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Example of *DEFINE_CURVE_FUNCTION


Starting in LS-DYNA version 970 and later, we can now use expressions instead of digitized values to define an XY curve. Optionally, the expressions can refer to other curves which could be defined using either digitized points or using expressions themselves. Here is an example of its usage:

Polynomial Expressions
You can define a generic polynomial of any order upto a maximum of 30 using the general expression label “POLY” (Please note that the current ls-dyna manual shows this as POLYL which is incorrect) and its argument list is given by:

POLY(abscissa, abscissa0, coeff0, coeff1, coeff2,..., coeff30)
or
POLY(x, x0, a1, a2,..., a30)

The built-in expression used is:

P(abscissa) =
coeff0+coeff1*(abscissa-abscissa0)+coeff2*(abscissa-abscissa0)*power(2)+...
or
P(x) = a0+a1(x-x0)+a2*(x-x0)*power(2)+...+an*(x-x0)*power(n)

Below is an example that prescribes a displacement to a node using some arbitrary coefficients. You can monitor the displacement history of node #1 which is prescribed.

*KEYWORD
*TITLE
use of curve function
*CONTROL_TERMINATION
0.1
*CONTROL_OUTPUT
0
,,,,1
*DATABASE_HISTORY_NODE
1
*DATABASE_NODOUT
0.1
*NODE
1, 0.0, 0.0, 0.0
2,0.0, 10.0, 0.0
3,0,10,0
*ELEMENT_BEAM
1,1,1,2,3
*PART
beam
1,1,1
*SECTION_BEAM
1,1,,,1
5,5
*MAT_ELASTIC
1,7.89e-9,2.1e+5,0.3
*DEFINE_CURVE_FUNCTION
100
POLY(TIME,0.0,0.1,0.2,0.4)
*BOUNDARY_PRESCRIBED_MOTION_NODE
1,1,1,100,1.0
*END

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