Edwin M. Sieveka

Experiences in reverse-engineering of a finite element automobile crash model

The experiences encountered during the development, modification, and refinement of a finite element model of a four-door sedan are described. A single model is developed that can be successfully used in computational simulations of full frontal, offset frontal, side, and oblique car-to-car impacts. The simulation results are validated with test data of actual vehicles. The validation and computational simulations using the model show it to be computationally stable, reliable, repeatable, and useful as a crash partner for other vehicles.

Lower limb response and injury in frontal crashes

This article examines two observational and two experimental data sets that emphasize lower limb injuries in passenger car crashes. Statistics show that 60% of moderate-to-severe below-knee injuries sustained by front seat occupants in head-on crashes occur with > 3 cm of footwell intrusion. Moreover, crash tests and computer simulations of car-to-car frontal offset collisions show no causal relationship between the magnitude of footwell intrusion and the axial load measured in the dummy leg. This article correlates below-knee injuries with several factors that influence their frequency and severity, such as the vehicle change in velocity, the magnitude of footwell intrusion, the rate and timing of the intrusion and the size of the vehicle. The vehicle change in velocity and the intrusion rate and timing had the greatest influence on the risk of lower limb injury, while the other factors had much less of an effect.

Experiences during development of a dynamic crash response automobile model

A finite element automobile model for use in crash safety studies was developed through reverse engineering. The model was designed for calculating the response of the automobile structure during full frontal, offset frontal, or side impacts. The reverse engineering process involves the digitization of component surfaces as the vehicle is dismantled, the meshing and reassembly of these components into a complete finite element model, and the measurement of stiffness properties for structural materials. Quasi-static component tests and full-vehicle crash tests were used to validate the model, which will become part of a finite element vehicle fleet.

Research Program to Investigate Lower Extremity Injuries

Biomechanical response and injury tolerance of the lower extremities is being investigated at the University of Virginia. This paper presents the experimental and simulation work used to study the injury patterns and mechanisms of the ankle/foot complex. The simulation effort has developed a segmented lower limb and foot model for an occupant simulator program to study the interactions of the foot with intruding toepan and pedal components. The experimental procedures include static tests, pendulum impacts, and full-scale sled tests with the Advanced Anthropomorphic Test Device and human cadavers. In these tests, the response of the lower extremities is characterized with analogous dummy and cadaver instrumentation packages that include strain gauges, electrogoniometers, angular rate sensors, accelerometers, and load cells. An external apparatus is applied to the surrogates lower extremities to simulate the effects of muscle tensing. Sled tests are performed with a toepan device that subjects the lower extremities to rotational, longitudinal, and vertical intrusion pulses typical of offset vehicle crashes. Based upon data from the component and full-scale sled tests, a risk function which correlates observed cadaver injury with dummy responses is developed.

Multi-Body Model of Upper Extremity Interaction with Deploying Airbag

Three-dimensional simulation models of a drivers right upper extremity interacting with a deploying airbag have been set up and run with the Articulated Total Body program. The goal of this study is to examine the significance of various occupant and airbag parameters during deployment, such as grip strength, upper extremity position, shoulder compliance, flap position, flap aggressivity, and deployment speed. Given a range of 250 N to 650 N, the grip strength did not affect the resultant loads. Also, the contact force and torque at the c.g. of the forearm are not sensitive to shoulder joint compliance. The flap aggressivity and the position of the airbag module relative to the upper extremity are most important in affecting the interaction. This study is used to justify cadaveric experiments involving disarticulated upper extremities. (A) For the covering abstract see IRRD 893297.

THREE YEAR OLD CHILD AND SIDE AIRBAG INTERACTION STUDY USING THE CVS/ATB MULTI-BODY SIMULATION PROGRAM

As part of a project to study a prototype side-impact airbag with a focus on child-to-airbag impacts, simulations were performed using the CVS/ATB multibody program to study several child dummy positions to find their probable injury severity level. This allowed a subset of the positions to be chosen for future laboratory testing. A secondary goal was to see how the predicted injury levels compared with the National Highway Traffic Safety Administrations current recommendations for child dummy protection reference values. The project also examined how the lack of lateral flexibility in the dummy would affect the testing of head, door, and airbag interactions for the case of an intruding door. Lastly, the effect of bag contact location, up and down the torso, was studied with regard to secondary loading of the neck and head. A nominal 3-year-old child size was used in the study, with two sets of neck and spinal joint characteristics to reflect humanlike and dummylike kinematic properties.

System identification of dynamic structures

Abstract A method is developed for determining the mass and the nonlinear stiffness and damping characteristics of structures subjected to crash-loading environments. The system identification is accomplished using adaptive time domain, constrained minimization techniques. The underlying assumptions are that the stiffness and damping characteristics of a structural element are separable and that characteristics can be idealized with piecewise linear segments. Incremental equations of motion, including error terms, are formulated and solved for nonnegative parameters using linear and quadratic programming algorithms. The parameters are estimated using three formulations: minimizing the sum of the absolute errors ( L 1 error norm), minimizing the sum of the squared errors ( L 2 error norm), and minimizing the maxium absolute error ( L ∞ error norm). Adaptivity is incorporated into the formulation for identifying discontinuities in the structural characteristics and for improving the parameter estimation. Finally, the methodology allows for the specification of upper and lower bounds for the damping forces. The motivation for this research is toward identifying the structural characteristics and developing lumped mass models of automobiles from acceleration and barrier load data collected during frontal barrier crash testing.

Reproducing the Structural Intrusion of Frontal Offset Crashes in the Laboratory Sled Test Environment

The response and risk of injury for occupants in frontal crashes are more severe when structural deformation occurs in the vehicle interior. The aim of this paper is to reproduce this impact environment in the laboratory. A sled system capable of producing structural intrusion in the footwell region was developed. The system couples the hydraulic decelerator of the sled to actuator pistons attached to the toepan and floorpan structure of the buck. Characterization of the footwell intrusion event is based on developing a toepan pulse analogous to the acceleration pulse used to characterize sled and vehicle decelerations. Preliminary sled tests with the system indicate that it is capable of simulating a complex sequence of toepan/floorpan translations and rotations. (A) For the covering abstract of the conference see IRRD 875833.

ANALYSIS OF HUMERUS ORIENTATION IN UPPER EXTREMITY EXPERIMENTS WITH A DEPLOYING AIRBAG

Computer simulations and experimental tests were used to examine the effect of humerus orientation on upper extremity interaction with a deploying airbag. The Articulated Total Body (ATB) program was used to simulate testing of three upper extremity positions ranging from 0-degree to 90-degree abduction. Results indicated little difference in peak forearm bending moment for the three positions, a finding which was confirmed with experimental tests of airbag deployment into a Society of Automotive Engineers (SAE) 5th% female dummy arm in the 0-degree and 90-degree positions. A comparison of simulation and dummy testing with experiments run using cadavers resulted in the conclusion that forearm position, not humerus orientation, plays a critical role in determining upper extremity injury during airbag deployment. Both 0-degree and 90-degree abduction tests were found to be valid methods for studying arm/airbag interaction while preserving the rest of the cadaver for future testing. (A) For the covering abstract of the conference see IRRD 492347.