Understanding how a crack like defect will grow and the path it will take can provide valuable information in to the risk assessment of a design. For example in the design study shown the model of the initial  design showed that the crack would grow through the wall and lead to catastrophic failure where the wall of a high pressure component fails. In the modified design the crack would take an alternate path which would simply lead to the weld failure of the bracket.

crack shape 1 smallThin base plate. Catastrophic failure

crack shape 2 small Thick base plate. Weld Failure