# Tangential stresses on shell using Karamba 3D

**URL:** <https://discourse.mcneel.com/t/tangential-stresses-on-shell-using-karamba-3d/114046>\
**Category:** Karamba3D\
**Created:** [December 8, 2020, 11:13am UTC](https://discourse.mcneel.com/t/tangential-stresses-on-shell-using-karamba-3d/114046 "2020-12-08T11:13:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![laura.sardone](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/laura.sardone/32/407965_2.png) [@laura.sardone](https://discourse.mcneel.com/u/laura.sardone)\
**Post date:** [December 8, 2020, 11:13am UTC](https://discourse.mcneel.com/t/tangential-stresses-on-shell-using-karamba-3d/114046/1 "2020-12-08T11:13:42Z")

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Hi Everyone! I’m having a small problem in calculating the tangential stresses on a shell.  
I want to apply the following (von mises)criterion:  
sqrt{\sigma\_max^2\*(z\*)+3tau^2\*(z\*)}\<sigma\_{id}  
but I really don’t know how to extrapolate tau (tangential stresses).

There is someone that can help?

Thanks a lot.

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**Author:** ![karamba3d](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/karamba3d/32/472725_2.png) [@karamba3d](https://discourse.mcneel.com/u/karamba3d)\
**Post date:** [December 9, 2020, 8:32am UTC](https://discourse.mcneel.com/t/tangential-stresses-on-shell-using-karamba-3d/114046/2 "2020-12-09T08:32:56Z")

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Hello @laura.sardone,  
you formula for the Von Mises stress is not correct (see e.g. [https://en.wikipedia.org/wiki/Von\_Mises\_yield\_criterion](https://en.wikipedia.org/wiki/Von_Mises_yield_criterion)). The in-plane shear stress ‘tau’ is sometimes denoted as ‘sigma\_12’.  
In Karamba3D 1.3.3. you can get the stresses in a certain layer of a shell from the cross section forces via the ‘Shell-Forces’-component. In Karamba3D 2.0.0 WIP you could use the ‘Shell Section’-component for retrieving the stresses along an arbitrary section through you shell.  
– Clemens

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<div class="post-metadata">

**Author:** ![laura.sardone](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/laura.sardone/32/407965_2.png) [@laura.sardone](https://discourse.mcneel.com/u/laura.sardone)\
**Post date:** [December 9, 2020, 9:31am UTC](https://discourse.mcneel.com/t/tangential-stresses-on-shell-using-karamba-3d/114046/3 "2020-12-09T09:31:31Z")

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Thank you so much, Clemens!

Yes, I’ve realized it a few moments after the question!

I’ve solved it using python by imposing the problem as follow:  
vonMises = ( (sigma1**2)+(sigma2**2) - (sigma1\*sigma2) )**0.5  
where sigma 1= ((x**2)+(y**2)+(z**2))**0.5  
and  
sigma2 = ((u**2)+(v**2)+(w**2))\*\*0.5

by connecting Sig1\_vec and Sig2-Vec from ShellVecResults as input I’ve obtained what I needed!

Thanks a lot.

l.s.