In the following video, I have tried to explain the concept of principal stress in a more physical way and without involving any mathematical equations, hope you can easily imbibe the concept.
Here is the link to the video : Principal stresses
This is an educational outreach initiative mainly targeted at the undergraduates (mechanical/civil/aerospace and materials engineering) studying mechanics and also other professionals that seek simpler explanations. Kindly share if you learn something out of this !
Link to my Youtube Channel : Mechanicians Classroom