I am reading "BASIC fracture mechanics" which is a very simple book.

You must know this expression

sigmaY = KI/sqrt(2

***pi***r)*cos(thita/2)*(1+sin(thita/2)

***sin(3***thita/2))

and I think this is symmetric about thita = 0.

My questions:

Is the expression dirived from a rectangular (infinite or finite)

plate with a crack at the center and under a symmetric load system

case? There are different expressions For other cases, say

non-symmetric cases?

Thank you in advance.