Welcome to Adams/Solver Subroutines - Kxcad.net

Welcome to Adams/Solver Subroutines
The force has two components: a spring or stiffness component and a damping or viscous component.
The stiffness component is a function of the penetration of the floating part into the restricting part. The
stiffness opposes the penetration.
The damping component of the force is a function of the speed of penetration multiplied by a damping
coefficient. The damping opposes the direction of relative motion. To prevent a discontinuity in the
damping force at contact, the damping coefficient is, by definition, a cubic step function of the
penetration. Therefore, at zero penetration, the damping coefficient is always zero. The damping
coefficient achieves a maximum, cmax, at a user-defined penetration, d. Even though the points of
contact between the floating part and the restricting part may change as the system moves, Adams/Solver
always exerts the force between the I and the J markers. Examples of systems you can model with the
BISTOP function include a ball rebounding between two walls and a slider moving in a slot. The slider
is the floating body, and the part containing the slot is the restricting body. As long as the slider remains
within the confines of the slot, there is no force acting on the slider. But if the slider tries to move beyond
the slot, a force turns on, effectively preventing the slider's escape.
The following summarizes the BISTOP function:
• When x1 x x2, force = 0.
• When x < x1, p = x1 - x and the force is positive.
• When x > x2, p = x - x2 and the force is negative.
• When p < d, the damping coefficient is a cubic step function of the penetration.
• When p d, the damping coefficient is cmax.
The values of k, e, cmax, and d depend on the materials used in the two parts and on the shapes
of the parts.
The following equation defines BISTOP:
STOP
Min k ( x1 – x)
e ( ⋅ – STEP ( x, x1 – d, cmax, x10) ⋅x′0
, )
0
Max – k ( x – x2) e ⎧
x < x1 ⎪
= ⎨
x1 ≤x ≤x2
⎪
⎩ ( ⋅ – STEP ( x, x2, 0, x2 + d, cmax ) ⋅x′0
, ) x > x2 See an explanation of the STEP function (C++ or FORTRAN).
Caution: • BISTOP is only used to determine forces or torques.
• When e is less than or equal to one, the rate of change of the force is discontinuous
at contact. This may cause convergence problems.
BODY_MASS_PROPERTY
The BODY_MASS_PROPERTY utility subroutine accepts specifiers for either a single part or the entire
ADAMS model and returns to the caller the mass properties (mass, center of mass and inertia tensor) for
that part or model.
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