Comparison of head and thorax cadaver and Hybrid III responses to a frontal sled deceleration for the validation of a car occupant mathematical model

Transcription

1 Comparison of head and thorax cadaver and Hybrid III responses to a frontal sled deceleration the validation of a car occupant mathematical model Philippe Vezin, Karine Bruyère, François Bermond INRETS-LBMC Biomechanics and Impact Mechanics Laboratory, France

2 PLAN Introduction and context of this study Methods and Instrumentation Results Discussion Conclusion

3 Introduction and context of this study Validation of a car occupant mathematical model? HUMOS MODEL : Whole Human Body Finite Element Model Geometry Acquisition Meshing Constitutive Law Validation Data Acquisition Validation of the Model

4 Introduction and context of this study Validation data and boundary conditions Validation of a Numerical Model : Imposed Constraints Simplified Geometry and Position Simplified Impact Conditions

5 Introduction and context of this study Validation data and boundary conditions Simplified Geometry and Position Geometry imposed Experimental set up

6 Introduction and context of this study Validation data and impact conditions Simplified impact conditions Velocity : km/h Stopping distance 6mm Deceleration close to the R44-3 Regulation H_1 H_1 H_2 H_2 H_3 H_3 H_4 H_4 D_1 D_1 D_2 D_2 D_3 D_3 D_4 D_4-3 -3

7 Methods and Instrumentation Surrogates : Post Mortem Human Subject Hybrid III Two series of tests : 1 st with a Load Limiting Shoulder Belt 2 nd with a Load Limiting Shoulder Belt

8 Methods and Instrumentation Instrumentation : Accelerometers Head Chest Pelvis Data Processing : Sample rate : 1 khz Filter : 6Hz Scaling parameter : λ = ( 7/ M i 1/3 )

9 Methods and Instrumentation Data analysis : Longitudinal (x) and vertical (z) acceleration component Resultant acceleration Head Injury Criterion - 3ms : HIC t 2 = γ t1 2 1 t 1 t ( t) dt 2. ( t t ) Thoracic Injury description with AIS quotation () compared with the injury risk curve (dummy) 2 1

10 RESULTS Pelvis HIII deceleration > > HIII deceleration < longitudinal vertical

11 RESULTS Pelvis HIII > Not the same distribution Not the same resultant Greater rigidity of the dummy pelvis resultant

12 RESULTS Pelvis longitudinal vertical

13 RESULTS Pelvis Change of load limit : Not a great influence on the dynamics of the dummy pelvis. Change of belt load limit increases the Z deceleration of the Pelvis 1 1 The resultant acceleration is higher with the belt, resultant it is a consequence of the greater rotation of the thorax due to his lower deceleration

14 RESULTS Chest HIII deceleration > HIII acceleration> > longitudinal vertical

15 RESULTS Chest HIII > Not the same distribution Not the same resultant Differences are not significant than the pelvis resultant

16 RESULTS Chest Longitudinal T8 Longitudinal T1

17 RESULTS Chest 3 3 Change of load limit : Not a great influence on the dynamics of the dummy thorax. Change of belt load limit decreases the x deceleration of the thorax 1 1 The resultant acceleration is higher with the belt, The x deceleration of T1 is reduced with the belt, Resultant T8

18 RESULTS Head HIII deceleration deceleration > HIII acceleration > longitudinal vertical

19 RESULTS Head HIII > resultant z and resultant accelerations are higher x deceleration are higher This difference increases the lower belt load value. Greater rigidity of the dummy neck?

20 RESULTS Head longitudinal vertical

21 RESULTS Head resultant Change of load limit : Not a great influence on the dynamics of the dummy head. Change of belt load limit decreases the Z acceleration of the head The resultant acceleration is lower with the belt It is a consequence of the lower load on the thorax

22 Hybrid III RESULTS Injury description Test AIS AIS AIS MAIS Thorax Sternum Clavicle H_1 () 2 2 H_2 () 2 2 H_3 () H_4 () 4 4 Test AIS Thorax deflection V*C D_1 () <2 21mm.4 D_2 () <2 31mm.8 D_3 () <1 1mm.2 D_4 () <1 16mm.2

23 RESULTS Injury description are massively injured Severity of the impact Rigidity of the seat Results distorted by the objective of the numerical model Dummies are not representative of the impact severity Rigidity of the thorax, pelvis, neck... Response of the sensor

24 DISCUSSION Comparison Hybrid III - To use these data the validation of a numerical model, The test configuration was simplified The influence of the configuration parameters was limited to the effect of the belt loading. Caution in applying results to living persons is necessary Due to the lack of muscle tone in. Variability in behaviour can not be avoided due to anthropometry and properties of the biological tissues. Considering these difficulties, the results presented in this paper allowed us to compare the Hybrid III and behaviours

25 DISCUSSION Comparison Hybrid III - The differences between dummy and cadaver behaviours, show that the biofidelity of Hybrid dummies is not ensured during injuring tests Difference has been observed between cadaver and dummy : For the resultant : higher the dummy Differences are also observed on the components The longitudinal acceleration is lower the PHMS than the dummy and the opposite is observed the vertical acceleration. An explanation is the greater rigidity of the dummy pelvis compared to a cadaver pelvis.

26 DISCUSSION Influence of the load limit Differences have been observed on dynamics of the : s lessened with the decreasing of the load This decreasing of accelerations lead to lower value of HIC HIC : 4 17 HIC : > 4 These effects on the dummy dynamics is less obvious.

27 DISCUSSION Influence of the load limit Rigidity of the dummy neck might filter the effect of the load-limiting system This rigidity simulates the muscle tone of living human - without considering any reaction time- The dummy is generally calibrated on slow speed volunteer tests. The influence of the reaction time in case of high speed is not clear. Concerning the, the absence of muscle tone is not a problem because the impact time is very short.

28 DISCUSSION Injury Location of the rib fractures corresponds to the contact area of the shoulder belt The load limiting system reduces the fractures Despite the use of a low deceleration of the sled (2g to 24g, the impact appeared severe in terms of injuries of the rib cage. For the subjects aged 7, a shoulder load corresponds to a 1% probability of AIS>3. These injury observations show the interest of the shoulder belt load as injury indicator, contrary to the chest acceleration measurements

29 CONCLUSION Two series, each comprising two cadavers and two Hybrid III dummy tests, were carried out The first series used a seat equipped with a load-limiting limiting shoulder belt The second used a load-limiting limiting belt. Concerning the effect of the shoulder loading Reducing load belt reducing the injury risks Dummies are less sensitive to the change of load than

30 CONCLUSION Biofidelity 1. biofidelity is not ensured in the case of injuring tests 2. This test device does not allow a precise analysis of the injury levels and mechanisms. 3. Numerical Models could reproduce the human behaviour 4. Biomechanical knowledge is needed to validate the model

31 CONCLUSION Some interrogations How is close to living driver? Importance of the muscle tone?

32 Acknowledgement The HUMOS project is supported by European Community (DG XII) and co-ordinated ordinated by LAB PSA Peugeot-Citroën Renault The partners involved in the HUMOS program are : PSA Peugeot-Citroën FR), Renault (FR), Volvo (SE), VW (DE), BMW (DE), ESI (FR), ISAM Gmbh (DE), TNO Automotive (NL), FAURECIA (FR), University of Chalmers (SE), University of Heidelberg (DE), University of Marseille (FR), National Technical University of Athens (GR). The authors would like to thank Doctor Eric J. Voiglïo (surgeon of the Hospital of Lyon) from the Faculty of Medicine, Lyon, Doctor Michelle Ramet from the INRETS-LBMC their contributions to the experiments, the autopsy and the injury description.