Webinars

Host: Mehrshad Mehrpouya (University of Twente, The Netherlands)

Speaker 1: Xiebin Wang (University of Shandong, China)

Title: Additive Manufacturing of NiTiNb Shape Memory Alloys

Adding ternary alloying elements is an efficient strategy to modulate the phase transformation behavior and functional properties, thus expanding the practical applications of NiTi-based shape memory alloys (SMAs). However, it is quite challenging to fabricate ternary SMAs via conventional metallurgical techniques, mainly due to the large difference in melting points, as well as the high chemical reactivity of the elements. Laser powder bed fusion (L-PBF), as an additive manufacturing technique, is attracting increasing interest due to its ability to fabricate geometrically complex structures. Also, L-PBF is a potential approach for in-situ alloying, since the melt-pool flow behavior is very dynamic due to the Marangoni convection and recoil pressure, which lead to intensive mixing of the melts. Together with the ability to fabricate complex structures and the feasibility to tune the phase transformation behavior, L-PBF provides great potential for producing NiTi-based shape memory alloy structures with novel functionalities.

• R. Xi, H. Jiang, S. Kustov, Z. Zhang, G. Zhao, K. Vanmeensel, J. Van Humbeeck, X. Wang. Influence of Nb addition and process parameters on the microstructure and phase transformation behavior of NiTiNb ternary shape memory alloys fabricated by laser powder bed fusion. Scripta Materialia, 2023, 222: 114996. https://doi.org/10.1016/j.scriptamat.2022.114996
• X. Wang, J. Yu, J. Liu, L. Chen, Q. Yang, H. Wei, J. Sun, Z. Wang, Z. Zhang, G. Zhao, J. Van Humbeeck. Effect of process parameters on the phase transformation behavior and tensile properties of NiTi shape memory alloys fabricated by selective laser melting. Additive Manufacturing, 2020, 36: 101545. https://doi.org/10.1016/j.addma.2020.101545

Speaker 2: Elyas Ghafoori (Leibniz University of Hannover, Germany)

Title: Memory-Steel for Smart Steel Structures

This presentation explores the development and application of iron-based shape memory alloy (Fe-SMA), the so-called memory-steel, for steel structures. First, the studies on the material properties of Fe-SMA in terms of shape memory effect and superelasticity are discussed. Next, the use of Fe-SMA in a prestressed strengthening of steel structures is explained, including the applications in strengthening steel girders, connections, and fatigue crack repairs. Various strengthening solutions such as using mechanically anchored or adhesively-bonded Fe-SMA, as well as the studies on the behavior of the Fe-SMA-to-steel bonded joints, are discussed. The use and application of Fe-SMA for strengthening a 113-years steel bridge has been explained. In addition, studies on the innovative application of the Fe-SMA as pipe couplers are presented. In the end, innovative ongoing research on the additive manufacturing of architected Fe-SMA (4D-printing) is discussed.

• Wang, S., Mohri, M., Li, L., Izadi, M., Jafarabadi, A., Pichler, N., & Ghafoori, E. (2023). Memory‐Steel for Smart Steel Structures: A Review on Recent Developments and Applications. ce/papers, 6(3-4), 949-958.

Host: Mohammad Elahinia (The University of Toledo, USA)

Speaker 1: Othmane Benafan (NASA Glenn Research Center, USA)

Title: Microstructural stability of shape memory alloys by additive manufacturing-dispersion strengthening

Shape memory alloys (SMA) are commonly strengthened by solid solution or precipitation strengthening, where the latter is only effective in certain chemistry ranges or at some applicable temperatures. (e.g., Ni-rich NiTi alloy, usage temperatures below precipitate solubility). This study is targeted towards augmenting the need for SMA strengthening via additive manufacturing-dispersion strengthening (AM-DS). This is accomplished by incorporating a fine dispersion of submicron particles such as oxides into a SMA powder followed by additive manufacturing using Laser Powder Bed Fusion (LPBF). This dispersion methods will aid in stabilizing alloys in achieving better dimensional and thermal stability, more effective training procedures, and higher strength. Details of this method, production challenges and preliminary results are presented.

• Othmane Benafan, Glen S. Bigelow, and Darrell J. Gaydosh, “Oxide, Carbide and Nitride Dispersion Strengthening of Shape Memory Alloys and Methods of Making the Same,” U.S. Patent, NASA Case No.: LEW 20059-1 (2022).

Speaker 2: Ala Qattawi (The University of Toledo, USA)

Title: Additive manufacturing of Fe-based shape memory alloys

Iron shape memory alloy (Fe-SMA) has outstanding superelasticity and consistent superplastic behavior across a wide temperature range. Alloy systems in the Fe-SMA family can provide a valuable counterpart for NiTi SMA in some applications. However, the viability and impact of manufacturing processing factors on Fe-SMA alloy are not well understood. The current study examines the impact of laser powder bed fusion (LPBF) processing parameters on Fe-Mn-Al-Ni shape memory alloy characteristics such as crack formation, surface roughness, laser-track morphology, density, dimensional accuracy, hardness, and phase transformation. To effectively capture thermal behavior and gather in-situ fabrication data, in-situ monitoring of sample printing was carried out utilizing a unique sensing system made up of a long wave infrared camera throughout a temperature range of −20 °C to 1500 °C.

• Algamal, A, Alhamdi, I, Ali, M, Almotari, A, Gandhi, U, & Qattawi, A. "Additive Manufacturing of Fe-Mn-Al-Ni Shape Memory Alloy: Microstructure and Phase Transformation Characteristics." Proceedings of the ASME 2023 Conference on Smart Materials, Adaptive Structures, and Intelligent Systems. ASME 2023, Austin, Texas, USA. September 11–13, 2023.
•  Alhamdi I, Algamal A, Almotari A, Ali M, Gandhi U, Qattawi A. Fe-Mn-Al-Ni Shape Memory Alloy Additively Manufactured via Laser Powder Bed Fusion. Crystals. 2023; 13(10):1505. https://doi.org/10.3390/cryst13101505.

Host: Wei Min Huang (NTU, Singapore)

Speaker 1: Rui Xiao (Zhejiang University, China)

Title: Modelling shape-memory effects in polymers

Shape-memory polymers have shown promising applications for biomedical devices. It is crucial to develop constitutive models with the ability to accurately predict the shape-memory performance. In the past several years, we have developed a series of models for amorphous shape-memory polymers based on the glass transition mechanism. The model can capture the dependence of mechanical properties on temperature, rate, and solvent concentration. The model can also predict shape-memory behaviours with different programming and recovery conditions. 

• Dai, L., Tian, C., Xiao, R. (2020). Modeling the thermo-mechanical behavior and constrained recovery performance of cold-programmed amorphous shape-memory polymers. International Journal of Plasticity, 127, 102654. https://doi.org/10.1016/j.ijplas.2019.102654
• Dai, L., Xiao, R. (2021). A thermodynamic-consistent model for the thermo-chemo-mechanical couplings in amorphous shape-memory polymers. International Journal of Applied Mechanics, 13(02), 2150022. https://doi.org/10.1142/S1758825121500228

Speaker 2: Ke-Ke Yang (Sichuan University, China)

Title: 4D printing of shape memory biodegradable Scaffolds

The complexity of surgical procedures for treating extensive soft tissue injuries presents challenges when implanting large devices. Scaffolds incorporating shape-memory effects (SME) offer a promising alternative to minimize the trauma associated with voluminous implantation. The emergence of 4D printing introduces a new avenue for crafting personalized or patient-specific shape-memory scaffolds. In this study, we develop an adaptable strategy, Ultraviolet irradiation-assisted fused deposition modeling printing (UV-assisted FDM), to produce diverse shape-memory scaffolds with intricate architectures. These scaffolds are constructed from biodegradable shape-memory copolymers featuring photo-cross-linkable groups. The resulting composite scaffolds hold great potential for applications in minimally invasive soft tissue repair, bone defect reconstruction, and more.

• Luo, K; Wang, L; Wang, MX; Du, R; Tang, L; Yang, KK; Wang, YZ. 4D Printing of Biocompatible Scaffolds via In Situ Photo-crosslinking from Shape Memory Copolyesters, ACS Applied Materials & Interfaces 2023, 15, 44373−44383. https://doi.org/10.1021/acsami.3c10747
• Du, R; Zhao, B; Luo, K; Wang, MX; Yuan, Q; Yu, L; Yang, KK; Wang, YZ. Shape Memory Polyester Scaffold Promotes Bone Defect Repair Through Enhanced Osteogenic Ability and Mechanical Stability. ACS Applied Materials & Interfaces 2023, 15, 36, 42930-42941. https://doi.org/10.1021/acsami.3c06902