for linear triangular element, the linear inerpolation using triangle with three nodes at its corners gives a constant derivitive. I wonder if some one aware about any remedial modification that can result with a derivative that is dependent on the location within the triangle element. The elemnet is still to be the same. I appreciate any reply

I do not know enough on this matter.

However, I've heard that it always gives constant stress (structural analysis) inside the triangle unless we are using quad-element.

I just want to check if that is true or not.

-Selina