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/*
This file is part of the FElt finite element analysis package.
Copyright (C) 1993-2000 Jason I. Gobat and Darren C. Atkinson
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/************************************************************************
* *
* File: spring.c *
* *
* Description: This file contains the definition structure and *
* stiffness function for a simple linear one-dimensional *
* spring element. *
* *
************************************************************************/
# include <math.h>
# include <stdio.h>
# include "allocate.h"
# include "fe.h"
# include "error.h"
# include "misc.h"
int springEltSetup ( ), springEltStress ( );
struct definition springDefinition = {
"spring", springEltSetup, springEltStress,
Linear, 2, 2, 1, 1, {0, 1, 0, 0, 0, 0, 0}, 0
};
int springEltSetup (element, mass_mode, tangent)
Element element;
char mass_mode;
int tangent;
{
double factor, L;
L = ElementLength (element, 1);
if (L <= TINY) {
error ("length of element %d is zero to machine precision",element -> number);
return 1;
}
if (element -> material -> E == 0) {
error ("spring element %d has 0.0 for Young's modulus (E)", element -> number);
return 1;
}
if (element -> material -> A == 0) {
error ("spring element %d has 0.0 for cros-sectional area (A)", element -> number);
return 1;
}
factor = (element -> material -> A * element -> material -> E / L);
if (element -> K == NullMatrix)
element -> K = CreateMatrix (2, 2);
MatrixData (element -> K) [1][1] = factor;
MatrixData (element -> K) [1][2] = -factor;
MatrixData (element -> K) [2][1] = -factor;
MatrixData (element -> K) [2][2] = factor;
if (mass_mode) {
if (element -> M == NullMatrix)
element -> M = CreateMatrix (2, 2);
ZeroMatrix (element -> M);
if (mass_mode == 'l') {
factor = (element -> material -> A * element -> material -> rho * L)/2.0;
MatrixData (element -> M) [1][1] = factor;
MatrixData (element -> M) [2][2] = factor;
}
else {
factor = (element -> material -> A * element -> material -> rho * L)/6.0;
MatrixData (element -> M) [1][1] = 2.0*factor;
MatrixData (element -> M) [2][2] = 2.0*factor;
MatrixData (element -> M) [1][2] = factor;
MatrixData (element -> M) [2][1] = factor;
}
}
return 0;
}
int springEltStress (element)
Element element;
{
double cx, dx1, dx2;
double L, EonL,
stress;
L = ElementLength (element, 1);
if (L <= TINY) {
error ("length of element %d is zero to machine precision",element -> number);
return 1;
}
cx = (element -> node[2] -> x - element -> node[1] -> x)/L;
EonL = element -> material -> E / L;
dx1 = element -> node[1] -> dx[1];
dx2 = element -> node[2] -> dx[1];
stress = EonL*(cx*dx2 - cx*dx1);
element -> ninteg = 1;
SetupStressMemory (element);
element -> stress[1] -> x = (element -> node[1] -> x +
element -> node[2] -> x)/2.0;
element -> stress[1] -> y = 0.0;
element -> stress[1] -> values[1] = stress;
return 0;
}
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