Mark O. Neal

A case study of FEA-based crash sensing system calibration

A case study of using non-linear finite element analyses to aid in calibrating an airbag crash sensing system is presented. Details that are crucial for using a single vehicle model to simulate multiple testing conditions were identified and incorporated in a chosen vehicle model. The vehicle model was then used to simulate a set of no-deployment and all-deployment calibration events. The simulated results were compared with test data to assess the capability of the existing non-linear finite element analysis in aiding sensing system calibration.

Front Structure Design Procedure for Optimal Pedestrian Leg Impact Performance

This paper describes a procedure to optimize the front structure of a vehicle for improved performance in the leg impact portion of pedestrian safety regulations proposed by the European Enhanced Vehicle-Safety Committee (EEVC). The first step in this procedure was to perform a simulation of the EEVC leg impact test with detailed finite element models of the EEVC leg impactor and the baseline design of a vehicle front structure. Next, a simplified, parametric finite element model of the vehicle front structure was used with the leg impactor model to simulate the leg impact test, and the results were correlated to the detailed finite element model and the test results. The leg impact simulation with the parametric vehicle model was then incorporated into an optimization procedure developed within the optimization code ISIGHT. In this procedure the parameters that controlled the vehicle geometry and structural stiffness in the simplified model were altered by ISIGHT to improve performance in the leg impact test.Copyright

An automated method to morph finite element whole-body human models with a wide range of stature and body shape for both men and women

Field data analyses have shown that small female, obese, and/or older occupants are at increased risks of death and serious injury in motor-vehicle crashes compared with mid-size young men. The current adult finite element (FE) human models represent occupants in the same three body sizes (large male, mid-size male, and small female) as those for the contemporary adult crash dummies. Further, the time needed to develop an FE human model using the traditional method is measured in months or even years. In the current study, an improved regional mesh morphing method based on landmark-based radial basis function (RBF) interpolation was developed to rapidly morph a mid-size male FE human model into different geometry targets. A total of 100 human models with a wide range of human attributes were generated. A pendulum chest impact condition was applied to each model as an initial assessment of the resulting variability in response. The morphed models demonstrated mesh quality similar to the baseline model. The peak impact forces and chest deflections in the chest pendulum impacts varied substantially with different models, supportive of consideration of population variation in evaluating the occupant injury risks. The method developed in this study will enable future safety design optimizations targeting at various vulnerable populations that cannot be considered with the current models.

Modeling and Simulations of Frontal Impact Crash Sensing Tests

An extensive study of using non-linear finite element analyses to aid in calibrating an airbag crash sensing system using multiple sensors is presented. Details that are crucial for using a single vehicle model to simulate multiple testing conditions were identified and incorporated in a chosen vehicle model. The vehicle model was then used to simulate a set of no-deployment and all-deployment calibration events. The simulation results were compared with test data to identify Finite Element Analysis compatible (FEA-compatible) measures. These measures could be used to develop a new generation of FEA-compatible crash sensing algorithms.Copyright

A response–surface–based tool for vehicle front–end design for pedestrian impact protection using human body model

This study introduces a response–surface–based design tool of vehicle front–end for pedestrian lower limb impact protection performance. Using a simplified parametric vehicle front–end model, a pedestrian human body model (HBM) and impact simulations, a design of experiment (DOE) study is conducted, and based on the results, response surfaces for lower limb injury predictions have been generated. The Latin Hypercube sampling scheme is used to create the models of the front structure of a variety of vehicles, and reasonable geometry and stiffness variables are included. The response surfaces have been implemented in a graphical user interface (GUI) to provide simple and intuitive feedback on human lower limb injury predictions as the vehicle front–end design changes.

Response Surface Generation for Kinematics and Injury Prediction in Pedestrian Impact Simulations

This study concerns the generation of response surfaces for kinematics and injury prediction in pedestrian impact simulations using human body model. A 1000-case DOE (Design of Experiments) study with a Latin Hypercube sampling scheme is conducted using a finite element pedestrian human body model and a simplified parametric vehicle front-end model. The Kriging method is taken as the approach to construct global approximations to system behavior based on results calculated at various points in the design space. Using the response surface models, human lower limb kinematics and injuries, including impact posture, lateral bending angle, ligament elongation and bone fractures, can be quickly assessed when either the structural dimensions or the structural behavior of the vehicle front-end design change. This will aid in vehicle front-end design to enhance protection of pedestrian lower limbs. Language: en

Development of a Parametric Vehicle Front Structure Model for Pedestrian Impact Simulations

In this study, a simplified, parametric vehicle front structure was proposed to represent the real vehicle when impacted with full-scale finite element pedestrian human body model (HBM). To capture the real impact responses of human lower limbs, the real vehicle energy-absorbing structures were modeled using distributed beam elements and deformable shell elements to replicate the contact characteristics between vehicle and HBM. An investigation of vehicle front-end profile characteristics in worldwide popular sedan models was conducted to determine the ranges of geometry variables. A local stiffness measurement approach is also proposed. The simplified model is further validated using a detailed sedan model, and the impact responses of HBM in the two simulations correlate quite well with each other. Therefore it can be further used in the DOE study or optimization work in the vehicle front structure design for pedestrian lower limb impact protection.

Does unbelted safety requirement affect protection for belted occupants

ABSTRACT Objective: Federal regulations in the United States require vehicles to meet occupant performance requirements with unbelted test dummies. Removing the test requirements with unbelted occupants might encourage the deployment of seat belt interlocks and allow restraint optimization to focus on belted occupants. The objective of this study is to compare the performance of restraint systems optimized for belted-only occupants with those optimized for both belted and unbelted occupants using computer simulations and field crash data analyses. Methods: In this study, 2 validated finite element (FE) vehicle/occupant models (a midsize sedan and a midsize SUV) were selected. Restraint design optimizations under standardized crash conditions (U.S.-NCAP and FMVSS 208) with and without unbelted requirements were conducted using Hybrid III (HIII) small female and midsize male anthropomorphic test devices (ATDs) in both vehicles on both driver and right front passenger positions. A total of 10 to 12 design parameters were varied in each optimization using a combination of response surface method (RSM) and genetic algorithm. To evaluate the field performance of restraints optimized with and without unbelted requirements, 55 frontal crash conditions covering a greater variety of crash types than those in the standardized crashes were selected. A total of 1,760 FE simulations were conducted for the field performance evaluation. Frontal crashes in the NASS-CDS database from 2002 to 2012 were used to develop injury risk curves and to provide the baseline performance of current restraint system and estimate the injury risk change by removing the unbelted requirement. Results: Unbelted requirements do not affect the optimal seat belt and airbag design parameters in 3 out of 4 vehicle/occupant position conditions, except for the SUV passenger side. Overall, compared to the optimal designs with unbelted requirements, optimal designs without unbelted requirements generated the same or lower total injury risks for belted occupants depending on statistical methods used for the analysis, but they could also increase the total injury risks for unbelted occupants. Conclusions: This study demonstrated potential for reducing injury risks to belted occupants if the unbelted requirements are eliminated. Further investigations are necessary to confirm these findings.