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

拟议的研究计划将材料的科学、技术和力学领域联系起来，目标是制造用于航空航天和医疗应用的多功能形状记忆和超弹性部件。为此，将使用两种类型的形状记忆合金(SMA)：钛镍合金(Ti-Ni)和近贝塔钛合金(Ti-Nb-Zr)。它们将使用激光粉床融合(LPBF)技术进行加工，以制造用于医疗和航空航天应用的工程网格结构。在医学上，具有高度生物相容性的单片可控孔梯度的Ti-Nb-Zr超弹性种植体可以降低与种植体整合问题相关的并发症风险。在航空航天领域，轻质的钛镍形状记忆结构可用于传感和驱动。*该计划从从每一种选定的合金中生产完全致密的成分开始。为此，将采用熔池模拟和实验设计相结合的方法来优化LPBF的工艺参数。用完全致密的印刷合金可以达到的最佳功能性能，将作为由这些材料制成的晶格结构的设计、制造和后处理的基准。*为了生成可变孔隙率的网格结构，设计空间将使用基于体素的原始算法填充钻石和八面体单元。接下来，这些结构将使用LPBF技术制造，并在不同温度下进行静态和疲劳力学测试，以建立蜂窝结构的功能特性与其块体材料当量之间的比例关系。*为了避免在优化这些结构时的试错方法，将使用多尺度数值模拟方法来模拟它们的超弹性和形状记忆行为。通过使用光学数字成像和X射线计算机层析成像技术将数值结果与实验观测结果进行比较，对所开发的模型进行实验验证。*最后，将设计、追加制造和测试两个中试部件：由Ti-Zr-Nb合金制成的超弹性变孔隙率颈椎植入物和由Ti-Ni合金制成的轻质形状记忆执行器。*本研究计划的成果旨在将加法制造的自由形式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量化结构在医学和航空航天领域的成功应用。拟议的项目还将有助于培养高素质的人才，并吸引顶尖外国学生来加拿大学习。**

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. **