Shell element transverse shear stresses calculation in ABAQUS VUMAT

Hi Everyone,

I've couple of quick questions:

1) I am planning to use ABAQUS 2D shell formulation (S4R) to estimate

3D state of stress (to reduce the computational cost). I've read several articles to estimate the

transverse shear stresses once the in-plane stresses are known by

integrating the 3D equilibrium equations. This is, of course, easily

done, if we have closed form solutions for in-plane stresses:

sigma_xz,z = - (sigma_xx,x + sigma_xy,y)

sigma_yz,z = - (sigma_xy,x + sigma_yy,y)

How do I estimate transverse shear stresses using ABAUAS VUMAT, when I

only know the in-plane stresses at one integration point in the element

(in case of S4R) in VUMAT? Else, is there any possibility to transfer/estimate the transverse shear strains within the VUMAT?

2) In my analysis, I will use progressive failure analysis, where

transverse stiffness cannot be kept constant in the analysis (I read in

ABAQUS manual, we cannot change the transverse stiffness. Is there any

possibility to control transverse stiffness, within VUMAT, in case of shell elements?

Thank you for your help,

Nagesh