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Femur Force

Description​

Femur Force reports the peak axial compressive load in a left or right femur and compares it with the occupant's available injury assessment reference value. Supported ATDs also receive an AIS 2+ femur-injury probability [1] [2].

When this feature is available​

Femur Force becomes available when either the current curve selection or any loaded test contains a femur measurement set that meets the requirements. Only channels with a usable data status count.

The required measurement set includes:

  • The signal attachment must be FEMUR - LEFT or FEMUR - RIGHT.
  • The group must contain a force channel with:
    • Axis: Z - LOCAL
    • Units: NEWTONS

WebSAT checks each femur independently and enables Femur Force if any left- or right-side measurement set contains the required channel.

Settings​

This feature has no settings.

How WebSAT processes the data​

  1. Validate the left- or right-femur Z-force channel.
  2. Convert the force signal to newtons.
  3. Filter the signal at CFC 600.
  4. Trim pre-zero data when it is present.
  5. Apply the expected compression polarity.
  6. Find the peak compressive force and its time.
  7. Compare the peak with the occupant's ATD-specific IARV, when the ATD has one.
  8. Report the peak, percent of IARV, and AIS 2+ probability when supported.

Reference values and injury risk​

The Hybrid III values follow the published ATD IARVs, and the THOR value follows the THOR injury-criteria report [4] [5].

ATDFemur compression IARV (N)
Hybrid III 5th female-6805
Hybrid III 50th male-10008
Hybrid III 95th male-12700
Hybrid III 6-year-old-2310
THOR 50th male-10577
THOR 5th female-6510

A negative sign denotes compression in the ATD coordinate convention. WebSAT compares force magnitudes when calculating percent of IARV.

Other ATDs, such as the EuroSID, ES-2re, SID-IIs, and WorldSID, have no femur compression IARV in WebSAT. For these ATDs, WebSAT reports the peak compressive force and its time, with no IARV or percent of IARV.

Hybrid III 50th male and 5th female use the NCAP AIS 2+ logistic relationships. For THOR, WebSAT uses the peak compressive femur force in kilonewtons in this AIS 2+ relationship [3] [4]:

WebSAT leaves probability blank for unsupported ATDs.

Results​

The summary reports test, occupant, left/right attachment, peak compression, peak time, IARV, percent of IARV, and AIS 2+ probability. The detail plot shows the filtered femur-force history and peak.

WebSAT femur-force summary table for test 10099
Femur-force summary for the left and right femurs of both front-seat occupants in test 10099.
WebSAT femur-force graph
Filtered femur-force history for the selected occupant and attachment.

References​

[1] Insurance Institute for Highway Safety. Frontal Offset Crashworthiness Evaluation—Guidelines for Rating Injury Measures, 2009.

[2] Eppinger, R. et al. Development of Improved Injury Criteria for the Assessment of Advanced Automotive Restraint Systems: II, 1999.

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

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

[5] Mertz, H. J., Irwin, A. L., and Prasad, P. “Biomechanical and Scaling Bases for Frontal and Side Impact Injury Assessment Reference Values.” Stapp Car Crash Journal, 47, 2003, pp. 155–188. SAE Technical Paper 2003-22-0009.