*MAT_068 (NONLINEAR_PLASTIC_DISCRETE_BEAM)

LS-DYNA Input Interface KeywordThis keyword defines a non-linear 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	${\rho }_i$	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

Definition

Field	Contents	SI Unit Example
mat_ID	Material identifier (Integer)
${\rho }_i$	Initial density (Real)	$\left[\frac{\text{kg}}{{\text{m}}^{\text{3}}}\right]$
TK_r, TK_s, TK_t	Stiffness in directions r, s, t (Real)	$\left[\frac{\text{N}}{\text{m}}\right]$
RK_r, RK_s, RK_t	Rotational stiffness for axis r, s, t (Real)	$\left[\frac{\text{N}•\text{m}}{\text{rad}}\right]$
TD_r, TD_s, TD_t	Damping in directions r, s, t (Real)	$\left[\frac{\text{N • s}}{\text{m}}\right]$
RD_r, RD_s, RD_t	Rotational damping in directions r, s, t (Real)	$\left[\frac{\text{Nms}}{\text{rad}}\right]$
LCPD_r, LCPD_s, LCPD_t	Force vs plastic displacement curve identifier in directions r, s, t. See Comment 4. (Real)	$\left[\text{N}\right]$
LCPM_r, LCPM_s, LCPM_t	Moment vs plastic rotations curve identifier in directions r, s, t. See Comment 4. (Real)	$\left[\text{Nm}\right]$
FO_r, FO_s, FO_t	Force preload in directions r, s, t	$\left[\text{N}\right]$
MO_r, MO_s, MO_t	Moment preload in directions r, s, t	$\left[\text{Nm}\right]$
FFAIL_r, FFAIL_s, FFAIL_t	Failure forces in directions r, s, t	$\left[\text{N}\right]$
MFAIL_r, MFAIL_s, MFAIL_t	Failure moments in directions r, s, t	$\left[\text{Nm}\right]$
UFAIL_r, UFAIL_s, UFAIL_t	Failure elongations in directions r, s, t	$\left[\text{m}\right]$
TFAIL_r, TFAIL_s, TFAIL_t	Failure rotation angles in directions r, s, t	$\left[\text{rad}\right]$

Comments

1. This keyword maps to /MAT/LAW108 (SPR_GENE).
2. The material is only used with *SECTION_BEAM, ELFORM = 6 discrete beam elements.
3. Beams with zero initial length are recommended.
4. Force vs displacement and moment vs angle curves can be specified in the 1st quadrant only. The spring will behavior in compression will be a mirror of the entered curve and so that compression and tension behavior will be the same.
5. If for a DOF both force-based and displacement-based failure is defined, then only force failure will be used.
6. The option “_TITLE” can be added to the end of this keyword. When “_TITLE” is included, an extra 80 character long line is added after the keyword input line which allows an entity title to be defined.