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This paper describes the testing and constitutive model development of polyurethane foams for characterization of their material dynamic properties. These properties are needed not only for understanding their behavior, but also for supplying essential input data to foam models, which help provide design directions through simulations of foam selection for cushioning occupant head impacts against the vehicle door and upper interior. Polyurethane foams of varying densities were tested statically and dynamically under uniaxial compressive impact loading at constant velocities of various rates and different temperatures. The test results were utilized for developing a constitutive model of polyurethane foams by taking the density, strain rate and temperature effects into consideration. Uniaxial constitutive models are developed in two ways.

This paper describes the development of a new component test methodology concept for simulating NHTSA side impact, to evaluate the performance of door subsystems, trim panels and possible safety countermeasures (foam padding, side airbags, etc.). The concept was developed using MADYMO software and the model was validated with a DOT-SID dummy. Moreover, this method is not restricted to NHTSA side impact, but can be also be used for simulating the European procedure, with some modifications. This method uses a combination of HYGE and VIA decelerator to achieve the desired door velocity profile from onset of crash event until door-dummy separation, and also takes into account the various other factors such as the door/B pillar-dummy contact velocity, door compliance, shape of intruding side structure, seat-to-door interaction and initial door-dummy distance.

The viscous criterion (V*C) has been proposed by biomechanics researchers as a generic biomechanical index for potential soft tissue injury. It is defined by the product of the velocity of deformation and the instantaneous compression of torso and abdomen. This criterion requires calculation and differentiation of measured torso/abdomen compression data. Various computational algorithms for calculating viscous criterion are reviewed and evaluated in this paper. These include methods developed by Wayne State University (WSU), NHTSA (DOT) and Ford. An evaluation has been conducted considering the accuracy of these algorithms with both theoretical and experimental data from dummy rib compressions obtained during a crash test. Based on these results, it is found that: V*C results depend on the scheme used in the computation process, the sampling rate and filtering of original raw data. The NHTSA method yields the lowest V*C value.

A new technique for body/frame cars to predict the vehicle collapse, velocity, and deceleration histories in a barrier crash at any speed between 10-30 mph has been developed. This approach requires data interpolation from a minimum of two, and preferably three, barrier tests conducted with no additional instrumentation than that already present in today's standard testing. Potential savings could be derived from using this technique to reduce the number of barrier tests that would otherwise be necessary for checking safety restraint performance throughout the crash speed spectrum contained within the test boundaries. Good correlation with tests was obtained with the 1969 Ford car line. Application of this technique to the 1971 Mercury showed similar favorable results, Applicability of the equations to body/frame configurations other than those tested has not been determined.

This paper describes the development of an automated Door Test Facility for implementing the Door Component Test Methodology for side impact analysis. The automated targeting and loading of the door inner/trim panels with Side Impact Dummy (SID) ribcage, pelvis, and leg rams will greatly improve its test-to-test repeatability and expedite door/trim/armrest development/evaluation for verification with the dynamic side impact test of FMVSS 214 (Occupant Side Impact Protection). This test facility, which is capable of evaluating up to four (4) doors per day, provides a quick evaluation of door systems. The results generated from this test methodology provide accurate input data necessary for a MADYMO Side Impact Simulation Model. The test procedure and simulation results will be discussed.

This paper describes the development of a Dynamic Door Component Test Methodology (DDCTM) for side impact simulation. A feasibility study of the methodology was conducted using a MADYMO computer model by taking parameters such as door pre-crush, door-to-SID (Side Impact Dummy) contact velocity and the deceleration profile into consideration. The prove-out tests of this methodology was carried out on a dynamic sled test facility. The DDCTM has been validated for various carlines. In addition, various existing dynamic component test methods are reviewed. In our approach, a pre-crushed door, mounted on a sled, strikes a stationary SID at a pre-determined velocity. A programmable hydraulic decelerator is used to decelerate the sled to simulate the barrier/door deceleration pulse during door-to-SID contact period. This test procedure provides excellent correlation of the SID responses between the component test and the full-scale vehicle test.

NHTSA is expected to publish a final rule on Interior Head Impact (as an amendment to FMVSS 201) by early 1995. One of the Interior Head Impact Study objectives is to develop a methodology for estimating the minimum head impact space requirements to meet this regulation. The physical parameters affecting the HIC (Head Injury Criterion) are impact velocity, maximum headform stopping distance, peak deceleration, and pulse duration. The equations for estimating the HIC vs. Head Impact Space Requirements are formulated by relating these physical parameters to the Idealized Waveforms of Square Wave, Sine Wave, and Haversine Wave. This methodology has been extended to include the Generic Waveform. Tabulations of Maximum Headform Stopping Distance Requirement vs. Peak Deceleration, Pulse Duration, and HIC for the three Idealized Waveforms at 6.7 m/s (15 mph) impact speed have been generated to provide an estimate of the head impact package space requirement.

This report describes an experimental validation of an ellipsoid-to-foam contact model. A series of static foam tests was conducted using Side Impact Dummy rib cage, pelvis, upper leg, and wooden ellipsoids as impactors to validate a theoretical foam contact model previously developed. Predicted results of contact forces, calculated using the uni-axial stress-strain relationship and contact areas, yield good correlation with the test data. These studies used CFC foams and were conducted prior to switching to water-blown foam material development. The ellipsoid-to-foam contact model is being integrated into a MADYMO side impact model. The MADYMO/foam simulation model can then be used to help evaluate design variable tradeoffs (e.g., door thickness vs. body side structures and foam padding requirement vs. interior package) thereby reducing the current dependency on testing, bolster development time, and cost.

Currently, the three (3) methods for calculating the HIC-value are: 1) direct computation method, 2) utilization of maximization requirement approach developed by Chou and Nyquist, and 3) a partitioning technique. A method which involves the adoption of an optimization approach for HIC calculation is discussed in this study. This optimization technique, which has previously been applied to Boundary Element Method (BEM), employs an improved constrained variable metric method in recursive quadratic programming. This technique was applied to three theoretical and ten experimental acceleration pulses; the results compare extremely well with exact solution and/or other numerical methods. It is concluded that this optimization scheme provides accurate HIC calculations. A study is planned to investigate the feasibility of extending the application of this optimization technique to an integrated trim/foam/sheet metal pillar system for improved interior head impact protection study.

A highly controlled six-vehicle crash test program was conducted to provide an estimate of the test-to-test variability of the NHTSA-proposed passenger car dynamic side impact test procedure. The results of this program showed that the rear seat test dummy response measurements are especially sensitive to various parameters of the test procedure. This paper provides estimates of front and rear seated SID dummy response measurement variability in four-door, 1990 Ford Taurus vehicles. Conclusions and recommendations from this controlled crash test program are made to provide guidance to help reduce the test-to-test variability of the test dummy responses.

This paper provides a methodology for adjustment of off-speed head impact test data to the required 24.14 km/h for interior head impact. The “Normalization Process” utilizes the Generic Waveform Concept for its basic foundation. Predicted results from FE Head Impact Simulation Model were used to validate the Normalization Process. It is recommended that Normalization should be applied to cases where impact velocities are within ±0.8 km/h speed difference. In general, Normalizing down-speed (from 24.94 to 24.14 km/h) is preferred over Normalizing up-speed (23.33 to 24.14 km/h). One must always check for potentially severe “bottom-out” condition by examining the pulse shape for any abrupt peaks in headform deceleration. The Normalization Process should not be applied to “glancing” impacts in which the impact and rebound vectors are not colinear.

This paper provides an overview of the Side impact Research program conducted by Vehicle Methods and Components Department of Ford Motor Company over the past three years. A simple spring-mass computer simulation model is developed for predicting crash behavior of the body side structure of a vehicle impacted on its side by another vehicle. The model was used in determining the degree of structural reinforcement required to effectively reduce body side intrusion of a compact size vehicle. Exellent agreement between the predicted and test results was obtained and the effectiveness of structural reinforcements in reducing occupant cushioning requirement was demonstrated.