A necessary condition for the MCCI method is uniform element length ( Δ Δ a ) along the crack face in the x 1 − − direction. Additionally, this method requires sufficient discretization such that over the length of one element stress fields are self-similar. This implies that K ( a + Δ Δ a ) ≈ ≈ K ( a ) as the crack propagates. Below are examples of the MCCI method with two types of common finite elements.