Testing and Modeling of Frequency Drops in Resonant Bending Fatigue Tests of Notched Crankshaft Sections

Resonant frequencies of a resonant bending system with notched crankshaft sections are obtained experimentally and numerically in order to investigate the effect of notch depth on the drop of the resonant frequency of the system. Notches with the depths ranging from 1 to 5 mm, machined by an EDM (Electrical-Discharging Machining) system, were introduced in crankshaft sections at the fillet between the main crank pin and crank cheek. The resonant frequencies of the resonant bending system with the crankshaft sections with various notch depths were first obtained from the experiments. Three-dimensional finite element models of the resonant bending system with the crankshafts sections with various notch depths are then generated. The resonant frequencies based on the finite element computations are in good agreement with those based on the experimental results. The information on the frequency drop for a given notch depth from the results in this investigation can be used as a guidance to infer the extent of fatigue crack depths in the resonant bending fatigue tests of crankshaft sections.