# Normal and Shear Stresses in Sub-contacts

**URL:** <https://forum.itascainternational.com/t/normal-and-shear-stresses-in-sub-contacts/721>\
**Category:** 3DEC\
**Created:** [August 22, 2022, 9:52am UTC](https://forum.itascainternational.com/t/normal-and-shear-stresses-in-sub-contacts/721 "2022-08-22T09:52:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![DariushJ](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@DariushJ](https://forum.itascainternational.com/u/DariushJ)\
**Post date:** [August 22, 2022, 9:52am UTC](https://forum.itascainternational.com/t/normal-and-shear-stresses-in-sub-contacts/721/1 "2022-08-22T09:52:06Z")

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Hi,

I am going to extract normal and shear stress values in sub-contacts of a DFN through a FISH by division of corresponding force values by sub-contact area. For some DFN examples (in my case DFNs with 50+ fractures) an error of “trying to divide by zero” pops up. Is this error still related to the famous so called “negative/zero block volume” error? If it is so, is there any solution other than those in Itasca website to get rid of this error?  
By the way, I am using 3DEC 5.20.

Any help will be highly appreciated.

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**Author:** ![jhazzard](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@jhazzard](https://forum.itascainternational.com/u/jhazzard)\
**Post date:** [August 26, 2022, 5:26pm UTC](https://forum.itascainternational.com/t/normal-and-shear-stresses-in-sub-contacts/721/2 "2022-08-26T17:26:47Z")

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Sometimes subcontacts have area = 0. You just need to check that the area \> 0 before dividing.

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**Author:** ![DariushJ](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@DariushJ](https://forum.itascainternational.com/u/DariushJ)\
**Post date:** [August 29, 2022, 10:17am UTC](https://forum.itascainternational.com/t/normal-and-shear-stresses-in-sub-contacts/721/3 "2022-08-29T10:17:11Z")

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Thanks for your help Jim.