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Comparison of TRL Legform Impactor and Flex Pedestrian Legform Impactor

This document discusses the differences in structure and injury criteria between the TRL legform impactor and the Flex pedestrian legform impactor. It also highlights the need for high biofidelity and good relationship with human injury criteria when using an impactor for regulation purposes.

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Comparison of TRL Legform Impactor and Flex Pedestrian Legform Impactor

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  1. 16 May 2011 Japan Informal documentGRSP-49-24 (49th GRSP, 16-20 May 2011, agenda items 4(a)) Difference of TRL legform impactor/injury criteria and Flex pedestrian legform impactor/injury criteria

  2. Flexible Pedestrian Legform Impactor TRL Legform Impactor Structure Structure Main unit Main unit • Femur • Flexible like human bone Femur RIGID • Knee • Ligaments like human knee Knee Steel Plate • Tibia • Flexible like human bone Tibia RIGID MCL LCL Knee Ligaments (Steel plate) ACL PCL MCL: Medial Collateral Ligament ACL: Anterior Cruciate Ligament PCL: Posterior Cruciate Ligament LCL: Lateral Collateral Ligament Difference of Structure

  3. Flexible Pedestrian Legform Impactor TRL Legform Impactor Instrumentation Instrumentation Injury Criteria Injury Criteria Femur-3 BM 297 mm Femur-2 BM 217 mm Femur-3 BM 137 mm Knee Shearing Displacement Knee-ACL Elongation Upper end of tibia Knee Bending Angle Knee-PCL Elongation Knee center Upper Tibia Acceleration Knee-LCL Elongation Knee-MCL Elongation 64 mm Real-world Accident Analysis Otte et al, 2007 Tibia-1 BM 134 mm Tibia-2 BM 214 mm No instrumentation Tibia-3 BM 294 mm Tibia-4 BM 374 mm BM: Bending Moment Difference of Instrumentation/Injury Criteria

  4. Basically, TRL acceleration and Flex bending moment has low relationship. • TRL acceleration tends to show higher value especially when bumper bottoming out happened, however it is because of lack of biofidelity of long bone and using acceleration as for injury criterion. • Beside, Flex has bending stopper cable especially to avoid high bending, so its influence also shall be considered. Difference of Tibia Injury Assessment Instrumentation Instrumentation Injury Assessment Items Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee Shearing Displacement Knee-ACL Elongation Knee Bending Angle Knee-PCL Elongation Upper Tibia Acceleration Knee-MCL Elongation Tibia-1 BM Tibia-2 BM No instrumentation Tibia-3 BM Tibia-4 BM BM: Bending Moment

  5. Instrumentation Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee-ACL Elongation Knee-PCL Elongation Knee-MCL Elongation Tibia-1 BM Tibia-2 BM Tibia-3 BM Tibia-4 BM BM: Bending Moment Difference of Tibia Injury Assessment • TRL tends to show higher value when bottoming out happened. • However, except those cases, not always either impactor is higher than other. Instrumentation Injury Assessment Items Knee Shearing Displacement Knee Bending Angle Upper Tibia Acceleration No instrumentation

  6. Difference of Knee MCL Injury Assessment Instrumentation Instrumentation • In this research, Flex MCL elongation is slightly higher values than TRL bending angle. • However, it has a chance that the relationship can be changed by car stiffness and/or geometry. Injury Assessment Items Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee Shearing Displacement Knee-ACL Elongation Knee Bending Angle Knee-PCL Elongation Upper Tibia Acceleration Knee-MCL Elongation Tibia-1 BM Tibia-2 BM No instrumentation Tibia-3 BM Tibia-4 BM BM: Bending Moment

  7. Instrumentation Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee-ACL Elongation Knee-PCL Elongation Knee-MCL Elongation Tibia-1 BM Tibia-2 BM Tibia-3 BM Tibia-4 BM BM: Bending Moment Difference of Knee MCL Injury Assessment Instrumentation • Not always either impactor is higher than other. Injury Assessment Items Knee Shearing Displacement Knee Bending Angle Upper Tibia Acceleration No instrumentation

  8. Difference of Knee ACL Injury Assessment Instrumentation • Basically, Flex ACL elongation and TRL shearing displacement has not clear relationship. • It has a chance that the relationship can be changed by car stiffness and/or geometry. Instrumentation Injury Assessment Items Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee Shearing Displacement Knee-ACL Elongation Knee Bending Angle Knee-PCL Elongation Upper Tibia Acceleration Knee-MCL Elongation Tibia-1 BM Tibia-2 BM No instrumentation Tibia-3 BM Tibia-4 BM BM: Bending Moment

  9. Difference of Knee ACL Injury Assessment Instrumentation Instrumentation • Not always either impactor is higher than other. Injury Assessment Items Injury Assessment Items Femur-3 BM Femur-2 BM Femur-3 BM Knee Shearing Displacement Knee-ACL Elongation Knee Bending Angle Knee-PCL Elongation Upper Tibia Acceleration Knee-MCL Elongation Tibia-1 BM Tibia-2 BM No instrumentation Tibia-3 BM Tibia-4 BM BM: Bending Moment

  10. Comments from Japan • Basically, TRL legform impactor and Flex pedestrian legform impactor have totally different structure and injury criteria. • Therefore, direct comparison tends to lead not clear relationship. • Basically, to make a regulation using impactor, following items are needed. • Impactor shall have high biofidelity. • Injury criteriashall havegood relationship with human one. • Otherwise, some misunderstandings and/or misleading results will be obtained.

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