Vatiable loading in lammps

Dear community,

Its been a long time since I am using lammps for my academic purpose. I stumbled upon a problem regarding stress-controlled deformation of material.

I have used ‘fix addforce’ to induce stress in every step and taken notes of deformation to yield stress induced deformation.

Now I want to move forward with variable loading system, eg. I want to induce a load in parabolic manner. But when I tried to do so using ‘variable’ inside the fix addforce, its just not doing right. Or I should say I am not being able to do it in a right way.

My question is, ‘Is lammps capable of doing what I wanted to?’ If yes then what is the wrong that I have done? Or are there any feasible way to do so?

Eagerly waiting for your valuable replies.