increasing size, as exemplified by the recent characterization of the highly porous comet 67P/Churyumov–Gerasimenko.

Thoracoabdominal injury analysis of a 6-year-old pedestrian finite element model in vehicle-pedestrian collisions

A holistic human body finite element model of a 6-year-old pedestrian was completed by integrating the skin, soft tissues and joint ligaments, based on the component models of a 6-year-old child. The complete model was verified by comparing to available cadaveric test data. Then it was used to simulate collisions of midsize car/SUV-paediatric pedestrian at different collision speeds, in order to study the effects of collision speed, and vehicle type on kinematic/biomechanical responses of paediatric chest and abdomen, and to predict the injuries of bones and internal organs according to compression/viscous criterion and strain. Simulation results showed that the number of rib fractures increased with the increase of collision speed in collision simulations of midsize car-paediatric pedestrian, but no rib fracture appeared in simulations of SUV-paediatric pedestrian impact. Maximum values of chest/abdomen/thigh impact forces, maximum deformation/VCmax of paediatric chest and abdomen, and maximum first principal strain of internal organs were proportional to collision speed. Predicted paediatric chest and abdominal injuries, obtained from the midsize car-pedestrian simulations, were found to be consistent when compression/viscous criterion and first principal strain were used as a yardstick for injury assessment. Additionally, compression/viscous criteria had some limitations on the prediction of rib fracture in SUV-pedestrian collision simulations.

Motion state recognition of debris ejected in vehicular collision after contact with the ground

The motion state of debris ejected from the vehicle involved in vehicular collision is important for finding out the vehicle collision speed. This research developed an analytical model to recognise the debris motion state. With the model, analyses were conducted, which reveal that if α, which is the contact angle between the debris and the ground at the moment when the debris collides the ground, is within the range from 0° to its boundary value, then the debris slides; if α is within the range from its boundary value to 90°, then the debris bounces. With debris' initial angular velocity ω = 0, the boundary value is 11.8° for sphere debris and 7.8° for rectangular debris; with ω ≠ 0, the boundary value for rectangular debris is arcsin(g / Rω2) where g represents the acceleration due to gravity and R is the distance from the debris centre to the point of its contact with the ground. Experiment tests were conducted for debris motion states with ω = 0, which confirmed the analytical results.

铝钢磁脉冲焊接性能及界面微观组织研究

本文研究了5052铝合金，HC420LA高强钢的磁脉冲焊接接头性能，并通过金相分析、电子扫描显微分析和X射线能谱分析等微观分析手段对不同工艺参数下的焊接接头进行了分析。结果表明，焊接工艺参数对铝–钢磁脉冲焊接接头影响显著，焊接接头表现出不同的失效形式。通过微观形貌分析，发现随着焊接间距的增大，碰撞速度和碰撞角度增大，焊接区域有效焊缝长度缩短，同时焊接界面塑性变形剧烈，产生了微观裂纹和孔洞等缺陷。通过能谱分析，发现在较大碰撞速度和碰撞角度下，焊接界面结合区出现了铝–钢的第二相化合物。 In this paper, properties of 5052 aluminum alloy and HC420LA high strength steel magnetic pulse welding joint were studied. Metallographic analysis, scanning electron microscopy and X-ray were applied to analyze the microscopic morphology of welded joints under different process parameters. Results indicated that the welding process parameters were significant of influence on welding joints. And the welded joints exhibit different failure modes. Morphology analysis showed that the effective weld length of welding area was shortened, and the welding interface was of severe plastic deformation, micro cracks and holes appeared with the increase of welding spacing. Elements analysis found Al-Steel phase compounds appeared in the bonding interface zone under larger collision speed and collision angle.

Analysis of tether anchored floating suspension bridge subjected to large ship collisions

The Norwegian public road administration wants to replace eight ferry crossings on the main road in western Norway with fixed crossings. This requires novel technologies and new solutions as several of them are too extreme for today’s technology. One challenge the bridges face is ship impacts. The concept studied in this paper is a tether anchored floating suspension bridge. It has a length of 4000m and water depths of over 500m. In addition to the fixed shore supports, two floaters support the three main spans, each with a length of 1385m. A shipping lane goes between the two floaters, making them susceptible to impacts. To remedy this, it was proposed to install a floating structure around each floater, connected to the floater by tethers. In a collision, the barrier dissipates energy through increased submersion, drag forces and hydrodynamic added mass as it moves. This will reduce the amount of energy absorbed as elastic and plastic strain energy and kinetic energy in the bridge. A review of the collision risk studies show that the largest risk is associated with a container vessel of 17000tons. The paper studies the global response of the bridge subjected to large and extreme container vessel collisions both with and without the barrier. The analyses are time domain dynamic simulations in the computer program USFOS. All structural elements in the model are beam elements. The ship beam accounts for both pitch and translational inertia, including the effect of hydrodynamic added mass. The ship mass is given an initial velocity corresponding to the collision speed. A series of springs connect the ship to the bridge. One of the springs represents the non-linear force deformation characteristic of the vessel bow, calculated by finite element modelling and simulation with LS-DYNA software. These simulations included both impact against a rigid wall, representative of collisions against unprotected pylons, and impact against a rigid toroidal surface, representative of a collision against the barrier. Response quantities included in the paper are lateral displacements of the floaters, accelerations at the bridge girder and towers, and forces in main cables and tethers.

Study on estimation of vehicle collision speed in the case of vehicle collision with guard-pipe

Study on estimation of vehicle collision speed in the case of vehicle collision with guard-pipe

Crash Injury Analysis of Knee Joint Considering Pedestrian Safety.

Background:Lower extremity injuries are frequently observed in car-to-pedestrian accidents and due to the bumper height of most cars, knee joint is one of the most damaged body parts in car-to-pedestrian collisions. Objective: The aim of this paper is first to provide an accurate Finite Element model of the knee joint and second to investigate lower limb impact biomechanics in car-to-pedestrian accidents and to predict the effect of parameters such as collision speed and height due to the car speed and bumper height on knee joint injuries, especially in soft tissues such as ligaments, cartilages and menisci. Materials and Methods: In this analytical study, a 3D finite element (FE) model of human body knee joint is developed based on human anatomy. The model consists of femur, tibia, menisci, articular cartilages and ligaments. Material properties of bones and soft tissues were assumed to be elastic, homogenous and isotropic. Results:FE model is used to perform injury reconstructions and predict the damages by using physical parameters such as Von-Mises stress and equivalent elastic strain of tissues. Conclusion:The results of simulations first show that the most vulnerable part of the knee is MCL ligament and second the effect of speed and height of the impact on knee joint. In the critical member, MCL, the damage increased in higher speeds but as an exception, smaller damages took place in menisci due to the increased distance of two bones in the higher speed.

NMR and EPR Studies of Free-Radical Intermediates from Experiments Mimicking the Winds on Mars: A Sink for Methane and Other Gases

A new kind of solid–gas chemical reactions has been investigated using solid-state powder 2H, 13C, and 29Si NMR and EPR spectroscopies. These studies involve reactions between a silicate-created Si free-radical intermediate and a few ordinary gases such as isotopically 2H-, 13C-, and 17O-enriched methane (13CH4 and CD4), carbon dioxide (13CO2), hydrogen (2H2), and oxygen (17O2). The solid-state Si free-radical intermediate and gas reaction and silicate products are formed in a specially designed rotating apparatus, which by mechanical tumbling mimics the winds and collision speed of the mineral particles on Mars. It is shown that the “hard” quartz (SiO2) or corundum (α-Al2O3) grain particles, used to simulate the collision particles in a rotating Pyrex (borosilicate) reaction flask, act as an abrasive on the “soft” Pyrex flask and thereby create a silicate Si free-radical intermediate. EPR studies show that this radical is identical to the silicate radical intensively investigated by EPR from γ-irradiatio...

MC2: DYNAMICAL ANALYSIS OF THE MERGING GALAXY CLUSTER MACS J1149.5+2223

ABSTRACT We present an analysis of the merging cluster MACS J1149.5+2223 using archival imaging from Subaru/Suprime-Cam and multi-object spectroscopy from Keck/DEIMOS and Gemini/GMOS. We employ two- and three-dimensional substructure tests and determine that MACS J1149.5+2223 is composed of two separate mergers among three subclusters occurring ∼1 Gyr apart. The primary merger gives rise to elongated X-ray morphology and a radio relic in the southeast. The brightest cluster galaxy is a member of the northern subcluster of the primary merger. This subcluster is very massive ( ). The southern subcluster is also very massive ( ), yet it lacks an associated X-ray surface brightness peak, and it has been unidentified previously despite the detailed study of this Frontier Field cluster. A secondary merger is occurring in the north along the line of sight (LOS) with a third, less massive subcluster ( ). We perform a Monte Carlo dynamical analysis on the main merger and estimate a collision speed at pericenter of km s−1. We show the merger to be returning from apocenter with core passage occurring Gyr before the observed state. We identify the LOS merging subcluster in a strong lensing analysis in the literature and show that it is likely bound to MACS J1149 despite having reached an extreme collision velocity of ∼4000 km s−1.

DESIGN PARAMETERS OF BUFFER STOPS

Paper discuses reasons of building buffer stops and situations that may occur in railway station leading to build safety tracks. Also discusses parameters of buffer stops that enter its design, such as collision speed and kinetic energy absorbing capacity. Furthermore, presents categories of<br />buffer stops depending on principles of absorbing the kinetic energy and points pros and cons of each structure.

Effectiveness of Bicycle Safety Helmets in Preventing Facial Injuries in Road Accidents.

BackgroundThe effectiveness of bicycle safety helmets in preventing head injuries is well- documented. Recent studies differ regarding the effectiveness of bicycle helmets in preventing facial injuries, especially those of the mid-face and the mandible.ObjectivesThe present study was conducted to determine the protective effect of a bicycle helmet in preventing mid-face and mandibular fractures.Patients and MethodsData from an accident research unit were analyzed to collect technical collision details (relative collision speed, type of collision, collision partner, and use of a helmet) and clinical data (type of fracture).ResultsBetween 1999 and 2011, 5,350 bicycle crashes were included in the study. Of these, 175 (3.3%) had fractures of the mid-face or mandible. In total, 228 mid-face or mandibular fractures were identified. A significant correlation was found between age and relative collision speed, and the incidence of a fracture. While no significant correlation was found between the use of a helmet and the incidence of mid-facial fractures, the use of a helmet was correlated with a significantly increased incidence of mandibular fractures.ConclusionsHigher age of cyclists and increasing speed of the accident opponent significantly increase the likelihood of sustaining facial fractures. The use of bicycle helmets does not significantly reduce the incidence of mid-facial fractures, while being correlated with an even increased incidence of mandibular fractures.

Analytical study of the accuracy of discrete element simulations

SummaryThe numerical errors was used to verify the correctness of key results. The truncation errors, which are larger than the round‐off errors by orders of magnitude, have a superlinear relationship with both the simulation time‐step and the interparticle collision speed. This remains the case regardless of the simulation details including the chosen contact model, particle size distribution, particle density or stiffness. Hence, the total errors can usually be reduced by choosing a smaller time‐step. Increasing the polydispersity in a simulation by including smaller particles necessitates choosing a smaller time‐step to maintain simulation stability and reduces the truncation errors in most cases. The truncation errors are increased by the dissipation of energy by frictional sliding or by the inclusion of damping in the system. The number of contacts affects the accuracy, and one can deduce that because 2D simulations contain fewer interparticle contacts than the equivalent 3D simulations, they therefore have lower accrued simulation errors. Copyright © 2016 John Wiley & Sons, Ltd.

Safety benefits of integrated pedestrian protection systems

This study developed a methodology for evaluating the effectiveness of an integrated pedestrian protection system (IPPS) based on simulations. The proposed IPPS consists of active and passive vehicular systems for protecting pedestrians, including a pedestrian warning information system (PWIS), an active hood lift system (AHLS), and pedestrian airbag system (PAS). Two simulation methods were applied in the proposed methodology: a driving simulation and a finite element simulation. A driving simulator was used to obtain the change in collision speed, which is a key parameter for evaluating driving behavior when a PWIS is applied. In addition, a well-known simulator for finite element analysis, LSDYNA was used to simulate the impact of a pedestrian on a vehicle hood in a pedestrian-vehicle collision. The head injury criterion (HIC), which is an outcome of LS-DYNA simulations, is a major parameter for evaluating passive safety systems. The probability of pedestrian fatalities by collision speeds and HICs were estimated to quantify the safety benefits of an IPPS based on the statistical analyses. The results showed that an IPPS is capable of reducing pedestrian fatalities by approximately 90 % associated with jaywalking in the midblock and walking on the roadside. The findings of this study can be used to boost the development of various vehicular technologies for pedestrians. The results can be effectively used for policy making and deriving legislative requirements associated with advanced vehicular technologies for enhancing pedestrian safety.

AN EFFICIENT AUTOMOTIVE COLLISION AVOIDANCE SYSTEM FOR INDIAN TRAFFIC CONDITIONS

The execution of a wide-ranging accident cautioning system is being visualised by ACAS Program, which is proficient in perceiving and cautioning the driver of potential hazard conditions forward, on the side, and rear sections of the vehicle. The structure would use: (a) long array sensor or visual devices to identify probable hazards in front of the vehicle, (2) short range sensors to caution the driver of nearby objects while changing traffic lanes or backing up, and (3) a track exposure arrangement to alert the motorist when the vehicle deviates from the intended traffic lane. Accident Prevention organisms, as a consequent step to collision mitigation, are one of the Great challenges in the area of active safety for road vehicles. The task of a collision avoidance system is to track objects of potential collision threat and govern any action to evade or diminish a crash. The main focus is how to make decisions based on ambiguous evaluations and in the presence of numerous hurdles. The first step in CA (Collision Avoidance) systems for automotive applications is adaptive cruise control (ACC). The ability of the car to protect its passengers is sometimes called crashworthiness. Generally, a CM (Collision Mitigation) system tries to reduce the severity of the accident as much as possible under some constraints. The situation may be observed with detector sensors, laser radar, vision sensors, ultrasonic sensors, GPS sensors and inter-vehicle communication. FCM (Forward Collision Mitigation) systems mainly try to avoid or mitigate frontal collisions. The CA decision is based on the current position estimate of the host vehicle and those of other objects. The focus is towards the method for determining the threat of a collision given that the state of other objects is known. Two collision mitigation by braking systems are considered for study. One system uses the probability of collision, to decide when to perform braking interventions. The other system has a multiple obstacle decision. The scenarios that are calculated in this segment are primarily those where a CMbB has a large potential of significantly reducing the collision speed. Therefore, the test results of main interest is those between 0 and 70 km/h also for simulations. Hence, this ACAS Program detects the potential hazards, warns the driver and takes action to avoid or mitigate a collision. Keywords: Collision Warning, Decision Making, Collision Mitigation Braking, Tracking Sensors Language: en

Damage Characteristics of the Logical Chip Module Due to Plasma Created by Hypervelocity Impacts**supported by National Natural Science Foundation of China (Nos. 10972145, 11272218, 11472178), Program for Liaoning Excellent Talents in University of China (No. LR2013008), Open Foundation of Key Laboratory of Liaoning Weapon Science and Technology, Liaoning Province Talents Engineering Projects of China (No. 2012921044)

To researching the damage characteristics of typical logical chip modules in spacecraft due to plasma generated by hypervelocity impacts, we have established a triple Langmuir probe diagnostic system and a logical chips measurement system, which were used to diagnose plasma characteristic parameters and the logical chip module's logical state changes due to the plasma created by a 7075 aluminum projectile hypervelocity impact on the 2A12 aluminum target. Three sets of experiments were performed with the collision speeds of 2.85 km/s, 3.1 km/s and 2.20 km/s, at the same incident angles of 30 degrees and logical chip module's positions by using a two-stage light gas gun loading system, a plasma characteristic parameters diagnostic system and a logical chip module's logical state measurement system, respectively. Electron temperature and density were measured at given position and azimuth, and damage estimation was performed for the logical chip module by using the data acquisition system. Experimental results showed that temporary damage could be induced on logical chip modules in spacecraft by plasma generated by hypervelocity impacts under the given experimental conditions and the sensors' position and azimuth.