# Thermal expansion with beam bending

**URL:** <https://calculix.discourse.group/t/thermal-expansion-with-beam-bending/2359>\
**Category:** Uncategorized\
**Created:** [August 1, 2024, 8:04am UTC](https://calculix.discourse.group/t/thermal-expansion-with-beam-bending/2359 "2024-08-01T08:04:20Z")\
**Posts on this page:** 1\
**Showing post:** 20

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**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [August 2, 2024, 4:41pm UTC](https://calculix.discourse.group/t/thermal-expansion-with-beam-bending/2359/20 "2024-08-02T16:41:42Z")

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This is my approach with isotropic expansion. Comparision with the expected value is above.

> **[Bending\_And\_Thermal\_Expansion.inp](https://wetransfer.com/downloads/2261c0c5e7ac01ba0e033643f018fd9b20240802160222/1e7150)**
>
> 1 file sent via WeTransfer, the simplest way to send your files around the world

Note that just with thermal expansion (if you remove load) , displacement results match with the Abaqus **linear** solution. That’s why we suspect nonlinear is not active for thermal expansion.  
Abaqus reports .49m of displacement to each direction with 0.98m overall length increase for the nonlinear process but that’s not a good reference to compare with ccx as they use different formulation.(SEE NOTE)

Ccx Strains without load shows an homogeneous S11=0.48 across the bar without load and zero Stresses.That means it’s using a Lagrange (Green) Strain formulation.  
Why do you want to include plasticity in the model and add more uncertainties before surfing all doubts?

NOTE: Don Guido commented about discrepancies between Abaqus and ccx with expansion an NLGEOM. Take a look at this :

> [@Comparison CalculiX-Abaqus with NLGEOM](https://calculix.discourse.group/t/comparison-calculix-abaqus-with-nlgeom/1748):
>
> Dear CalculiX users, in the past differences were reported in the results between CalculiX and Abaqus in the presence of NLGEOM on the \*STEP card. Further analysis has revealed at least 3 sources for these differences: In Abaqus the logarithmic strain is used (unless a hyperelastic material is selected). This implies that also thermal strains, if present, are logarithmic, i.e. the thermal expansion coefficient must have been determined based on the actual length of the specimen, not the initi…

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