Acetabulum/Iliac Force

Description

This metric evaluates pelvis loading measured at the acetabulum and iliac load cells. WebSAT uses a combined lateral-force method for side-impact dummies and a resultant acetabulum-force method for THOR [1] [2] [3].

When this feature is available

Acetabulum/Iliac Force becomes available when either the current curve selection or any loaded test contains one of the required pelvis measurement sets. Only channels with a usable data status count.

WebSAT accepts one of these measurement sets:

• Side-impact path:
  • Left or right acetabulum Y - LOCAL force; and
  • Pelvis-iliac Y - LOCAL force; and
  • Units NEWTONS for both channels.
• THOR left path:
  • Left acetabulum X-, Y-, and Z-local forces; and
  • Left femur Z - LOCAL force; and
  • Units NEWTONS for all four channels.
• THOR right path:
  • Right acetabulum X-, Y-, and Z-local forces; and
  • Right femur Z - LOCAL force; and
  • Units NEWTONS for all four channels.

WebSAT selects the appropriate path from the occupant's ATD information and enables the metric if any eligible left- or right-side group satisfies that path.

Settings

This feature has no settings. WebSAT selects the path from the ATD information.

How WebSAT processes the data

1. Select the side-impact or THOR calculation path from the occupant's ATD information.
2. Convert the required force channels to newtons.
3. Filter every force channel at CFC 600.
4. For the side-impact path, sum the acetabulum and iliac Y forces at each time sample.
5. For the THOR path, calculate resultant acetabulum force from the X, Y, and Z components.
6. For the THOR path, suppress samples during femur tension so the result represents compressive hip loading.
7. Find the governing combined or resultant force and its time.
8. Report the result with the applicable IARV and injury risk when supported.

Reference values and injury risk

The supported SID-IIs combined-force IARV and AIS 3+ relationship come from the NHTSA side-impact requirements [4]:

$P(AIS\,3+)=\frac{1}{1+e^{6.3055-0.00094|F|}}$

where $F$ is combined pelvis force in newtons. For THOR, WebSAT uses the peak resultant acetabulum force in kilonewtons to calculate hip-fracture probability [5]:

$P(\text{hip fracture})=\Phi\left(\frac{\ln(1.429F_{AR})-1.6058}{0.2339}\right)$

WebSAT reports the risk only when the ATD has a supported relationship.

Results

The result summary reports combined Y force and IARV information for the side-impact path, or resultant acetabulum force and hip-fracture probability for THOR. Supporting plots show the filtered component and combined/resultant curves.

Acetabulum and iliac-force summary for the left- and right-front-seat occupants in test 10099.

Filtered component forces and resultant acetabulum force for the selected occupant.

References

[1] Zhu, J. Y., Cavanaugh, J. M., and King, A. I. “Pelvic Biomechanical Response and Padding Benefits in Side Impact Based on a Cadaveric Test Series.” SAE Technical Paper 933128, 1993.

[2] Bouquet, R. et al. “Pelvis Human Response to Lateral Impact.” 16th International Technical Conference on the Enhanced Safety of Vehicles, 1998.

[3] SAE International. Sign Convention for Vehicle Crash Testing. SAE Standard J1733, 2018.

[4] National Highway Traffic Safety Administration. 49 CFR § 571.214—Side Impact Protection.

[5] Craig, M. et al. Injury Criteria for the THOR 50th Male ATD. National Highway Traffic Safety Administration, 2020.