# The nonlinear spring does not behave properly

**URL:** <https://calculix.discourse.group/t/the-nonlinear-spring-does-not-behave-properly/2484>\
**Category:** Uncategorized\
**Created:** [November 20, 2024, 4:15pm UTC](https://calculix.discourse.group/t/the-nonlinear-spring-does-not-behave-properly/2484 "2024-11-20T16:15:59Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![June](https://avatars.discourse-cdn.com/v4/letter/j/8e7dd6/32.png) [@June](https://calculix.discourse.group/u/June)\
**Post date:** [November 20, 2024, 4:15pm UTC](https://calculix.discourse.group/t/the-nonlinear-spring-does-not-behave-properly/2484/1 "2024-11-20T16:15:59Z")

</div>

I tried to compute spring2.inp from the test cases. I only modified the force-displacement curve, but the displacement result becomes Infinity. What could be the possible reason？Any help is appreciated.

The input is,

\*\*  
\*\* Structure: spring.  
\*\* Test objective: static calculation of a nonlinear spring.  
\*\*  
\*NODE,NSET=NALL  
1,0.,0.,0.  
2,1.,0.,0.  
\*ELEMENT,TYPE=SPRINGA,ELSET=EALL  
1,1,2  
\*BOUNDARY  
1,1,3  
2,2,3  
\*SPRING,ELSET=EALL,NONLINEAR

0.,0.  
1.,1.  
20.,2.  
\*STEP,NLGEOM  
\*STATIC  
\*CLOAD  
2,1,11.  
\*NODE PRINT,NSET=NALL  
U  
\*END STEP

And the output is:  
displacements (vx,vy,vz) for set NALL and time 0.1000000E+01

```
     1 0.000000E+00 0.000000E+00 0.000000E+00
     2 -Infinity 0.000000E+00 0.000000E+00

```

---

<div class="post-metadata">

**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\
**Post date:** [November 20, 2024, 6:46pm UTC](https://calculix.discourse.group/t/the-nonlinear-spring-does-not-behave-properly/2484/2 "2024-11-20T18:46:17Z")

</div>

![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/e/e163ea799462093e2c15ce1a617016091b8ddd96.png)  
A very sharp kink for default convergence parameters, try with:

```auto
*STEP,NLGEOM
*STATIC
0.01,1.0

```

---

<div class="post-metadata">

**Author:** ![June](https://avatars.discourse-cdn.com/v4/letter/j/8e7dd6/32.png) [@June](https://calculix.discourse.group/u/June)\
**Post date:** [November 21, 2024, 7:56am UTC](https://calculix.discourse.group/t/the-nonlinear-spring-does-not-behave-properly/2484/3 "2024-11-21T07:56:54Z")

</div>

It works. Thank you.