# Looks like artificial wavy in stress

**URL:** <https://community.geodynamics.org/t/looks-like-artificial-wavy-in-stress/1198>\
**Category:** ASPECT\
**Created:** [April 9, 2020, 3:00pm UTC](https://community.geodynamics.org/t/looks-like-artificial-wavy-in-stress/1198 "2020-04-09T15:00:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sungho](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/sungho/32/365_2.png) [@sungho](https://community.geodynamics.org/u/sungho)\
**Post date:** [April 9, 2020, 3:00pm UTC](https://community.geodynamics.org/t/looks-like-artificial-wavy-in-stress/1198/1 "2020-04-09T15:00:48Z")

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Hello.

I have a question.

I’ve attached a figure.  
The figure shows pressure, stress xx, yy, zz.

Unlike pressure, stress looks wavy even though the solution converges in the given criteria (1e-5).

Do you have any idea or any experience?

Best regards

Sugnho

 ![question](https://canada1.discourse-cdn.com/flex036/uploads/geodynamics/original/1X/3267a72c8f8904663fb71a66bc3444a798125ddd.jpeg)

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**Author:** ![tjhei](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/tjhei/32/1163_2.png) [@tjhei](https://community.geodynamics.org/u/tjhei)\
**Post date:** [April 25, 2020, 3:19pm UTC](https://community.geodynamics.org/t/looks-like-artificial-wavy-in-stress/1198/2 "2020-04-25T15:19:56Z")

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Hi Sungho,

the stress often looks quite noisy/wavy with over-/undershoots. This might looks incorrect, but is a result of the finite element solution only being continuous between cells, which means that its derivatives, and therefore stress and strain, have jumps between cells.  
I created a pull request to change the default in ASPECT to output stress averaged per cell here: [https://github.com/geodynamics/aspect/pull/3478](https://github.com/geodynamics/aspect/pull/3478)  
If you want, you can take a look at it to see if this makes your output look more reasonable.