Influence of an eccentricity imperfection on the stability and vibration behavior of fluid-conveying functionally graded pipes

An eccentricity imperfection may be occurred in the pipes due to the inappropriate manufacturing process. Hence, the dynamic behavior of such geometrically imperfect pipes is extremely required to be explored and compared with the perfect ones. This work investigates the stability and free vibration of fluid-conveying homogenous and functionally graded (FG) pipes with consideration of eccentricity as a geometric imperfection. Three different fluid-conveying pipes are investigated; (i) the homogenous pipe with an eccentricity imperfection, (ii) the FG pipe without imperfection or concentric FG pipe and, (iii) the fluid-conveying FG pipe with an eccentricity imperfection. The governing equations of the fluid-structure interaction system are derived by including the effect of shear deformation using the Timoshenko beam theory. The finite element method is applied to discretize the governing equations and solve the eigenvalue problem of a clamped-clamped pipe. Consequently, the complex modal analysis is used to obtain the natural frequencies and critical velocities of homogenous and FG pipelines with and without eccentricity imperfection. Finally, the effects of different magnitudes of eccentricity and power-law exponent on the critical fluid velocity are investigated. This investigation is expected to provide more insight for the applications of geometrically imperfect pipes in the pipeline systems.