*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	${\rho }_i$	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 versus plastic displacement curve identifier in directions r, s, t. 44 (Real)	$\left[\text{N}\right]$
LCPM_r, LCPM_s, LCPM_t	Moment versus plastic rotations curve identifier in directions r, s, t. 44 (Real)	$\left[\text{Nm}\right]$
FO_r, FO_s, FO_t	Force preload in directions r, s, t. (Real)	$\left[\text{N}\right]$
MO_r, MO_s, MO_t	Moment preload in directions r, s, t. (Real)	$\left[\text{Nm}\right]$
FFAIL_r, FFAIL_s, FFAIL_t	Failure forces in directions r, s, t. (Real)	$\left[\text{N}\right]$
MFAIL_r, MFAIL_s, MFAIL_t	Failure moments in directions r, s, t. (Real)	$\left[\text{Nm}\right]$
UFAIL_r, UFAIL_s, UFAIL_t	Failure elongations in directions r, s, t. (Real)	$\left[\text{m}\right]$
TFAIL_r, TFAIL_s, TFAIL_t	Failure rotation angles in directions r, s, t. (Real)	$\left[\text{rad}\right]$

Comments

1. This keyword maps to /MAT/LAW113 (SPR_BEAM) if SCOOR = -2/2 in the *SECTION_BEAM card or /MAT/LAW108 (SPR_GENE) in any other cases.
2. The material is only used with *SECTION_BEAM, ELFORM = 6 discrete beam elements.
3. Beams with zero initial length are recommended if SCOOR is different from -2 or 2.
4. 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.
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 characters long line is added after the keyword input line which allows an entity title to be defined.