Simulation on the motion of crankshaft with crack in crankpin-web fillet region

A new method for simulating nonlinear motion of cracked crankshaft is proposed, and the transient vibration response of a cracked crankshaft is evaluated and analyzed. First, the crankshaft without crack is simplified as a finite element model based on spatial Timoshenko beam element, and the vibration modes of the crankshaft are calculated and compared with the results presented in other published literatures. Then, the frequently occurred crack in crankpin-web fillet region is studied. According to the characteristic of this kind of crack, a new spatial crack beam element is developed, and a cracked crankshaft model, which combines crack beam element and Timoshenko beam elements, is established. Subsequently, the breathing behavior of the crack under operating condition is discussed, and the nonlinear equation of motion of cracked crankshaft is set up. Finally, the transient vibration response of the cracked crankshaft under fire condition is evaluated, and the influence of the crack depth on the vibration response of torsion, translation and bending are analyzed. The modeling and analysis procedures are applied to a crankshaft system of a four in-line cylinder engine. This investigation provides a useful tool for the vibration analysis and crack detection of cracked crankshaft system.