Research On Crack Detecting Of Crankshaft Based On Finite Element Modal Analysis

The accident often happened that the crankshaft ruptured in the course of using because of the fatigue crack, This thesis is focused on how to discern the fatigue crack method on the crankshaft.This thesis study the dynamics characteristics of the crankshaft with and without the transverse crack, regarding mechanical vibration mode theory as guide, based on finite element software ANSYS study platform , For offering a certain criterion to discern the transverse crack in the crankshaft .Main research content including:1) Have studied a same diameter shaft, study how to make use of the change of natural frequency to discern the transverse crack. The result indicates: adopting certain data processing method, it is feasible to make use of the change of natural frequency to discern the transverse crack in the shaft, and the precision discerned is very high.2) Have studied the natural vibration characteristic of the crankshaft with and without the transverse crack. The result indicates: when the transverse crack was contained in the crankshaft, the crankshaft's natural frequency reduced obviously, But does not change the vibration form of every type.3) Have studied the dynamics characteristics of the crankshaft at the instantaneous impact. The result shows that when contain the transverse crack in the crankshaft, and the depth of the crack is strengthened gradually, Its acceleration signal responding frequency moves toward high frequency gradually .4) Have studied the natural vibration characteristic of the piston - connecting rod - crankshaft while keeping in touch with the condition each other adopting systematic methods., The result indicates: not only can find the piston - connecting rod - crankshaft system vibration form of each crankshaft angle within one period, but also can find the frequency helpful to producing the transverse crack in the crankshaft .Though this text is the research on the transverse crack in the crankshaft, but the method and the conclusion should have reference value to other scholars.