Stress concentrations lead to premature failure of a part, particularly when subjected to shock loads.
The Graph below shows the stress concentration factor as a function of the radius a transition in wall section.






Stress concentrations are caused by notches, such as radii that are too small, threads, self tapping screws, and also by any sudden change in stiffness of a part, such as ribbing, bosses, changes in wall section, inserts etc. In any of these cases, try and optimise the design of the part