Format

Description

The IMPACT function models impact forces acting on bodies during collision.  The elastic properties of the boundary surface between the two bodies can be tuned as desired.

Example

<Reference_Variable

    id                    = "30300700"

    type                  = "EXPRESSION"

    expr                  = "IMPACT(DZ(10301030,30302030),
                             VZ(10301030,30302030),2.5,2500,1,1000,2.5)"

/>

OR

<Force_Vector_TwoBody

    id                    = "10501"

    type                  = "ForceOnly"

    i_marker_id           = "10515721"

    j_floating_marker_id  = "10516722"

    ref_marker_id         = "10516720"

    fx_expression         = "0"

    fy_expression         = "0"

    fz_expression         = "IMPACT(DZ(10515720,10516720,10515720),
                             VZ(10515720,10516720,10515720),1,10000.0,1.0,0.5,0.1)"

/>

Arguments

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 impact function returns a positive value, otherwise it returns zero.

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