Study on the vibrational stability of functionally graded fluid-conveying flanged pipes

Fluid flow through pipe flanges can excite flow-induced vibration, leading to pipeline vibration and instability. Traditional flow-induced vibration theories exhibit limited applicability for such complex scenarios. This study investigates a functionally graded material (FGM) fluid-conveying pipeline system with flanges, establishing a dynamic model that explicitly accounts for the flange's influence, gradient distribution of interlayer materials, porosity, and graphene platelet (GPL) reinforcement to achieve lightweight design while maintaining high structural strength. The governing equations of motion are derived using the substructure synthesis modal method, the Galerkin truncation method, and Lagrange's equations. Model accuracy is validated through numerical solutions obtained in MATLAB and finite element simulations performed in ANSYS. The results demonstrate that shortening the length of the flanged pipe enhances the critical flow velocity. Regarding material parameters, an X-type GPL distribution pattern and low porosity significantly increase the critical flow velocity, while the GPL weight fraction positively correlates with system stability. Importantly, installing the flange at the mid-span of the pipe significantly enhances stability. This research provides a theoretical foundation for the lightweight design and stability optimization of fluid-conveying flanged pipes, offering significant value for engineering applications.