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

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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. **