A study of the modal characteristics of curved pipes

Finite element procedures are employed to investigate the dynamic behavior of curved pipes, specifically resonance frequencies and modeshapes. Pipe geometries are chosen to reflect industry norms and the study is limited to frequencies below 1600 Hz. Experimental and theoretical procedures are employed to verify finite element results where appropriate. A parametric study is undertaken to observe the effect of changing various geometric parameters on the resonances and modeshapes of a curved pipe. The focus of the parametric study is upon the effects of changing the pipe's toroidal bend angle. As the bend angle is increased, each mode responds differently, some becoming monotonically more stiff, some becoming monotonically less so and others remaining at an approximately constant stiffness. Finite element procedures also readily provide a graphical representation of the change in various modeshapes as the toroidal bend angle is varied. Increasing the wall thickness, reducing the sectional radius or reducing the bend radius of the pipe each yield an overall increase in the stiffness of all modes studied. Further to these results, the finite element procedures suggest that, for some modes, magnitudes of in-plane components are of a similar order to those of the out-of-plane (flexural) components, an observation confirmed by subsequent experimental procedures. (C) 2001 Elsevier Science Ltd. All rights reserved.