Özet:

Developments in technology require the new materials, lighter and more efficient structures and also new manufacturing methods. In this study, after doing researches about topology optimization, regular honeycomb and re-entrant structures the regular honeycomb and re-entrant structures were designed, and then Ti-6Al-4V material was chosen for these structures in finite element (FE) analyzing. The three different rib thickness values (t) of 1 mm, 1.5 mm and 2 mm were assigned for honeycomb and re-entrant structures in FE analyses. Also, the crack was created on the models, and then 2-D FE analyses were done for both cracked and un-cracked honeycomb and re-entrant structures under tensile forces through y axis. Afterwards, the effect of crack on stress intensity factor, stresses, strains and displacement were obtained and characterized the auxetic behavior of the regular honeycomb and re-entrant structures. Furthermore, increase in rib thickness decreases stress and strains for each structure. Moreover, re-entrant structures have negative Poisson’s ratio due to their geometric properties and the notable effect of crack on the equivalent stress in re-entrant was emerged in comparison with honeycomb structure.  As a result, the only possible fracture in honeycomb for thickness of 1 mm might be observed owing to stress intensity factor obtained from analyses bigger than fracture toughness of honeycomb structure.    

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