Effect of temperature gradients on critical speeds of rotating shafts

In this paper, a simplified rotating shaft is analyzed to investigate the effect of different temperature gradients on the critical speeds of rotating machinery using ANSYS software. First, a thermal - structural static coupling analysis is carried out to obtain the thermal stresses due to restrained expansion of the rotating shaft. Next, a pre-stressed modal analysis of the rotating shaft under thermal and gyroscopic effects is performed to obtain the natural frequencies for different rotational speeds. Finally, Campbell diagram is plotted to extract the critical speeds of the rotating system under different temperature gradients. The results show that the compressive thermal stresses due to elevated temperature cause reduction in the critical speeds of rotating machinery. Also, critical speeds are highly affected by the different temperature distributions along the rotating shaft.