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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Fig. 1. Radial stresses distributions.

3. Results and discussion The analysis of the numerical results presented in Fig. 1 shows a significant dependence on the influence of the mechanical, physical, and microstructural characteristics of polyurethane foams on their vibration-absorption properties. The influence of the internal structure of the material is significant on the speed of propagation of waves in the foam medium. This is confirmed by the results of numerical calculations of normal stresses in the layer that is 14ℓ away from the surface boundary to which the ex ternal load is applied. The time parameter corresponding to the time of reaching the elastic impulse of the corresponding layer is 4.6 larger for the case of WF300 foam compared to the WF110 foam. Accounting for such effects allows us to adjust the thickness of the foam to achieve optimal vibration and stress-absorption characteristics. In the layers located near the boundary of application of the external load, the normalized normal stresses differ slightly both in intensity and in the time of their propagation. To evaluate the change in the intensity of normal stresses during the propagation of an elastic impulse in the medium, we will investigate the dependence of the change in their maximum values, related to the maximum value of the applied impulse, on the distance to the layer in which they are determined. In brackets, the percentage of stress reduction compared to the previous layer is calculated. The corresponding calculation results are shown in Table 2.

Table 2. Maximum values of normal stresses

related to .

Sample number

 = 2 ℓ

 = 6 ℓ

 = 10 ℓ

 = 14 ℓ

I (WF300)

0.601 (-39.9%) 0.6197 (-38.03%) 0.6372 (-36.28%) 0.6696 (-33.04%)

0.3242 (-46.06%) 0.3567 (-42.44%) 0.3901 (-38.78%) 0.4428 (-33.87%)

0.2048 (-36.83%) 0.2379 (-33.31%) 0.2788 (-28.53%) 0.3403 (-23.15%

0.1436 (-29.88%) 0.172 (-27.72%) 0.2099 (-24.71%) 0.2777 (-18.4%)

II

III

IV (WF110)

The analysis of the numerical results presented in Table 2 shows that in the layers that are far from the load application boundary (  = 14 ℓ ) the intensity of normal stress attenuation is lower than in the other studied layers. The maximum effect of wave attenuation is achieved in layers that are distant from the boundary of the application of external forces by a distance of  = 6 ℓ . Numerical calculations show that in all considered cases, the intensity of the applied external load decreases by two times in the layers that are distant from the limit of load application by a distance of 5ℓ.