Neck Injury Criterion (Nij)

Overview:

Neck Injury Criterion (Nij) uses the neck axial force and the neck flexion/extension moment of the upper or lower neck to predict injury [1]. A Nij value greater than 1.4 correlates to a 40% risk of AIS ≥ 3 neck injury, which inlcudes serious injuries such as cervical spine fractures or dislocations [1]. The Polarity Permutations below represent the four combinations of axial force direction (tension or compression) and bending moment direction (flexion or extension) [1]. These permutations represent different loading modes that the neck can experience during a crash, and each has distinct critical values for injury [1].

Required Signals:

• Flexion/Extension Moment of the Upper or Lower Neck (Y)
• Tension/Compression Force of the Upper or Lower Neck (Z)

Calculation:

1. Filter neck force data (CFC = 1000) and neck moment data (CFC = 600) according to J211-1
2. Apply Neck Moment Corrections
3. Calculate Nij for each polarity permutation

$$\tag{Equation 1}N_{ij} = \frac{F_z}{F_{zc}} + \frac{M_y}{M_{yc}}$$

$F_z$ = Axial Force, $F_{zc}$ = Critical Force Value, $M_y$ = Flexion/Extension Moment, $M_{yc}$ = Critical Moment Value

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Polarity Permutations [1]

$N_{ij}$	Force Condition	Moment Condition
Ntf	$F_z>0$, Tension	$M_y>0$, Flexion
Nte	$F_z>0$, Tension	$M_y<0$, Extension
Ncf	$F_z<0$, Compression	$M_y>0$, Flexion
Nce	$F_z<0$, Compression	$M_y<0$, Extension

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Reference Values [1] [2] [3]

Upper Neck Critical Values In-Position

ATD	$F_{zc} (N)$ ($F_{zc}>0$, Tension)	$F_{zc} (N)$ ($F_{zc}<0$, Compression)	$M_{yc} (Nm)$ ($M_{oc,y}>0$, Flexion)	$M_{yc} (Nm)$ ($M_{oc,y}<0$, Extension)
HIII - M95	8180	-7480	405	-177
HIII - M50	6806.0	-6160.0	310.0	-135.0
HIII - F05	4287	-3880	155	-67
HIII - 10yo	3710	-3390	125	-54.8
HIII - 6yo	3080	-2820	96	-42
HIII - 3yo	2330	-2130	67	-29.3
CRABI - 18mo	1760	-1610	46.8	-20.4
CRABI - 12mo	1610	-1470	42.5	-18.6
CRABI - 6mo	1510	-1380	39.5	-17.3
THOR - M50	4200	-4520	60	-79.2
SID - IIs	4260	-3900	153	-66.9

In position testing refers to crash testing where the ATD is properly seated and restrained, similar to a typical driving scenario [4]. Out of position testing refers to crash testing where the ATD may be in a non-seated posture or have shifted from their seat [4].

Upper Neck Critical Values Out-of-Position

ATD	$F_{zc} (N)$ ($F_{zc}>0$, Tension)	$F_{zc} (N)$ ($F_{zc}<0$, Compression)	$M_{yc} (Nm)$ ($M_{oc,y}>0$, Flexion)	$M_{yc} (Nm)$ ($M_{oc,y}<0$, Extension)
HIII - M95	7480	-7480	405	-162
HIII - M50	6200	-6200	305.0	-122.0
HIII - F05	3880	-3880	155	-61
HIII - 10yo	3710	-3390	125	-50.1
HIII - 6yo	2820	-2820	96	-38.4
HIII - 3yo	2130	-2130	67	-26.8
CRABI - 18mo	1610	-1610	46.8	-18.7
CRABI - 12mo	1460	-1460	43	-17
CRABI - 6mo	1380	-1380	39.5	-15.8
SID - IIs	4260	-3900	153	-66.9

Lower Neck Critical Values In-Position

ATD	$F_{zc} (N)$ ($F_{zc}>0$, Tension)	$F_{zc} (N)$ ($F_{zc}<0$, Compression)	$M_{yc} (Nm)$ ($M_{oc,y}>0$, Flexion)	$M_{yc} (Nm)$ ($M_{oc,y}<0$, Extension)
HIII - M95	8180	-7480	810	-354
HIII - M50	6780	-6200	610.0	-266.0
HIII - F05	4260	-3900	306	-134
HIII - 10yo	3710	-3390	250	-110
HIII - 6yo	3080	-2820	96	-42
HIII - 3yo	2330	-2130	67	-29.3
CRABI - 18mo	1760	-1610	93.6	-40.8
CRABI - 12mo	1610	-1470	85	-37.2
CRABI - 6mo	1510	-1380	79	-34.6
SID - IIs	4260	-3900	306	-134

Lower Neck Critical Values Out-of-Position

ATD	$F_{zc} (N)$ ($F_{zc}>0$, Tension)	$F_{zc} (N)$ ($F_{zc}<0$, Compression)	$M_{yc} (Nm)$ ($M_{oc,y}>0$, Flexion)	$M_{yc} (Nm)$ ($M_{oc,y}<0$, Extension)
HIII - M95	7480	-7480	810	-324
HIII - M50	6200	-6200	610.0	-244.0
HIII - F05	3900	-3900	155	-61
HIII - 10yo	3390	-3390	250	-100
HIII - 6yo	2820	-2820	192	-76.8
HIII - 3yo	2130	-2130	68	-27
CRABI - 18mo	1610	-1610	93.6	-37.4
CRABI - 12mo	1470	-1470	85	-34
CRABI - 6mo	1380	-1380	79	-31.6
SID - IIs	3900	-3900	306	-122

Injury Criteria [1]

Parameter	IARV	Good - Acceptable	Acceptable - Marginal	Marginal - Poor
$N_{ij}$	1.00	0.80	1.00	1.20
Neck Axial Tension (kN)	3.3	2.6	3.3	4.0
Neck Compression (kN)	4.0	3.2	4.0	4.8

NCAP Combined Injury Rating [5]

$$P_{N_{ij}} (3+) \tag{Equation 2} = \frac{1}{1+e^{3.2269-1.9688*N_{ij}}}$$ $$P_{\text{neck force}} (3+) \tag{Equation 3} = \frac{1}{1+e^{10.9745-2.375*N_{force}}}$$

Where ${\text{neck force}}$ represents the neck tension or compression force for HII M50

$$P_{\text{neck force}} (3+) \tag{Equation 4} = \frac{1}{1+e^{10.958-3.770*N_{force}}}$$

Where ${\text{neck force}}$ represents the neck tension or compression force for HII F05

$$P_{neck} \tag{Equation 5} = maximum(P_{N_{ij}}, P_{\text{neck tens}}, P_{\text{neck comp}})$$

Nij Injury Risk Curve

Neck Tension and Neck Compression Injury Risk Curve

References

[1] Mertz, Harold J. "Anthropomorphic test devices." Accidental injury: Biomechanics and prevention. New York, NY: Springer New York, 1993. 66-84.

[2] National Highway Traffic Safety Administration. (2000). Federal Motor Vehicle Safety Standards; Occupant Crash Protection; Final Rule. Federal Register, 65(208), 67691–67703.

[3] Craig, M., et al. "Injury criteria for the THOR 50th male ATD." National Highway Traffic Safety Administration (2020).

[4] "Guidelines for Using the UMTRI ATD Positioning for ATD and Seat Positioning (Version I)". Insurance Institute for Highway Safety, January 2003.

[5] Wong, Yeun, et al. "A Data Processing System for the NCAP Combined Injury Rating". National Highway Traffic Safety Administration.