PSI - Issue 40

L.R. Akhmetshin et al. / Procedia Structural Integrity 40 (2022) 7–11 L.R. Akhmetshin / Structural Integrity Procedia 00 (2022) 000 – 000

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equidistant fixed points, it can be found that the deviations along the X -axis and Z -axis are commensurate. This means that the transverse strain is absent or tends to zero. The longitudinal compression strain is constant and not equal to zero. On this basis, it can be concluded that the value of the effective Poisson's ratio is zero. The zero value of the Poisson’s ratio can be explained by the fact that there are transverse elements in the structure. During longitudinal compression, the transverse faces do not rotate, which could lead to a contraction in the cross section of the rod. The transverse edges of the cells also do not expand due to the design features of the unit cell. This effect appears at small values of longitudinal deformations.

Fig. 2. The fixed points’ d eviation from the initial position.

4. Conclusion During uniaxial compression of the rod consisting of the chiral mechanical metamaterial, the effective Poisson's ratio was calculated to be zero in the cellular tetrachiral structure. This value is probably due to the small longitudinal strain. The Poisson's ratio is the value of the ratio of relative transverse compression to relative longitudinal extension. Therefore, in order to determine its effective value, it was necessary to determine the transverse strain. To do this, 80 fixed points on the sample were considered (20 points on each edge). Comparison of the values of deviation of the reference points from the initial position along the X-axis and Z-axis showed the absence of transverse deformation. From this, it was concluded that the value of the effective Poisson's ratio is zero. Acknowledgements The work was performed according to the Government research assignment for ISPMS SB RAS, project FWRW

2022-0003. References

Akhmetshin, L. R., Smolin, I. Yu., 2020. Influence of Unit Cell Parameters of Tetrachiral Mechanical Metamaterial on Its Effective Properties. Nanoscience and Technology: An International Journal 11(3), 265 – 273. doi: 10.1615/NanoSciTechnolIntJ.202003373