Enabling Protection for Older Children
SEVENTH FRAMEWORK PROGRAMMETHEME 7
Transport (including AERONAUTICS)
EPOCh 218744
FINAL PROJECT REPORT
Work Package 1Task 1.3a and Task 3.2a
Extension of biofidelity and injury risk curvedevelopment for the Q10
by J A Carroll, M Pitcher and M Hynd
Extension of biofidelity and injury risk curve development for the Q10
by J A Carroll, M Pitcher and M Hynd
Copyright EPOCh Consortium 21/12/2011
EPOCh 218744
FINAL PROJECT REPORT
Name DateApproved
Administrativecoordinator
Maria McGrath 21/12/2011
Technicalcoordinator
Marianne Hynd 21/12/2011
Contents
Executive summary 1
1 Introduction 2
1.1 Background 2
1.2 Previous work for EPOCh 3
2 Q10 biofidelity 5
2.1 Hybrid III family biofidelity 5
2.2 Q10 table-top testing 52.2.1 Measurement sites 82.2.2 Instrumentation 82.2.3 Test matrix 92.2.4 Expected results 10
2.3 Results 12
2.4 Summary of biofidelity evaluations 16
3 Upward scaling from Q3 17
3.1 ChILD project output 17
3.2 Risk function review 20
3.3 Comparison with alternative scaling 24
3.4 Comparison with real-world expectations 25
4 Other criteria 27
4.1 Head acceleration 27
4.2 Head excursion 28
4.3 Upper neck force and moment 28
4.4 Thorax acceleration 30
5 Conclusions 31
6 Recommendations 33
References 35
List of Figures
Figure 2-1 Belt position and deflection measurement points (L'Abbé et al., 1982) ......... 6
Figure 2-2 Test set-up from a previous installation of the apparatus ............................ 7
Figure 2-3 Image of set-up from TRL test with Q10 .................................................. 7
Figure 2-4 Another image of set-up from TRL test with THOR-NT ............................... 7
Figure 2-5: LVDT attachment points provided by plates glued to the Q10 dummy ribcage..................................................................................................................... 8
Figure 2-6 THORAX Project requirements for relative peak external deflectionmeasurements compared with the mid-sternum point ........................................ 11
Figure 2-7: Comparison of mean peak Hybrid III deflection results relative to themid-sternum measurement for low mass, low speed tests .................................. 11
Figure 2-8: Comparison of mean peak Hybrid III deflection results relative to themid-sternum measurement for low mass, high speed tests ................................. 12
Figure 2-9: Q10 low velocity, low and high mass results shown with THORAX Projectrequirements ................................................................................................ 13
Figure 2-10: Response to diagonal belt or hub loading on the thorax, low speed, lowmass conditions............................................................................................. 14
Figure 2-11: Response to diagonal belt or hub loading on the thorax, low speed, highmass conditions............................................................................................. 15
Figure 2-12: Response to diagonal belt or hub loading on the thorax, higher speed, lowmass conditions............................................................................................. 15
Figure 3-1: CREST and ChILD data points and AIS ≥ 3 logistic regression injury riskcurve for Q3 chest deflection........................................................................... 20
Figure 3-2: CREST and ChILD data points and AIS ≥ 3 logistic regression and survivalanalysis injury risk curves for Q3 chest deflection .............................................. 21
Figure 3-3: Injury risk curves for AIS ≥ 3 thoracic injury including the Probit analysis ofHybrid III sternal deflection scaled for the Q3 ................................................... 22
Figure 3-4: Injury risk curves for AIS ≥ 3 thoracic injury including the survival analysisof Hybrid III sternal deflection scaled for the Q3................................................ 23
Figure 3-5: CREST and ChILD data points and AIS ≥ 3 survival analysis injury risk curvefor Q10 chest deflection ................................................................................. 24
Figure 3-6: AIS ≥ 3 survival analysis injury risk curves for Q10 chest deflection derivedfrom the CREST and ChILD data or from scaling of the adult 50th percentile Hybrid IIIsternal deflection........................................................................................... 25
Figure 4.1: Head injury risk curve for an older child dummy (Q10) based on peak linearacceleration .................................................................................................. 27
List of Tables
Table 2-1: Measurement site coordinates (mm) ........................................................ 8
Table 2-2 Instrumentation and filtering.................................................................... 9
Table 2-3 Matrix of tests completed....................................................................... 10
Table 2-4 Normalised thorax compression biofidelity requirements for Cesari andBouquet table-top test condition...................................................................... 10
Table 3-1: Chest sample description with values for AIS and chest deflection (PSA,ChILD Deliverable D6).................................................................................... 18
Table 3-2: Q3 Chest deflection and injury data (as used by Wismans et al., 2008) ...... 19
Table 4-1: Head excursion limits proposed for use with the Q10 for equivalence with P10limits in the current Regulation 44 ................................................................... 28
Table 4-2: Neck injury values ............................................................................... 29
Table 6-1: Proposed injury criteria for use with the Q10 dummy in Regulation 44 frontalimpact conditions .......................................................................................... 31
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Executive summaryThe EPOCh Project has produced a 10.5 year old dummy, the Q10.
It is necessary to specify injury risk functions and accepted thresholds or criteria for usewith this new dummy, which are appropriate to this age and size of occupant.
Due to the lack of biomechanical information about children, the development of injuryrisk functions cannot follow exactly the same method as for adult dummies.
Within Task 1.3 of the EPOCh project, work has already been carried out to determineinjury risk functions suitable for use with an older child dummy. The task sought toreanalyse the potential methods available for scaling adult data to be relevant for anolder child. It also made an initial effort to scale injury criteria up from those developedfor use with the Q3 dummy.
Since preparing the report for Task 1.3, the Q10 dummy has been designed, made andtested within other work packages of the EPOCh Project. Based on the knowledge thatthe design and biofidelity performance of the dummy is in keeping with other dummiesin the Q-series, the approach of scaling up risk functions from the smaller Q-dummieswas revisited.
In addition a programme of experimental work was undertaken to investigate thethoracic biofidelity in more detail. In particular the regional thoracic stiffness underdiagonal belt loading was compared with adult dummy requirements. The thoraxstiffness in response to belt or hub loading was also investigated. From the results itseems that the Q10 response shows similar trends to the responses obtained previouslywith adult PMHS and in this regard demonstrates good biofidelity.
With new injury risk functions for the thorax, all of the proposed criteria were assessedagainst expectations based on the real-world injury incidence for older children. Testresults from EPOCh Project Task 3.2, where booster seats and cushions were testedunder UNECE Regulation 44 conditions, gave information as to the feasibility ofimplementing new thresholds and balanced the real world injury expectations.
Taking the Q10 design, feasibility and real world injury risk into consideration, thefollowing limits are proposed for use with the Q10, under Regulation 44 conditions.
Proposed injury criteria for use with the Q10 dummy in Regulation 44 frontalimpact conditions
Measurement Threshold
Head acceleration (3 ms exceedence) 80 g
Head horizontal excursion 465 mm
Head vertical excursion 885 mm
Upper neck tension †
Upper neck flexion 125 Nm
Upper neck extension 37 Nm
Chest deflection (either IR-Tracc) – x-axis 56 mm
Chest acceleration (resultant 3ms exceedence) 45 g
† It was recommended that a pragmatic neck tension limit is set after further testingwith the Q10.
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1 IntroductionThe implementation of the European Directive 2003/20/EC means that children up to150 cm in height and less than 12 years old must use a child restraint appropriate totheir size when travelling in cars or goods vehicles fitted with seat-belts. The affect ofthis legislation has led to children remaining in child restraints until they are older.
The concept of the EPOCh Project is to drive the improvement of safety for older childrentravelling in vehicles. To enable this, the EPOCh Project has produced a 10.5 year olddummy, the Q10.
It is necessary to specify injury risk functions and accepted thresholds or criteria for usewith this new dummy, which are appropriate to this age and size of occupant.
1.1 Background
It is widely accepted that data from the literature are not available to support thedevelopment of injury risk functions for children; e.g. functions which are directlyapplicable for use with fully biofidelic child dummies.
In the European Enhanced Vehicle-safety Committee (EEVC) Working Groups (WGs) 12and 18 report on the Q-dummies (Wismans et al., 2008), two methods are used toderive injury risk functions for the Q-dummies. The two methods are:
Correlation of dummy measurements made in laboratory reconstructions withdata and injury outcomes from well-documented real world accident events.
Scaling of injury risk functions and assessment thresholds already developed foruse with an adult dummy
The CREST (1996-2000) and ChILD (2002-2006) projects, co-funded by the EuropeanCommission, included a program of 98 real world accident reconstructions using P- andQ-dummies. These two projects provided information used by Wismans et al. to proposeinjury risk functions for the Q-dummies available at that time. For that purpose, theinjuries observed in the real world accidents were paired with Q-dummy measurementsfrom around 70 validated reconstruction tests. As the reconstructions were performedwith dummies from 0 to 6 years old, all data were scaled to the Q3 dummy size/age inorder to normalise the data for a single age whilst maintaining the size of the dataset tobe analysed. Risk curves for injuries with an Abbreviated Injury Scale score of at least 3(AIS ≥ 3) for the Q3 were then developed using both the Certainty Method and LogisticRegression. Resulting injury risk curves were drawn for the head, the neck and thethorax.
Due to the usual project constraints and available number of reconstruction events,some parameters had only limited data to relate Q-dummy measurements to theaccident data. Therefore, to support the direct use of child dummy measurements,scaling techniques were also applied to injury assessment values available for the 50thpercentile male adult dummy (Hybrid III 50th).
The scaling technique is used in biomechanics to derive the response and the injurythresholds of a specimen from the response and the injury thresholds of another subject,the size and/or material properties of which are different. For that purpose, thevariations of stiffness, geometry and failure stress are either observed from tests orassumed, as a function of age or size of the specimen. In the work of Wismans et al.,this technique is used to derive the information regarding the Q-dummies from theinformation available for the 50th percentile male adult dummy (Hybrid III 50th). Asnoted above, it was also used to transform measured values between Q-dummies ofdifferent ages.
It should be noted that in both approaches to develop risk functions for the Q-dummies,the scaling was based on both dummy geometrical ratios and human material propertyratios for different ages. The scaling did not account for the differences in performance
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of the dummies used (i.e. the dummy thoraxes of different ages may respond differentlyrelative to their stiffness corridors). It is stated by Wismans et al. that, “Ideally thisshould be accounted for when combining the data to the Q3 size/age, and also whenscaling the risk functions back to the other dummy sizes.”
1.2 Previous work for EPOCh
Within Task 1.3 of the EPOCh project, work has already been carried out to determineinjury risk functions suitable for use with an older child dummy (Carroll and Pitcher,2009). As this work was undertaken before a Q10 dummy was available, the option toperform any direct measurements and correlate those with accident data was notavailable. Instead, the task sought to reanalyse the potential methods available forscaling adult data to be relevant for an older child. Wherever possible various methodsof scaling were tried and the latest relevant material properties were sought from thebiomechanical literature.
Based on the interpretation of the available scaling techniques and material propertyinformation, the Task 1.3 report proposed injury risk functions for a 10 or 12 year oldchild. For the majority of criteria proposed, the limits were generated by scaling downfrom the adult human or Hybrid III injury risk functions.
Since preparing the report for Task 1.3, the Q10 dummy has been designed, made andtested within other work packages of the EPOCh Project. The biofidelity performance ofthe dummy is discussed in the following chapter.
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2 Q10 biofidelityThe biofidelity design requirements for the Q10 dummy were defined in Deliverable D1.2(Waagmeester et al., 2009). The approach used in the preparation of these requirementswas to scale up those already set for the Q6. The dummy performance against theserequirements was demonstrated by Waagmeester (2010). At this time it became clearthat the way in which the Q10 met the design requirements was similar to the way inwhich the Q6 met its requirements.
In parallel to the Q10 design work in EPOCh, within the THORAX Project considerationwas being given not only to how adult dummies performed in the sternal hub loadingimpactor tests, but also their sensitivity to belt and more distributed loading. It wasdecided that benefit could be given to the EPOCh Project if such considerations could beextended to the Q10. For this reason the Q10 biofidelity investigation was extended toinclude table-top tests as reported with adults by Cesari and Bouquet (1994) andpreviously by other authors. The Q10 results are discussed in Section 2.2.
Further to the table-top test work it was thought to be important to consider alsowhether alternative ten-year-old dummies would be expected to offer similar levels ofbiofidelity to the Q10. This investigation could not be completed fully within the EPOChProject constraints; however, some initial notes relating to the biofidelity of theHybrid III ten-year-old are given below.
2.1 Hybrid III family biofidelity
The design and development of the Hybrid III 10-year-old crash test dummy was firstpresented formally by Mertz et al. (2001). That paper presented the biofidelity guidelinesfor the dummy and gave an overview of the design features. In essence, the Hybrid III10-year-old is similar in construction to the other Hybrid III dummies.
“… a scaled-up version of the Hybrid III 3-year-old or 6-year-old, or ascaled-down version of the small female, midsize male or large male adultdummy.” (Mertz et al., 2001 – description of dummy design)
In principle it should be possible to relate the biofidelity performance of the Hybrid IIIten-year-old as reported by Mertz et al. with the performance of the Q10 (as given byWaagmeester, 2010). However, the tests used for assessing biofidelity are not alwaysequivalent. For instance, with the thorax, the Hybrid III was tested with a 6.89 kgpendulum, whereas the Q10 was tested with an 8.76 kg pendulum. Therefore tocomplete this line of enquiry, comparative tests using equivalent conditions would needto be undertaken.
The Hybrid III six-year-old was shown by Parent et al. (2010) to have a thoracic impactresponse which correlated very well with a corridor derived from the child PMHSimpactor tests by Ouyang et al. (2006). However, Parent et al. again note that therewere differences between the impactor test conditions used by Ouyang et al. and thetwo-mass piston system with which the dummy was tested.
2.2 Q10 table-top testing
L’Abbe et al. (1982) reported a series of tests that included dynamic and static seatbeltloading to examine the thoracic deflection characteristics of adult human volunteers. Thevolunteers were lying supine on a rigid table with the legs in a sitting position. They wereloaded by a diagonal seatbelt passing from the left clavicle down to the lower right ribs.The belt was centred on the sternum and was at an angle of 36 to the mid-sagittalplane. The deflection of the thorax was measured at the eleven locations includingmid-clavicle (see Figure 2-1). Dynamic chest loading was applied through an impactmechanism that had a pre-load and a dynamic pendulum striker.
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Continuing this work, Cesari and Bouquet (1990) reported the results from tests withPMHS using a very similar test configuration to that used by L'Abbé et al. (1982). Inthese tests the impactor which loaded the belt had a mass of either 22.4 or 76.1 kg andthe impact velocities ranged from 3 to 9 m/s.
Figure 2-1 Belt position and deflection measurement points(L'Abbé et al., 1982)
An image from a previous installation of the original test equipment is shown in Figure2-2. The two ends of the seat belt passed through the table over low friction supportsand were attached to a horizontal spreader bar. This bar was pulled down by a cable,around a system of pulleys, to a suspended catcher plate. The movement of the rod wasactivated by a dynamic impactor. The force at each end of the belt was measured with aload cell before connection to the rod.
In the TRL reproduction, the belt movement was generated by a bungee-powered sled,this had seat-belt webbing linking it to the spreader bar.
The TRL testing also included a condition where the diagonal seat belt was replaced witha hub of the same geometry as the pendulum impactor used to certify the dummy. Thecomparison between the belt and hub loading was intended to give insight as to thesensitivity of the dummy chest with regard to different distributions of applied loading.
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Figure 2-2 Test set-up from a previous installation of the apparatus
Figures 2-3 and 2-4 show the TRL set-up with the Q10 dummy. The load cell under thedummy was inserted to measure the posterior reaction force. This was important tocompare with later tests where a hub was used to apply the loading to the chest ratherthan a seat belt.
Figure 2-3 Image of set-up from TRLtest with Q10
Figure 2-4 Another image of set-upfrom TRL test with THOR-NT
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2.2.1 Measurement sites
L’Abbe et al. (1982) noted that the measurement points included the “centres of theright and left clavicles” and the “3rd, 5th and 7th rib bilaterally lined up below themid-clavicle”. Equivalent points were defined for the Q10 using scaled UMTRIcoordinates. The initial alignment with the dummy was based on the position of themidline of the superior anterior ribcage being consistent with the top of the sternum.
The distances between the attachment points are provided in Table 2-1.
Table 2-1: Measurement site coordinates (mm)
y zMid clavicle ±72 -16
3rd rib ±72 66
5th rib ±72 117
7th rib ±72 168
Upper sternum 0 0Mid sternum 0 66
Lower sternum 0 110
2.2.2 Instrumentation
For each test the internal chest deflection of the Q10 was measured using both 2DIR-Traccs. As well as the dummy chest deflection measurement, external deflectionmeasurements were required to compare directly with the original studies. Directmeasurements were made through the use of LVDTs (linear variable differentialtransformers). Ten LVDTs were used for the belt loading scenario. These were mountedabove the supine dummy with vertical attachments to the anterior aspect of the dummy.As shown in Figures 2-1 and 2-2, three attachments were to the surface of the belt(where a metal plate was glued to the belt). The other attachments were to the ribcageof the dummy. Again metal plates were glued to the ribcage in order to allow rigidmounting points (Figure 2-5). To reach the ribcage, holes were cut into the jacket/skinof the dummy.
A limitation of this attachment is that ribcage deformation may cause rotation of themounting plates and thereby influence the displacement measurements. However, thisaffect is considered to be small relative to the variation in original PMHS measurements.This limitation (along with other potential differences between the dummy and PMHStests) has been considered pragmatically when comparing dummy results to theexpected biofidelity requirements.
Figure 2-5: LVDT attachment points provided by plates glued to the Q10 dummyribcage
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All tests required measurement of the load applied through the belt. This was measuredwith webbing load cells, mounted just beneath the table, one for each side of the belt.
As mentioned above, another load plate (with three supporting load cells) was positionedunder the dummy to measure the reaction force.
Finally, for hub (rather than belt) loading tests, another load cell was positioned betweenthe hub face and the mounting bracket.
The following table (Table 2-2) summarises the instrumentation used in these tests andthe filtering applied.
Table 2-2 Instrumentation and filtering
Area Channel Filter Channel count
External chestdisplacement
LVDT x 10
(mm)
CFC_600 10 or 11
Internal chestdisplacement
2D IR-TRACC x 2
(mm)
CFC_600 4
Belt force Webbing loadcell x 2
(N)
CFC_60 2
Posterior reaction force Loadcell (single axis) x 3
(N)
CFC_1000 3
Hub force Loadcell (single axis) x 1
(N)
CFC_1000 1
Total Up to 25
2.2.3 Test matrix
The test matrix consists of three tests carried out at each of three conditions:
Low mass, low speed
High mass, low speed
Low mass, high speed
This was repeated for the belt loading and for hub loading; although with the hub, onlytwo tests were carried out at the high mass condition and the low mass high speed testswere omitted due to concerns over potential dummy breakage (Table 2-3). One lowmass, higher speed test was conducted, at a speed below that planned originally.
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Table 2-3 Matrix of tests completed
Loading device Sled mass (kg) Sled speed (m/s) Energy (J)
Seat belt 21.6 1.54 26
Seat belt 21.6 1.61 28
Seat belt 21.6 1.66 30
Seat belt 73.9 1.92 136
Seat belt 73.9 1.68 104
Seat belt 73.9 1.56 89
Seat belt 23.0 4.87 273
Seat belt 23.0 4.93 280
Seat belt 23.0 4.82 267
Hub 23.0 1.44 24
Hub 23.0 1.41 23
Hub 23.0 1.47 25
Hub 74.9 1.70 108
Hub 74.9 1.68 106
Hub 23.0 3.20 118
2.2.4 Expected results
The biofidelity requirements for these table-top tests are defined in the THORAX Projectdeliverable D2.1 (Hynd et al., 2011). The requirements relate to the low velocity tests,at either mass. They define relative displacement of each measurement point withregard to the mid-sternum measurement.
The normalised chest compression biofidelity requirements are reproduced in Table 2-4.
Table 2-4 Normalised thorax compression biofidelity requirements for Cesariand Bouquet table-top test condition
Right Side Sternum Left Side
Clavicle 0.30 –0.46
Upper (3) 0.5 –0.83
Clavicle (6) 0.51 –0.89
Rib 5 (7) 0.99 –1.22
Mid (1) 1.0 Rib 5 (5) 0.07 –0.45
Rib 7 (8) 1.01 –1.34
Lower (2) 0.84 –1.18
Rib 7 (4) -0.06 –0.32
The following figure (Figure 2-6) shows these requirements.
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Figure 2-6 THORAX Project requirements for relative peak external deflectionmeasurements compared with the mid-sternum point
The following figures demonstrate how well the adult Hybrid III 50th percentile maledummy meets the requirements. The low speed, low mass results are shown in Figure2-7 and the high mass, low speed results in Figure 2-8.
Figure 2-7: Comparison of mean peak Hybrid III deflection results relative tothe mid-sternum measurement for low mass, low speed tests
-0.2
0.0
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0.4
0.6
0.8
1.0
1.2
1.4
1 2 3 4 5 6 7 8
Rel
ativ
eD
efor
mat
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Chest deflection measurement point
THORAX Project requirement
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Rel
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Chest deflection measurement point
Relative Deformation, BMI 17-27THORAX Project req.s Hybrid III
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Figure 2-8: Comparison of mean peak Hybrid III deflection results relative tothe mid-sternum measurement for low mass, high speed tests
A paper by Kent et al. (2004) presents thoracic response corridors developed usingfifteen adult post-mortem human subjects (PMHS) subjected to table-top tests withsingle and double diagonal belt, distributed, and hub loading on the anterior thorax. Thedynamic tests were conducted with input displacement rate of about 1.5 m/s, which isbroadly equivalent to the rate used in the low speed tests conducted for this study.
The thoracic response was characterised by Kent et al. using the deflection at themidline of the sternum and a load cell mounted between the subject and the loadingtable. Responses were defined by cross-plotting the mid-sternal deflection (normalisedto 50th male) and the posterior force (scaled to a 45-year-old, 50th male based on sizeand modulus). The distributed loading condition generated the stiffest response (3.33 kNat 4.6 cm), followed by the double diagonal belt condition (3.18 kN at 4.6 cm), thesingle diagonal belt (2.28 kN at 4.6 cm) and the hub (1.14 kN at 4.6 cm).
From this we can assume that the response of the human chest is approximately twiceas stiff when loaded by a single diagonal belt as when loaded by a hub. Therefore similarstiffness behaviour is expected when testing with the Q10.
It should be noted that in equivalent table-top tests, the Hybrid III 50th percentile adultdummy does demonstrate a substantially stiffer response to hub loading than to loadingfrom a single diagonal belt. It is almost two times stiffer with the hub loading.
2.3 Results
The primary purpose of conducting the diagonal belt tests was to enable the comparisonof the relative measurements made across the thorax of the Q10 dummy with theranges defined from PMHS tests (see Figure 2-6). The comparison with that of the Q10results from low speed tests with the THORAX Project requirements is shown in Figure
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1 2 3 4 5 6 7 8
Rel
ativ
eD
efor
mat
ion
Chest deflection measurement point
Relative Deformation, BMI 17-27
THORAX Project Req.s Hybrid III
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2-9. Also shown in the figure are the peak deflection measurements from test with aHybrid III 50th percentile adult dummy.
The Q10 meets the requirements with the exceptions of the points 4, 5, 6 and 8. Foreach of those points, the dummy allows too much displacement. These points relate tothe lower left of the thorax (away from the diagonal belt), the loaded left clavicle and thepoint on the belt to the lower right of the thorax.
As a caveat for the points on the belt that moved too far, it may be that the exactgeometry of the test set-up with the Q10 was in some way compromised by the reducedsize of the dummy. Every effort was taken to ensure that the belt lie and angles from thetable to the clavicle or lower ribcage were consistent between tests with the Q10 andadult Hybrid III. However, the smaller chest depth may accentuate the possibility of themarkers pulling away from the intended anatomical measurement point. This couldexplain a slight overestimation of the displacement for points 6 and 8.
For the lower left of the thorax the measurement points were maintained on the thoraxthrough the direct attachment to the ribcage of the dummy. However, it should be notedthat the absolute distance from these measurement points to the belt would have beensmaller than for adult dummies and PMHS. As such one may expect more coupling to thesternal displacement and this is evident from the results.
On the basis of these results alone it is difficult to judge whether the points thatexceeded the required displacement did so on account of a lack of stiffness, too muchregional coupling or as a result of features of the set-up for the Q10. A general lack ofstiffness seems unlikely taking into account other biofidelity tests of the thorax.Therefore these results seem to be a function of the precise test set-up and the couplingto the belt loading. Further evaluation would be required to determine the balance ofthese two aspects, precisely.
Figure 2-9: Q10 low velocity, mean of low and high mass results shown withTHORAX Project requirements
The other aspect of the testing was to compare the stiffness of the Q10 thorax whenloaded either by a diagonal belt or by a hub. The following three figures show the belt or
-0.2
0.0
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1.0
1.2
1.4
1.6
1 2 3 4 5 6 7 8 9
Rela
tive
Def
orm
atio
n
Chest deflection measurement point
THORAX Project requirement
Hybrid III
Q10
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hub loading responses as a comparison. The y-axis represents the posterior reactionforce as measured by the load cells underneath the thorax of the dummy and the x-axisis the displacement of the belt or hub above the middle of the sternum. The low mass,low speed results are shown in Figure 2-10; the high mass, low speed results in Figure2-11 and the low mass, high speed results in Figure 2-12.
As with the PMHS tested by Kent et al. (2004), the dummy responses in the low speedtests are, very approximately, half as stiff when tested with the hub compared with thediagonal belt.
At 5 percent of the chest depth for the Q10 (8.6 mm), the mean belt test reaction forcein the low speed, low mass tests (0.77 kN) was 2.9 times the mean hub test reactionforce (0.27 kN). The equivalent factor for the low speed, high mass tests was also 2.9(0.70 to 0.24 kN).
This is a slightly higher ratio than may have been expected from the PMHS testing.However, it should be remembered that whilst the Q10 hub loading area had been scaledto reduce the size in relation to the adult specification, the belt width was not reducedfrom a conventional seat belt. As a result, the loading area for the diagonal belt testwould have been proportionally larger for the smaller thorax of the Q10 than for theadults. This may explain why the diagonal belt response was slightly stiffer in relation tothe hub response than was the case with the adult PMHS.
Please note that the energy put into the low mass, high speed test with a hub was notthe same as the energy input from the low mass, high speed belt tests. The energy ofthe hub test was reduced to limit the magnitude of the chest displacement to anacceptable level. This explains why the peak force in Figure 2-12 is not as high in thehub test compared with the belt tests.
Figure 2-10: Response to diagonal belt or hub loading on the thorax,low speed, low mass conditions
-0.4
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0
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1
1.2
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0 5 10 15 20 25 30
Post
erio
rrea
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nfo
rce
(kN
)
Displacement (mm)
Belt, Test 1
Belt, Test 2
Belt, Test 3
Hub, Test 1
Hub, Test 2
Hub, Test 3
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Figure 2-11: Response to diagonal belt or hub loading on the thorax,low speed, high mass conditions
Figure 2-12: Response to diagonal belt or hub loading on the thorax,higher speed, low mass conditions
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Belt, Test 5
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Hub, Test 5
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Belt, Test 7
Belt, Test 8
Belt, Test 9
Hub, Test 6
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2.4 Summary of biofidelity evaluations
In response to the usual biofidelity requirements it has been reported that the Q10 has asimilar level of biofidelity to the other Q-dummies.
As an extension to the usual assessments, table-top test work has been carried out withthe Q10 to investigate the thoracic biofidelity in more detail. In particular the regionalthoracic stiffness under diagonal belt loading was compared with adult dummyrequirements. Additionally, the thorax response to belt or hub loading was investigated.From the results it seems that the Q10 response shows similar trends to the responsesobtained previously with adult PMHS and in this regard demonstrates good biofidelity.
It is difficult to comment on the biofidelity of the Q10 in relation to other older childdummies. As the Hybrid III 10 year old and P10 dummies have not been evaluatedunder the same conditions.
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3 Upward scaling from Q3Knowing the relationship of the Q10 biofidelity to the other dummies in the Q-series, itseems appropriate to try and relate the risk functions to those reported byWismans et al. (2008) in a similar way. By doing so one can reason that the Q10 isgenerally a scaled up version of the Q3. The alternative would be the suggestion that theQ10 is a scaled down adult human (or Hybrid III dummy), which may require moreassumptions within the scaling process. This is particularly important where deviationsfrom the scaled biofidelity targets for the Q-series dummies means that effectivestiffness would need to be incorporated when scaling down from adult humans. Anexample of a body region where stiffness may be important would be the thorax, wherethe Q10 biofidelity performance has the same relative stiffness with respect to thebiofidelity corridor as the smaller Q-dummies (e.g. Q6 and Q3).
In the case of the risk function for chest deflection, in the previous Task 1.3 report, theproposed injury risk function was scaled down from the Hybrid III, belt loading, riskfunction as reported by Mertz et al. (1991). With the biofidelity performance of the Q10thorax being consistent with the smaller Q-dummies’ performance, it seems as thoughmore weight should be given to the approach which derives the Q10 injury risk functionthrough scaling up from the Q3.
3.1 ChILD project output
At the end of the ChILD project, results of the CREST and ChILD Project accidentreconstructions were made available for the development of injury risk functions. In theChILD deliverable D6 (PSA) 24 test results are shown relating to chest deflectionmeasurements. These results are reproduced in the following table, Table 3-1. It shouldbe noted that these data are scaled from both the Q3 and Q6 dummies, with which theaccidents were reconstructed, to the Q6.
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Table 3-1: Chest sample description with values for AIS and chest deflection(PSA, ChILD Deliverable D6)
Casenumber
Dummy AIS Deflection(mm)
Scalingratio
Deflectioncorrected
(mm)
AIS 3+
89 Q6 0 20 1 20 0
38 Q6 0 48 1 48 0
182 Q6 0 27 1 27 0
297 Q3 3 44 0.884 39 1
56 Q3 0 7 0.884 6 0
329 Q3 3 21 0.884 19 1
225 Q3 1 31 0.884 27 0
95 Q6 0 6 1 6 0
113 Q6 0 34 1 34 0
1079 Q3 3 68 0.884 60 1
1102 Q3 0 51 0.884 45 0
ITF E Q3 0 37 0.884 33 0
1081 Q3 0 19 0.884 17 0
1082 Q3 0 33 0.884 29 0
1067 Q3 0 26 0.884 23 0
1104 Q6 0 30 1 30 0
1149 Q6 0 19 1 19 0
391 Q6 4 1 1 1 1
1006 Q6 0 30 1 30 0
1104 Q6 0 50 1 50 0
1119 Q3 3 51 0.884 45 1
1079 Q6 3 5 1 5 1
177 Q6 3 50 1 50 1
132 Q3 0 6 0.884 53 0
The data contained in Table 3-1 were passed onto EEVC WGs 12 & 18 to be reported inconjunction with other aspects of the Q-dummy family development. As part of thishandover, a further quick review of the data was carried out. This review identified thatthe Q6 test 1079 demonstrated an unexpectedly low deflection for an AIS 3 injury andtherefore a measurement problem was suspected. For this reason it was removed fromfurther analysis. Indeed, the ChILD Project accident reconstruction database has thecomment against this result stating that it is “probably incorrect”. This is also true of the1 mm deflection associated with the AIS 4 injury in Test 391. The Deflection of Q3 Test
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1079 was changed because it exceeded the maximum deflection of the dummy. It wasset at the maximum value of 55.6 mm (Trosseille, 2011).
The data used by Wismans et al. to draw up the Q3 injury risk functions are shown inTable 3-2. Here it should be noted that all of the test data have been scaled to makethem appropriate for the Q3 dummy.
Table 3-2: Q3 Chest deflection and injury data(as used by Wismans et al., 2008)
Caseidentification
Dummy AIS Deflection(mm)
Scalingratio
Deflectioncorrected
(mm)
AIS 3+
ITF-VTI Q3 0 37 1 37.0 0
225/1 Q3 1 31.4 1 31.4 0
329/1 Q3 3 20.6 1 20.6 1
297 Q3 3 44 1 44.0 1
56 Q3 0 7 1 7.0 0
1079 Q3 3 55.6 1 55.6 1
1102 Q3 0 51 1 51.0 0
1081 Q3 0 19 1 19.0 0
1082 Q3 0 33 1 33.0 0
1067 Q3 0 26 1 26.0 0
1119 Q3 3 51 1 51.0 1
132 Q3 0 6 1 6.0 0
089/1 Q6 0 20 1.1 22.2 0
113/2 Q6 0 34 1.1 37.8 0
038/1 Q6 0 48 1.1 53.3 0
177/1 Q6 3 50 1.1 55.6 1
182/1 Q6 0 27 1.1 30.0 0
95 Q6 0 6 1.1 6.7 0
1104 Q6 0 30 1.1 33.3 0
1149 Q6 0 19 1.1 21.1 0
1006 Q6 0 30 1.1 33.3 0
1104 Q6 0 50 1.1 55.6 0
Based on these data Wismans et al. (2008) drew injury risk functions for the Q3 dummy.Those authors used the Certainty Method and logistic regression to derive the functions.The logistic regression is reproduced in Figure 3-1
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Figure 3-1: CREST and ChILD data points and AIS ≥ 3 logistic regression injuryrisk curve for Q3 chest deflection
3.2 Risk function review
Since publication of the EEVC Q-dummy document, ISO WG5 has issued advice thatinjury risk functions should be developed primarily using survival analysis. The followingfigure (Figure 3-2) adds a risk curve generated using survival analysis to the data andcurve already shown in Figure 3-1. The survival analysis shown assumes a Weibulldistribution for the underlying data. As shown in Figure 3-2, the survival and logisticregression curves are similar, but not the same, up to about 50 mm of deflection and a40 % risk of AIS ≥ 3 injury. From this point onwards, the curves diverge with thesurvival function predicting a lower risk of injury for a given chest deflection.
0
0.1
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0 20 40 60 80 100
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Logistic regression
L.R. confidence interval
Q3 data
Q6 data
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Figure 3-2: CREST and ChILD data points and AIS ≥ 3 logistic regression andsurvival analysis injury risk curves for Q3 chest deflection
In the EEVC approach to the development of the injury assessment threshold values,Wismans et al. also considered scaling the adult risk function down to the appropriatesize of Q-dummy. The only existing well-established risk function for chest deflection isthat in use with the Hybrid III adult dummy. This was generated by Mertz et al. (1991)through the laboratory reconstructions of French car accidents. The laboratory conditionsreplicated those of the real world accidents by mimicking not only general features of theseat position, such as seat padding and belt geometry, but also the same level ofseat-belt (shoulder belt portion) loading. The level of load experienced at the shoulderbelt was deduced via the use, at the time, of tearing of stitching as the means of loadlimitation. The laboratory tests then established the relationship between Hybrid IIIsternal deflection and shoulder belt load. In turn this shoulder belt load could be relatedback to the real-world risk of injury coming from the original accident data, where theinjury outcome and amount of stitching torn was documented for each case.
In the work of Wismans et al. the adult risk function is scaled to the Q3 deflection bymultiplying the Hybrid III adult deflection by 0.93. Repeating this exercise resulted inthe injury risk curve shown in Figure 3-3. The scaled adult curve has been added to thecurves shown in Figure 3-2 to offer ease of comparison between the approaches ofscaling down from the adult Hybrid III and using the CREST and ChILD data.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Logistic regression
L.R. confidence interval
Survival (Weibull)
Survival (Weibull) confidenceinterval
Q3 data
Q6 data
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Figure 3-3: Injury risk curves for AIS ≥ 3 thoracic injury including the Probitanalysis of Hybrid III sternal deflection scaled for the Q3
If the scaled adult data are plotted using the survival analysis instead of Probit, then aslightly different curve is produced. This is shown in Figure 3-4. In this case the survivalanalysis showed a best fit to the scaled Hybrid III adult data with the assumption of alog-normal distribution.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Logistic regression
L.R. confidence interval
Survival (Weibull)
Survival (Weibull) confidenceinterval
Scaled adult - Probit
Probit confidence interval
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Figure 3-4: Injury risk curves for AIS ≥ 3 thoracic injury including the survivalanalysis of Hybrid III sternal deflection scaled for the Q3
Based on the scaling values provided by Trosseille, it is possible to scale the injury riskcurves to make them relevant for the Q10 dummy. In practice this means multiplyingthe Q3 data by 0.67 and the Q6 data by 0.75. The resulting curve is shown in Figure3-5.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Logistic regression
L.R. confidence interval
Survival (Weibull)
Survival (Weibull) confidenceinterval
Scaled adult - Probit
Probit confidence interval
Scaled adult survival (log-normal)
Scaled adult survival -confidence interval
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Figure 3-5: CREST and ChILD data points and AIS ≥ 3 survival analysis injuryrisk curve for Q10 chest deflection
3.3 Comparison with alternative scaling
In order to compare the curve presented in Figure 3-5 with the other approach of scalinginformation down from the adult size, scaling factors are needed for the Q10.Unfortunately, Wismans et al. do not provide scaling factors for a Q10. However, usingthe rationale of Wismans et al. and some further interpretation of the available materialproperty data, Task 1.3 work has already addressed the need for scaling factors. Usingthe Q10 scaling ratio as proposed previously, it is possible to scale the Hybrid III 50th
percentile adult sternal deflection injury risk function down to make it appropriate for theQ10. The resulting curve is shown in the following figure (Figure 3-6). A log-normaldistribution assumption was used in the survival function. The curve scaled up from theCREST and ChILD data is also shown for comparison.
It can be seen from Figure 3-6 that the scaled down adult risk function predicts a lowerrisk of injury for a given chest deflection than the scaled up Q3 function. The two curvesdiverge with increasing deflection. This means that the difference between the scaled upCREST and ChILD data and the scaled down Hybrid III data for a 20 percent risk of anAIS ≥ 3 thoracic injury is between 23 and 28 mm. Whereas the difference is greater fora 50 % risk of injury, and is between 37 and 56 mm.
Knowing that the Q10 thorax biofidelity is in keeping with the performance of the otherQ-dummies, then one might expect the scaled up Q3 injury risk curve to be moreappropriate for use with the Q10 than the scaled down adult. However, before use ofeither function it is important to consider how the curve matches testing experience withthe dummy. This is also linked with the concept of choosing a pass/fail threshold and theimplications of such a choice on feasibility for CRS manufacturers to meet that limit. Thisis discussed further in Section 3.4.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Survival (Q10)
Survival (Q10) confidenceinterval
scaled Q3 data
scaled Q6 data
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Figure 3-6: AIS ≥ 3 survival analysis injury risk curves for Q10 chest deflectionderived from the CREST and ChILD data or from scaling of the adult 50th
percentile Hybrid III sternal deflection
3.4 Comparison with real-world expectations
The ability of the Q10 dummy to be used as a measurement tool in UNECE Reg.44 wasassessed within Task 3.2 of the EPOCh Project. For that evaluation, tests with a varietyof CRS (booster seats and cushions) were carried out under Reg.44 impact conditions.From the EPOCh tests with the Q10, results for the upper and lower chest compressionmeasurement points have been obtained. The smallest peak value from either IR-Traccwas 44 mm and the highest value was 60 mm.
Based on these results all of the CRSs would have exceeded a 50 percent risk of AIS ≥ 3thoracic injury using the risk function scaled from the CREST and ChILD data. SomeCRSs would also have exceeded the 50 percent risk level based on the function scaleddown from the adult (Hybrid III) data.
The high estimates of potential injury risk call into question the relationship between thedummy values measured in laboratory tests and real world injury rates. Thoracic injurieshave not been identified as a priority for prevention for restrained older children infrontal impact accidents. Therefore, it may not be necessary (or perhaps evenadvantageous) to implement a stringent chest deflection criterion. It is important thatchild restraints that position the 3 point belt across the torso of the dummy, thus toengage the belt correctly, are not penalised by a chest compression criterion. Instead itseems appropriate to maintain a similar level of performance for future restraintsystems. On this basis it is suggested that a chest deflection threshold of about 56 mmis used with the Q10 initially.
It should be noted that the Q10 has two IR-Traccs to measure anterior-posterior chestdeflection, an upper and lower measurement. The chest depth for the Q10 is not thesame along these two measurement axes, with the upper chest being slightly smaller.
0
0.1
0.2
0.3
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0.5
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0.8
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1
0 10 20 30 40 50 60 70
Prob
abili
tyof
AIS
3+th
orac
icin
jury
Deflection (mm)
Survival (Q10)
Survival (Q10) confidenceinterval
Scaled adult - survival
Scaled adult - survivalconfidence interval
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Also, from the table-top testing described above, there was an indication that the lowerthorax for the Q10 is slightly less stiff than the upper thorax (particularly where beltloading can provide coupling to a clavicle). For these reasons one may expect a greaterapplied force to be required to generate an equal chest displacement at the upper andlower thorax. This may result in a greater risk of injury in the upper portion than lowerdown as the proportional compression (displacement as a proportion of the chest depth)would be greater at the upper thorax. Therefore, a slightly lower limit for the uppermeasurement point should provide an equivalent risk of injury to that at the lowermeasurement point.
It is not clear from the initial tests with the Q10 whether a limit lower than 56 mmshould be implemented at the upper position (with 56 mm at the lower), or a limit higherthan 56 mm should be allowed at the lower measurement position (with 56 mm at theupper). This decision needs to take into account the feasibility for CRS manufacturers tomeet the thresholds and the likely injury risk levels implied. It also needs to be taken inconfidence that the Q10 progressively measures chest deflection beyond the limitsproposed. If the limit is set too close to the measurement capacity of the dummy, thenpeak values may be misleading or repeatability/reproducibility issues may beencountered.
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4 Other criteriaAs with the chest compression measurements, taking the results from the Task 3.2testing allowed real-world injury risk expectations and feasibility considerations to beextended to all body regions. The following chapter describes a review of the originallyproposed injury risk functions or criteria, as taken from the previous Task 1.3 report,after comparison with the test results. The criteria are considered body region by bodyregion. In each case new proposals for the limits that could potentially be used in Reg.44testing with the Q10 are proposed.
4.1 Head acceleration
In the previous Task 1.3 report, the curve shown in Figure 4.1 was suggested as a headinjury risk curve which could be used with the Q10 dummy.
The risk curves produced in that report showed there was a 20 percent risk of skullfracture at 77 g for the Q10 and there is a 50 percent risk of skull fracture at 251 g.
Functions for the risk of skull fracture, based on Q10 HIC (Head Injury Criterion) valueswere also developed through scaling the adult risk function or risk values for use withthe Q3. Concerns were raised over the validity of either approach and therefore it wassuggested that HIC injury risk threshold values should be adopted with caution and adegree of pragmatism.
Figure 4.1: Head injury risk curve for an older child dummy (Q10) based onpeak linear acceleration
The adult 3 ms head acceleration exceedence limit of 80 g was also considered to be areasonable and conservative threshold for use with the older child dummy.
It is known from the sled tests with the Q10, carried out within the EPOCh Project (Task3.2), that modern booster seats and cushions should be able to limit the measured 3 ms
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Inju
ryR
isk
Acceleration (g)
Adult
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exceedence to within 80 g, under Reg.44 conditions. As such, it is recommended thatthis is taken forward for use with the Q10.
4.2 Head excursion
Within the Q10 testing evaluation reported by EPOCh Task 3.2 head excursion limitswere proposed (Table 4-1). The proposal was based on back-to-back testing of CRS withthe P10 and Q10; changing the limits to achieve an equivalent assessment with theQ dummy, compared to that of the P. The limits used currently in UNECE Regulation 44with the P10 were adjusted by a factor accounting for the difference in mean excursionbetween P10 and Q10 dummies. The calculated head horizontal excursion limit for theQ10 is shorter than the current Regulation 44 limit for the P10, whereas the vertical limitis larger than the current limit. These changes reflect the differences in dummykinematics observed with the two dummies.
While these excursion limits are not linked directly with any particular risk of injury, theyare an obvious way to manage the likelihood of a head contact through CRS design. Itseems sensible to keep such a limit for use with the new Q10 dummy in order to at leastmaintain the status-quo relating to product performance.
Table 4-1: Head excursion limits proposed for use with the Q10 for equivalencewith P10 limits in the current Regulation 44
Criterion Q10 limits
Head horizontal excursion (mm) 465 mm
Head vertical excursion (mm) 885 mm
4.3 Upper neck force and moment
In the original Task 1.3 report, neck tension and shear corridors were produced.However, it became apparent that a simple limit for neck tension and flexion momentwould be more readily acceptable for use with the Q10. Such limits were also generatedin the 1.3 report, using a variety of scaling ratios. These limits for tension, shear,extension and flexion are reproduced in Table 4-2.
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Table 4-2: Neck injury values
Method Q10 Adult
Tension (N)
Irwin & Mertz 1834 3300
WG 12 & 18 2241 3300
Nuckley and Ching 2294 3300
Ouyang 2521 3300
Shear (N)
Irwin & Mertz 1723 3100
WG 12 & 18 2105 3100
Nuckley and Ching 2155 3100
Extension (Nm)
Irwin & Mertz 38 57
WG 12 & 18 37 57
Nuckley and Ching 24 57
Flexion (Nm)
Irwin & Mertz 126 190
WG 12 & 18 123 190
Nuckley and Ching 80 190
In the EPOCh Task 3.2 tests with the Q10 the results for the upper neck force on theQ10 ranged between 2,055 and 2,932 N for the booster cushions, where all but onebooster seat produced a larger result up to 4,239 N. These results suggest that the neckforce thresholds derived above are not feasible for modern CRS to meet underRegulation 44 test conditions.
The Regulation 44 test conditions are intended to represent the typical severity forfrontal impact accidents, in cars from the 1970s. Therefore if scaled injury thresholdvalues are being exceeded regularly in this test, one might expect to see neck injuries(relating to a tension mechanism) in the child accident data. However, the neck has notbeen identified as a frequently injured body region for older children when restrained(EPOCH Task 1.1; Visvikis et al., 2009).
On the basis that the accident data would not support the need for a substantialimprovement in tensile loading to the neck, a pragmatic threshold could be chosen toprevent any future degradation of safety in this area.
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The adult neck tension threshold is 3,300 N. Adopting this limit would lead to a failurefor three of the five booster seats tested for EPOCh Task 3.2. As such a stringentthreshold is not desired it is recommended that further testing should be carried outbefore defining the exact neck tension limit.
Accompanying any tensile value, a neck extension limit of 37 Nm and a flexion limit ofabout 125 Nm seem feasible and can be supported by the scaling approach.
4.4 Thorax acceleration
In agreement with the car occupant and pedestrian accident reconstructions by Stürtz(1980), the Task 1.3 report proposed to maintain the current UNECE Reg.44 chestacceleration criteria of 55 g (3ms exceedence).
The data recorded in EPOCh Task 3.2, for resultant chest accelerations indicate lowervalues for the Q10 dummy tests compared with those seen in the P10 for all childrestraints. Therefore, there is some scope for this value to be reduced for use with theQ10 dummy. A limit of 45 g for the Q10 is now suggested to maintain the same level ofperformance as would be achieved using 55 g with the P10, as based on the EPOCh testresults.
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5 ConclusionsIt has been shown within the EPOCh Project that the Q10 has a similar level of biofidelityto the other Q-dummies.
As an extension to the usual assessments, table-top test work has been carried out withthe Q10 to investigate the thoracic biofidelity in more detail. This work was reportedwithin this document. The results demonstrate that the regional stiffness of the Q10response to belt loading is similar to the responses obtained previously with adult PMHS.The sensitivity to belt or hub loading also appears to be similar.
Following the provision of information about the Q10 biofidelity, the injury risk functionsproposed in the original Task 1.3 report were reviewed. This review also allowedconsideration of the feasibility of suggested thresholds when compared with results fromReg.44 tests with the Q10, as carried out for Task 3.2.
As a result of this injury risk function investigation, it is proposed that the followinglimits are used with the Q10 under Regulation 44 conditions.
Table 5-1: Proposed injury criteria for use with the Q10 dummy in Regulation44 frontal impact conditions
Measurement Threshold
Head acceleration (3 ms exceedence) 80 g
Head horizontal excursion 465 mm
Head vertical excursion 885 mm
Upper neck tension †
Upper neck flexion 125 Nm
Upper neck extension 37 Nm
Chest deflection (either IR-Tracc) – x-axis 56 mm (‡)
Chest acceleration (resultant 3ms exceedence) 45 g
† It is recommended that a pragmatic neck tension limit is set after further testing withthe Q10.
‡ Possibly to be refined to give specific limits for the upper and lower IR-Tracc positionsafter further testing with the Q10.
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6 RecommendationsThe Q10 dummy is fitted with two 2-dimensional IR-Traccs to measure chest deflection.With such a multi-point measurement system there is some scope for combining datafrom the two sensors to give more information about potential injury risk. For instance,it may be that loading one part of the chest in isolation is more injurious than distributedloading over the whole chest. In this case, there may be benefit to using an advancedcriterion which accounts for force distribution somehow. The appropriateness of such aproposal would need further research and validation than has been possible within theEPOCh Project. However, work has been carried out investigating the response of theQ10 thorax to hub or diagonal seat belt loading in table-top test conditions. This workshould help understanding of the regional stiffness of the Q10 thorax and perhaps informlater discussions on the balance of importance given to either the upper or lower chestdeflection measurement. In the meantime it is suggested that the deflection limit isapplied to either sensor.
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ReferencesCarroll, J. A. and Pitcher, M. (2009). The development of injury risk functions. EuropeanCommission, EPOCh Project, Work Package 1, Task 1.3, Deliverable D1.3.
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Waagmeester, K. (2010). Q10 dummy development status review biofidelityperformance validation. Protection of children in cars, 2-3 December 2010, Munich,Germany.
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Wismans, J., Waagmeester, K., Claire, M. L., Hynd, D., Jager, K. d., Palisson, A.,Ratingen, M. v. and Trosseille, X. (2008). Q-dummies Report - Advanced child dummiesand injury criteria for frontal impact. EEVC Working Group 12 and 18 report, DocumentNo. 514 (available from the EEVC web site (http://eevc.org/publicdocs/publicdocs.htm).
