Lattice-based shape memory and superelastic structures: design, manufacture, modeling, and applications

拟议的研究计划桥接科学，技术和材料力学领域，旨在为航空航天和医疗应用创造多功能形状记忆和超弹性组件。为此，将使用两种类型的形状记忆合金（SMA）：钛镍合金（Ti-Ni）和近β钛合金（Ti-Nb-Zr）。它们将使用激光粉末床融合（LPBF）技术进行加工，以制造用于医疗和航空航天应用的工程晶格结构。在医学上，具有可控孔隙率梯度的单件高生物相容性Ti-Nb-Zr超弹性植入物可以降低与植入物整合问题相关的并发症风险。在航空航天领域，轻质Ti-Ni形状记忆结构可用于传感和驱动目的。** 该计划从每种选定合金的完全致密组件的生产开始。为此，LPBF工艺参数将使用熔池建模和实验设计方法的组合进行优化。使用完全致密的打印合金可以达到的最佳功能特性将作为由这些材料制成的晶格结构的设计，制造和后处理过程中的基准。** 为了生成可变孔隙率晶格结构，设计空间将使用原始的基于体素的算法用菱形和八面体单位单元填充。接下来，这些结构将使用LPBF技术生产，并在不同温度下进行静态和疲劳机械测试，以建立蜂窝结构的功能特性与其散装材料等效物之间的比例关系。** 为了避免在优化这些结构时采用试错法，将使用多尺度数值建模方法模拟其超弹性和形状记忆行为。实验验证所开发的模型将进行比较的数值计算结果与实验观察，使用光学数字成像和X射线计算机断层扫描技术。* 最后，将设计、增材制造和测试两个试验组件：由Ti-Zr-Nb合金制成的超弹性可变孔隙度颈椎植入物和由Ti-Ni合金制成的轻质形状记忆致动器。*该研究计划旨在将增材制造的自由成形能力与形状记忆和超弹性材料的功能相结合，将促进新一代多功能轻质结构在医学和航空航天领域的成功应用。拟议的计划还将有助于培养高素质的人才，并吸引高水平的外国学生到加拿大。**

The proposed research program bridges the fields of science, technology and mechanics of materials with the objective of creating multifunctional shape memory and superelastic components for aerospace and medical applications.******To this end, two types of shape memory alloys (SMA) will be used: titanium-nickel alloy (Ti-Ni) and near-beta titanium alloy (Ti-Nb-Zr). They will be processed using laser powder bed fusion (LPBF) technology to manufacture engineered lattice structures for medical and aerospace applications. In medicine, single piece highly-biocompatible Ti-Nb-Zr superelastic implants with controlled porosity gradient could reduce the risks of complications related to the implant integration problems. In aerospace, lightweight Ti-Ni shape memory structures could be used for sensing and actuation purposes. ******The program starts from the production of entirely-dense components from each of the selected alloys. To this end, the LPBF processing parameters will be optimized using a combination of the melt pool modeling and the design of experiment approaches. The best functional properties, which can be reached with the entirely-dense printed alloys, will serve as benchmarks during the design, manufacture and post-treatment of lattice-contained structures made from these materials. ******To generate variable porosity lattice structures, the design space will be populated with diamond and octahedron unit cells using an original voxel-based algorithm. Next, these structures will be produced using the LPBF technology and subjected to static and fatigue mechanical testing at different temperatures in order to establish scaling relations between the functional properties of cellular structures and their bulk material equivalents. ******To avoid the trial-and-error approach when optimizing these structures, their superelastic and shape memory behavior will be simulated using a multi-scale numerical modeling approach. Experimental validation of the developed model will be carried out by comparing the numerical results with experimental observations using optical digital imaging and X-ray computed tomography techniques. ***Finally, two pilot components will be designed, additively-manufactured and tested: a superelastic variable-porosity cervical implant made of Ti-Zr-Nb alloy and a lightweight shape memory actuator made of Ti-Ni alloy.******The results of this research program, aimed at the combination of freeform capacity of additive manufacturing with functionality of shape memory and superelastic materials will promote successful application of new-generation multifunctional lightweight structures in medicine and aerospace. The proposed program will also contribute to the training of highly qualified personnel and attract top-level foreign students to Canada. **