## Card 12 - Terrain Friction Coefficients

 XBP(1) YBP(1) XBP(2) YBP(2) XMU1 XMU2 CMU NoMirror 12

 Card:  Field Variable Description Original Units Default Units Metric Units 12:1 12:2 12:3 12:4 XBP(1) YBP(1) XBP(2) YBP(2) XB1 YB1 XB2 YB2 These coordinates define two points, 1=(XB1,YB1) and  2= (XB2,YB2),  in the plane of the tire  forces. These two points determine a boundary line,  dividing the plane into two zones which may be assigned different coefficients of friction.   This allows the user to simulate a vehicle running onto a dirt shoulder, a  field, etc., or any similar situation which demands two adjacent areas of different frictional properties. The methodology for the friction zones was that the area on the origin side of the specified friction zone line was specified as friction zone No. 1.  The area on the non-origin side of the line was specified as friction zone No. 2. (Note: This creates a mirror image for friction lines which occur near the origin, i.e., friction zone 2 is repeated on the opposite (mirror image) side of the origin).(For Additional terrain friction specifications, see Friction Polygons option, To disable the mirror image characteristic, see NoMirror,  field 9 below. inches   inches   inches   inches ft.   ft.   ft.   ft. Meters   meters   meters   meters 12:5 XMU1 μ The coefficient of friction in zone 1.  It can be made to vary with speed (see  12:7); it is assumed independent of  other factors within a zone.  Suggested values are ~0.7 for dry pavement, ~0.5 for wet. See References 17 & 18 for approximate values for friction coefficients. 12:6 XMU2 μ2 The coefficient of friction in zone 2. 12:7 CMU Cμ The coefficient of linear decrement of friction, varies μ with tire speed based on speed in in/sec. Please see discussion below. sec/in sec/cm 12.8 CMU2 Cμ2 The coefficient of linear decrement of friction for Vehicle2, If CMU2 is 0.0, then program will set CMU2=CMU. Please see discussion below. sec/in sec/cm 12:9 NoMirror Normally = 0.0 If set = 1.0, Option turns off the Mirror Image characteristic of the friction zone. The  friction zone will only be effective in the quadrant(s) defined by the endpoints.

More: DISCUSSION: Friction decrement with speed