Application of Viscoelastic Materials in Ship Collision

With the expansion of global trade routes, ship collision has become a major problem. This article proposes an approach by laying viscoelastic material on the inner side of the ship to increase the crashworthiness. By using the nonlinear finite element model software, this study simulates ship collisions as well as models and analyzes ships along with viscoelastic materials. The results from the simulation suggest that viscoelastic materials can effectively protect ships during collisions.

Identification of the Fractional Zener Model Parameters for a Viscoelastic Material over a Wide Range of Frequencies and Temperatures

The paper presents an analysis of the rheological properties of a selected viscoelastic material, which is dedicated to the reduction of vibrations in structures subjected to dynamic loads. A four-parameter, fractional Zener model was used to describe the dynamic behavior of the tested material. The model parameters were identified on the basis of laboratory tests performed at different temperatures and for different vibration frequencies. After proving that the material is thermoreologically simple, the so-called master curves were created using a horizontal shift factor. The Williams–Landel–Ferry formula was applied to create graphs of the master curves, the constants of which were determined for the selected temperature. The resulting storage and loss module functions spanned several decades in the frequency domain. The parameters of the fractional Zener model were identified by fitting the entire range of the master curves with the gradientless method (i.e., Particle Swarm Optimization), consisting in searching for the best-fitted solution in a set of feasible solutions. The parametric analysis of the obtained solutions allowed for the formulation of conclusions regarding the effectiveness of the applied rheological model.

Topology optimization for 3D microstructures of viscoelastic composite materials

Materials with high stiffness and good vibration damping properties are of great industrial interest. In this paper, a topology optimization algorithm based on the BESO method is applied to design viscoelastic composite material by adjusting its 3D microstructures. The viscoelastic composite material is assumed to be composed of a non-viscoelastic material with high stiffness and a viscoelastic material with good vibration damping. The 3D microstructures of the composite are uniformly represented by corresponding periodic unit cells (PUCs). The effective properties of the 3D PUC are extracted by the homogenization theory. The optimized properties of the composites and the optimal microscopic layout of the two materials phases under the conditions of maximum stiffness and maximum damping are given by several numerical examples.

Analysis of Sound Absorption Performance of Underwater Acoustic Coating considering Different Poisson’s Ratio Values

Viscoelastic material acoustic coating plays an important role in noise and vibration control of underwater equipment. The dynamic mechanical properties of the viscoelastic material have a direct effect on the sound absorption performance of the acoustic coating. The influence of Poisson’s ratio on sound absorption performance is studied. A finite element model was established to calculate the sound absorption performance of three typical acoustic coatings: homogeneous acoustic coatings, Alberich acoustic coatings, and trumpet cavity acoustic coatings, and the influence of Poisson’s ratio on the sound absorption performance of the three kinds of acoustic coatings was analyzed. The results show that when Poisson’s ratio varies from 0.49 to 0.4999, the larger Poisson’s ratio is, the larger the frequency of the first absorption peak is, the smaller the absorption coefficient below the frequency of the first absorption peak is, and the smaller the average absorption coefficient in the whole analysis frequency range is. The dynamic Poisson’s ratio with the change of frequency is obtained by interpolating the test results and static Poisson’s ratio finite element calculation results. The calculation results show that the dynamic Poisson’s ratio can get more accurate calculation results. This work can provide a reference for researchers to set Poisson’s ratio in theoretical analysis and finite element analysis of acoustic coating.