Strain Energy Release Rate

 , where:

G = Strain Energy Release Rate (Pa*m)

a = Length of Crack (m)

 = Stress at Fracture Point (Pa)

E = Young's Modulus (Pa)

Strain on a Beam

 , where:

 = Strain

z = Distance to Neutral Axis (m)

w = Deflection (m)

x = Length (m)


 , where:

 = Stress (Pa)

F = Force (N)

A = Relevant Cross-Sectional Area (m^2)

Stress in a Beam

and for coordinates system where Ixy = 0:  

and for bending about one axis:  , where:

Stress Intensity


Note: Fracture occurs when KI > KC , where:

KI = Stress Intensity (Pa*m^.5)  

= Stress (Pa)

a = Length of Crack (m)

KC = Fracture Toughness (Pa*m^.5)