# Is Zienkiewicz-Zhu Stress better than "regular" Stress?

**URL:** <https://prepomax.discourse.group/t/is-zienkiewicz-zhu-stress-better-than-regular-stress/3459>\
**Category:** General Questions\
**Tags:** results\
**Created:** [May 6, 2026, 9:26am UTC](https://prepomax.discourse.group/t/is-zienkiewicz-zhu-stress-better-than-regular-stress/3459 "2026-05-06T09:26:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Fran](https://avatars.discourse-cdn.com/v4/letter/f/a4c791/32.png) [@Fran](https://prepomax.discourse.group/u/Fran)\
**Post date:** [May 6, 2026, 9:26am UTC](https://prepomax.discourse.group/t/is-zienkiewicz-zhu-stress-better-than-regular-stress/3459/1 "2026-05-06T09:26:03Z")

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Hello,

I’ve read a bit about the [Zienkiewicz-Zhu Stress in the Calculix doc](https://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node157.html) and I was wondering: is there a reason why I should not always look at this stress instead of the “regular” stress? According to the doc this method gives a more accurate stress at the nodes.

And this brings another question: [given that](https://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node159.html)

> Notice that element variables are more accurate at the integration points. The values at the nodes are extrapolated values and consequently less accurate.

Why are node values displayed in the results and can these values actually be trusted?

I understand these are Calculix/general FEA questions rather than PrePoMax questions.

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [May 6, 2026, 9:41am UTC](https://prepomax.discourse.group/t/is-zienkiewicz-zhu-stress-better-than-regular-stress/3459/2 "2026-05-06T09:41:27Z")

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> [@Fran](#):
>
> I’ve read a bit about the [Zienkiewicz-Zhu Stress in the Calculix doc](https://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node157.html) and I was wondering: is there a reason why I should not always look at this stress instead of the “regular” stress? According to the doc this method gives a more accurate stress at the nodes.

This output is typically used as an error measure. Abaqus offers similar outputs, they are meant to evaluate extrapolation errors due to too coarse meshes. CalculiX also has ERR for that (mutually exclusive with ZZS).

However, you could use ZZS for more accurate output if you take into account the differences in how it’s calculated with neighboring elements.

> [@Fran](#):
>
> Why are node values displayed in the results and can these values actually be trusted?

Unlike Abaqus or some other solvers, CalculiX provides only nodal averaged stress in .frd contour map results. However, you can use element history output (\*EL PRINT) to print the integration point stresses from the seleted elements to .dat file (displayed in tabular form in PrePoMax too). There’s also this script: [Stresses at the integration points in ParaView - #2 by mkraska](https://prepomax.discourse.group/t/stresses-at-the-integration-points-in-paraview/797/2)

> [@Fran](#):
>
> I understand these are Calculix/general FEA questions rather than PrePoMax questions.

Yes, I think that it would be better to ask on the CalculiX forum: [https://calculix.discourse.group/](https://calculix.discourse.group/)

Check this thread too: [Zienkiewicz-Zhu superconvergent patch recovery (SPR) of stress - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/zienkiewicz-zhu-superconvergent-patch-recovery-spr-of-stress/83)