Robertson S W, Ritchie R O
Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.
J Biomed Mater Res B Appl Biomater. 2008 Jan;84(1):26-33. doi: 10.1002/jbm.b.30840.
Several key fracture-mechanics parameters associated with the onset of subcritical and critical cracking, specifically the fracture toughness, crack-resistance curve, and fatigue threshold, have recently been reported for the superelastic alloy Nitinol, in the product form of the thin-walled tube that is used to manufacture several biomedical devices, most notably endovascular stents. In this study, we use these critical parameters to construct simple decision criteria for assessing the quantitative effect of crack-like defects in such Nitinol devices with respect to their resistance to failure by deformation or fracture. The criteria are based on the (equivalent) crack-initiation fracture toughness and fatigue threshold stress-intensity range, together with the general yield strength and fatigue endurance strength, and are used to construct a basis for design against single-event (overload) failures as well as for time-/cycle-delayed failures associated with fatigue.
最近，已经报道了与亚临界和临界开裂起始相关的几个关键断裂力学参数，特别是断裂韧性、抗裂曲线和疲劳阈值，这些参数是针对超弹性合金镍钛诺而言的，其产品形式为薄壁管，用于制造多种生物医学装置，最显著的是血管内支架。在本研究中，我们使用这些关键参数来构建简单的判定标准，以评估此类镍钛诺装置中裂纹状缺陷对其抗变形或断裂失效能力的定量影响。这些标准基于（等效）裂纹起始断裂韧性和疲劳阈值应力强度范围，以及一般屈服强度和疲劳持久强度，并用于构建针对单事件（过载）失效以及与疲劳相关的时间/周期延迟失效的设计基础。
