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First off, they are both force divided by area. Pounds per square inch. Newtons per

meter squared. That sort of thing.

Pressure is often used with fluids (gases or liquids), whereas stress is more often used

with solids.

ne ma!or difference is that pressure only acts perpendicular to a surface, whereas

stress can also be parallel to a surface as well as perpendicular to it. " stress parallel to

a surface is called shear stress. The perpendicular part is called normal stress.

Pressure can only be positive wheres normal stress can be negative or positive. "

negative normal stress is called tension. " positive normal stress is called

compression, or compressive stress. #ome to thin$ of it, sometimes the sign

convention is he other way around, with tension being positive and compression beingnegative. For some reason, structural analysts seem to do it that way. "nd they should

be the e%perts, eh& 'ut always thin$ of compression as being positive.

f you want to get fussy and mathematical, stress is a tensor of order . r is it ran$ &

*omething li$e that. Pressure is usually considered a scalar. r sometimes people

thin$ of it as a tensor too, but with the diagonal entries all equal to p and the off+

diagonal terms equal to . *o then it-s basically a stress tensor with constraints.

don-t $now where all this internal e%ternal mumbo !umbo came from. This is

mentioned a lot in the answers to the other thread that someone mentioned.

hat is the difference between pressure and stress as they have the same units&

*everal people there are saying that pressure is applied to the outside of things and

that causes stress on the inside. ell, that-s rot. Nice and simplistic sounding and

they all !umped on the bandwagon, guess. Pressure e%ists in the interior of fluids !ust

the same as stress in solids. /ou can have stress in fluids too, by the way. t-s !ust that

shear stress in fluids requires continuous shearing motion (and viscosity) in the fluid

whereas solids can sustain the stress continuously without moving. 'ut inside the

water in a swimming pool, there is pressure. /ou can feel it pressing on your ear

drums when you dive down. 'ut !ust becuase it-s pressing in on the outside doesn-t

mean it is only on the outside. The pressure continues all the way to the inside of your

body too. *ure, you could call that stress too if you li$e, but it-s still pressure. /ou can

also have stress on the e%terior of a solid as well as inside. t-s !ust the force applied at

the surface divided by the area that it-s applied to.

Pressure is a special stress.

https://www.quora.com/What-is-the-difference-between-pressure-and-stress-as-they-have-the-same-unitshttps://www.quora.com/What-is-the-difference-between-pressure-and-stress-as-they-have-the-same-units

7/25/2019 What is Stress & Pressure

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0) *tress occurs when a force is applied on a ob!ect in any direction.

n image, force is applied and stress acts on each plane of the ob!ect. t means that

stress can be in any direction and any angle. t can be tensile or compressive.

) Pressure is always compressive and perpendicular in nature. t tries to compress thesuface on which it acts.

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*omeone can say that, compressed air or fluid inside a closed vessel e%pands it, while

pressure is compressive in nature. The fact is that the pressure acts normally and

compresses the atmosphere surrounding the vessel, which results in e%pansion of

vessel surface.

1emember, pressure is always normal and compressive while stress can be at any

angle and in at any direction.

"s both are force acting on some area, that why carries same unit (Newton per unit

area).

They are basically the same thing and the terms used tend to refect context

rather than physics. You would use 'Stress' when dealing with stretching etc,

pressure when dealing with gases etc.

Reerence https:www.physicsorums.comthreadsdi!erence"between"

pressure"and"stress.#$%&$$