Failure Mechanisms

· The crack tip region has a complex stress distribution that depends upon (r, θ) as illustrated. Both tensile and shear stresses are present in an element of material near the crack.
· For the element at (r, θ) :

From: Callister,
"Materials Science & Engineering,"
Wiley (1994)

· The crack lies along the x-axis ( θ= 0) and the tensile stress at the crack tip, σ_y = K/(2πr)^0.5 , where K is the Stress Intensity Factor.