Deformable Face - ATD-6240

Overview

The Head Assembly Deformable Face was commercialized by FTSS in 1989 following research on facial impact injury by J. Melvin and T. Shee.¹

The deformable face models the response of the human face for a 25 mm diameter impactor similar to a steering wheel rim. The response curve of the face in force versus time simulates nasal bone fracture. This occurs at approximately 3 kN force, 6 to 8 ms after impact, and at 25 mm deflection for impact speeds from 2.8 to 7.1 m/s.

Use

The deformable face is mounted to a Hybrid III neck on the dummy and is used in frontal impact tests of the vehicle.

If the face hits an object inside the car when the head moves forward during a test the foam will be crushed in the contact area and register the impact as a deformation.

The deformable face makes the forces transmitted to the head from the face more accurate during steering wheel impact due to the simulated crushing of the facial bones.

Inertial forces, the force transmitted to the head from the neck and the impact forces are used to calculate head motion. Inertial forces may be measured with linear and rotational accelerometers and the neck transducer can be used to measure forces and moments transmitted through the neck. Resultant impact forces transmitted through the face are derived in the paper.¹

The acceleration of the head may be used as a predictor of brain injury by referring to the biomechanical data.

Summary

The deformable face yields biofidelic force transmission for facial impact which improves the dynamic response characteristics of the head. The face also records the location of impact. This allows more accurate calculation of head kinematics for better injury prediction.

Dummy Features

Head

The head assembly deformable face is based on a Hybrid III head with modifications. It has a removable vinyl cover in the front, similar to a knight’s visor. Underneath, a piece of crushable foam mounts to an elastomeric locator mounted on a vertical surface created in the front of the skull by cutting and welding in an aluminum plate.

The head does not come with a transducer replacement, pivot pin, or hardware. These items must be ordered separately or the customer may use the ones from a standard Hybrid III head. These items will mount the head to a Hybrid III neck on a Hybrid III dummy.

Construction

The head assembly deformable face is based on modifying a standard Hybrid III automotive head. To accommodate the deformable components a horizontal cut back 25 mm and a vertical cut from it is made down the full front of the skull. Flat aluminum plates are welded in to form a shelf. In this area face components are added consisting of a front layer of vinyl, the crushable foam and a back layer of rubber having a total thickness of approximately 41 mm varying with the face profile. Up to 19 mm of the crush will permanently deform the foam so that the contact location can be determined. This helps in calculating the force balance at impact and also registers the impact area.

Bibliography: 1. “Facial Injury Assessment Techniques”. J. Melvin and T. Shee. SAE paper 896072 in SAE book PT-44 “Hybrid III: The First Human-Like Crash Test Dummy” by Stanley H. Backaitis and Harold J. Mertz. SAE Warrendale PA 1994.

Technical Specifications

Instrumentation, Suggested

Location	Description	Channels	Quanity
Head:	Accelerometer, IE-103 Force and Moment, IF-205	1 6	3 1
Head:	Accelerometer, IE-103 Force and Moment, IF-205	1 6	3 1

Assembly Weights

Part	Weight (lb)	Weight (kg)
Upper Neck transducer replacement, hardware, accels and mounts	10.00 ± 0.10	4.5 ± .05

External Dimensions

Description	Dimension (in)	Dimension (cm)
CG-X, Forward of skull=cap vertical mating surface	2.50	6.35
CG-Z, Above bottom surface of skull base plane	1.40	3.56