What distinguishes pressure from normal stress in bird transport phenomena?

[Est120]

What's really the difference between pressure and normal stress? Also I know pressure acts normal to a surface from the outside
Do normal stress acts from inside?
I'm reading bird transport phenomena and this is confusing

 

[PhanthomJay]

What's really the difference between pressure and normal stress? Also I know pressure acts normal to a surface from the outside
Do normal stress acts from inside?
I'm reading bird transport phenomena and this is confusing

Well you can get real technical about it and state that pressure is a scalar quantity and stress is a tensor. But in essence, pressure when , say , it is exerted (applied) on the end of a solid block, acts perpendicular to the surface on the outside . In turn, the applied pressure deforms the block axially , giving rise to normal perpendicular stresses within the block. There are other differences as well, if you want to get deep into the subject.