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The constrained layer damping materials are thoroughly used to control the vibration duo to their high capacity to dissipate vibration energy. Researchers have handled the vibration and damping behavior of the constrained layer damping structures accurately. However, for the constrained layer damping pipeline conveying fluid, there are few works on the investigation of the vibration characteristics. This paper is aimed to investigate the vibration and damping characteristics of the constrained layer damping pipeline conveying fluid under elastic boundary supports. Considering the fluid–structure interaction, the developed finite element method is employed to establish the motion equations of the constrained layer damping pipeline. The influence of the support stiffness, the fluid velocity and pressure, the thickness and the elasticity modulus of viscoelastic, and constraining layer parameters are all considered. The results indicate that an appropriate selection of the boundary support stiffness, the viscoelastic, and constraining layer parameters can obtain desirable modal properties, which can provide an efficient tool in the design and maintenance of aerospace pipeline for passive vibration control.

The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sands were reproduced and the slump test and the direct shear test of the conditioned sands were implemented. A DEM equivalent model that can simulate the macro mechanical characteristic of the conditioned sands was proposed, and the corresponding numerical models of the slump test and the shear test were established. By selecting proper DEM model parameters, the errors of the slump values between the simulation results and the test results are in the range of 10.3%−14.3%, and the error of the curves between the shear displacement and the shear stress calculated with the DEM simulation is 4.68%−16.5% compared with that of the laboratory direct shear test. This illustrates that the proposed DEM equivalent model can approximately simulate the mechanical characteristics of the conditioned sands, which provides the basis for further simulation of the interaction between the conditioned soil and the chamber pressure system of the EPB machine.

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