Technical Bulletin

Brain Injury Calculation
Version 1.0.1

21st March 2023
TB 035TitleVersionDocument Number
AuthorDate
Related Documents
StatusApplication Date

Brain injury calculation
1.0.1
TB 035J Ellway, V Sandner, A Eggers, M Masuda
21st March 2023
MPDB testing protocol, AOP Assessment protocol
Information
1st January 2023

Copyright ©Euro NCAP 2023 - This work is the intellectual property of Euro NCAP. Permission is granted for thismaterial to be shared for non-commercial, educational purposes, provided that this copyright statement appears on
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Preface
DISCLAIMER: Euro NCAP has taken all reasonable care to ensure that the information
published in this document is accurate and reflects the technical decisions taken by theorganisation. In the unlikely event that this protocol contains a typographical error or any
other inaccuracy, Euro NCAP reserves the right to make corrections and determine theassessment and subsequent result of the affected requirement(s).

EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP)

Table of Contents
1.

Introduction ................................................................................................................................. 1

2.

2023 Criterion ............................................................................................................................. 2

3.

2025 Criterion ............................................................................................................................. 6

4.

References ................................................................................................................................... 7

1.

Introduction

Mild traumatic brain injury is a frequent occurrence in vehicle accidents. Over the last fiveyears, the Euro NCAP Frontal Impact Working Group (FIWG) and Brain Injury WorkingGroup (BIJ) have been investigating rotational brain injury metrics. With the adoption of theMPDB frontal impact test and a more capable test tool in the THOR dummy, moremeasurement possibilities are available upon which to base a brain injury criterion.
The FIWG has reviewed kinematic injury criteria, human brain Finite Element (FE) models
along with their associated injury risk curves. A large number of brain injury criteria and injury
risk curves are available that are supported by a broad range of injury databases. It is important
to ensure that any criterion offers a relevant prediction of brain tissue injury risk. Euro NCAP
aims to address reversible brain injuries of AIS2 severity.
Implementation of a brain injury assessment will be applied to Euro NCAP assessments
published from the 1st of January 2023 in combination with the existing skull fractureassessment. A more complex FE based assessment will be implemented in 2025.

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2.

2023 Criterion

2.1DAMAGE
2.1.1 Calculation of the Diffuse Axonal Multi-Axis General Evaluation (DAMAGE)
criterion is defined in the THOR dummy technical report ISO TR 19222, see Section
4.1.
2.1.2 This criterion is applied to the THOR driver dummy in the MPDB frontal impact for
all assessments published from 1st January 2023.
2.1.3 Head rotational velocity, filtered at CFC 60, shall be used to generate rotational
acceleration throughout the impact.
2.1.4 DAMAGE is not evaluated for vehicles without frontal airbags. 0 points will beawarded to the head and neck assessment as detailed in the Euro NCAP Adult OccupantProtection Assessment protocol.
2.1.5 Calculation:
𝑚𝑥[000𝑚𝑦0𝛿𝑥̈00 ] {𝛿𝑦̈ } +𝑚𝑧 𝛿̈𝑧𝑐𝑥𝑥 + 𝑐𝑥𝑦 + 𝑐𝑥𝑧
−𝑐𝑥𝑦
[−𝑐𝑥𝑧

−𝑐𝑥𝑦
𝑐𝑥𝑦 + 𝑐𝑦𝑦 + 𝑐𝑦𝑧−𝑐𝑦𝑧

𝑘𝑥𝑥 + 𝑘𝑥𝑦 + 𝑘𝑥𝑧−𝑘𝑥𝑦−𝑘𝑥𝑦
𝑘𝑥𝑦 + 𝑘𝑦𝑦 + 𝑘𝑦𝑧[−𝑘𝑥𝑧−𝑘𝑦𝑧
𝑚𝑥 00𝑢̈ 𝑥0𝑚0
𝑢̈[] { 𝑦}𝑦00 𝑚𝑧 𝑢̈ 𝑧𝛿𝑥̇−𝑐𝑥𝑧−𝑐𝑦𝑧] {𝛿𝑦̇ } +𝑐𝑥𝑧 + 𝑐𝑦𝑧 + 𝑐𝑧𝑧 𝛿̇𝑧−𝑘𝑥𝑧
𝛿𝑥−𝑘𝑦𝑧] {𝛿𝑦 } =𝑘𝑥𝑧 + 𝑘𝑦𝑧 + 𝑘𝑧𝑧 𝛿𝑧

𝐷𝐴𝑀𝐴𝐺𝐸 = β𝑚𝑎𝑥𝑡 {|𝛿⃗(𝑡)|}𝛿⃗(𝑡) = [𝛿𝑥 (𝑡) 𝛿𝑦 (𝑡) 𝛿𝑧 (𝑡)]𝑇 , β = scale factor
m = mass, 𝑐𝑖𝑗 = damping, 𝑘𝑖𝑗 = stiffness𝛿,̈ 𝛿̇ , 𝛿 = 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛, 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦, 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
𝑢̈ = 𝑎𝑝𝑝𝑙𝑖𝑒𝑑 𝑎𝑛𝑔𝑢𝑙𝑎𝑟 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛
𝑚𝑥 = 1 𝑘𝑔, 𝑚𝑦 = 1 𝑘𝑔, 𝑚𝑧 = 1 𝑘𝑔
𝑘𝑥𝑥 = 32142 N/m, 𝑘𝑦𝑦 = 23493 𝑁/𝑚, 𝑘𝑧𝑧 = 16935 𝑁/𝑚,
𝑘𝑥𝑦 = 0 𝑁/𝑚, 𝑘𝑦𝑧 = 0 𝑁/𝑚, 𝑘𝑥𝑧 = 1636.3 N/m, a1=5.9148 ms,
𝛽 =2.9903 1/m[𝑐] = a1 × [𝑘]Version 1.0.1
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2.2Assessment
2.2.1 0.47 > DAMAGE ≥ 0.42 (50% risk AIS2) -1 point modifier applied to the driver’s headassessment.
2.2.2 DAMAGE ≥ 0.47 -2 point modifier applied to the driver’s head assessment.

2.3

DAMAGE Injury risk curves (AIS2)

2.3.1 The probability of injury P is calculated as follows:
𝑃 =1−𝑒1𝑎( ∗ln(𝑑𝑦+𝑐)− )𝑏 )(−𝑒 𝑏

Where a and b are coefficients corresponding to the shape (1/b) and scale (ea)parameters in the Weibull distribution and y is the kinematics-based brain injury metric(DAMAGE). The coefficients and quality indexes are:
Scale (ea) = 0.459
Shape 1/ b = 3.875
Intercept (c) = 0.017
Slope (d) = 0.957 (AIS 2)

2.4
Calculation window
2.4.1 When calculating DAMAGE, a time window is specified to exclude certain secondary
contacts between the head and vehicle interior. Note, this window does not apply toeither HIC or 3ms exceedance calculations.
2.4.2 The exclusion criteria are based upon those used by JNCAP.
2.4.3 This criterion will be evaluated during the loading and early rebound phases of theimpact over a max period from T0 up to 200ms.
2.4.4 The time window will be reduced to less than 200ms if, during head rebound, asecondary impact results in an external force on the head drops below -500N.
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2.4.5 The external force acting on the head shall be calculated using the head x acceleration
and upper neck x force using the formula below.
2.4.6 End the calculation when: F external x < -500N
𝐹𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑥 = −𝑀𝐻𝑒𝑎𝑑 × 𝑎𝐻𝑒𝑎𝑑 𝑥 + 𝐹𝑁𝑒𝑐𝑘𝑢𝑝𝑝𝑒𝑟 𝑥
Where MHead = 4.2kg.

2.4.7 Example:
In the example below, Fexternal x (green line) calculates a force of <-500N (I.e. morenegative) at a time of 180ms. The high-speed film confirmed the presence of asecondary contact between the dummy head and vehicle interior. Therefore, theDAMAGE criterion shall be calculated between T0 and 180ms.

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3.
3.1
3.2
3.3

2025 Criterion
Euro NCAP is undertaking accident data analyses and reconstruction via CAE toevaluate predicted brain injury risk of candidate criteria.
Brain injury numerical simulation tools and associated injury risk curves arecurrently under review.
An advanced brain injury criterion will be implemented in 2025.

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4.

References

4.1
DAMAGE
Development of a Second-Order System for Rapid Estimation of Maximum Brain StrainDAMAGE. Lee F Gabler, Jeff R Crandall, Matthew B Panzer, 2019.
4.2

Injury risk curves

pAIS2+ (BRIC) MPS = 1 EXP( POWER(BRIC/0,602;2,84)) Takhounts 2013
pAIS2+ (BRIC) CDSM = 1 EXP( POWER((BRIC 0,523)/0,324;1,8 Takhounts 2013
pAIS2+ (BRIC) = 1/(1+ 7,82+BRIC*9,1352))) UVA
pAIS2+ (UBRIC) = 1/(1+ 6,4706+UBRIC*17,1171))) Gabler 2018
pAIS2+ (DAMAGE) = 1/(1+ 7,1552+DAMAGE*19,9975))) Gabler 2018
pAIS2+(KTH_strain ) = 1/(1+EXP(3,7151 8,0517* KTH_strain Kleiven
pAIS2+(Δω) = 1/( EXP(5,4314 0,0913* Δω)) Kleiven
pAIS2+(SUFEHM_vm_stress ))= 1/(1+ 3,178+0,087* SUFEHM_vm_stress Willinger

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