模拟体液环境中医用钛合金的长寿命腐蚀疲劳损伤机制与寿命预测

Titanium-based implants are subjected to the interaction of cyclic load and the corrosive environment. Several reports indicated that fatigue-related mechanisms are responsible for the most part of mechanical failures of implantable medical metallic components. Therefore, in order to ensure its performance and reliability, this biomaterial should be tested to evaluate the in?uence of the human body environment on its long-term performence. In this project, taking the initiation and development of failure, damage cumulated effect and its evolution rule as the route, the long life corrosion fatigue performance including fatigue strength and fatigue crack propagation of biomedical Titanium alloys cycled in simulated body fluid is studied systematically. The relationship between stress and fatigue life (S-N) will be quantitatively illustrated. A reliable prediction model of fatigue life will be proposed based on full understanding of corrosion fatigue crack initiation and propagation mechanisms and damage evolution rules. The effect of environment (PH value, loading frequency and stress ratio) on the corrosion fatigue behaviors of Titanium alloys will be investigated. Furthermore,the effect of hybrid surface nanocrystallization with different treatments on the long term corrosion fatigue performance of biomedical Titanium alloys will be analyzed to explore an optimum method.

钛合金植入物在服役期间要承受生理环境的腐蚀与疲劳载荷的长期作用而导致腐蚀疲劳失效，为了保证植入材料的可靠性和安全性，需要对其在服役生理环境中的长期服役力学行为进行评估和寿命预测。本项目以交变载荷作用下医用钛合金在生理环境中失效破坏的成因和发展、损伤累积效应以及演化规律为主线，通过对医用钛合金在模拟体液环境中的长寿命腐蚀疲劳性能和疲劳裂纹扩展行为进行系统试验研究，定量描述应力寿命(S-N)关系，阐明腐蚀疲劳裂纹萌生和扩展机理、损伤演变规律，建立合理的寿命预测模型。并研究环境（PH值、载荷频率、应力比）变化对医用钛合金腐蚀疲劳性能的影响规律。另外，对医用钛合金表面进行不同方式混合纳米化，寻求提高钛合金生理环境中长寿命腐蚀疲劳性能有效的处理方式。

钛合金植入物植入人体后，在长期服役过程中，面临着交变载荷与生理环境的相互作用，其高可靠长寿命的验证和评价已成为迫切的工程需求。本项目首先针对长寿命疲劳加速试验方法和技术问题，研发了腐蚀环境下的拉压载荷超声加速长寿命疲劳试验系统，打破国内不能对材料1E7周以上交变载荷循环后的腐蚀环境进行试验研究的局面，为项目的开展提供了实验平台。继而利用研制的系统，重点针对常用的医用Ti-6Al-4V合金，开展了空气和模拟生理环境（模拟体液和生理盐水）中的长寿命疲劳研究，获得了应力寿命（S-N）关系、疲劳裂纹萌生和扩展机理，提出了一个描述裂纹扩展驱动力和阻力随裂纹长度变化的模型，同时分析了材料表面处理（打磨、抛光、表面纳米化和缺口）、生理环境预腐蚀、PH值的影响，获得相应的影响规律，探索了提高钛合金疲劳性能的表面处理方式；另外，针对新型的医用钛合金（Ti-6Al-7Nb和TAMZ），进行了模拟生理环境中的长寿命疲劳行为的测试与分析，获得了S-N关系、疲劳裂纹萌生机理。获得的成果可为评价医用钛合金的可靠性和安全性以及进一步研究钛合金植入物在长期服役生理环境中的疲劳行为提供参考和技术支持。