6year old child human fe model - biomechanics … safety final... · ifsttar michel behr n°2 wp2:...

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Ifsttar LBMC contributors

P. Beillas, F. Berthet, X. Bourdin, M-C. Chevalier, E. Zapata

Ifsttar LBA contributor

M. Behr, Y. Godio

UdS contributors

F. Meyer, C. Deck., R. Willinger

CASPER WP2: Child human body modeling

6Year Old Child Human FE Model

Frank MEYER N°2UDS

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Geometry: dimensions and scaling

•Source: Anonymized CT-scans from local hospital

•Subject scaling / verifications– Thorax, pelvis and skin: comparison with UMTRI datasets– Organ volumes and other dimensions from the literature

•Summary: scaling factor of 0.93 brings most internal metrics within 10% of literature average

– but subject external surface larger than literature

WP2: Child human body modeling – 6YO Torso Model

Example: comparisons of CT based data before scaling with UMTRI datasets

UMTRI

pelvis & thorax

Org. Vol.

Bodyspace

HIII 6YO

UMTRI

External

LBA

external

S=0.93

-8%2%-1%

6%

9%

4%-9%-3%

2%

3%

-5%26%31%

13%

12%

-6%26%

14%

-2%0%

11%21%

5%

-4%-8%

18%16%

10%

Definition

Pelvic widthDepthChest depth

Chest breadth

Liver vol

LiverLeft kidneyRight kidney

Spleen

shoulder height

shoulder breadth hip breadthchest depth

abdominal depth

shoulder height

shoulder breadth hip breadth

abdominal depth

shoulder height shoulder breadth

hip breadthchest depth

abdominal depth

shoulder height shoulder breadth

hip breadthchest depth

abdominal depth

Within 10% of ref.After scaling

Philippe BEILLAS N°2

LBMC

IFSTTAR

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Geometry: positioning and final comparisons

•Postural change from supine to seated (using Beillas et al., 2009)

– Skeletal: transformation derived from closest scaled adult– Organ: manual shift based on average results

•Comparison of resulting geometry with Q6 dummy: close overall. UMTRI skin usable with adjustments

WP2: Child human body modeling – INRETS-LBMC, 6YO Torso Model

Skeletal Change from

supine to seated

Final geometry

vs. Q6 dummy model

vs. UMTRI skin envelope

vs. LBA femur

LBMC

Philippe BEILLAS N°2IFSTTAR

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Full mesh and model description:

•Skeleton: Vertebrae, arms and sacrum: rigid (shells) with articulations, Pelvic bones, ribs and cartilage: deformable

•Soft tissues: continuous mesh when possible (e.g. lung/ribcage); Solid organs, stomach, lungs, intercostal muscle, abdominal cavity, flesh, etc

•Around 230 000 elements, solid + shell

•Material properties: Ruan et al (2003) used as starting point � modifications depending on response

WP2: Child human body modelingLBMC


CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Validation datasets: 7 configurations testedTwo boundary conditions for fixed back: constraints (SPC) or rigid wall (RW)

Look at influent parameter sets (material etc) affecting the response

WP2: Child human body modeling

Ouyang et al. (2006) (n=5) thoracic impacts on PMHS

Kent et al. (2011) thoracic and abdominal loading (n=2)4 loading types (belts…)

EEVC 2008 Report on scaled corridor for Q abdomen (derived from Miller 1989 porcine data) Dummy torso flexion test

(to test kinematics)

LBMC


CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

KENT Lower Belt KENT Upper Belt KENT Distributed Belt

KENT Diagonal BeltEEVC report on Q dummies corridor

Abdomen compressionOUYANG thoracic

impact

Example of results for a recent iteration of model parameters

Red: original adult parameters; Green: adjusted parameters; SPC boundary conditions

LBMC

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Discussion & conclusions

�Boundary conditions sensitive in some cases

�Continue working on identification of best regional stiffness / material adjustment in order to improve model response

� Based on pediatric material data when available

� Still: May not be possible to match all conditions

�Thorax seems to stiff overall� Investigate further lung and rib modeling� Abdomen seems more ok

�Integrate to with neighboring regions and test in full sled configuration

� Mesh integration performed with the lower extremities

�Use with reconstruction pulse in Casper

WP2: Child human body modeling – INRETS-LBMC, 6YO Torso Model

LBMC


CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Geometry and Mesh – General Procedure :

Child Anthropometric database

+ 50th percentile scans + existing FE

models

+T2.1 specs and T2.2 material properties

Child Anthropometric database

+ 50th percentile scans + existing FE

models

+T2.1 specs and T2.2 material properties

« Aprosys » Scaling Tool

+ specific corrections

LBA

Michel BEHR N°2IFSTTAR

WP2: Child human body modeling – IFSTTAR-LBA, 6YO Lower Limb Model

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Geometry and Mesh

� General-shells for bones, skin

-tetras and hexas for cartilage and muscles

-springs for tendons and joints

� Coupling with trunk done via the pelvis-Femur Head and pelvis geometry sent by IFSTTAR-LBMC

� Mesh corrections-Mesh corrections at long bones extremities

according to 6YO child specifities


LBA


• ~40 000 elements� Materials

-Viscoelastic muscles (adult properties : E = 0.530 Mpa, …)

-Growth Cartilage: properties of articular cartilage

-Scaled Elastoplastic properties of bones (Franklin 2007):

– Young Modulus, factor 0.7

– Failure strain, factor 1.29

– Cortical thickness reduced according to X ray images of 6YO,

• Joints definition

-6 dof springs:

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Long bones validation : three point bending tests

Femur Tibia Fibula

• Loading conditions of Beillas 2009

Impactor:

– Cylinder moving in translation,

– 12kg mass,

– Constant speed of 1,2 m/s.

CASPER Kress et al. Funk et al.

Femur Max Force (N) 4 900 5 697 4 400

LBA



CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Joint kinematics Validation

• Initial position in flexion

• Constrained Proximal Femur extremity

• Gravity applied to all nodes

� Validation criteria: 10°Knee hyperextension

• Real world frontal impact conditions :

� Imposed displacement applied on the pelvis

LBA



CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

6 YO : Head-Neck FEM (based on the adult Head-Neck UdS FEM)

Intervertebral Discs

Atlas

Axis

C3

C4

C5

C6

C7

T1

Brain

CSF

Falx

Tentorium Skull

Face

Adult Head-Neck UdS FEM

Scalp

12121212

WP2: Child human body modeling – UDS, 6YO Head-Neck Model

UDS :Frank MEYER N°2

~25 000 elements

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Description CHILD 50th 6 YOC (mm) 6 YOC FE Model (mm)A 180 177B 182 185C 127 138D 87 83E 76 87F 16 11G 40 51H 49 -J 95 94

Geometrical Aspect

Adult Head-Neck FEM 6 YOC Head-Neck FEM

13131313


The reference used to obtain the geometrical factors is Irwin et al. 1997 and for the dynamical factor it was referred to Kumaresan et al. 2001.

WP2: Child human body modeling – UDS, 6YO Head-Neck Model

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

6 YOC : Head/neck FEM : Neck Validation against N.B.D.L. Test (Scale Irwin et al 1997)

Frontal impact

0 50 100 150 200 250 300 350 400-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

0

50

100

Acce

lera

tio

n [m

/s²]

Time [ms]

Exp

Num

(a)

0 50 100 150 200 250 300 350 400-300

-250

-200

-150

-100

-50

0

50

100

150

200

250

300

Acc

ele

rati

on

[m

/s²]

Time [m s]

Exp

Num

(b)

0 50 100 150 200 2 50 30 0 350 400

-40

0

40

80

120

160

Dis

pla

ce

me

nt

[mm

]

Time [ms]

Exp

Num

(c)

0 50 100 150 200 250 300 350 400-250

-200

-150

-100

-50

0

Dis

lacem

en

t [m

m]

Time [ms]

Exp Num

(d)

T= 0 ms T= 125 ms


WP2: Child human body modeling – UDS 6YOC Head-Neck Model

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

6 YOC : Head/neck FEM : Neck Validation against N.B.D.L. Test (Scale Irwin et al 1997)

Lateral impact

0 50 100 150 200 250 300 350 400-100

-80

-60

-40

-20

0

20

40

60

80

100

Acce

lera

tion

[m

/s²]

Time [ms]

Exp

Num

(a)

0 50 100 150 200 250 300 350 400

-40

-20

0

20

40

60

80

Dis

pla

ce

me

nt [m

m]

Time [ms]

Exp

Num

(d)

0 50 100 150 200 250 300 350 400

-40

-20

0

20

40

60

80

100

120

140

160

180

Acce

lera

tio

n [

m/s

²]

Time [ms]

Exp

Num

(b)

0 50 100 150 200 250 300 350 400

-150

-100

-50

0

50

100

Dis

lacem

ent [m

m]

Time [ms]

Exp

Num

(e)

0 50 100 150 200 250 300 350 400

-60

-40

-20

0

20

40

60

80

100

Acce

lera

tio

n [m

/s²]

Time [ms]

Exp

Num

(c)

0 50 100 150 200 250 300 350 400

-100

-80

-60

-40

-20

0

20

Dis

pla

ce

me

nt [m

m]

Time [ms]

Exp

Num

(f)

T= 0 ms T= 120 ms


CASPERCASPER

ORGANISATION | | WP

CASPERCASPER


WP2: Child human body modeling – 6YOC WHOLE BODY Model

• ~ 500 000 elements

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Numerical road accident reconstruction

Frank MEYER N°2UDS


0,000 0,005 0,010 0,015 0,020

-2000

-1500

-1000

-500

0

500

Tra

nsla

tio

nn

al accele

rati

on

[m

/s²]

Time [s]

Linearaccelera ons

6YOCHead-NeckFEM

Roadaccident

T1kinema cs

CHESTKinema cs

VonMisesStress,Pressure,

Deforma on,HIC…

Fx,Fz,My

Extrac onofmechanicalparametersand

correla onwithinjuries

BrainInjuriesNeckInjuries

Injuries T1

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Fixation CRS: Seat belt. No Misuse

Head: AIS 0 Neck: AIS 0

Example: Reconstruction of the case CCN-0002

Frank MEYER N°2UDS


CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

0 50 100 150 200 250 300 350

-500

-400

-300

-200

-100

0

100

200

300

400

Acce

lera

tio

n X

[m

/s²]

Time [ms]

6 YOC HEAD-NECK FEM

Q6

0 50 100 150 200 250 300

-600

-500

-400

-300

-200

-100

0

100

200

Acce

lera

tion

[m

/s²]

Time [ms]

6 YOC HEAD-NECK FEM

Q6

Head Acceleration Q6 / 6 YOC FEM

Ax

Az

Head and Neck criteria Q6 / 6 YOC Head-Neck FEM

Example: Reconstruction of the case CCN-0002

Frank MEYER N°2UDS


0

200

400

600

800

1000

1200

1400

1600

1800

EXP

Num

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Reconstruction of 12 CASPER accident cases

Cases included Head impact are not reconstruded

AIS HEAD AIS NECK

CCN_002 0 0

CCN_0089 2 0

CCN_0391 3 0

CCN_1043 1 0

CCN_1149 0 0

CCN_1079 0 0

CCN_1104 0 0

CCN_1104 0 0

CCN_1229 0 0

CCN_1215 0 1

CCN_1148 1 0

CCN_2061 0 0

Frank MEYER N°2UDS



CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Comparaison of the Head Max Acceleration Q6 / 6 YOC Head-Neck FEM m/s²

Frank MEYER N°2UDS



Difference are due to� Neck Stiffness Q dummy/FEM

� Loading(Chest and not T1) & Boundary condition

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

� Coupling to be finalized,

� Need to improve validation of each part (Head/Neck, Thorax, lower limb) under impacts,

� Evaluate the robustness of the whole body model through accident reconstructions. Compare dummy responses within the FE model,

� Improve "Dummy/FEM" compatibility. Example accelerometers must be integrated at T1 level etc...

� Development of injury criteria for each part.

Discussion

Frank MEYER N°2UDS

WP2: Child human body modeling – 6YOC Whole body FE Model

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Frank MEYER N°2UDS

� Development of a thorax , Lower limb and Head-Neck 6 YOC FEM

� A first element of validation is proposed for each part

� Development of a methodology for road accident reconstruction (Head-Neck FEM)

� Reconstruction of 12 CASPER road accidents in frontal impact with the Head-Neck FEM and a first comparison of the head and neck global (HIC, Accelerations, Fx, My….) parameters was undertaken.

Conclusions

WP2: Child human body modeling – 6YOC Whole body FE Model

CASPERCASPER

ORGANISATION | | WP

CASPERCASPER

Ifsttar LBMC contributors

P. Beillas, F. Berthet, X. Bourdin, M-C. Chevalier, E. Zapata

UdS contributors

F. Meyer, C. Deck, R. Willinger

Ifsttar LBA contributor

M. Behr, Y. Godio

CASPER WP2: Child human body modeling

6Year Old Child Human FE Model

Frank MEYER N°2UDS

6year old child human fe model - biomechanics … safety final... · ifsttar michel behr n°2 wp2:...

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