FlexPLI vs. EEVC LFI Correlation Action List Item 1. j) Evaluate and decide on performance / injury criteria and threshold values 5 th IG GTR9-PH2 Meeting 6-7/December/212 Japan Automobile Standards Internationalization Center (JASIC) 1
IWG Questions from NHTSA Reference : National Highway Traffic Safety Administration (NHTSA), Overview of NHTSA Pedestrian Activities, 4 th IG GTR9-PH2 Meeting Document, GTR9-4-19 (212) 2
Leg Fracture Evaluation EEVC LFI FlexPLI Injury Criterion Injury Criteria Femur-3 Femur-2 Femur-1 217 mm 137 mm 297 mm Upper Tibia Acceleration Knee center 64 mm Upper end of tibia No instrumentation Tibia-1 Tibia-2 Tibia-3 Tibia-4 134 mm 214 mm 294 mm 374 mm : Bending Moment EEVC LFI measures upper tibia acceleration at one location FlexPLI measures tibia bending moment at four locations 3
Leg Fracture Evaluation Mizuno et al. (212) EEVC LFI Upper Tibia Acceleration Equation of Motion of tibia m x 2 2 F b F s T F b T 2 x a A.66 m a A x x 2.66 ( L L 2 2.66) 2 F s L x 2 a A x 2 Fb F m 2 s Tibia acceleration Bumper force Spoiler force Predominant factor for EEVC LFI upper tibia acceleration Applied force magnitude Reference : Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #212-1-27 (212) 4
Leg Fracture Evaluation Mizuno et al. (212) FlexPLI Tibia Bending Moment F b R 1 M(z b ) Max. tibia bending moment M F ( L z ) F ( L z b b s s ( zs ) zs L ) L zb z s F s M M(z s ) M M F z F z b b s s ( zb) L zb L max max{ M( z s ), M( z b )} R 2 Bending moment Bumper and spoiler force Point of force application Predominant factor for FlexPLI tibia bending moment Applied force magnitude AND point of force application Reference : Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #212-1-27 (212) 5
Leg Fracture Evaluation Mizuno et al. (212) FE Validation of Predominant Factors for EEVC LFI Upper Tibia Acceleration Presumed from Rigid body model Tibia acc. Bumper force Spoiler force F b F s Tibia acceleration (G) 25 2 15 1 5 TRL legform FE Model 5 1 15 2 F b + F s (kn) Reference : Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #212-1-27 (212) 6
Leg Fracture Evaluation Mizuno et al. (212) FE Validation of Predominant Factors for FlexPLI Tibia Bending Moment Presumed from Rigid body model Bumper and spoiler force Bend moment Point of force application F b F s R 1 R 2 Bending moment diagram M(z b ) M(z s ) Flex-PLI FE model max{m(z s ), M(z b )} (knm) Reference : Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #212-1-27 (212) Tibia bend moment (knm).4.3.2.1..6.8 1. 1.2 7
Leg Fracture Evaluation Takahashi et al. (212) Baseline Model 275 mm 65 mm BP 45 mm SP 3 mm 25 mm BLE BP/SP Stiffness SP Location 15 BP 15 SP Force (kn) 1 5 Base Stiff 4 8 12 Deflection (mm) Force (kn) 1 5 4 8 12 Deflection (mm) -2 mm mm 3 mm Reference : Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (212) Base Stiff 8
Leg Fracture Evaluation Takahashi et al. (212) EEVC Legform Model Stiffness of Tibia Case Stiffness Steel Material parameters of steel Bone Flexural rigidity = 555.6 Nm 2 Case Simulation Matrix Stiffness SP Stiffness Location Case BP SP (L2 in mm) Tibia BP SP Tibia SP Location (L2 in mm) ^ Base Base Bone 3 V1-S Base Base Steel 3 V2-B Stiff Base Bone 3 V2-S Stiff Base Steel 3 V3-B Base Stiff Bone 3 V3-S Base Stiff Steel 3 V4-B Base Stiff Bone V4-S Base Stiff Steel V5-B Base Stiff Bone -2 V5-S Base Stiff Steel -2 Reference : Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (212) 9
2.5 Leg Fracture Evaluation Takahashi et al. (212) Effect of BP/SP Stiffness Tibia Bending Moment @ BP Height 2.5 Tibia Acceleration @ BP Height Bone Steel Normalized Measure Normalized Measure 2. 1.5 1..5. 2.5 2. 1.5 1..5. V1 V2 V3 Normalized Measure 2. 1.5 1..5. V1 V2 V3 Baseline Stiff BP Stiff SP Baseline Stiff BP Stiff SP Tibia Bending Moment @ BP Height V3 V4 V5 Effect of SP Location Normalized Measure 2.5 2. 1.5 1..5. Tibia Acceleration @ BP Height V3 V4 V5 Bone Steel SP Forward SP Forward 1
GTR9-1-5r1 18 Leg Fracture Evaluation CAE Correlation Study Correlation of Tibia Injury Measures TRL Legform 5 Flex-PLI TEG-96 (Flex-PLI) TRL Legform Model Upper Tibia Accel. (m/s 2 ) 15 12 9 6 3 y =.482x + 131 R =.14 Flex-PLI Model Tibia Bending Moment (Nm) 4 3 2 1 y = 1.259x - 72.798 R =.9 1 2 3 4 5 Human Model Tibia Bending Moment (Nm) Konosu et al. (29) 1 2 3 4 5 Human Model Tibia Bending Moment (Nm) No correlation between TRL legform upper tibia acceleration and human tibia bending moment Good correlation between Flex-PLI and human tibia bending moment Reference : Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1 st IG GTR9-PH2 Meeting Document, GTR9-1-5r1 (211) 11
Leg Fracture Evaluation EEVC LFI upper tibia acceleration is solely determined by the magnitude of applied forces FlexPLI tibia bending moment depends on both the magnitude of applied forces and loading locations Excessive stiffness of the tibia of EEVC LFI results in much higher sensitivity to the change in the applied force magnitude compared to human bone stiffness EEVC LFI upper tibia acceleration shows no correlation with human tibia bending moment due to the use of acceleration as a measure and an excessive stiffness of the tibia Direct correlation of EEVC LFI upper tibia acceleration and FlexPLI tibia bending moment makes no sense 12
EEVC LFI Knee Injury Evaluation FlexPLI Individual Measurement Bending Angle Shear Disp. LCL PCL Shearing force + ACL MCL Bending force Injury Criteria Femur-3 Femur-2 Femur-1 Knee-ACL EL Knee-PCL EL Knee-MCL EL Tibia-1 Tibia-2 Tibia-3 Tibia-4 Combination EEVC LFI individually evaluates bending and shear FlexPLI measures elongation of ligaments sensitive to both bending and shear EL: Elongation 13
Knee Injury Evaluation Knee Anatomy (Anterior-oblique view) Valgus Bending LCL ACL MCL ACL Shear Otte et al. (25) PCL MCL: Medial Collateral Ligament ACL: Anterior Cruciate Ligament PCL: Posterior Cruciate Ligament LCL: Lateral Collateral Ligament MCL PCL (Posterior View) LCL Center of Rotation Lateral Impact ACL/PCL elongations are sensitive to both bending and shear MCL elongation is not sensitive to shear due to its length and distance from center of knee rotation in valgus bending 14
GTR9-1-5r1 Knee Injury Evaluation TRL Legform Model Knee Bending Angle (deg) 4 3 2 1 TRL Legform y =.9821x - 1.628 R =.75 Correlation of MCL Injury Measures 1 2 3 4 Human Model MCL Elongation (mm) Flex-PLI Model MCL Elongation (mm) 4 3 2 1 Flex-PLI TEG-96 (Flex-PLI) y =.5584x + 1.335 R =.55 1 2 3 4 Human Model MCL Elongation (mm) Both TRL legform knee bending angle and Flex-PLI MCL elongation show good correlation with human MCL elongation Reference : Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1 st IG GTR9-PH2 Meeting Document, GTR9-1-5r1 (211) 15
GTR9-1-5r1 Knee Injury Evaluation TRL Legform Model Knee Shear Displacement (mm) 12 1 8 6 4 2 TRL Legform Correlation of ACL Injury Measures y = -.2699x + 3.8541 R =.13 2 4 6 Human Model ACL Elongation (mm) Flex-PLI Model ACL Elongation (mm) 12 1 8 6 4 2 Flex-PLI y = 1.3654x + 3.1228 R =.68 2 4 6 Human Model ACL Elongation (mm) No correlation between TRL legform knee shear displacement and human ACL elongation Good correlation between Flex-PLI and human ACL elongation Reference : Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1 st IG GTR9-PH2 Meeting Document, GTR9-1-5r1 (211) 16
Knee Injury Evaluation EEVC LFI individually evaluates knee bending and shear FlexPLI directly evaluates elongations of knee ligaments Human MCL elongation is insensitive to knee shear due to its length and the distance from the center of knee rotation Both EEVC LFI and FlexPLI correlate with human MCL elongation EEVC LFI knee shear does not correlate with human ACL elongation due to sensitivity of human ACL elongation to knee bending angle Correlation analysis between EEVC LFI knee shear displacement and FlexPLI ACL elongation does not make sense, while correlation analysis between EEVC LFI knee bending angle and FlexPLI MCL elongation is valid 17
GTR9-4-18 Correlation Study - MCL BASt Study Reference : BASt, FlexPLI vs. EEVC WG 17 PLI Benefit Estimation, 4 th IG GTR9-PH2 Meeting Document, GTR9-4-18 (212) 18
35 3 Correlation Study - MCL JAMA Study Correlation of Knee Bending Measures Flex-GTR Test Flex-GTR CAE TRL-LFI Knee Bending Angle (deg) 25 2 15 1 5 Threshold 19 deg Threshold 22 mm 5 1 15 2 25 3 35 FlexPLI MCL Elongation (mm) R=.675 18 Simp. Model Com-A Com-B Com-C (CAE) Com-C Com-E Com-E (CAE) Com-F Com-F (CAE) Com-G Com-H Com-H (CAE) Linear Regression FlexPLI tends to provide more conservative results than EEVC LFI 19
References National Highway Traffic Safety Administration (NHTSA), Overview of NHTSA Pedestrian Activities, 4th IG GTR9-PH2 Meeting Document, GTR9-4-19 (212) Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #212-1-27 (212) Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (212) Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1st IG GTR9-PH2 Meeting Document, GTR9-1-5r1 (211) BASt, FlexPLI vs. EEVC WG 17 PLI Benefit Estimation, 4th IG GTR9-PH2 Meeting Document, GTR9-4-18 (212) 2
Thank you for your attention 21