Steve Summers
2002 SAE GOVT/INDUSTRY MEETING - PRESENTATION	

SLIDE 1:
OVERVIEW OF IHRA COMPATIBILITY TEST DEVELOPMENT
Stephen Summers, NHTSA


SLIDE 2:
IHRA VEHICLE COMPATIBILITY

Improve occupant protection by developing internationally agreed upon test procedures designed to improve the compatibility of car structures in front-to-front and front-to-side impacts


SLIDE 3:
IHRA VEHICLE COMPATIBILITY

Enhanced prospects for improved frontal evaluation procedures;
Agreed-upon relevant aspects include:
 - good structural interaction
 - maintaining occupant compartment integrity
 - predictable structural performance
 - controlling deceleration time histories


SLIDE 4:
Candidate test procedures include:
 - full frontal barrier test with load cells 
 	* rigid wall with or without a deformable element
 - offset deformable barrier (ODB) with load cells
 - passenger comparment integrity test using ODB
 - progressive deformable barrier (PDB)
 - moving deformable barrier
	* using load cell criteria or PDB


SLIDE 5:
FULL BARRIER TESTING

Several barrier designts are being evaluated
 - with and without deformable faes

Evaluation criteria are being developed for vehicle geometry and stiffness
 - average height of force
 - coefficient of variation
 - linear stiffness, peak power, others...


SLIDE 6:
AVERAGE HEIGHT OF FORCE

compute the effective height of the applied force on the barrier face


SLIDE 7:
AVERAGE HEIGHT OF FORCE
The height of the center of force varies over the duration of the crash. To compute an average height, the Force-Time curve is used as a "weighting" function to bias the average height towards the height where the higher loads were transferred.


SLIDE 8:
COEFFICIENT OF VARIATION	
Standard deviation / Mean
 - for each time interval when total force > 50kN
 - average across 4 adjoining load cells 
	[smooth out or average localized forces]
 - ignore outer rows or columns with <5kN peak force

Intended to measure homogeneity or distribution of stiffness
 - applicable for high resolution barriers


SLIDE 9:
DEFORMABLE BARRIER TESTING

Full barrier load cell testing using deformable barrier face
 - removes initial force spikes measured on rigid wall

300mm of low to moderate psi honeycomb
 - slotted to reduce shear effects
 - minimal effect on measured occupant compartment acceleration
 - does not change AHOF measurements
 - affects coefficient of variation



SLIDE 10:
FULL BARRIER DEFORMABLE FACE
[graph]


SLIDE :11
FULL DEFORMABLE BARRIER 
[photo] post-collision impact of deformable barrier


SLIDE 12:
OFFSET BARRIER TESTING
Several variations of offset tests are under investigation for compatibility testing
 - load cells to measure peak loads
 - progressive deformable barrier (PDB)
 - overload or high speed compartment stiffness test


SLIDE 13:
OFFSET LOAD CELL BARRIER
Limit the Peak Force measured on the barrier
 - limited energy absorption for heavy vehicles
 - barrier design needs to accomodate taller LTVs
 - Evaluates only x axis force


SLIDE 14:
OFFSET LOADCELL BARRIER FORCES
Offset test x axis response [graph]


SLIDE 15:
PROGRESSIVE DEFORMABLE BARRIER
- limits deformation measured on an offset barrier
- barrier design includes variable stiffness to reflect vehicle design
  * based on the ADAC barrier
  * represents a European small car
  * depth and height of crush of the barrier face are used to evaluate aggressivity


SLIDE 16:
PROGRESSIVE DEFORMABLE BARRIER	
[diagram]


SLIDE 17:
PROGRESSIVE DEFORMABLE BARRIER	
[graph] global barrier force


SLIDE 18:
PDB TEST METHODOLOGY
- 60 km/h test into fixed PDB
- Constant overlap of 750 mm
- no instrumented dummies
- analysis of PDB deformation profile to determine an aggressivity rating
  * barrier crush depth is divided into 50 mm increments
  * rating is based on area, avg. depth, and avg height within the 50 mm zones


SLIDE 19:
PDB TESTING
[photo] post crash barrier


SLIDE 20:
OVERLOAD TEST
- high speed offset test:  insures that occupant compartment exceeds a minimum crush force that is greater than the crush force for the engine compartment

- no dummies

- measures occupant compartment crush force: ideally occupant compartment will not crush in typical offset testing

- 80 kmph
 
- 50% overlap


SLIDE 21:
OVERLOAD TEST
[bar chart?]
intended to encourage stiffness compatibility between crash partners


SLIDE 22:
MDB TEST PROCEDURES
- all of the MDB test procedures are variations on fixed barrier tests

- intended to provide "constant energy" tests: delta V of test vehicle depends upon its mass

- MDB can be adjusted to match current fleet: can account for fleet differences in US, Europe, Asia and Australia


SLIDE 23:
LOAD CELL MDB
- Provides similar measures as the rigid load cell wall, but accounts for the mass of the striking vehicle.

- measures peak acceleration on partner vehicle

- could also be used to assess self-protection of smaller vehicles

- testing includes full frontal and offset test methods


SLIDE 24:
PDB MOVING BARRIER	
- looks to utilize the PDB assessment methodology on an MDB

- Accomodates a wider range of vehicle masses than the fixed PDB


SLIDE 25:
RESEARCH STATUS
- All proposed test methods are under active research by multiple research groups.

- there is a wide diversity of opinions and preferences for test methods

- there is significant ongoing discussion