基于柔顺性的血管支架优化设计及强度可靠性分析

Optimization of vascular stent for its flexibility based on response surface method and strength reliability analysis of vascular stent caused by machining accuracy

目的建立血管支架的参数化模型,进行血管支架柔顺性能的优化设计。基于优化结果考虑加工精度引起的设计尺寸的不确定性,进行血管支架强度的概率计算以验证优化结果的可靠性。方法探寻结构特征,建立血管支架参数化模型。取弯曲刚度作为优化目标,血管支架支撑筋宽度、支撑筋长度、连接筋宽度和支架厚度为设计变量,采用响应面法进行血管支架优化设计,选取应力局部灵敏度较低的候选设计点作为最优设计点。基于优化血管支架,取受加工精度影响的设计尺寸作为随机变量,利用六西格玛工具进行血管支架强度的概率计算。结果建立了参数化的血管支架模型,优化后的血管支架弯曲刚度相比原始血管支架减小32.91%,累积分布概率为99.85%时,血管支架最大应力满足强度条件。结论连接筋宽度对血管支架的柔顺性影响最大,支架厚度次之,支撑筋长度和宽度影响较小;加工精度影响下优化血管支架强度可靠。血管支架在工程实际中会受到一些不确定性因素的影响,在进行确定性优化设计之后,要考虑不确定性因素引起的设计变量的不确定性进行强度可靠性分析验证。

Objective A parameterized model of vascular stents was established,and vascular stent was optimized for its flexibility.Based on the optimization results,the uncertainty of design dimensions caused by machining accuracy was considered,and the strength probability analysis of vascular stents was conducted to verify the reliability of the optimization results.Methods The structural features were explored to establish a parameterized model of vascular stents.The bending stiffness was taken as the optimization objective,and the width of the stent strut,the length of the stent strut,the width of the stent link,and the thickness of the vascular stent were the design variables.The response surface method was used for optimization design.Candidate design point with low local stress sensitivity was selected as the optimal design points.Based on the optimized vascular stent,the design dimensions caused by machining accuracy were taken as random variables,and the strength probability analysis of the vascular stent was conducted using the six sigma analysis tool.Results Compared to the original stent,the bending stiffness of the optimized vascular stent decreased by 32.91%.The maximum stress of the vascular stent met the strength requirements when the reliability reached 99.85%.Conclusion The width of the stent link had the greatest impact on the flexibility of the vascular stent,followed by the thickness of the stent,and the length and width of stent strut had a smaller impact.Strength of the optimized vascular stent under the influence of processing accuracy was reliable.Vascular stents are affected by some uncertainty factors in engineering practice.After conducting deterministic optimization design,the uncertainty of design variables caused by uncertainty factors should be considered for strength reliability analysis verification.