Tire Friction Table Example

The Optional TIRMU inputs permits the simulation of individual tires which have drag factors different than the nominal MU (i.e., metal gouging, etc.). If entered as 0.0, the program assumes default value of 1.0 (normal).A value of TIRMU of 0.86 would reduce the effective friction coefficient for a tire from a nominal of 0.70 to 0.60. The nominal friction coefficient is determined for an individual wheel by either the friction zone as specified on msmac input card 12 or by a polygon friction zone specified on msmac input card(s) 30,31,32.

For simulation of a constant variation of the effective individual tire friction factor, for example to simulate the difference between a truck and car tire, the following msmac input cards are used:

•    Input cards 6 and 7, fields 6-9 are for veh1 and veh2,

•    Input card 20 & 22, fields 5 & 6 are for the trailer wheels of veh1 & veh2

•    Input card 56, fields 6-9, are for veh3

To permit the simulation of a tire friction factor changing during a simulation run, msmac input card(s) 44 & 49 are used. These input tables permit varying the tire friction factor multipliers during a simulation run (e.g., to simulate the changing friction at individual wheels as a tire deflates and/or rim gouging occurs.

In the example. There are two smac input files:

•    TIRMU Option.si5

•    TIRMU Option OFF.si5

In the first file, please note input cards 44 & 49.. These tables indicate the change in the front and rear tire firction factors from 0.9 sec to 1.5 seconds. The friction is varied to rise in the front and lower in the rear.

 

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