# Shear strains in 3DEC v5.2

Greetings to all! I’m curious about how to obtain shear strains from particular zones by utilizing specified grid points. Can this be accomplished using LIST commands?

Furthermore, with over 30 strain commands available in 3DEC, which one allows us to obtain the Shear strain (%) and Maximum shear strain (%)? Additionally, could you explain the difference between “increment” and “rate” in this context?

• ssi2 second strain increment invariant
• ssideterm inant strain increment determinant
• ssid eviatoric deviatoric strain increment
• ssij2 second deviatoric strain increment invariant
• ssimax maximum principal strain increment
• ssimid intermediate principal strain increment
• ssimin minimum principal strain increment
• ssin orm norm of strain increment
• ssio ctahedral octahedral strain increment
• ssiv olumetric volumetric strain increment
• ssiv onmises von Mises strain increment
• ssixx xx -strain increment
• ssixy xy -strain increment
• ssixz xz -strain increment
• ssiyy yy -strain increment
• ssiyz yz -strain increment
• ssizz zz -strain increment
• ssrd eterminant strain rate determinant
• ssrd eviatoric deviatoric strain rate
• ssri2 second strain rate invariant
• ssrj2 second deviatoric strain rate invariant
• ssrmax maximum principal strain rate
• ssrmid intermediate principal strain rate
• ssrmin minimum principal strain rate
• ssrn orm norm of strain rate
• ssro ctahedral octahedral strain rate
• ssrv olumetric volumetric strain rate
• ssrv onmises von Mises strain rate
• ssrxx xx -strain rate
• ssrxy xy -strain rate
• ssrxz xz -strain rate
• ssryy yy -strain rate
• ssryz yz -strain rate
• ssrzz zz -strain rate
1 Like

Hello,
The strain increment is calculated based on the displacement while the strain rate is based on the velocity.
In your case, it should be the strain increment. And you can get the maximun shear from the principal strain increments

Greetings, @Huy !
I appreciate your quick reply. Among the options listed earlier, could you kindly specify which one is more suitable for achieving maximum shear strain?

Hello,
As mentionned earlier, you can get from the principal strain increment.
The maxinum shear strain is the difference between maximun and minimun principal strain increment.
So you need ssimax and ssimin
Huy

Understood, Huy! Thank you very much.

Hi @Huy
I appreciate your previous response. Following your advice, I aimed to acquire ssi values. I’ve written two simple FISH scripts to record strains during loading, with the goal of plotting shear strain against time. Regrettably, neither of these scripts is yielding the expected results. I have validated the accurate extraction of variables gp1, bi1, and z1, except for the ssi value, which stubbornly stays at zero. Your assistance in resolving this issue would be immensely valued.

;-------------------------; Code: 1 ;---------------------------------------------------

def _ssi
gp1 = gp_near(x, y, z)
bi1 = gp_block(gp1)
z1 = b_zone(bi1)
ssi1 = z_ssi(z1)
end
@_ssi

hist @ssi1

;----------------------; Code: 2 ;------------------------------------------------------

def _ssi
z1 = z_near(x, y, z)
ssi1 = z_ssi(z1)
end
@_ssi

hist @ssi1

;----------------------------------------------------------------------------

Hi, I’ve replied in your other topic.