PSI - Issue 39

Branko Nečemer et al. / Procedia Structural Integrity 39 (2022) 34 – 40 Author name / Structural Integrity Procedia 00 (2019) 000–000

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5. Conclusions The experimental and computational investigation of the fatigue behaviour of re-entrant and rotated re-entrant auxetic specimens made of the aluminium alloy 7075-T651 was proposed in this study. The experimental tests were performed in a load control at five amplitude load levels. The same loading conditions were then applied in the computational model built in the framework of ANSYS software package. For the fatigue life calculation, the strain life approach was applied, based on the Coffin-Manson model with a Morrow mean stress correction. The experimental and computational results showed that the fatigue lives of analysed structures are almost the same while the crack path was not. Based on this findings, we can conclude that the unit cell's orientation does not influence on the fatigue life of the analysed auxetic specimens but effects the direction of the fatigue failure path. The computational results showed that the number of cycles to failure decreases from cell to cell for the analysed auxetic specimen. The experimental and computational results were also showed that the fracture cell struts appeared in the corner of the individual unit cell and then expanded in the direction of the maximum stress concentration. Base on the good correlation between experimental and computational results it can be concluded that the proposed computational model is suitable for simulation of the fatigue behaviour of auxetic cellular structures. Acknowledgements The authors acknowledge the financial support of the Research Core Funding (No. P2-0063) and the basic research project (No. J2-8186) from the Slovenian Research Agency. X. Ren, J. Shen, P. Tran, T. D. Ngo, and Y. M. Xie, “Auxetic nail: Design and experimental study,” Compos. Struct., vol. 184, no. October, pp. 288–298, 2018. S. Hou, T. Liu, Z. Zhang, X. Han, and Q. Li, “How does negative Poisson’s ratio of foam filler affect crashworthiness?,” Mater. Des., vol. 82, pp. 247–259, Oct. 2015. J. N. Grima, R. Gatt, N. Ravirala, A. Alderson, and K. E. Evans, “Negative Poisson’s ratios in cellular foam materials,” Mater. Sci. Eng. A, vol. 423, no. 1–2, pp. 214–218, 2006. K. Meena and S. Singamneni, “A new auxetic structure with significantly reduced stress concentration effects,” Mater. Des., vol. 173, p. 107779, 2019. X. Zhao, Q. Gao, L. Wang, Q. Yu, and Z. D. Ma, “Dynamic crushing of double-arrowed auxetic structure under impact loading,” Mater. Des., vol. 160, pp. 527–537, 2018. B. Nečemer, M. Vesenjak, and S. Glodež, “Fatigue of Cellular Structures – a Review,” Strojniški Vestn. – J. Mech. Eng., vol. 65, no. 9, pp. 525– 536, Aug. 2019. B. Nečemer, J. Kramberger, T. Vuherer, and S. Glodež, “Fatigue crack initiation and propagation in re -entrant auxetic cellular structures,” Int. J. Fatigue, vol. 126, pp. 241–247, Sep. 2019. G. W. Milton, “Composite materials with poisson’s ratios close to - 1,” J. Mech. Phys. Solids, vol. 40, no. 5, pp. 1105–1137, 1992. S. Shan, S. H. Kang, Z. Zhao, L. Fang, and K. Bertoldi, “Design of planar isotropic negative Poisson’s ratio structures,” Extrem. Mech. Lett., vol. 4, pp. 96–102, 2015. B. Nečemer, S. Glodež, N. Novak, and J. Kramberger, “Numerical modelling of a chiral auxetic cellular structure under multiax ial loading conditions,” Theor. Appl. Fract. Mech., vol. 107, no. October 2019, pp. 1–9, 2020. J. Kramberger, B. Nečemer, and S. Glodež, “Assessing the cracking behavior of auxetic cellular structures by using both a numerical and an experimental approach,” Theor. Appl. Fract. Mech., vol. 101, 2019. B. Nečemer, J. Kramberger, T. Vuherer, and S. Glodež, “Fatigue crack initiation an d propagation in re-entrant auxetic cellular structures,” Int. J. Fatigue, vol. 126, no. May, pp. 241–247, Sep. 2019. B. Nečemer, J. Klemenc, and S. Glodež, “The computational LCF -analyses of chiral and Re-entrant auxetic structure using the direct cyclic algorithm,” Mater. Sci. Eng. A, vol. 789, no. May, 2020. D. Tomažinčič, B. Nečemer, M. Vesenjak, and J. Klemenc, “Low -cycle fatigue life of thin-plate auxetic cellular structures made from aluminium alloy 7075-T651,” Fatigue Fract. Eng. Mater. Struct., no. October 2018, pp. 1–15, 2019. References