Equation

This option can be used to create a curve by definining an equation of the form 'y=f(x)'. Here 'x' can be replaced by any of x, X, t, T, time or TIME.

The usual operators + - * / ^ % can all be used. The following standard mathematical functions can be used: SIN, COS, TAN, SEC, CSC, COT, ASIN, ACOS, ATAN, ATAN2, SINH, COSH, TANH, ASINH, ACOSH, TANH, ASINH, ACOSH, ATANH, EXP, CEIL, FLOOR, LOG, LOG10, SQRT, MOD, MAX, MIN, SIGN, ABS, INT, AINT, NINT, FLOAT.

Additonally, some of the functions specified in the Ansys LS-DYNA manual under *DEFINE_CURVE_FUNCTION are also available. These are: IF, STEP, POLY, CHEBY, FORSIN, FORCOS, SHF.

This allows PRIMER to send *DEFINE_CURVE_FUNCTION definitions to T/HIS, as long as they only depend on TIME and no other values that change during the Ansys LS-DYNA run. In the *DEFINE_CURVE_FUNCTION edit panel, if the expression is suitable for evaluation, then the T/HIS button will be active and the equation can be sent across. The curve will be plotted from TIME = 0 until the termination time specified on the *DATABASE_CONTROL_TERMINATION card. The value of any parameters appearing in the expression will be maintained. The curve can be edited via right-clicking and selecting Edit equation.... It can then be sent back to PRIMER by right-clicking and selecting Update curve in PRIMER.

Curves can be referenced in equations using variables of the form 'c1', 'C1' or '#1' to refer to curve #1. For example, equations such as 'y = 2*#1 + 3*#3' are valid. This allows multiple curve operations to be replaced by a single equation.

There are multiple options for defining the x-values used to plot the equation curve. There is an option to specify directly the start value, end value and interval between points. Alternatively, the X values can be copied from a specified curve. The final option is only relevant if the equation contains curve variables. The x-values from all of the curves that appear in the equation will be combined to give one potentially larger set of x-values, which will then be used to plot the equation curve.

Equation curves can also be created using the JavaScript API, see 'Read.Equation' in the JavaScript API reference manual.