# Creep calculation and results

**URL:** https://calculix.discourse.group/t/creep-calculation-and-results/868
**Category:** Uncategorized
**Created:** [November 28, 2021, 12:14am UTC](https://calculix.discourse.group/t/creep-calculation-and-results/868 "2021-11-28T00:14:44Z")
**Posts on this page:** 1
**Showing post:** 26

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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: [September 8, 2022, 7:11am UTC](https://calculix.discourse.group/t/creep-calculation-and-results/868/26 "2022-09-08T07:11:30Z")

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Hi,

I have start to search about Creep and I have recently found a very interesting explanation of why convergence could be difficult with Calculix in some cases. The origin could be the Creep LAW=NORTON formulation itself. (Explained in the first two minutes of the vid).

According to the manual the stress is not normalized in Calculix, and it could lead to a tiny A parameter which further leads to rounding/convergence issues. Reviewing the example shown in the previous posts of ZFDong , I can see he is using an A parameter of A=2.5E-27. That seems a bad starting point for any numerical analisys. Maybe other unit system for the model would help to reduce that A value.  
¿What do you think? ¿Or maybe directly normalizing the NORTON LAW and changing A by the initial Strain rate parameter in Calculix?

[![](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/e/eb0edff477e4022b1f57627dcb45a67c98d7e6f0.jpeg "Abaqus Creep Models: Which One Should You Use?") ](https://www.youtube.com/watch?v=W6bIDjkOX9o)

![screenshot.38](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/3144bc8528922578e00c8fa8163262433ef59615.png)

Regards,

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