18kg Ejection Mitigation Headform

 

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Overview

In 1991 the National Highway Traffic Safety Administration (NHTSA) initiated research programs concerning motor vehicle rollover protection. As part of that research, NHTSA conducted a crashworthiness research program to evaluate ways to reduce the number of fatalities due to ejection from the vehicle. The program was then expanded from side impact ejections to include ejections from rollover, front, and rear impacts.

More recently, on November 30, 2006, NHTSA released a Memorandum to explain the test procedure guidelines for automotive manufacturers to use for research into the performance of ejection mitigation countermeasures (NHTSA docket 2006-26467). The guideline does not represent a regulatory or compliance test procedure but was put in place for the manufacturers to replicate as an option.

In response to this Memorandum, First Technology Safety & Analysis (FTSA) was approached to supply the 18 kg headform required for this test procedure. The Ejection Mitigation headform was originally produced by FTSA back in 1988 but was discontinued in 1991. FTSA recently created new molds and castings and has launched the headform back into production. It is now available for purchase.

Simulation Models

Humanetics offers highly detailed and fully validated Finite Element Models of its headforms in the codes LS-DYNA, PAM-CRASH, ABAQUS and RADIOSS, along with FE modeling consultancy services.

Dummy Features

Head

The 18 kg headform consists of a vinyl skin on an aluminum skull with a steel back plate in place of a skull cap. The skull accommodates an accelerometer mount and the back plate is designed to be machined to attach to the user's impactor device. The head assembly mass is approximately 4.6 kg. 18 kg is the mass of the headform plus the moving mass of the impactor. This is the effective mass of the human head and shoulders.

Featureless Face Form

The 18 kg head has a featureless face to simplify contact interactions. The form of the face is a surface of revolution formed using a third degree polynomial curve equation, (X/Xo)2 + (Z/Zo)3 = 1. The upper quadrant is the region where X and Z are both positive. This part of the curve is reflected about the plane Z = 0 to form the lower quadrant. The entire curve is rotated plus and minus 90 degrees from the mid-saggital plane, Y = 0, to form the front surface of the head.

Technical Specifications

Summary Chart

Feature X Location Y Location Z Location
Origin Reference Point Skull-Head Back Mating Surface  Mid-Saggital Plane Machined Surface Underside of Skull Horizontal Plate
Head Coordinates  2.2 in. / 56 mm  0.0 .8 in. / 20 mm
Test Lab Impact Line  N/A  0.0 .8 in. / 20 mm
Vehicle Impact Test Location  N/A  0.0 1.8 in. / 46 mm
Accelerometer A.I.P.  2.2 in. / 56 mm  0.0 1.8 in. / 46 mm
Center of Gravity  2.13 in. / 54 mm  0.0 1.46 in. / 37 mm

Specifications

Parameter Spec.Humanetics
Headform Mass (w/Accelerometers and Mount) 4.18 / 5.08 kg
CG-X forward from skull-cap mating surface .0490 / .0592 m
CG-Y to the left from MSP -.0051 / .0051 m
CG-Z upward from lower horizontal machined surface .0320 / .0422 m
Probe Mass 12.00 ± .026 kg
Probe Velocity 1.10 / 1 .30 m/s
Probe Force 7.0 / 10.0 kN
Temperature 20.6 / 22.2 ºC
Relative Humidity 10 / 70 %

 External Dimensions

Description Dimension (in, ±.1) Dimension (meter)(ref.)
Height  8.90  .226
Width  6.96  .177
Length  5.68  .144