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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.

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In order to enhance the mechanical property of auxetic lattice structures, a new enhanced auxetic lattice structure was designed by embedding narrow struts into a three-dimensional (3D) re-entrant lattice structure. A series of enhanced lattice structures with varied parameters were fabricated by 3D printing combined with the molten metal infiltration technique. Based on the method, parameter studies were performed. The enhanced auxetic lattice structure was found to exhibit superior mechanical behaviors compared to the 3D re-entrant lattice structure. An interesting phenomenon showed that increasing the diameter of connecting struts led to less auxetic and non-auxetic structures. Moreover, the compressive property of the enhanced structure also exhibited obvious dependence on the base material and compression directions. The present study can provide useful information for the design, fabrication and application of new auxetic structures with enhanced properties.

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This paper proposes a novel optimization layout method for supporting clamps in a pipeline system. In this method, the global sensitivity analysis based on the Sobol method is presented to determine the influence of clamp position on the first-order frequency difference, the maximum vibration response displacement, and the maximum vibration stress. The modeling density of the finite element calculation is determined, and then a surrogate model of the relationship between the optimized input and the output is established through the neural network. The optimized position and orientation of the clamp are obtained by the genetic algorithm. Finally, a typical pipeline with clamps are conducted as an example to verify the effectiveness of the proposed optimization method. The simulations were compared with the experiment, and the result shows that the proposed optimization method can reduce the vibration of the pipeline system significantly, thus providing a new method for the arrangement of clamps in pipeline system.

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