project deliverable

CASPER- OCTOBER 2012 - IDIADA – WP4-D4.4 _vfinal
PROJECT DELIVERABLE
CASPER
CHILD ADVANCED SAFETY PROJECT FOR EUROPEAN ROADS
Grant Agreement number: 218564
Date of latest version of Annex I against which the assessment will be made: 31/12/2011
Deliverable No.
D4.4
Deliverable Name
Report of the feasibility from physical testing to numerical criteria
Dissemination level
Public
Written By
Xavier Trosseille (GIE RE PR)
Tel: +33 1 76 87 35 16, xavier.trosseille@lab-france.com
Ines Lehmann (VFSB)
Tel: +49 30 692057212, Lehmann@Fahrzeugsicherheit-Berlin.de
Checked by
Heiko Johannsen (TUB)
Tel: +49 30 31 47 29 88, Johannsen@Fahrzeugsicherheit-Berlin.de
Philippe Lesire (GIE RE PR)
Tel: +33 1 76 87 35 60, philippe.lesire@lab-france.com
Approved by
Alejandro Longton (Applus IDIADA)
Tel: +34 600 927 756, alongton@idiada.com
Issue date
08th October 2012
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EXECUTIVE SUMMARY
The objective of this delivery was to demonstrate the feasibility of using the virtual track for the
development of enhanced Child Restraint Systems.
Physical development requires the availability of physical dummies, test setups, CRS prototypes as
well as injury criteria and limits. In the same way, virtual development first requires virtual dummies
and CRS and test setup models. In that particular case, injury criteria and limits can be the same for
physical development. However, all the components of this approach have to be validated and have to
demonstrate their ability to mimic reality.
In addition to this, human body models were developed aiming at a better understanding of injury
mechanisms and better predictions of injuries. These models may also be used to go further in the
development of enhanced CRS. However, whereas their potential is higher than dummy models, their
level of validation requires much more attention and data. This is all the more important as we can not
physically check the results.
The analysis of the work performed in CASPER shows that dummy models together with CRS
models, setups and criteria are almost mature and can be used to help develop CRS. They can mimic
physical tests and may speed-up the development process as well as allowing the investigation of new
solutions.
Besides, the use of Human body models is still in a research phase. Progress was made during
CASPER, with the creation of a family of human child models, the development of generic CRS and a
first step into the development of tolerances. However, further efforts are needed to fully exploit the
potential of the developed tools and make them available as design safety tools. The feasibility of the
virtual process was demonstrated as well as the necessary steps to take for it to become a routine
process.
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TABLE OF CONTENTS
1
INTRODUCTION ..................................................................................................................................................8
2
CRS MODEL DEVELOPMENT ................................................................................................................................9
2.1
GENERIC CRS MODELLING .......................................................................................................................................... 9
2.1.1
General Practice............................................................................................................................................. 10
2.1.2
CRS Group 0+.................................................................................................................................................. 11
2.1.2.1
2.1.2.2
2.1.2.3
2.1.3
CRS Group 1.................................................................................................................................................... 16
2.1.3.1
2.1.3.2
2.1.3.3
2.1.4
3
Choosing a CRS....................................................................................................................................................... 16
Model Information................................................................................................................................................. 17
Model Validation ................................................................................................................................................... 18
CRS Group 2/3 ................................................................................................................................................ 20
2.1.4.1
2.1.4.2
2.1.4.3
2.2
2.3
Choosing a CRS....................................................................................................................................................... 11
Model Information................................................................................................................................................. 13
Model Validation ................................................................................................................................................... 14
Choosing a CRS....................................................................................................................................................... 20
Model Information................................................................................................................................................. 21
Model Validation ................................................................................................................................................... 21
PRINCIPLE OPERATION WITH THE GENERIC CRS MODELS ................................................................................................ 23
GENERIC CRS APPLICATION ....................................................................................................................................... 24
CHILD MODEL STATUS ...................................................................................................................................... 24
3.1
DUMMY MODELS ..................................................................................................................................................... 24
3.1.1
Model development ....................................................................................................................................... 24
3.1.2
Injury criteria and risk curves (IRC)................................................................................................................. 24
3.2
HUMAN MODELS ..................................................................................................................................................... 25
3.2.1
Model development ....................................................................................................................................... 25
3.2.2
Injury criteria and risk curves (IRC)................................................................................................................. 26
3.2.2.1
3.2.2.2
3.2.2.3
Head....................................................................................................................................................................... 26
Neck, chest, abdomen ........................................................................................................................................... 26
Lower limbs............................................................................................................................................................ 26
4
USE OF CRS, HUMAN MODELS AND INJURY CRITERIA........................................................................................ 26
5
CONCLUSION AND PERSPECTIVES ..................................................................................................................... 26
ACKNOWLEDGEMENTS ............................................................................................................................................... 28
REFERENCES ............................................................................................................................................................... 29
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LIST OF FIGURES
Figure 1: Favoured CRS brands............................................................................................................. 11
Figure 2: Group 0+ FE and hardware CRS dimensions ........................................................................ 12
Figure 3: Generic group 0+ CRS model ................................................................................................ 13
Figure 4: HEAD Acceleration results (side impact) .............................................................................. 14
Figure 5: CHEST Acceleration results (side impact) ............................................................................ 15
Figure 6: PELVIS Acceleration results (side impact)............................................................................ 15
Figure 7: Group 1 FE and hardware CRS dimensions........................................................................... 16
Figure 9: Head acceleration results (Side impact) ................................................................................. 18
Figure 10: Chest acceleration results (Side impact) .............................................................................. 19
Figure 11: Pelvis acceleration results (Side impact).............................................................................. 19
Figure 12: Group 2/3 FE and hardware CRS dimensions...................................................................... 20
Figure 13: Generic group 2/3 CRS model ............................................................................................. 21
Figure 14: Head acceleration results (Side impact) ............................................................................... 22
Figure 15: Chest acceleration results (Side impact) .............................................................................. 22
Figure 16: Pelvis acceleration results (Side impact).............................................................................. 23
LIST OF TABLES
Table 1: The five CRS groups, according to ECE-R 44 ........................................................................ 10
Table 2: General steps in creating a generic computer simulation model ............................................. 11
Table 3: Dummy models available ........................................................................................................ 24
Table 4: Human body models developed in CASPER .......................................................................... 25
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1 Introduction
The objective of this delivery was to demonstrate the feasibility of using the virtual track for the
development of enhanced Child Restraint Systems.
Physical development requires the availability of physical dummies, test setups, CRS prototypes as
well as injury criteria and limits. In the same way, virtual development first requires virtual dummies
and CRS and test setup models. In that particular case, injury criteria and limits can be the same for
physical development. However, all the components of this approach have to be validated and have to
demonstrate their ability to mimic reality.
In addition to this, human body models were developed aiming at a better understanding of injury
mechanisms and better predictions of injuries. These models may also be used to go further in the
development of enhanced CRS. However, whereas their potential is higher than dummy models, their
level of validation requires much more attention and data. This is all the more important as we can not
physically check the results.
We will, in this report, review the availability of the different components of dummy and human
virtual testing, make a critical evaluation of the existing possibilities and provide some advice for the
future.
2 CRS model Development
2.1 Generic CRS Modelling
One important objective of the CASPER project is to develop tools for improving the use of CAE
techniques for the development of CRS and cars. While a complete CAE chain has been used for adult
safety for decades, numerical simulation for child safety is still underrepresented. In order to achieve
this aim, it is essential to have CRS models available to check both dummy model and human model
behaviour and also check test procedure model behaviour. As no models of actual CRS were available
for the CASPER consortium it seemed beneficial to develop generic CRS models that average the
properties of real CRS within one type of CRS (e.g., forward facing (FF) harness system). It was not
expected to get perfect validated CRS models but to have first models with general properties which
are capable to make first analysis and experiences. At the end no exact results with these models may
be expected but trends for whether or not measures or modifications would improve the child safety. It
should also be possible to take the generic models as basic templates to create or educe special CRS
models.
The models were developed in LS-Dyna code to be compatible with the CASPER dummy models, the
CASPER human models and the CASPER models of the test procedures.
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According to ECE-R 44 regulation CRS are subdivided in five groups shown in Table 1:
Group 0
Group 0+
Group 1
Group 2
Group 3
up to 10 kg
from birth to 6 - 9 months
up to 13 kg
from birth to 12-15 months
9 - 18 kg
from 9 months - 4 years
15 - 25 kg
from 4 - 6 years
22 - 36 kg
from 6 - 11 years
Table 1: The five CRS groups, according to ECE-R 44
From these five groups the three main groups could be derived. They are, first a rearward-facing baby
shell (group 0+), followed by a forward-facing harness type child seat (group 1) and for older children
the booster seats (group 2/3). The generic CRS models were created according to these three groups.
The general practice to create the CRS models will be explain in the next chapter and afterwards the
three CRS models will be described.
2.1.1 General Practice
For creating a generic CRS model the first step was to make an overview of which different types of
CRS were available on the market for each group. Afterwards the main dimensions from a number of
CRS from each group were measured and one type was chosen as the basic design which would
represent the average for the group. From this chosen type all relevant dimensions were measured so
that the geometry with 3D xyz coordinates were available and could be meshed with a special tool.
The FE mesh model was adjusted to the average group dimensions and assembled with contact, joint
and material definitions. Available material definitions were used for the first simulations. Then the
first simulations were compared with existing test results from corresponding CRS for the group and
the material definitions were altered if necessary. The decision was to use the GRSP test procedure for
the validation because it would be the new side impact test procedure for CRS homologation. So
experiences with the CRS test procedure proposal could be made and at TUB were such test results
with different dummies and several CRS available. A concise version of this process is shown in Table
2.
The focus for the validations laid on side impact because there is the important impact between
dummy and CRS. For frontal impact the belt definition and interaction with the dummy is more
important than the CRS. The dummy acceleration output from head, chest and pelvis was the main
analysed data for the validation (for Q0 only head and pelvis output exist).
Additional parts like an inlay, ISOFIX and support leg were created and they can be added into the
model as optional included files. Furthermore transformation cards were defined to position the
moveable parts like back rest, wings and/or the CRS shell. So analyses with different positions like in
the reclining position were possible.
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General practice:
 Analyse available CRS on market
 Measure CRS dimensions
 Select a CRS as basic
 Measure all dimensions from chosen CRS
 Create the FE mesh
 Resize the CRS model to group average dimensions
 Assemble the CRS model
 Compare CRS model simulations with test results
 Validate the CRS model with test results
Table 2: General steps in creating a generic computer simulation model
2.1.2 CRS Group 0+
2.1.2.1 Choosing a CRS
From the previous project CHILD a CRS model group 0+ in LS-Dyna code was available which was
used as a basic model. Six hardware CRS from known manufactures were measured and the average
dimensions calculated.
The CRS that parents prefer and recommend are listed in Figure 1. The data was from a survey of
netmoms.de [Source: Survey 2010/2011 on www.netmoms.de]. Therefore Maxi Cosi is a good and
representing basic model.
Other brands; 15%
Chicco; 3%
Cybex; 4%
Maxi‐Cosi ; 49%
Hauck; 9%
Römer; 20%
Figure 1: Favoured CRS brands
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The basic model dimensions were adjusted to the corresponding average value from the hardware
CRS. The values from the average hardware CRS and FE model are compared in Figure 2.
CRS group 0+
Description
Harness - backward edge
Harness - middle point
Lower belt guide - middle point
Lower upper belt guide
Upper belt guide - forward edge
Width backward edge
Width harness
Width middle point
Width lower belt guide
Width upper belt guide
With edge at the top
Hight wing between edge at top + lower belt
Hight wing upper belt guide
Hight wing lower belt guide
Hight wing middle point
Hight wing harness
Distance wing between front edge + upper belt
Distance wing upper belt guide
Distance wing lower belt guide
Distance wing middle point
Distance wing harness
Distance foot rear
Distance foot middle point
Length foot middle point front
Length foot middle point rear
Thickness styrofoam frontal
Thickness styrofoam shoulder belt
Thickness styrofoam wing (head)
Thickness styrofoam average
Maxi Cosi
Cabrio Fix
105
160
263
43
184
264
290
217
250
234
137
142
136
117
183
110
244
274
283
298
323
225
243
262
145
14
10
15
12
Concord
ION
145
135
230
105
180
240
252
242
236
230
190
145
155
160
135
70
273
294
300
304
312
200
204
265
130
15
20
40
22
Avanti
0+
140
143
210
80
180
283
262
291
230
230
190
80
89
91
157
100
250
265
275
301
288
232
220
194
115
10
10
10
10
Römer
Maxi Cosi Maxi Cosi
Baby Safe
Citi
Pebble
120
110
130
140
150
135
190
240
250
112
50
48
210
177
195
253
260
260
269
280
290
267
270
223
250
240
240
225
225
230
170
140
120
155
100
150
140
110
145
113
120
140
160
180
200
90
90
100
270
267
220
285
285
265
287
290
280
300
320
286
287
317
303
225
230
225
248
245
245
250
250
210
128
133
145
10
10
12
10
10
12
10
10
40
10
10
21
Average Value
Hardware CRS
125
144
231
73
188
260
274
252
241
229
158
129
129
124
169
93
254
278
286
302
305
223
234
239
133
12
12
21
14
Size
FE Model
118
147
227
78
193
267
275
260
236
233
161
135
128
115
169
93
243
283
279
304
309
220
243
257
122
18
13
18
16
Figure 2: Group 0+ FE and hardware CRS dimensions
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Figure 3: Generic group 0+ CRS model
Rearward facing baby shells have a removable inlay for the small newborn babies. So this part is
available as separate included file and can be simple integrated into the model for simulations with the
Q0 dummies. This can be seen as the green part in figure 3.
Some group 0+ CRS are available with an ISOFIX base to be anchored simply and quickly. This base
can mostly also be fixed in the car by the car belt. This system isn’t really popular on the market.
Therefore the rearward facing baby shell isn’t modelled with a base. But this system can be simply
created and included in the model if necessary.
2.1.2.2 Model Information
Model name:
Generic_CRS_Group0+_1.0.k
Model numbering:
Parts
Nodes
Elements
from 8.000
from 80.000
from 80.000
CRS to environment
Contact definition:
8000_CRS_to_env_contact
Optional include parts:
Generic_CRS_Group0+_Inlay.k
CRS position file:
Generic_CRS_Group0+_position-file.k
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2.1.2.3 Model Validation
The existing group 0+ CRS model was designed for a frontal sled test environment. For the generic
CRS model validation a side sled test environment according to the new GRSP proposal was
configured. It included the test bench, the group 0+ CRS and the positioned Q0 dummy. All parts were
loaded with the initial velocity and the bench was decelerated in the given corridor.
The first simulation showed that the CRS model was too stiff for side test configuration. The
connection between handle bar and baby shell was defined as a rigid component and too stiff with the
impactor input. Therefore the parts were defined with elastic material. The specific material values
were adapted to better comply with the test results. For the generic group 0+ CRS model validation
with the Q0 dummy no test curve results and movies were available. Only averaged maximum values
from sled tests performed outside CASPER were existent. For this reason the generic model was
validated to catch the maximum test values. The Q0 load values results for the validated model in
Figure 4 - Figure 6.
Figure 4: HEAD Acceleration results (side impact)
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Figure 5: CHEST Acceleration results (side impact)
Figure 6: PELVIS Acceleration results (side impact)
The inlay which is important for the Q0 positioning is defined with a low density foam material. This
material can have stability problems in LS-Dyna simulations and bring an error termination with
negative solid element volume.
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2.1.3 CRS Group 1
2.1.3.1 Choosing a CRS
To choose a CRS for group 1 nine different hardware CRS were analysed and measured. At the end
the Maxi Cosi PrioriFix was selected as the basic design. This CRS was the most sold one and also on
the first position in the category “satisfaction” for the customers [Source: Survey 2010/2011 on
www.netmoms.de]. The seat was measured, meshed, adjusted and assembled. The values from the
average hardware CRS and FE model are compared in Figure 7.
CRS group 1
Description
Britax Römer Bebe Confort
Iseos Isofix
King TS
Maxi Cosi
XP
Chicco
Key 1
Concord
Trimax
Maxi Cosi
Priori Fix
Fair
G0/1
Chicco Key
One X-Plus
Nania Safety
Paris SP 0/1
Average Value
Hardware CRS
Size
FE Model
Width seating area frontal
300
300
290
310
300
290
300
310
290
299
299
Width seating area rear/back rest
290
280
280
270
300
280
270
260
260
277
274
Width back rest min. position belt
280
240
280
270
230
290
270
260
270
266
267
264
Width back rest max. position belt
240
240
265
260
240
265
250
260
250
252
Width back rest upper
240
250
240
250
230
270
240
240
230
243
252
Depht seating area
260
300
280
310
310
300
270
300
300
292
292
Hight back rest
580
540
590
590
610
590
550
570
550
574
578
Hight wing rebound
160
190
160
130
100
170
150
130
130
147
148
Hight min. position belt
310
300
310
250
330
310
260
260
260
288
280
Hight max. position belt
410
420
410
360
440
410
380
350
390
397
408
Depth shoulder wing max. pos belt
190
190
170
160
140
180
160
150
180
169
161
Depth shoulder wing min. pos belt
130
130
120
140
160
140
120
110
120
130
127
Depth shoulder wing rebound
80
90
90
100
90
90
90
80
70
87
81
Hight leg wing from anchorage
120
170
150
120
110
150
100
120
70
123
128
Thickness leg wing
50
50
60
55
40
60
40
60
60
53
53
Thickness shoulder wing
30
50
50
40
50
50
30
40
50
43
54
Seating angle
101
95
95
91
93
92
97
102
--
96
100
15
20
Leg wing angle
5
13
16
17
23
16
18
98
--
Shoulder wing angle
25
21
22
23
28
19
28
--
--
24
25
Anchorage 5-point-belt seating area
160
170
150
150
180
150
170
160
100
154
156
Anchorage 5-point-belt pelvis
120
100
130
120
100
120
130
130
130
120
121
Anchorage 5-point-belt shoulder
50
50
60
50
50
50
60
60
60
54
57
Figure 7: Group 1 FE and hardware CRS dimensions
Figure 8: Generic group 1 CRS model with support leg and ISOFIX
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The group 1 CRS is modelled with an elastic seat shell and a rigid seat base. In the seat shell back rest
the holes for the belt anchorage are visible. Depending on the child dummy used and the repetition of
misuse different harness belt positions can be used. The seat shell is covered with a foam covering
(Figure 8, covering is the purple part).
Some group 1 CRS are equipped with the additional anchoring system ISOFIX with support leg, top
tether or anti-rotation system. The most popular system is ISOFIX with a support leg. The Maxi Cosi
PrioriFix is equipped with ISOFIX and support leg. For this reason these parts were also created to
have the possibility of analysis with this kind of connection. These parts are available as separate
included files and can be simply integrated into the model if desired. The top tether anchorage can be
simply integrated into the model but has a lot of variables. So the user must develop and integrate the
top tether anchorage if necessary. The anti-rotation system isn’t widely-used and therefore was not
included.
In the positioning file the rotation of the CRS shell is defined to have the possibility to move the seat
into a reclining position. The CRS is created in the normal seating position. In the position file there
are predefined middle and end reclining positions.
2.1.3.2 Model Information
Model name:
Generic_CRS_Group1_1.0.k
Model numbering:
Parts
Nodes
Elements
CRS to environment
Contact definition:
from 8.000
from 80.000
from 80.000
8000_CRS_to_env_contact
Optional include parts:
Generic_CRS_Group1_ISOFIX.k
Generic_CRS_Group1_support_leg.k
CRS position file:
Generic_CRS_Group1_position-file.k
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2.1.3.3 Model Validation
To validate the group 1 CRS three test results with corresponding seats and a Q3 dummy were
available. From the test pulses an average pulse and an average initial velocity for the simulation were
derived. The generic CRS was fixed to the bench, the impactor was positioned, a Q3 dummy model
was placed in the CRS and then the simulation was started with the test initial velocity and test pulse.
The covering defined with solid elements caused some problems because the hard impact with the
dummy produced negative volume in the solid elements and resulted in error terminations. Therefore
the simulations were conducted without the covering first. The simulation acceleration output curves
from the Q3 dummy model were compared with the test result curves. The corridor represents the
limits from the respective measurement course from the test results. For validation the outputs from
head, chest and pelvis were observed. By adapting the seat shell stiffness the dummy load values were
adjusted to within the test result corridor (Figure 9 - Figure 11). With a stiff seat shell definition the
dummy will be decelerated harder than with a softer seat shell definition. So the intention was to find a
good middle value to catch the test result corridor.
Figure 9: Head acceleration results (Side impact)
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Figure 10: Chest acceleration results (Side impact)
Figure 11: Pelvis acceleration results (Side impact)
At the end some analyses with the covering were made. The curve characteristic shows that with the
covering the dummy will be smoothly decelerated. But the hard impact to the covering with the small
thickness still causes problems with the solid element stability and error terminations with negative
volume problem results. With other solvers (for example PAM Crash, ABAQUS) a more stable or
better validated/defined material could improve the covering definition.
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2.1.4 CRS Group 2/3
2.1.4.1 Choosing a CRS
Four different CRS types from group 2/3 were measured to choose a basic CRS design. The type of
designs for booster CRS are more variable than for example for baby shells. Therefore it was less
simple to choose a good CRS basic design. At the end the chosen CRS was the Jane Indy Racing seat
because it has separate moveable wings in the head and chest area. Therefore the model has a lot of
variable parts and can be well adjusted. Also the backrest is displaceable to customise it to the size of
the used dummy. The hardware CRS was measured and meshed. Afterwards the mesh was adjusted to
the average hardware seat dimensions. The values from the average hardware CRS and FE model are
compared in Figure 12.
CRS group 2/3
Description
Hight upper wing
Width upper wing
Hight belt guide
Width belt guide
Hight lower wing outside
Hight lower wing inside
Width lower wing up
Width upper wing up
Width upper wing center
Hight lower wing
Width lower wing up
Width lower wing center
Width lower wing down
Hight lower wing down
Width back rest
Length seat
Hight seat frontal
Hight seat center
Hight seat belt guide
Hight seat at hump
Length seat belt rear
Length seat upper rear
Width seat inside at back rest
Width seat inside at belt guide
Width seat outside
Length seat inside
Length seat outside
Ultra Fix Chicco
220
180
40
-300
130
150
190
-220
310
310
270
340
180
400
155
210
80
70
100
270
260
310
420
280
400
Maxi Cosi Rody XP
220
160
20
---180
230
150
230
150
270
210
380
--170
230
110
110
160
280
260
280
380
290
330
no name XYAP
150
160
100
40
200
150
160
-210
-220
250
---420
160
230
120
70
140
300
290
290
-290
370
Average Value
Hardware CRS
197
167
53
40
250
140
163
210
180
225
227
277
240
360
180
410
162
223
103
83
133
283
270
293
400
287
367
Size
FE Model
190
160
40
60
230
120
180
180
180
210
230
240
250
330
190
380
160
220
120
70
120
280
260
320
400
280
325
Figure 12: Group 2/3 FE and hardware CRS dimensions
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Figure 13: Generic group 2/3 CRS model
At the end the model was assembled with contact, joint and material definitions. Also all possible
movements for the wings and back rest were defined and stored in the positioning file. Figure 13
shows the group 2/3 model.
2.1.4.2 Model Information
Model name:
Generic_CRS_Group23_1.0.k
Model numbering:
Parts
Nodes
Elements
from 8.000
from 80.000
from 80.000
CRS to environment
Contact definition:
8000_CRS_to_env_contact
Optional include parts:
-
CRS position file:
Generic_CRS_Group23_position-file.k
2.1.4.3 Model Validation
For the validation of the generic group 2/3 CRS model side sled test results with a Q6 dummy,
different CRS were available. As described in 2.1.4.1 the designs for group 2/3 CRS are more variable.
This fact made the validation difficult. After many validation cycles it was decided that a model below
the best compromise for the dummy load values would be acceptable. Figure 14 to Figure 16 show the
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generic model which is not well modelled for the pelvis acceleration. The pelvis decelerated to late
and to excessively. Also an additional cushion couldn’t reduce the effect significantly.
Figure 14: Head acceleration results (Side impact)
Figure 15: Chest acceleration results (Side impact)
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Figure 16: Pelvis acceleration results (Side impact)
The Q6 dummy chest acceleration output from the simulation shows a swinging characteristic. The
reason for the swinging output in the dummy can’t be currently clarified. Hopefully the source for that
can be found by communicating with HUMANETICS.
With LS-Dyna it is partly difficult to reproduce stabile edge contacts. Such problems occurred in the
generic CRS model where soft Styrofoam parts hit the hard ribs from the outer shells. For this reason
the edges of the fins were additionally defined with beam elements to ensure a clear contact.
The generic group 2/3 CRS model is applicable for basic kinematics’ analysis. For special analysis or
for comparison with a special CRS type the generic model should be checked if the side wings have to
be positioned or modified. See more about using the models in the next chapter.
2.2 Principle Operation with the Generic CRS Models
The aim of the generic CRS models was to have CRS simulation models available for general analysis.
Therefore the three created models have generally accepted properties.
Due to this two general principles for the operation of the models shall be considered:
1. If an analysis with a specific CRS should be done, the corresponding generic model could
serve as a basis for a more specific CRS model. As the first step a comparison between the
specific CRS and the generic CRS model should be done, especially for the parts that are
expected to mainly influence dummy performance. Afterwards the generic CRS model has to
be modified and validated if necessary.
2. If a general analysis should be done, then it depends on the problem definition if the generic
CRS model is sufficient or should be modified. Maybe more validation is necessary with
another dummy or another test environment to improve the CRS model. For simple kinematics
analysis especially without deciding contact between CRS and dummy the generic model is
sufficient. Simple statements and trends for improvements could be done.
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2.3 Generic CRS Application
The generic CRS models are available for the CASPER project partners on the CASPER internal web
site. The models will be made available to third parties with licensing conditions requiring that user
report back on improvements.
3 Child model status
3.1 Dummy models
3.1.1 Model development
Several dummy models were developed in CASPER and others are available from dummy or code
manufacturers (Table 3).
They are generally available in several codes (LS-Dyna, Pam-crash or Radioss).
Their level of validation is acceptable and consortiums were created to reach industrial quality, like for
the Q6 dummy.
Moreover, positioning tools are available.
Table 3: Dummy models available
Age
Dummy FE models
DUMMY
TUB
Q0
1 Y
FTSS
Q1
1.5 Y
FTSS
Q1.5
3Y
FTSS
Q3
6Y
TUB
Q6
VSFB initiated
modeling works on
Q10 model
Q10
6W
6M
10 or 12 Y
3.1.2 Injury criteria and risk curves (IRC)
The same injury criteria that are used for adults can be used for the children. They include head
acceleration, HIC, neck force or moment, chest acceleration, chest deflection, VC, abdominal pressure,
pelvis acceleration or pubic force. In addition, force and moment in the upper and lower limbs can be
measured.
IRC were developed in WP1 from accident reconstructions. Results were provided in an IRCOBI
paper (Johannsen et al., 20121) and a Stapp paper (Beillas et al., 20122).
1
Heiko Johannsen, Xavier Trosseille, Philippe Lesire, Philippe Beillas (2012) Q-Dummy Injury Criteria Using the
CASPER Project Results and Scaling Adult Reference Values, Proceedings from IRCOBI Conference, Dublin, 2012.
2
Philippe Beillas, François Alonzo, Marie-Christine Chevalier, Philippe Lesire, Franck Leopold, Xavier Trosseille, Heiko
Johannsen (2012) Abdominal Twin Pressure Sensors for the Assessment of Abdominal Injuries in Q Dummies: In-Dummy
Evaluation and Performance in Accident Reconstructions, Stapp Car Crash Journal, Vol 56.
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IRC were not provided for all segments. However, when not available, IRC can be scaled from the
adult version. Injury Assessment Reference Values are selected either from reconstruction or from
scaling by regulatory bodies or consumer organizations. They can be applied to dummy models as
well as to physical dummies.
3.2 Human models
3.2.1 Model development
Child human body models were created within CASPER as can be seen in Table 4, these were aimed
at achieving a better understanding of injury mechanisms.
Head and neck models were developed by Uds for all ages. However, due to a lack of literature data,
no validation was provided for the head. Thorax and abdomen models were developed by Chalmers,
and TUB and INRETS respectively for the 1 YO, 3 YO and 6 YO children. Lower leg and pelvis
models were developed by Chalmers for the 1 YO and the 3 YO and by INRETS for the 6 YO.
Segments were then assembled and full models tested for numerical stability.
All the model segments (Head and neck, chest and abdomen, lower limbs and pelvis) were checked
against available data (either child tests or scaled adult tests).
Positioning tools are not yet available and the process of model positioning is still tricky.
Table 4: Human body models developed in CASPER
Age
\segment
6W
6M
1Y
3Y
6Y
Thorax
abdomen
Lower L + pelvis
UdS
CHA
CHA
CHA
~15 000
~20 000
20000
20000
20000
UdS
UdS
TUB
15.00020.000
CHA
Head
Neck
Institution Name
UdS
UdS
Estimation of
elements number
~15 000
~15 000
Institution Name
UdS
UdS
Estimation of
elements number
~15 000
~15 000
Institution Name
UdS
Estimation of
elements number
Institution Name
Estimation of
elements number
~15 000
TUB
15.000~20 000
20.000
Institution Name
UdS
UdS
Estimation of
elements number
~15 000
~15 000
INRETS
INRETS
?
INRETS
~25 000
200 000 ‐ 300 000 (HUMOS ~ 80 000)
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3.2.2 Injury criteria and risk curves (IRC)
IRC were developed from accident reconstructions in WP2.
3.2.2.1 Head
For domestic accident reconstructions, an isolated head-neck segment was launched against the
ground. For crash reconstructions, an isolated head-neck segment was loaded at T1 level by dummy
measurements obtained in physical reconstructions. The injury criteria developed for the adults were
calculated for all the reconstructed cases. While the number of cases is quite small, some first limits
were suggested for skull fracture and DAI.
3.2.2.2 Neck, chest, abdomen
No injury criteria or limits were provided.
3.2.2.3 Lower limbs
Ultimate stress and strain were provided in the model, which allow for the reproduction of fractures in
subsystem tests (3 point bending tests). These values were not evaluated in accident reconstructions.
4 Use of CRS, human models and injury criteria
While dummy models are already used, even in industrial processes, the use of full Child HBM in a
complete crash environment is still seldom. Tentative were made in CASPER, mainly for
reconstruction purposes.
Chalmers simulated an accident reconstruction with a full 1 YO child model in a CRS developed by
TUB. It demonstrated the feasibility of the principle, but also the limits.
IFSTTAR simulated an accident reconstruction with a partial 6 YO child model in a CRS. It
demonstrated the potentiality of the process, but also the work to be done before it can be operational.
5 Conclusion and perspectives
Dummy models together with CRS models, setups and criteria are almost mature and are already used
to help developing CRS. They can mimic physical tests and may speed-up the development process as
well as allow investigations for new solutions.
Besides, the use of Human body models is still in a research phase. The following items have to be
considered:

Improving biofidelity and performance of the models (starting with the full human model)
o Perform robustness and stability testing
o Tissue mechanical properties and model validation: use recent results (PMHS and
volunteer)
o Need for basic research for data collection effort
o Geometry/mesh: increase detail where needed

Use the models in Casper/Child/Crest accident simulations and develop numerical injury criteria
o Approaches can give results even with missing biomechanical data (model based criteria)
o Links using the dummy when possible
o May require procedural work to ensure quality of results
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
Extend the domain of application / environment
o Positioning tools
o Develop models for more ages (e.g. 18 months) + geometrical/child variability
o Active models (if/when needed)
o Application to other types of loading conditions: pedestrian models and domestic accidents
 Would also allow reinforcing the injury risk curve
o More FE codes (currently: LS-Dyna3D only)

Apply the models as support tools for CRS and dummy development
o Help improve dummy hardware and instrumentation
o CRS: Still a perspective as of now.
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ACKNOWLEDGEMENTS
The CASPER Project (Grant Agreement 218564) is funded by
the European Commission under the EC 7th Framework Programme.
The authors would like to thank the child safety experts who have supplied local knowledge
on child restraint use in their countries.
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References
For more information on Generic CRS, please contact:
Verein für Fahrzeugsicherheit Berlin e.V.
c/o Technische Universität Berlin
Fachgebiet Kraftfahrzeuge
Gustav-Meyer-Allee 25, TIB 13
13355 Berlin
Dr.-Ing. Heiko Johannsen
+49 30 692 057 210
kontakt@fahrzeugsicherheit-berlin.de
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