shear stress S12

[mirelala]

I have a question about how ABAQUS define stresses. Is S12 the stress in the direction perpendicular to 1 in the direction of 2? Thanks for your help.

[mirelala]

I would like also to understand the convention for sign for angular velocity (- means clockwise or counterwise).

Thanks a lot for your help. I really appreciate it.

Regards

[FEguru]

Regarding your first question S12 is usually referred to as the shear stress in the 1-2 plane, since it is equal to S21 (due to moment equilibrium). However, strictly speaking it is the shear stress in direction 1 on face with normal direction 2. You need that convention (rather than the reverse) for the equilibrium equation Sij,j + bi = 0 to hold.

Regarding your second question rotations and angular velocities should be positive counter-clockwise.

[mirelala]

Thanks a lot