Format

Description

The BISTOP function models a gap element.  It can be used to model forces acting on a body while moving in the gap between two boundary surfaces, which act as elastic bumpers.  The properties of the two boundary surfaces can be tuned as desired.

Example

<Force_Vector_TwoBody

    id                    = "30101"

    type                  = "ForceOnly"

    i_marker_id           = "30102031"

    j_floating_marker_id  = "30101031"

    ref_marker_id         = "30101010"

    fx_expression         = BISTOP(DX(30102030,30101010,30101010),VX30102030,30101010,30101010),0.5,9.5,10000000,2.1,1,0.001)"

    fy_expression         = "0"

    fz_expression         = "0"

 />

Arguments

The expression used for the independent variable.  For example, to use the z-displacement of I marker with respect to J marker as resolved in the reference frame of RM marker as the independent variable, specify as DZ({marker_i.idstring}, {marker_j.idstring}, {marker_rm.idstring}).

The time derivative of the independent variable. For example, if is specified as above, then will be
VZ({marker_i.idstring}, {marker_j. idstring}, {marker_rm.idstring}).

The lower bound of . If is less than , the bistop function returns a positive value.  The value of must be less than the value of .

The upper bound of . If is greater than , the bistop function returns a negative value.  The value of must be greater than the value of .

The stiffness of the boundary surface interaction.  It must be non-negative.

The exponent of the force deformation characteristic.  For a stiffening spring characteristic, must be greater than 1.0 and for a softening spring characteristic, must be less than 1.0. It must always be positive.

The maximum damping coefficient.  It must be non-negative.

The penetration at which the full damping coefficient is applied.  It must be positive.

Definition