To measure the stresses acting on the crankshaft of an engine, signals must be taken out from the rapidly spinning shaft. This paper discusses the measurement of stress signals from the crankshaft using a slip ring, which is the conventional method.
By developing a special fixture that allowed us to measure rotations up to 14,000 rpm and using the four-gauge method, we succeeded in accurately measuring stress waves.
We confirmed that, during the motoring operation, stresses due to the secondary component of the inertia forces of the reciprocating parts are dominant and that, during the firing operation, deformation occurs at various frequency bands.
As the engine speed increased, the stress amplitude increased and reached a maximum around the highest engine speed. The results of a static analysis predicted values close to actual measurements. The experiment confirmed the possibility of developing an effective analysis method, by repeating validations, for predicting the reliability of crankshafts.