And then as a0 & a1 in the APPENDIX
When and why were these changed to the CRASH A&B coefficients?
A: For an introduction please see What is CRASH for background on the CRASH program.
- A quick overview:
- The damage analysis procedure of CRASH was developed as an auxiliary program to help with the NHTSA crash investigations come up with initial speeds to run the much more sophisticated SMAC Program. So much of the early development of CRASH was done as appendix material while refining and developing SMAC. Ultimately NHTSA adopted mainly the CRASH damage analysis procedure for their NASS crash investigations due to simplicity and inexpensive cost to run the program
- The 1970s were the days of mainframe timeshare computers like MCAUTO where you paid for computer the memory space & CPU time for each computer program run. For a peek at the mainframe to mini to PC computer transitions see our 1996 discussion Why develop for the PC?.
- The damage analysis procedure of CRASH was developed as an auxiliary program to help with the NHTSA crash investigations come up with initial speeds to run the much more sophisticated SMAC Program. So much of the early development of CRASH was done as appendix material while refining and developing SMAC. Ultimately NHTSA adopted mainly the CRASH damage analysis procedure for their NASS crash investigations due to simplicity and inexpensive cost to run the program
- From the McHenry SAE Paper 750893 "Comparison of Results Obtained with Different Analytical Techniques for Reconstruction of Highway Accidents":
- From bottom of page 6
- DAMAGE ANALYSIS
- "Hand calculation techniques for damage analysis that yield reasonable estimates of the impact velocity in frontal collisions (i.e., the relative velocity of approach) have been developed initially by Emori SAE 68-0016 , and Emori SAE 70-0017 (full width contact only) and then further refined by Campbell SAE 74-0565(partial width contact) , using linear approximations of the relationship between residual crush and impact velocity. The SMAC program applies a similar analytical approach to the entire peripheral structure, and it has been demonstrated to yield good approximations of both impact velocity and speed change, DeltaV, in general collision configurations including oblique, non-central impacts. The objective of the present research has been to develop a simple, closed-from damage analysis technique that is applicable to general collision configurations."
- Absorbed Energy -
"The calculation of absorbed energy is based on residual crush and is patterned after that developed by Campbell. The only significant difference is in the treatment herein of the energy absorbed without residual crush as being proportional to the contact width rather than a constant".
The following relationship is applied:
- DAMAGE ANALYSIS
The Force per unit width (F) as a function of A, B & C: - From bottom of page 6
- McHenry SAE Paper 750893 "Comparison of Results Obtained with Different Analytical Techniques for Reconstruction of Highway Accidents"
- McHenry The Algorithms of CRASH, 2001
For additional information on damage analysis & CRASH, please see:
- The Algorithms of CRASH, paper presented at 2001 SECCC, Aug 2001
- NHTSA CRASH3 Technical Manual - 1986 NHTSA collection/summary of CRASH papers
- From the McHenry Forum Topic on CRASH:
- Why was the CRASH program created?
- What Speed Should I Use to Calculate CRASH3 A&B Coeff?
- Is CRASH damage analysis a virtual relationship?
- Should a CRASH type damage analysis include induced damage?
- What is the "No Damage Intercept" of CRASH
- Can You Use Maximum Crush For CRASH A&B Crush Coefficients?
- Effects of Restitution in the Application of Crush Coefficients
- Crush Coefficients Conversions: CRASH (McHenry), Campbell, WinSMASH (Prasad)
..and more, see the McHenry Forum and specifically the McHenry Forum topic CRASH and Damage Analysis