Hi,
i think the word "source" confused you, "source" refers to the location of the defect in the atom arrangement. when the stress is applied, the disclocation moves along the slip plane. it is easier to cause slip on a plane with dislocation.
hope this helps
cheers.
I can presume you want the equations in order to determine the maximum heat generated in order to try and accommodate it in your design.
There seem to be an agreement that this is changing with many parameters. Unless you want to conduct a parametric study, I advise you to conduct an experiment...