ABSTRACT
This chapter provides engineers with several more examples and should give them the ability to better solve actual failures. Most auto mechanics will realize that one of the reasons there is a flywheel on an engine is to smooth out the power pulses, and anyone who’s worked with large steam turbines knows there are rotating speeds that have to be avoided because of torsional resonances. Torsional fatigue only comes into play when that torsional stress varies over a relatively short time. The pure torsion and multiple origins on the left ended up with that truly conical fracture face, while the center one had a substantial rotating bending component and the fracture plane was much flatter. The horizontal axis, the mean tensile stress, is a combination of all the steady state stresses operating on the part, plus one-half of the absolute value of the fatigue stress. The last of the fatigue failure surface features to be discussed are of river marks.
