A unique feature of the original SMAC program (and therefore the m-smac program) is the ability to simulate and therefore reconstruct vehicle collisions that include sideslaps and/or secondary impacts. In the SMAC program, each vehicle is represented by a rectangular box with the length and width dimensions of the actual vehicle. Collision detection is accomplished by continually checking the corners of each vehicle "box" to determine if it is within the periphery of the other vehicle "box".
Once a corner point is found to be in contact, the program begins calling the collision routine to use the collision model to scan for interference and contacts and to calculate the associated collision forces. The program also changes to the integration time increment to the user specified collision integration interval ( DTCOLL, normally 1 millisecond (0.001), set on m-smac input card 1, field 4).
The end of the collision event is assumed when a fixed time increment has passed wherein the accelerations for each vehicle are both below 1 g-unit. The program then changes into a separation mode and utilizes the separation time increment (DTCOLT, normally 5 milliseconds (0.005), set on m-smac input card 1, field 5).
If a fixed number of separation time increments are passed without any accelerations greater than 1 g-unit, then the program shifts to the trajectory time increment (DTTRAJ, normally 10 milliseconds (0.010), set on m-smac input card 1, field 3).
Much of the logic associated with the changing of the integration time increment was created to reduce the computer overhead and costs associated with running a SMAC simulation on time-share mainframe computer systems. With the use of SMAC on PC computers, there is no cost associated with the use of one millisecond time increments for all the time increments at least for final checkout runs to insure that secondary sideslap collisions are not missed or inadequately modeled. Problems have been found and reported in our recent SAE paper, SMAC-97 (Ref. 10), with applications of the EDSMAC program where the program may miss the accelerations associated with "side-slap" impacts. We have implemented a number of changes/options in the m-smac program to help avoid this problem from occurring. The following is a brief description of the changes/options implemented in m-smac related to side-slaps and/or secondary impacts:
m-smac inputs, Card 90, Field 7
DamageOutFull option of m-smac:
From m-edit, Select the Tools menu
Select the m-smac tab, and the DOSX32 m-smac tab (note that this tab sets options for all versions)
Click OK and then run either version of m-smac
If you run with and without this option set, you will find that the size of the output file increase dramatically (by a factor of 7 to 10). You should only use this option for checkout runs and/or if a problem occurs. Reset the Option field to blank after testing/use)
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