Tibia Index (TI)

Overview

The Tibia Index (TI) injury metric uses A-P Moment (Y), L-M Moment (X), and Axial Force (Z) to understand the combined loading of compression and bending moment during frontal crashes. The leg has upper and lower tibia load cells that can be used to calculate TI.

Signals

• Tibia A-P Moment (Y)
• Tibia L-M Moment (X)
• Tibia Axial Force (Z)

Calculation

Calculation from SAE 1727 [1]

1. Filter Tibia Force and Moment data (CFC = 600)
2. Apply Tibia Moment Correction
3. Calculate TI using Equation 1 [1]

$$\tag{Equation 1}TI = ABS(\frac{M_r}{M_c}) + ABS(\frac{F_z}{F_c})$$ $$\tag{Equation 2}M_r = (M_x^2 + M_y^2)^{1/2}$$

Hybrid-III Dummy Tibia Upper and Lower Load Cells [1]. The Y-Axis is into the page.

Tibia Index Critical Values [2]

ATD	$F_c$ (kN)	$M_c$ (N-m)
HIII - M95	44.1	306
HIII - M50	35.9	225
HIII - F05	22.9	114

References

[1] "Calculation Guideline for Impact Testing" No. J1727-2015-02 SAE International. SAE Technical Report, 2015.

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