NOLIN4

(1)

P_{i} (t) = {\begin{matrix} - S \cdot {[- X_{j} (t)]}^{A}, & X_{j} (t) > 0 \\ 0, & X_{j} (t) \leq 0 \end{matrix}

$P_{i} (t) = {\begin{matrix} - S \cdot {[- X_{j} (t)]}^{A}, & X_{j} (t) > 0 \\ 0, & X_{j} (t) \leq 0 \end{matrix}$

Where, $X_{j} (t)$ $X_{j} (t)$ may be a displacement or a velocity at point GJ in the direction of CJ.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
NOLIN4	`SID`	`GI`	`CI`	`S`	`GJ`	`CJ`	`A`

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
NOLIN4	2	4	6	2.0	101		16.3

Field	Contents	SI Unit Example
`SID`	Nonlinear load set identification number. No default (Integer > 0)
`GI`	Grid or scalar point identification number at which nonlinear load is to be applied. No default (Integer > 0)
`CI`	Component number for `GI`. No default (1 ≤ Integer ≤ 6; blank or 0, if `GI` is a scalar point)
`S`	Scale factor. No default (Real)
`GJ`	Grid or scalar point identification number. No default (Integer > 0)
`CJ`	Component number for `GJ`, `GK` according to the following table.
`A`	Exponent of the forcing function. No default (Real)

Type	Displacement	Velocity
Grid	1 ≤ Integer ≤ 6	11 ≤ Integer ≤ 16
Scalar	Blank or 0	Integer = 10

Nonlinear loads must be selected by the Subcase Information data selector NONLINEAR.
Nonlinear loads may not be referenced on a DLOAD entry.
All degrees-of-freedom referenced on NOLIN4 entries must be members of the solution set.
Nonlinear loads may be a function of displacement $(X_{j} = u_{j})$ $(X_{j} = u_{j})$ or velocity $(X_{j} = {\dot{u}}_{j})$ $(X_{j} = {\dot{u}}_{j})$ . Velocities are denoted by components ten greater than the actual component number; that is the component 11 indicates velocity in the 1 component direction. The velocity is determined by:(2)
${\dot{u}}_{j, t} = \frac{u_{j, t} - u_{j, t - 1}}{Δ t}$ ${\dot{u}}_{j, t} = \frac{u_{j, t} - u_{j, t - 1}}{Δ t}$

Where,

$Δ t$ $Δ t$

Time step interval

$u_{j, t - 1}$ $u_{j, t - 1}$

Displacement of GJ-CJ for the previous time step.
Use a NOLIN3 entry for the positive range of $X_{j} (t)$ $X_{j} (t)$ .
The time step algorithm in transient solution sequences may loose unconditional stability when this load entry is used. In most practical cases, the time step size chosen to reach a certain accuracy is below the stability limit. It is recommended to decrease the time step if results diverge.