BISTOP

Description

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.

Arguments

$x$

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 the RM marker as the independent variable, specify $x$ as DZ({marker_i.idstring}, {marker_j.idstring}, {marker_rm.idstring}).

$\dot{x}$

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

$x_1$

The lower bound of $x$ . If $x$ is less than $x_1$ , the bistop function returns a positive value. The value of $x_1$ must be less than the value of $x_2$ .

$x_2$

The upper bound of $x$ . If $x$ is greater than $x_2$ , the bistop function returns a negative value. The value of $x_2$ must be greater than the value of $x_1$ .

$k$

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

$e$

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

$c_{\text{max}}$

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

$d$

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

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),VX(30102030,30101010,30101010),0.5,9.5,10000000,2.1,1,0.001)"
     fy_expression         = "0"
     fz_expression         = "0"
  />