The protection of second row occupants in rear crashes is an important issue.  Intrusion has been shown to be a significant factor in the injury mechanism of second row children (Viano, Parenteau 2008, Parenteau, Viano 2020, Parenteau et al. 2020).  In this study, a new method was developed to assess the effect of dynamic occupant compartment structural intrusion displacement, velocity, and acceleration on rear occupant responses as a function of time.

A mathematical method was developed using striking and struck vehicle acceleration, velocity, and displacement data, as well as vehicle dimensions.  The mathematical method was originally developed using FMVSS 301R type test data.  High-speed rear crash tests were used to validate the method. 

The crash test pulse data and videos from FMVSS 301R type tests were analyzed to determine the timing and magnitude of second-row intrusion into the occupant compartment.  High speed rear crash tests involving high-hooded vehicles striking the rear of modern passenger cars were used to validate the method.  The tests used instrumented ATDs (Anthropometric Test Device) seated in the second-row area of the struck vehicles.  The head and biomechanical responses (HIC and acceleration) were recorded and used to assess the validity of the mathematical method.

The comparison between the mathematical method and the test data showed good agreement.  For example, the method correctly showed that the dynamic second-row intrusion was significantly greater than residual/static intrusion/displacement.  The acceleration levels obtained with the mathematical method also showed good correlation with the test data. 

The head and chest biomechanical responses in the crash tests were above the injury assessment reference values (IARVs).  Analysis of the head and chest acceleration time histories indicated that intrusion occurred early and was a significant factor in the occupant responses.  The results from the method further indicated that both the amount and velocity of dynamic intrusion influenced the biomechanical responses of rear occupants. 

The results from the mathematical method also indicated that the rear ATD head and chest accelerations due to the occupant compartment intrusion were significantly greater than the overall vehicles accelerations resulting for the collision forces.  In the validation tests, the ATD head and chest accelerations were significantly greater than the vehicle accelerations, largely due to the localized severity levels present as a result of structural intrusion.

Field accident data highlights the effect of second-row structural intrusion on rear occupant injury outcome and pattern.  Vehicle crash tests are often used to assess occupant responses.  Occupant-vehicle interaction and kinematics are generally obtained from acceleration and video analysis.  The mathematical method developed in this study is a first to assess the dynamic effect of second-row intrusion on rear occupant responses.  This type of information is important to assess the effect of various countermeasures.  Understanding the source of the injury risk is the first step in understanding the potential effectiveness of countermeasures such as increased vehicle stiffness or additional compliance to the rear seat.  As vehicle and second-row seats structures evolve, the importance of occupant to vehicle coupling increases. 


A Mathematical Model to Assess Occupant Compartment Intrusion on Rear Occupant Responses in Rear Crashes

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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