This paper investigates the control performance of pounding tuned mass damper (PTMD) in reducing the dynamic responses of SDOF (Single Degree of Freedom) structure. Taking an offshore jacket-type platform as an example, the optimal damping ratio and the gap between mass block and viscoelastic material are presented depending on a parametric study. Control efficiency influenced by material properties and contact geometries for PTMD is analyzed here, as well as robustness of the device. The results of numerical simulations indicated that satisfactory vibration mitigation and robustness can be achieved by an optimally designed PTMD. Comparisons between PTMD and traditional TMD demonstrate the advantages of PTMD, not only in vibration suppression and costs but also in effective frequency bandwidth.

The 7050 aluminum alloy orifice plate is extruded and strengthened by the cold expansion process of slotted bushing holes. A three-dimensional finite element model was established for cold expansion strengthening of holes, and the residual stress distribution of 7050 aluminum alloy orifice plates is studied after cold expansion. The influence of different relative extrusion amounts and different sample thicknesses on the residual stress around the sample hole was analyzed, and the relationship between the extrusion amounts and the thicknesses of the substrate and the residual stress was obtained by analysis. The research results indicate that the cold expansion process of slotted bushing holes can enhance the residual stress distribution around the hole and form a strong residual stress layer. As the amounts of extrusion increase, the residual stress tends to increase, reaching the maximum when the amounts of extrusion are 4%. The residual stress on the surface of the extrusion inlet increases with the increase in the thickness of the substrate. Within the range of 3%-4% of the extrusion amounts, with the continuous increase of the extrusion amounts, the fatigue life has been substantially enhanced, and the number of fatigue life is more than 3 times that of the empty plate fatigue test.

Based on the summary of existing pounding force analytical models, an updated pounding force analysis method is proposed by introducing viscoelastic constitutive model and contact mechanics method. Traditional Kelvin viscoelastic pounding force model can be expanded to 3-parameter linear viscoelastic model by separating classic pounding model parameters into geometry parameters and viscoelastic material parameters. Two existing pounding examples, the poundings of steel-to-steel and concrete-to-concrete, are recalculated by utilizing the proposed method. Afterwards, the calculation results are compared with other pounding force models. The results show certain accuracy in proposed model. The relative normalized errors of steel-to-steel and concrete-to-concrete experiments are 19.8% and 12.5%, respectively. Furthermore, a steel-to-polymer pounding example is calculated, and the application of the proposed method in vibration control analysis for pounding tuned mass damper (TMD) is simulated consequently. However, due to insufficient experiment details, the proposed model can only give a rough trend for both single pounding process and vibration control process. Regardless of the cheerful prospect, the study in this paper is only the first step of pounding force calculation. It still needs a more careful assessment of the model performance, especially in the presence of inelastic response.

Polyethylene terephthalate (PET) foam sandwich structure is widely used in the fields of construction, aerospace and shipbuilding. We have conducted research on its hygroscopic phenomenon. Take different sizes of GFRP panels, PET foam and PET foam sandwich structure for moisture absorption tests, analyze the data on the basis of the classic Fick’s law of diffusion to obtain the moisture absorption curves of each sample. And get the diffusion coefficient of the specimen. Then, we use the multi-physics software COMSOL to model and analyze the moisture absorption properties of the specified samples. The moisture absorption curve obtained by theoretical calculation was compared with the experimental moisture absorption curve, and the results showed that the two Good agreement. Tests have proved that the moisture absorption performance of PET foam is much greater than that of GFRP panel material, and the relative moisture absorption is related to the specific surface area of the sample. In the PET foam sandwich structure, the GFRP panel can effectively inhibit the hygroscopicity of the PET foam and has an excellent protective effect on the PET foam.

To enhance the floating raft vibration isolation system’s effect, a new two-stiffness floating raft vibration isolation experimental was constructed. First, the system’s mathematical model was established. The vibration transfer function was deduced via substructure derivative synthesis and four-end parameter matrix methods, and the structural parameter impacts on it were analyzed. Then, a modal test was conducted, and a finite element model was built. Comparing finite element analysis with test results verified the model’s validity, followed by a study of the support structure’s vibration characteristics. Finally, by measuring acceleration responses at the isolator’s upper and lower ends and using the difference as an evaluation index, the isolator’s vibration isolation effect on land and underwater was investigated, along with its impact on the device’s underwater acoustic radiation. The results demonstrate that the two-stiffness vibration isolator can reduce vibration transmission within a specific frequency range both on land and underwater, guiding practical engineering vibration isolation research.