www.elsevier.com/locate/jmbbm Available online at www.sciencedirect.com Research Paper Computational micromechanics of bioabsorbable magnesium stents J.A. Grogan, S.B. Leen, P.E. McHugh n Biomechanics Research Centre (BMEC), Mechanical and Biomedical Engineering, National University of Ireland, Galway, Ireland article info Article history: Received 21 August 2013 Received in revised form 10 January 2014 Accepted 13 January 2014 Available online 30 January 2014 Keywords: Bioabsorbable stent Magnesium Crystal plasticity Finite element abstract Magnesium alloys are a promising candidate material for an emerging generation of absorbable metal stents. Due to its hexagonal-close-packed lattice structure and tendency to undergo twinning, the deformation behaviour of magnesium is quite different to that of conventional stent materials, such as stainless steel 316L and cobalt chromium L605. In particular, magnesium exhibits asymmetric plastic behaviour (i.e. different yield beha- viours in tension and compression) and has lower ductility than these conventional alloys. In the on-going development of absorbable metal stents it is important to assess how the unique behaviour of magnesium affects device performance. The mechanical behaviour of magnesium stent struts is investigated in this study using computational micromechanics, based on finite element analysis and crystal plasticity theory. The plastic deformation in tension and bending of textured and non-textured magnesium stent struts with different numbers of grains through the strut dimension is investigated. It is predicted that, unlike 316L and L605, the failure risk and load bearing capacity of magnesium stent struts during expansion is not strongly affected by the number of grains across the strut dimensions; however texturing, which may be introduced and controlled in the manufacturing process, is predicted to have a significant influence on these measures of strut performance. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Coronary stents are small tubular scaffolds that are widely used in the treatment of coronary heart disease. Stents have typically consisted of high strength, corrosion resistant alloys, such as stainless steel 316L and cobalt chromium L605. A new genera- tion of absorbable metal stents (AMSs) has shown promise in early clinical trials (Erbel et al., 2007; Haude et al., 2013) and has the potential to address limitations in the performance of the current generation of permanent stents, in particular in-stent restenosis and late stent thrombosis (Mitra and Agrawal, 2006; Ong et al., 2005; Waksman, 2007). AMSs developed to date have consisted of magnesium alloys (e.g. AZ31, AZ61, WE43) and pure iron. Of these, AMSs based on a non-commercial derivative of magnesium alloy WE43 have shown the most promise to date, having progressed to two in-human clinical trials (Erbel et al., 2007; Haude et al., 2013). The deformation of hexagonal-close-packed (HCP) magne- sium alloys is quite different to that of typical face-centred-cubic (FCC) stent materials (e.g. 316L and L605). In particular, due to the limited number of available slip systems at room temperature the alloys exhibit relatively low formability and a significant 1751-6161/$ - see front matter & 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jmbbm.2014.01.007 n Corresponding author. E-mail address: peter.mchugh@nuigalway.ie (P.E. McHugh). journal of the mechanical behavior of biomedical materials34 (2014)93–105