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Experimental characterisation for micromechanical modelling of CoCr stent fatigue

机译:CoCr支架疲劳微力学建模的实验表征

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Fatigue of CoCr alloy stents has become a major concern in recent times, owing to cases of premature fracture, often driven by microstructural phenomena. This work presents the development of a micromechanical framework for fatigue design, based on experimental characterisation of a biomedical grade CoCr alloy, including both microscopy and mechanical testing. Fatigue indicator parameters (FIPs) within the micromechanical framework are calibrated for the prediction of microstructure-sensitive fatigue crack initiation (FCI). A multi-scale CoCr stent model is developed, including a 3D global J2 continuum stent-artery model and a 2D micromechanical sub-model. Several microstructure realizations for the stent sub-model allow assessment of the effect of crystallographic orientations on stent fatigue crack initiation predictions. Predictions of FCI are compared with traditional Basquin-Goodman total life predictions, revealing more realistic scatter of data for the microstructure-based FIP approach. Comparison of stent predictions with performance of a 316L stent for the same generic design exposes the design as over-conservative for the CoCr alloy. In response, the micromechanical framework is used to modify the stent design for the CoCr alloy, improving design efficiency.
机译:由于过早断裂的情况(通常是由微观结构现象引起的),CoCr合金支架的疲劳问题已成为近来的主要问题。这项工作基于生物医学级CoCr合金的实验表征,包括显微镜和机械测试,提出了用于疲劳设计的微机械框架的开发。校准了微机械框架内的疲劳指标参数(FIP),以预测对微结构敏感的疲劳裂纹萌生(FCI)。开发了多尺度CoCr支架模型,包括3D全局J2连续体支架-动脉模型和2D微机械子模型。支架子模型的几个微结构实现允许评估晶体学取向对支架疲劳裂纹萌生预测的影响。将FCI的预测与传统的Basquin-Goodman的总寿命预测进行了比较,揭示了基于微结构的FIP方法的更真实的数据散布。对于相同的通用设计,将支架预测结果与316L支架的性能进行比较后,发现该设计对CoCr合金而言过于保守。作为响应,微机械框架用于修改CoCr合金的支架设计,从而提高设计效率。

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