Kassim A. Abdullah

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.

Parametric study for head injury criteria response of three-year olds in a child restraint system in oblique and lateral intrusive side impact

A parametric study is undertaken to ascertain the sensitivity of the child restraint system (CRS) design, with respect to oblique side impact at standard velocities in consideration of intrusion. A hybrid model is constructed using a combination of both finite elements and multi-body ellipsoids where a three-year-old Hybrid III child dummy is placed inside a CRS and restrained with a harness system. A prescribed structural motion simulation of a side-impact crash is carried out based on experimental data. Validation is performed and the model is shown to be acceptable for common standard injury responses as well as being greatly economical in terms of computational processing time. A plan of experiments is prepared based on the Latin hypercube sampling for six parameters involving two different crash velocities. The head injury criterion (HIC) is considered as the response in this study. The model is adapted for intrusion and oblique impact. Response surface models are shown to be suitable for the mathematical modelling of the problem and Students t-test is used to assess the parameter sensitivity both qualitatively and quantitatively. Most of the parameters are seen to have greater significance for wider principle direction of force (PDOF) angles above 60°. In general, a gradual decrease in significance is observed for parameters with increasing impact velocity, with the notable exception of the impact angle. The impact angle is shown to most notably affect the HIC especially from PDOF angles 45°–75°, identified as the critical impact angle range. The far side shoulder harness slack parameter is also found to be significant in reducing the HIC.

Lateral Side Impact Crash Simulation of Restrained 3 Year Old Child

Motor vehicle crashes have become the leading cause of death for children in many developed countries and the trend is on the rise in Malaysia. Child anatomy and physiology necessitates a separate restraints system to be implemented during vehicle travel. Although approximately twice as many crashes with a child fatality are frontal compared to lateral, it is shown that side impacts are nearly twice as likely to result in a child fatality as frontal impacts. Due to the complexity and the highly non-linear nature of vehicle crash affecting occupants, much work still remains to be looked into. This is especially so in the study of injury mechanisms towards efforts of improving CRS design as well as vehicle parameters that may offer more effective and robust injury mitigation. The study here presents a methodology which outlines the development and testing of a simulation model where a 3 year old child, restrained in a CRS within a vehicle, is subjected to lateral side impact by a bullet vehicle. A combined environment of both Finite Element as well as Multi-body is used for the model development. A HYBRID III dummy model is used to represent the child while an FE model is used for the CRS model. A hybrid modelling method is utilized for the belt harness system. The model and simulation conditions are set based on the global FMVSS standard. Head injury criterion and Neck injury criterion are primarily considered in the model assessment. Model development as well as validation steps are presented with discussion of the model’s salient features for greater insights in the study of injury mechanisms.

Injury analysis validation of a deformable vehicle front end model

In the event of an impact with an automobile, pedestrians suffer multiple impacts with the bumper, hood and the windscreen. The characteristics of a vehicles front end and structural stiffness have a significant influence on the kinematics and injury risk of the pedestrians body regions, in a vehicle-to-pedestrian collision. In this present study, the injury risk of the pedestrian is investigated in an impact with a deformable vehicle front end model for the purpose of validating the developed model. A simplified vehicle front end model consisting of a multi body windscreen and a finite element cowl, hood and bumper is developed. The MADYMO human pedestrian multi body dummy model is impacted by the vehicle front end model at the speed of 40 km/h. The injuryto the various body segments namely the head, neck, sternum, lumbar, femur and tibia is obtained. The simulation values are compared to the experimental values for verification of the vehicle front end model.

Design optimization of a hybrid electric vehicle powertrain

This paper presents an optimization work on hybrid electric vehicle (HEV) powertrain using Genetic Algorithm (GA) method. It focused on optimization of the parameters of powertrain components including supercapacitors to obtain maximum fuel economy. Vehicle modelling is based on Quasi-Static-Simulation (QSS) backward-facing approach. A combined city (FTP-75)-highway (HWFET) drive cycle is utilized for the design process. Seeking global optimum solution, GA was executed with different initial settings to obtain sets of optimal parameters. Starting from a benchmark HEV, optimization results in a smaller engine (2 l instead of 3 l) and a larger battery (15.66 kWh instead of 2.01 kWh). This leads to a reduction of 38.3% in fuel consumption and 30.5% in equivalent fuel consumption. Optimized parameters are also compared with actual values for HEV in the market.

Neck Moment Characterization of Restrained Child Occupant at Realistic Nontest Standard Higher Impact Speed of 32.2 km/h

The effects of bullet vehicle crash impact angle, child restraint system design, and restraint harness slack at side impact speed of 32.2 km/h (20 mph) on moments sustained at the neck by a three-year-old child are investigated. Mathematical models are built using the response surface method based on simulation results whereby good fitness is achieved. The singular and cross interactive effect of each predictor on the neck moment are analyzed. The number of significant parameters affecting the neck moment is shown to be the largest for wide impact angles and the impact angle parameter is largely revealed to be the most sensitive. An ideal safe range for low neck moment has been established to be within angles 45° and 65°. It is further shown that the nature of all parameters effect on the neck moment is highly dependent on the impact angle range.

Assessment of crashworthiness of the frontal part of a local car model

For an integral body or a body–on–frame vehicle, the vehicles frontal part is the major structural subsystem to absorb the impact energy in a frontal vehicle impact. Ideally, for each serious crash situation, the whole available deformation length must be used and all the impact energy must be absorbed without deforming the passenger compartment. It is also important to manage the intensity during the crash time because the resulting crash pulse has a large influence on the injury level. Crash simulation software is widely used by the automotive industry to evaluate occupant risks and injuries. Therefore, the accuracy of the finite element frame model has significant influence on the quality of vehicle impact predictability. This work aims at building an understanding of structural and design features that can optimise structural integrity in terms of strength, stiffness and crashworthiness of front–part structures. For this purpose, a local car model is selected for analysis so as to study and analyse the crushing behaviour and suggest ways for possible modifications to be made on the structures at the weak zones to enhance crashworthiness of the vehicle.

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.

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 models notable features are its economical computational processing time and eases of modification.

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.