Modal Analysis Techniques for Torsional Vibration of Diesel Crankshafts

Torsional vibration in diesel engines, creates a potentially dangerous condition in that there may be no visible or audible indication of its existence, but catastrophic shaft fatigue failure can result. Classical methodology for torsional vibration analysis is cumbersome to employ and provides limited useful information. A methodology is presented which allows a quick, and complete analysis of vibratory stress in the circular portion of the shaft. The method, based on modal analysis techniques is adapted for use on a microcomputer. A stress history at all locations along the circular portion of the shaft is provided for all shaft natural modes due to total torsion input. Various parameters, including engine configuration, cylinder number, firing order, damping characteristics, and gas pressure characteristics are also investigated.