Front-end Profile Research Articles

A study on the cyclist lower extremity injury risk by using German in-depth accident data

The lower extremities of cyclists are the most vulnerable body parts in vehicle-bicycle traffic accidents. However, few studies have been conducted on the effects of vehicle front-end profile parameters on cyclist lower extremity injuries by using real accident data. This paper aimed to explore the correlation between the cyclist’s severe lower extremity injury (AIS2+) risk and impact speed, vehicle front-end profile variables, and cyclist parameters via using real cyclist accidents. A subsample of 390 cyclist accident cases with lower extremity injuries was selected from the German In-Depth Accident Study (GIDAS) to conduct statistical analysis. Furthermore, an independent samples t-test was performed to analyse the associations between the selected predictive parameters and the risk of cyclists with AIS2+ lower extremity injuries. Finally, the risk function for cyclists with AIS2+ lower extremity injuries was developed by using the logistic regression method. The research results indicated that vehicle impact speed, lower bumper height (LBH), bumper depth (BD), cyclist age, and weight were statistically significant factors for cyclists with AIS2+ lower extremity injuries. The higher vehicle speed, higher LBH and BD corresponded to a greater likelihood of the cyclist suffering an AIS2+ lower extremity injury. These findings contribute to developing more effective safety measures for vehicle front designs and establishing regulations to protect the lower extremities of cyclists.

Effects of vehicle's front-end profiles on pelvis injury of small female pedestrian

Effects of vehicle's front-end profiles on pelvis injury of small female pedestrian

Global Optimisation of Car Front-End Geometry to Minimise Pedestrian Head Injury Levels

AbstractThe paper presents a multidisciplinary design optimisation strategy for car front-end profile to minimise head injury criteria across pedestrian groups. A hybrid modelling strategy was used to simulate the car- pedestrian impact events, combining parametric modelling of front-car geometry with pedestrian models for the kinematics of crash impact. A space filling response surface modelling strategy was deployed to study the head injury response, with Optimal Latin Hypercube (OLH) Design of Experiments sampling and Kriging technique to fit response models. The study argues that the optimisation of the front-end car geometry for each of the individual pedestrian models, using evolutionary optimisation algorithms is not an effective global optimization strategy as the solutions are not acceptable for other pedestrian groups. Collaborative Optimisation (CO) multidisciplinary design optimisation architecture is introduced instead as a global optimisation strategy, and proven that it can enable simultaneous minimisation of head injury levels for all the pedestrian groups, delivering a global optimum solution which meets the safety requirements across the pedestrian groups.

Can new passenger cars reduce pedestrian lower extremity injury? A review of geometrical changes of front-end design before and after regulatory efforts

ABSTRACTObjective: Pedestrian lower extremity represents the most frequently injured body region in car-to-pedestrian accidents. The European Directive concerning pedestrian safety was established in 2003 for evaluating pedestrian protection performance of car models. However, design changes have not been quantified since then. The goal of this study was to investigate front-end profiles of representative passenger car models and the potential influence on pedestrian lower extremity injury risk.Methods: The front-end styling of sedans and sport utility vehicles (SUV) released from 2008 to 2011 was characterized by the geometrical parameters related to pedestrian safety and compared to representative car models before 2003. The influence of geometrical design change on the resultant risk of injury to pedestrian lower extremity—that is, knee ligament rupture and long bone fracture—was estimated by a previously developed assessment tool assuming identical structural stiffness. Based on response surface generated from simulation results of a human body model (HBM), the tool provided kinematic and kinetic responses of pedestrian lower extremity resulted from a given car's front-end design.Results: Newer passenger cars exhibited a “flatter” front-end design. The median value of the sedan models provided 87.5 mm less bottom depth, and the SUV models exhibited 94.7 mm less bottom depth. In the lateral impact configuration similar to that in the regulatory test methods, these geometrical changes tend to reduce the injury risk of human knee ligament rupture by 36.6 and 39.6% based on computational approximation. The geometrical changes did not significantly influence the long bone fracture risk.Conclusions: The present study reviewed the geometrical changes in car front-ends along with regulatory concerns regarding pedestrian safety. A preliminary quantitative benefit of the lower extremity injury reduction was estimated based on these geometrical features. Further investigation is recommended on the structural changes and inclusion of more accident scenarios.

Development of Economical Vehicle Model for Pedestrian-Friendly Front-End Profile Study

An economical and deformable, hybrid model is developed for studying the effect of vehicle geometry on pedestrian fall kinematics and associated head injury. A simplified structure consisting of finite element surfaces and a Multi-body windshield is built using a series of iterative and no-iterative steps. The primary focus is not the stiffness characteristics of the structure but rather the fall pattern and kinematics data of the pedestrian due solely to the vehicle front-end shape.Comprehensive validation is carried out wherbey the fidelity of the model is reviewed for pedestrian crash kinematics and injury criteria as well as piecewise vehicle parts impact tests. The model is shown to hold up acceptably well against benchmarked values especially for the former, whereby very close head injury criteria values are obtained at identical impact locations. The model's notable features are its economical computational processing time and eases of modification.

Crash Kinematics and Injury Criteria Validation for a Deformable Hybrid Vehicle Model

Pedestrians are vulnerable road users who are at high risks in a road traffic collision with motor vehicles. A large number are getting killed in traffic accidents each year, the majority of them being children and senior citizens. During impact with an automobile, pedestrians suffer multiple impacts with the bumper, hood and windscreen. Fatality is seen mostly due to the head injuries obtained by the pedestrians. Thus this paper aims to introduce the development and validation of a simplified hybrid vehicle front end profile for the mitigation of head injury. The vehicle model is represented by a multi body windscreen and finite element cowl, hood and bumper. A two step validation procedure is performed, firstly the crash kinematics validation to determine the overall kinematics and fall pattern of the pedestrian during impact. Secondly, the hybrid vehicle model is tested against the pedestrian injury criteria values for pertinent body parts namely the neck, sternum, lumbar, femur and tibia. The hybrid vehicle model is made to impact an adult human dummy model obtained from TNO (TASS Netherlands). The injury criterias are reprensented through the Head Injury Criteria (HIC), neck compression force, sternum and tibia accelerations and lumbar and femur bending moments. The simulation results were compared to the experimental values and a good correlation was achieved.

The Head Injury Mitigation of an Adult and Child Pedestrian in a Frontal Vehicle Impact Using Response Surface Methodology

This work aims at achieving an optimized vehicle front-end profile for improved protection for both adult and child pedestrian groups. A seven parameter simplified vehicle front end model is used in which the Central Composite Design(CCD) is utilized to generate a Plan of Experiments for the adult and child pedestrian cases each. Head Injury Criteria (HIC) results from the simulations are tabulated as the response function f(y). The Response Surface method is used to obtain mathematical models for all cases for which optimization is carried out. A close correlation is obtained between the predicted response and the response observed via simulation for the optimized models. The optimized vehicle front-end profile for the adult pedestrian group is shown to be different than that of the optimized profile for the child pedestrian. Moreover, the study shows that both optimized profiles are not mutually applicable for safety. A simple weighted biasing method is used to obtain responses that minimize the response for both adult as well as child pedestrian groups mutually within a single profile. The final optimized model is shown to achieve a safe vehicle front-end profile which equally caters for both adult and child pedestrians.

Optimisation of vehicle front-end geometry for adult and pediatric pedestrian protection

This study proposes a method of achieving an optimised vehicle front-end profile for improved protection for both adult and child pedestrian groups, which at the same time is able to avoid designs that may cause Run-over scenarios. A hybrid model of a seven-parameter vehicle front-end geometry and a pedestrian dummy is used. Latin Hypercube sampling is utilised to generate a Plan of Experiments for the adult and child pedestrian cases. Head injury criteria results from the simulations that are tabulated as the response functions. The radial basis function method is used to obtain mathematical models for the response functions. Optimised front-end geometries are obtained using the Genetic Algorithm method. The optimised vehicle front-end profile for the adult pedestrian is shown to be different from that of the optimised profile for the child pedestrian, and optimised profiles are shown to be not mutually applicable for safety. Furthermore, Run-over scenario is observed in child pedestrian optimised profiles, where its occurrence invalidates the optimisation. A simple weighting method is used to optimise the geometry for both adult and child pedestrian groups. The Run-over occurrences are mapped using Logistic Regression and is subsequently used as a constraint for optimisation. The final optimised model is shown to achieve a safe vehicle front-end profile which equally caters for both adult and child pedestrians while simultaneously avoiding Run-over scenarios.

Validation of pedestrian impactor testing upon hybrid vehicle front end profile

A large number of pedestrians are killed in traffic accidents each year and majority of these fatalities are caused by head injuries and leading to permanent damage. This paper presents the development of a hybrid vehicle front end profile and its validation against head and leg impactors. The vehicle model is represented by a simple vehicle hybrid front end profile consisting of multi body and finite element segments. Four piecewise vehicle parts validation is performed namely the windshield, cowl, hood and bumper. An adult headform obtained from TNO is used to impact the windshield, cowl and hood using the given conditions to study the head injury. Similarly, the hybrid vehicle profile is made to impact the TNO legform to assess the lower limb injuries. The injury criteria are represented in their various forms and the simulation results were compared with the experimental values. A good correlation was achieved.

Different Factors Influencing Post-crash Pedestrian Kinematics

Pedestrian crashes are the most frequent cause of traffic-related fatalities worldwide. The high number of pedestrian accidents justifies more active research work on passive and active safety technology intended to mitigate pedestrian injuries. Post-impact pedestrian kinematics is complex and depends on various factors such as impact speed, height of the pedestrian, front-end profile of the striking vehicle and pedestrian posture, among others. The aim of this study is to investigate the main factors that determine post-crash pedestrian kinematics. The injury mechanism is also discussed. A detailed study of NASS-PCDS (National Automotive Sampling System - Pedestrian Crash Data Study, US, 1994-1998), showed that the vehicle-pedestrian interaction in frontal crashes can be categorized into four types: Thrown forward, Wrapped position, Slid to windshield and Passed over vehicle. A Principal Component Analysis (PCA) was performed and 11 independent factors were identified for study from a set of 26 variables, as defined in NASS-PCDS. Pedestrian-vehicle size ratio and the impact speed are the two most influential factors that determine post crash pedestrian kinematics. However, the standing posture of a taller pedestrian can also cause rotational movement around the local Z axis, leading to a face-up/down mode of head-face impact before falling on the hood. The findings from the NASS-PCDS study were also confirmed and verified with the help of numerical simulations performed using two modified JAMA human FE models. An adult model (male, 175cm and 72kg) and a properly scaled child model (6 years old, 120cm and 21kg) were effectively utilized to investigate the post-crash kinematics in different conditions. Language: en

The influence of the vehicle's front-end profile upon adult pedestrian kinematics and dynamics, multibody approach

The research aims to simulate and compare with experimental data road traffic accidents involving adult pedestrians. The analysis focuses on the contact phase between the pedestrian and the vehicle's front end, using a multibody model. Taking into account the wide range of vehicles involved in such events as mentioned in the analyses from work of Depriester and Masson, the researchers aim to establish a correlation between the vehicle's front end and the pedestrian's kinematics and dynamics. By modifying certain frontal geometry parameters, various vehicle profiles were obtained in accordance with the classification from the Dettinger's study. The impact velocity and motor vehicle frontal structures, including geometry and rigidity, have proved to be important factors that produce trauma. In this paper, the vehicle's bumper assembly parameters were modified; and experimental researches and simulations were completed to determine the influence of the front-end vehicle design on the adult pedestrian kinematics and head dynamics.

Improved synthetic aperture focusing technique by Hilbert-Huang transform for imaging defects inside a concrete structure

A useful nondestructive testing tool for civil engineering should immediately reveal defects inside concrete structures at the construction sites. To date, there are few effective methods to image defects inside concrete structures. In this paper, a new nondestructive testing method using elastic waves for imaging possible defects inside concrete is developed. This method integrates the point-source/point receiver scheme with the synthetic aperture focusing technique (SAFT) to increase functioning depth and enhance received signals. To improve image quality, received signals are processed by Hilbert-Huang transform (HHT) to get time-frequency curves for the SAFT process. Compared with conventional SAFT method processing with time-amplitude signals, this new method is capable of providing a better image of defects not only in the numerical simulation but also in the experimental result. The image can reveal the number of defects and their locations and front-end profiles. The results shown in this paper indicate that this new elastic-wave-based method exhibits high capability in imaging the defects of in situ concrete structures.

Impact of Concentration-Dependence of Diffusion Coefficient on VAPEX Drainage Rates

Abstract The VAPEX analytical model is extended to cover situations when diffusion coefficients are dependent on concentration due to the extreme viscosity reduction with solvent dissolution into bitumen. The new analytical model covers such situations along with the cases in which the diffusion coefficient and viscosity relate to each other under the Stokes-Einstein law. In the process, a new concept of the 'average flow fraction of bitumen' in the flowing mixtures is introduced. The modelled result on overall functionality of the drainage rate of bitumen has confirmed the square-root relationships to most of the key reservoir parameters as the previous theories indicate. However, its dependence to the inverse of kinematic viscosity at the interface is closer to linear rather than square-root correlation with the concentration-dependent diffusion coefficient. The theoretical relationships are confirmed by the correlations of the unified bitumen rates to kinematic viscosity at the interface using the existing VAPEX and SAGD experimental data in the literature. This finding indicates that VAPEX process in heavy oils with lower native viscosity can be more effective than originally recognized. Introduction Dunn et al.(1) developed the theoretical model of the gravity drainage process for bitumen recovery known as VAPEX based on the model of the steam-assisted gravity drainage (SAGD) process by Butler et al.(2) This model assumed that the diffusion coefficients of solvent-bitumen systems are constant similar to the case of thermal diffusivity. Thus, the steady-state profiles of solvent concentration ahead of the solvent-bitumen interface is the smooth exponential decay towards an infinite distance. In reality, the diffusion coefficients of both solvent and bitumen are strongly dependent upon compositions due to the extreme viscosity contrasts between the solutes and solvents. As a result, the observed concentration profiles in diffusion experiments exhibit the abrupt front-end profiles(3). The theoretical endeavour here is to understand the impact of the non-exponential concentration profiles on the VAPEX drainage and bitumen rates. Governing Mechanisms The most fundamental mechanism of the process is the gravity drainage caused by the density difference between the liquid-bitumen phase and the injected vapour phase. The drainage flow of the bitumen phase occurs only from viscosity reduction due to the impact of the injected solvent (or heat in the case of SAGD) of the otherwise semi-solid bitumen. Therefore, how the injected solvent penetrates into the bitumen phase in the reservoir is of primary importance to the process. According to Fick's law, a material balance across a differential distance, dx, in this situation can be expressed as a continuity equation for the change of concentration (volume fraction is chosen), C, with time, t, by using the diffusion coefficient, D: Equations (available in full paper)

A new elastic-wave-based imaging method for scanning the defects inside the structure

In this paper, a new nondestructive testing method using elastic waves for imaging possible voids or defects in concrete structures is proposed. This method integrates the point-source/point receiver scheme with the synthetic aperture focusing technique (SAFT) process to achieve the effect like scanning with a phase array system. This method also is equipped with large functioning depth because of the high-energy feature that elastic waves usually possess over traditional ultrasound. Both numerical simulations and experimental tests were carried out to explore the capabilities of this method in revealing single or multiple defects implied in a matrix material. The results from numerical simulations indicate that this method can clearly reveal the number of the voids or defects, their locations, and front-end profiles. The influence of the accuracy of the wave velocity determination on the resultant image also was evaluated in this study. Furthermore, the effects of the types of the responses to be recorded and the wavelength of the introduced waves also were evaluated so that very good resultant images may be obtained. Both the results from the numerical simulations and the experimental tests indicate that this elastic-wave-based method exhibits high potential in inspecting the defects of in-situ concrete structures by imaging.