*MAT_S15 (SPRING_MUSCLE)

LS-DYNA Input Interface KeywordDefines a muscle model for discrete elements.

Format

Field	Contents	SI Unit Example
`mat_ID`	Material identifier. (Integer)
`L0`	Initial muscle length. (Real)	$[m]$
`Vmax`	Maximum shortening velocity. (Real)	$[\frac{1}{s}]$
`At`	Activation factor versus time. < 0 Curve identifier of activation level versus time. < 0 This constant value is used as activation level. (Real)
`Force`	Peak isometric force. (Real)	$[N]$
`FL`	Active tension as function of length. < 0 Curve identifier. > 0 Constant value of 1.0 is used. (Real)
`FV`	Active stress factor as function of velocity. < 0 Curve identifier. > 0 Constant value of 1.0 is used. (Real)
`FP`	Normalized force as function of length for parallel elastic element. < 0 Curve identifier. = 0 Exponential equation is used. > 0 Constant value of 1.0 is used. (Integer)
`LMAX`	Relative length at Force. Used only when `FP` = 0. (Real)
`KSH`	Constant for passive element. Used only when `FP` = 0. (Real)

This keyword maps to /PROP/TYPE46 (SPR_MUSCLE).
This keyword is used only with discrete elements.
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.