Shell-based finite element model for predicting buckling stability of superelastic structures for elastocaloric cooling

Porenta, Luka (author), Brank, Boštjan (author), Tušek, Jaka (author), Brojan, Miha (author)

Elastocaloric cooling devices loaded in compression have shown significant potential for fatigue-resistant operation, but for efficient operation they require thin-walled elements to facilitate heat transfer. This can cause elastocaloric elements made of superelastic materials, such as shape memory alloys (SMA), to collapse due to buckling. A common approach for computationally predicting the buckling response of these materials, which exhibit phase transformations during operation, is either to use 3D solid finite elements that can be easily coupled with 3D constitutive equations (which is accurate but extremely time consuming), or to use shell or beam finite elements coupled with simplified constitutive models (which is usually faster but has limited accuracy). In this work, we present a novel numerical approach that combines a highly accurate 7-parameter shell formulation and full 3D constitutive equations that account for the phase transformation between austenite and martensite as well as the compression–tension asymmetry in shape memory alloys (SMA) to study buckling stability. A combination of a perturbation of the structural mesh in the radial direction and a perturbation force was used to model imperfections that triggered the instability processes in the numerical simulations. The numerical responses are compared with experimental observations and show good agreement in terms of stress–strain behavior and buckling modes. Phase diagrams of the buckling modes are numerically determined for tubes with an outer diameter between 2 and 3 mm and a diameter-to-thickness ratio in the range between 5 and 25, which appear to be promising candidates for use in elastocaloric technology. We have thus demonstrated the potential of the proposed computational model as a fast and reliable tool to simulate the buckling and post-buckling behavior of SMA elements not only for elastocaloric technology but also for other applications where superelastic SMA elements are used.

• Language: English
• Keywords: buckling stability, shell finite elements, shape memory alloys, elastocaloric effects, phase diagrams
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering; FGG - Faculty of Civil and Geodetic Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 15 str.
• Numbering: Vol. 208, art. 112825
• PID: 20.500.12556/RUL-166277
• UDC: 620.1/.2
• ISSN on article: 1879-3223
• DOI: 10.1016/j.tws.2024.112825
• COBISS.SI-ID: 220697347
• Publication date in RUL: 30.12.2024

Record is a part of a journal

• Title: Thin-walled structures
• Publisher: Elsevier
• ISSN: 1879-3223
• COBISS.SI-ID: 23273989

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Projects

• Funder: EC - European Commission
• Funding programme: H2020
• Project number: 803669
• Name: Superelastic Porous Structures for Efficient Elastocaloric Cooling
• Acronym: SUPERCOOL