• 1 N/m² = 1x10^-6 N/mm² = 1 Pa = 1.4504x10^-4 psi
• 1 psi (lb/in²) = 144 psf (lb_f/ft²) = 6,894.8 Pa (N/m²) = 6.895x10^-3 N/mm²

Note! Use the pressure unit converter on this page to switch the values to other units.

Strain

Strain can be expressed as

strain = dL / L         (1)

where

strain = (m/m) (in/in)

dL = elongation or compression (offset) of the object (m) (in)

L = length of the object (m) (in)

Stress

Stress can be expressed as

stress = F / A         (2)

where

stress = (N/m²) (lb/in², psi)

F = force (N) (lb)

A = area of object (m²) (in²)

Young's Modulus (Tensile Modulus)

Young's modulus or Tensile modulus can be expressed as

E = stress / strain = (F / A) / (dL / L)         (3)

where

E = Young's modulus (N/m²) (lb/in², psi)

Elasticity

Elasticity is a property of an object or material which will restore it to its original shape after distortion.

A spring is an example of an elastic object - when stretched, it exerts a restoring force which tends to bring it back to its original length. This restoring force is in general proportional to the stretch described by Hooke's Law.

Hooke's Law

One of the properties of elasticity is that it takes about twice as much force to stretch a spring twice as far. That linear dependence of displacement upon stretching force is called Hooke's law which can be expressed as

F_s = -k dL         (4)

where

F_s = force in the spring (N)

k = spring constant (N/m)

dL = elongation of the spring (m)

Yield strength

Yield strength, or the yield point, is defined in engineering as the amount of stress that a material can undergo before moving from elastic deformation into plastic deformation.

Ultimate Tensile Strength

The Ultimate Tensile Strength - UTS - of a material is the limit stress at which the material actually breaks, with sudden release of  the stored elastic energy.