Peridynamic modelling of bioresorbable screw degradation
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In this work, a computational framework is presented to predict in-vitro degradation of bioabsorbable fixation screws made of Mg alloys. To capture the coupled interaction between interfacial corrosion and ionic mass transport in the surrounding electrolyte, the process is described by a moving-boundary problem: the anodic dissolution at the solid–liquid interface generates dissolved Mg ions, and diffusion in the liquid results in spatial concentration gradients, driving the ions away. To handle evolving, potentially non-smooth corrosion fronts, we adopt a peridynamic (PD) diffusion/corrosion formulation based on the Perifast 3D/Corrosion code. Building on its fast convolution/FFT PD implementation, we extend the original constant-current approach to a space and time dependent anodic current density j(x,t), aimed at reproducing the nonuniform morphologies in corroded Mg alloys observed experimentally. We demonstrate the approach on a 60-day degradation simulation of an M2 Mg-10Gd screw in a biomimetic electrolyte, comparing uniform versus pitting-like scenarios. Outputs include spatiotemporal dissolved-ion concentration fields, global volume loss evolution for calibration against experimental measurements, and surface roughness descriptors to quantify corrosion-induced asperities. Overall, the proposed nonlocal, FFT-accelerated PD strategy offers a practical route for simulating coupled degradation–transport in biodegradable implants while directly linking experimentally informed corrosion kinetics to predictive morphological metrics.
