Compressive behaviour of chiral auxetic cellular structures at different strain rates. (July 2020)

• Record Type: Journal Article
• Authors: Novak, Nejc; Vesenjak, Matej; Tanaka, Shigeru; Hokamoto, Kazuyuki; Ren, Zoran
• Is Part Of: International journal of impact engineering. Volume 141(2020)
• Publication Date: 2020-07
• Subjects: Chiral auxetic cellular structures -- High strain rate -- Strain-rate sensitivity -- Critical velocities -- Experimental testing -- Computational modelling; Impact -- Periodicals; Shock (Mechanics) -- Periodicals; Impact -- Périodiques; Choc (Mécanique) -- Périodiques; Impact; Shock (Mechanics); Periodicals; 620.1125
• DOI: 10.1016/j.ijimpeng.2020.103566
• Languages: English
• ISSNs: 0734-743X

Abstract

Highlights: experimental testing of chiral auxetic structures at low and high strain rates (up to 5000 s −1 ). development and validation of the computational models. analytical calculation and computational evaluation of critical velocities. analysis of deformation modes and mechanisms based on experimental testing and subsequent parametric computational simulations. the development of empirical polynomial approximation, which enables estimation of the plateau stress of auxetic cellular structures at arbitrary loading velocity. Abstract: The quasi-static and high strain rate response of chiral auxetic cellular structures were evaluated in this work. Samples of the chiral auxetic structures were fabricated with the Selective Electron Beam Melting (SEBM) technique from copper powder. Uniaxial quasi-static and low-speed dynamic compression tests were performed on a universal testing machine, while high strain rate tests up to 5000 s −1 were performed using the one-stage powder gun. The experimental measurements together with infrared thermography and high-speed camera images were used to study the deformation mechanism of chiral auxetic structures. A significant effect of the shock enhancement observed in experiments at higher loading velocities was characterised by evaluating the specific energy absorption and specific strength. This phenomenon was further analysed in more detail by using parametric computational simulations, which offered more detailed analysis of mechanical behaviour at different strain rates. The computational results indicate that the plateau stress of chiral auxetic structure increases exponentially with increasing loading velocity. An empirical polynomial approximation was extracted from the computational results, which enables estimation of the plateau stress of auxetic cellular structures at arbitrary loading velocity in between the analyses velocity limits.