*MAT_068 (NONLINEAR_PLASTIC_DISCRETE_BEAM)

LS-DYNA Input Interface KeywordDefines a nonlinear elasto-plastic discrete beam material with 6 decoupled DOFs with an optional preload.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
MAT_068 or MAT_NONLINEAR_PLASTIC_DISCRETE_BEAM
`mat_ID`	$ρ_{i}$ $ρ_{i}$	`TK_r`	`TK_s`	`TK_t`	`RK_r`	`RK_s`	`RK_t`
`TD_r`	`TD_s`	`TD_t`	`RD_r`	`RD_s`	`RD_t`
`LCPD_r`	`LSPD_s`	`LCPD_t`	`LCPM_r`	`LCPM_s`	`LCPM_t`
`FFAIL_r`	`FFAIL_s`	`FFAIL_t`	`MFAIL_r`	`MFAIL_s`	`MFAIL_t`
`UFAIL_r`	`UFAIL_s`	`UFAIL_t`	`TFAIL_r`	`TFAIL_s`	`TFAIL_t`
`FO_r`	`FO_s`	`FO_t`	`MO_r`	`MO_s`	`MO_t`

Field	Contents	SI Unit Example
`mat_ID`	Material identifier. (Integer)
$ρ_{i}$ $ρ_{i}$	Initial density. (Real)	$[\frac{kg}{m^{3}}]$ $[\frac{kg}{m^{3}}]$
`TK_r`, `TK_s`, `TK_t`	Stiffness in directions r, s, t. (Real)	$[\frac{N}{m}]$ $[\frac{N}{m}]$
`RK_r`, `RK_s`, `RK_t`	Rotational stiffness for axis r, s, t. (Real)	$[\frac{N • m}{rad}]$ $[\frac{N • m}{rad}]$
`TD_r`, `TD_s`, `TD_t`	Damping in directions r, s, t. (Real)	$[\frac{N • s}{m}]$ $[\frac{N • s}{m}]$
`RD_r`, `RD_s`, `RD_t`	Rotational damping in directions r, s, t. (Real)	$[\frac{Nms}{rad}]$ $[\frac{Nms}{rad}]$
`LCPD_r`, `LCPD_s`, `LCPD_t`	Force versus plastic displacement curve identifier in directions r, s, t. 44 (Real)	$[N]$ $[N]$
`LCPM_r`,`LCPM_s`, `LCPM_t`	Moment versus plastic rotations curve identifier in directions r, s, t. 44 (Real)	$[Nm]$ $[Nm]$
`FO_r`, `FO_s`, `FO_t`	Force preload in directions r, s, t.	$[N]$ $[N]$
`MO_r`, `MO_s`, `MO_t`	Moment preload in directions r, s, t.	$[Nm]$ $[Nm]$
`FFAIL_r`, `FFAIL_s`, `FFAIL_t`	Failure forces in directions r, s, t.	$[N]$ $[N]$
`MFAIL_r`, `MFAIL_s`, `MFAIL_t`	Failure moments in directions r, s, t.	$[Nm]$ $[Nm]$
`UFAIL_r`, `UFAIL_s`, `UFAIL_t`	Failure elongations in directions r, s, t.	$[m]$ $[m]$
`TFAIL_r`, `TFAIL_s`, `TFAIL_t`	Failure rotation angles in directions r, s, t.	$[rad]$ $[rad]$

This keyword maps to /MAT/LAW108 (SPR_GENE).
The material is only used with *SECTION_BEAM, ELFORM = 6 discrete beam elements.
Beams with zero initial length are recommended.
Force versus displacement and moment versus angle curves can be specified in the 1^st (and optionally 3^rd ) quadrants . The 1^st quadrant (+ve) values are used for Tensile (or clockwise) behavior and the 3^rd quadrant (-ve) values for Compressive (or anti-clockwise) behavior. If only the 1^st quadrant data (starting at 0,0) is defined, the curve will be mirrored for the 3^rd quadrant such that spring behavior is the same/symmetrical.
If for a DOF both force-based and displacement-based failure is defined, then only force failure will be used.
The option “_TITLE” can be added to the end of this keyword. When “_TITLE” is included, an extra 80 characters long line is added after the keyword input line which allows an entity title to be defined.