Testing and mesoscale modelling of hydrogen assisted cracking of magnesium

Abstract

To rationalise the results of stress corrosion cracking tests on smooth tensile specimens of a magnesium alloy, performed as constant extension rate tensile tests, a mesoscale fibre bundle model is employed in which the material being tested is represented by a bundle of parallel fibres The effect of hydrogen embrittlement oil the stress-Strain curves measured at various strain rates is simulated by assuming that the hydrogen is generated in localised corrosion pits and subsequently diffuses into the bulk. thereby reducing the strain-to-failure of individual fibres. The stress-strain curves obtained from these simulations show the same strain rate effect as was experimentally observed

A strain-mediated corrosion model for bioabsorbable metallic stents

“…Several experimental studies have provided correlations between the magnitude of specimen stress and corrosion behaviour in magnesium alloys [5,13,14]. Clearly therefore stress-induced strain also has a role to play in corrosion of biodegradable materials.…”

“…Models of other corrosion processes have been developed and applied to magnesium alloys such as stress corrosion cracking (SCC) [5] fatigue cracking [6] and crevice corrosion [7]. However, many of the aforementioned modelling approaches focus on specific corrosion processes that are not easily applicable to coronary stents due to the difficulty of establishing the 3 model parameters using experimental calibration procedures.…”

Modeling and simulation of material degradation in biodegradable wound closure devices

“…24 Stress corrosion cracking mechanism of Mg alloy was studied by Dietzel with a mesoscale fiber bundle model. 25 Computer-based methods like finite element (FE) had been used to model and investigate mechanical properties for stents under different conditions: expansion, 26,27 flexibility, 28,29 fatigue, 30,31 and interaction with tissues. 32 Nevertheless, few studies pay attention to the degradation mechanism of biodegradation clips which has important use in wound closure application.…”

Environmentally Assisted Cracking of Magnesium Alloys

“…Details of this model can be found in the literature [6,10,[16][17][18][19]. A bundle-of-parallel model had earlier been employed to mimic SCC/HE in steel, where the heterogeneity of the material was taken into account by assuming a site-dependent critical strain [6].…”

“…In various studies by the authors group experimental data which had been obtained from fracture mechanics tests on smooth and pre-cracked specimens were analysed using a number of modelling approaches for crack initiation and growth caused by hydrogen embrittlement [6][7][8][9][10]. The models proved that they had the potential to simulate the effects of hydrogen embrittlement in the material under investigation.…”