PSI - Issue 59

Olena Mikulich et al. / Procedia Structural Integrity 59 (2024) 466–470 Olena Mikulich et al./ Structural Integrity Procedia 00 (2024) 000 – 000

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good thermal insulation and vibration absorption characteristics. Currently, a lot of foams with different characteristics and properties are produced. However, the development of approaches to the study of the influence of changes in the properties of foam polymers when changing their structural and physical characteristics of materials proves not only to expand the direction of their application but also to optimize the modes of loading and operation of the corresponding structural elements. All this substantiates the scientific interest in the development of accordant research methods for the influence of changes in the characteristics of foams on their vibration-absorbing properties.

Nomenclature G

Shear modulus Young’s modulus Foam density

E



Bending scale parameter in Cosserat elasticity Scale parameter in couple stress elasticity

l b

ℓ

N 2

Couple number

B Microstructure characteristic of foam ̅̅̅̅ Normalized radial stress Time ̅ Normalized time parameter ¯ Normalized value of impulse duration Speed of the expansion wave

In the literature, a lot of scientific works present the results of experimental studies of the mechanical and physical properties of certain types of foams. Thus, Pradel et al. (2018) present the results of experimental studies on the ability of polyurethane foam to mitigate intense and short-term stress waves. The level of compaction stress was used as an indicator of the softening capacity of the pins. Schiffer et al. (2018) through experiments and simulations, the interaction of solitary waves in a granular crystal with a plastically compressible and speed-sensitive medium in the form of rigid polyurethane foam was investigated. Placido et al. (2021) experimentally investigated the effect of impact loads on samples of sand and sand-polyurethane composite under different holding pressures. Among the numerical methods of analysis of structurally inhomogeneous materials, two main directions have been developed in the literature. The first of them is based on purely numerical modelling and is mostly implemented based on the finite element method. Numerical analysis based on the finite element method allows modelling for minor changes in the structural and physical characteristics of materials. Bayat et al. (2019) based on the wave method and finite element analysis, the phenomenon of elastic wave propagation in open-pore foams was investigated. Wangab et al. (2019) analyzed the wave propagation characteristics of nanobeams from nanoporous metal foams. Chen et al. (2021) investigated the effects of cell size, cohesion, and relative pore diameter on the sound absorption of polyurethane foam using numerical simulation analysis. The second approach is based on analytical-numerical approaches that combine the use of analytical methods within the framework of refined continuum mechanics models together with numerical methods. Such approaches are characterized by greater accuracy of calculations in comparison with purely numerical methods and the possibility of conducting research in much wider ranges of changes in the structural and physical characteristics of materials. Such methods of analytical and numerical study of the stress state of materials with a microstructure are based on the use of continuous Cosserat models, which account for the effect of rotational-shear deformations of material microparticles and are realized based on the boundary element method (Mikulich et al., 2021). In view of this, the development of analytical and numerical methods for the study of non-stationary processes in foam media has scientific interest. Such approaches will allow for the optimisation of the performance characteristics of foam materials by choosing characteristics of appropriate materials. The article is devoted to studying the influence of changes in the mechanical and physical characteristics of foamed polymers on their vibration-absorbing properties. The indirect approach of the boundary element method within the framework of couple stress elasticity was used or the research. In this research, the method of analysis of the stress state of structurally heterogeneous materials within couple stress elasticity (Mikulich et al., 2021) with the method of simulation numerical modelling within Cosserat elasticity (Mikulich, 2023) was used.