Critical speed analysis of bi-layered rotating cylindrical shells made of functionally graded materials

This study analyzed the free vibrations and critical speed of rotating bi-layered circular cylindrical shells made of functionally graded materials (fgm). the characteristics of the materials in both layers change continuously according to volume fraction power-law distribution. the coriolis effects,centrifugal force and initial hoop tension created by the rotation and the sanders' thin shells theory equations were extracted. the effect of the ratios of length to radius and thickness to radius,the rotation speed of the shell,the composition of the materials in the layers,the power law index and circumferential and longitudinal wave numbers on the backward and forward natural frequencies and critical speed of the shells were investigated. the results indicate that the bi-layered shells improved vibration behavior over single-layered shells of the same thickness. the results were confirmed by comparison with the results of previous studies. the natural frequencies of the results for non-rotating bi-layered fgm cylindrical shells and rotating single-layered fgm shells were compared and confirmed the accuracy of the results. © 2017,university of mohammed premier oujda morocco.