## What is BEV?

General Questions related to the CRASH Program and clones
Damage Analysis & Momentum Based Analysis programs
ray

### What is BEV?

What is BEV??
From McHenry Accident Reconstruction:
• "Confusion in the interpretation of damage in actual accidents can be created by the use of the term Barrier Equivalent Velocity as opposed to Barrier Impact Velocity in the specification of corresponding test conditions. Such confusion comes from the following definition (e.g., Reference [1]) of the Barrier Equivalent Velocity (BEV):
BEV is “the equivalent impact velocity of a vehicle into a fixed, rigid barrier that would result in the same magnitude of crush as observed on a subject vehicle under analysis.
Clearly, when a vehicle with a stiff front structure collides with the softer rear of another vehicle, the magnitude of crush on the striking vehicle will be less than that in a corresponding barrier crash with the same impact speed-change. Thus, a simplistic crush comparison on the striking vehicle, using the above BEV definition and the specified BEV values for air bag deployment, will generally lead to the conclusion that the BEV was below that specified for the airbag deployment threshold. Note that this confusion could be overcome by either (a) the definition of deployment thresholds in terms of Barrier Impact Velocity rather than BEV, or (b) a more proper definition of BEV as meaning “that portion of the impact speed-change that precedes the achievement of a common velocity.”
The concept of assessing impact severity by relating the damage sustained in a collision to that which the same vehicle sustains in an experimental barrier impact test (e.g., the Barrier Equivalent Velocity (BEV) concept) was first described by Mackay in 1968 (Ref. [2]). When the two vehicles involved in a car-to-car collision have essentially similar deformation and weight characteristics, such a BEV method of assessing impact severity can be reasonably reliable for use in statistical studies. However, if the vehicles have dissimilar characteristics, the BEV ratings can be considerably in error as a measure of impact severity. For example, if a heavy soft car collides with a light stiff car, it is possible for the stiffer car to experience a substantial change in velocity with no appreciable damage (Ref. [2], [3]).
A barrier impact velocity of X MPH produces an impact speed-change, Delta-V, of X MPH plus the rebound velocity, if any. If the barrier is replaced by a standing, “mirror-image” vehicle, the same extent of damage and the same impact speed-change, Delta-V, as occurred in the barrier impact will be produced by a closing velocity twice as large as the barrier impact velocity (i.e., a closing velocity of 2X). The interpretation of damage in actual collisions in terms of BEV, or Delta-V, requires proper consideration of the mass and stiffness ratios of the collision partners and of the effects of any collision offset (e.g., 4)".
References

brian
Posts: 500
Joined: Tue Jul 14, 2009 10:52 am

### Re: What is BEV?

October 26, 2010: Q: Is there such a thing as "Barrier Equivalent Speeds" for tractors? Who has done the testing?
A: As has been demonstrated in the previous thread, there is some confusion about Barrier Equivalent Velocity or Speed, etc. That would obviously also be applicable to trucks. .
However, doing a quick check I found the following article which apparently equates using EDCRASH/damage analysis for determination of the 'Equivalent Barrier Speed (EBS) and then also throws in a Peterbuilt rollover accident. The Peterbuilt analysis seems to be mainly an advertisement for their crush determination techniques (they used it to determine compartment intrusion) rather than having anything to do with EBS? Not sure why that is in the paper?
The paper is as follows:
1999-01-0439 "Using Digital Photogrammetry to Determine Vehicle Crush and Equivalent Barrier Speed (EBS)" By Fenton, Johnson, LaRocque, et al
ABSTRACT
• This paper presents a method of determining a vehicle crush and equivalent barrier speed using digital photogrammetry. A state-of-the-art documentation technique called close-range photogrammetry allows engineers and accident reconstructionists to create three-dimensional computer models of damaged vehicles utilizing photographs. Utilizing photogrammetric software, engineers can digitize accident scene photographs to create accurate three-dimensional computer models of the vehicles, which can be used to quantify structural damage sustained by the vehicles. Crush deformation can be quantified utilizing this process and the resulting crush dimensions can be input into engineering software to determine a vehicle’s equivalent barrier speed.
The also include the following under a section UTILIZING THE THREE-DIMENSIONAL MODEL
• Determining EBS – There are several software programs available on the market to determine equivalent barrier speed (EBS) utilizing crush data. For this process, EDCRASH developed by Engineering Dynamics Corporation [5] was used to calculate EBS. These authors will not discuss the details of how data is input into EDCRASH. This information can be found in the EDCRASH technical manuals [5]. In general, crush data is gathered from the three-dimensional computer model generated from the photogrammetric process (see Figure 8). This data is input into the EDCRASH system along with other vehicle data such as the vehicle stiffness coefficients, weight, and dimensions. Utilizing this information EDCRASH can calculate the amount of energy required to crush the vehicle and subsequently the vehicle equivalent barrier speed (see Figure 9).
CONCLUSION
• Utilizing close-range photogrammetric techniques, engineers can measure vehicle crush utilizing photographs instead of physically measuring the vehicle. This method is of great value when the vehicle is no longer available, and photographs are the only documentation of the vehicle damage, which is quite common when an engineer must reconstruct an accident years after the accident occurred. Utilizing close-range photogrammetry, a three dimensional model of the damaged vehicle can be created, and the crush deformation can be reconstructed with an accuracy of one inch under typical circumstances. Knowing the crush dimensions allows engineers to calculate a vehicle’s equivalent barrier speed and changes in occupant compartment dimensions.
NOTE: The appendix includes some of their technique applied to a Peterbuilt truck 'in a rollover accident'. They talk about the technique used to determine compartment intrusion? And don't equate determination of crush in that rollover to then apply EDCRASH? (just where would they get Crush coefficients for that?)
Question? Comment? Please email forum@mchenrysoftware.com. Also see the McHenry Forum Index
Visit McHenrySoftware.com for technical information & software. McHenryConsultants.com for litigation consulting.