Elastocaloric effect vs fatigue life : exploring the durability limits of Ni-Ti plates under pre-strain conditions for elatocaloric coolling

Tušek, Jaka (author), Žerovnik, Andrej (author), Čebron, Matjaž (author), Brojan, Miha (author), Žužek, Borut (author), Engelbrecht, Kurt (author), Cadelli, Andrea (author)

Structural fatigue is the major obstacle that prevents practical applications of the elastocaloric effect (eCE) in cooling or heat-pumping devices. Here, the eCE and fatigue behaviour of Ni-Ti plates are systematically investigated in order to define the fatigue strain limit and the associated eCE. Initially, the eCE was evaluated by measuring adiabatic temperature changes at different strain amplitudes and different mean strains along the loading and unloading transformation plateaus. By comparing the eCE with and without pre-strain conditions, the advantages of cycling an elastocaloric material at the mean strain around the middle of the transformation plateau were demonstrated. In the second part of this work, we evaluated the fatigue life at the mean strain of 2.25% at the loading plateau and at the unloading plateau after initial pre-straining up to 6% and 10%, respectively. It is shown that on polished samples, durable operation of 10 5 cycles can be reached with a strain amplitude of 0.50% at the loading plateau, which corresponds to adiabatic temperature changes of approximately 5 K. At the unloading plateau (after initial pre-strain of 10%), durable operation was reached at a strain amplitude of 1.00%, corresponding to adiabatic temperature changes of approximately 8%K. The functional fatigue was analysed after the cycling and it is shown that once the sample has been stabilized there is no further degradation of the eCE, even after 10 5 cycles. These results present guidelines for the design and operation of efficient and durable elastocaloric devices in the future.

• Language: English
• Keywords: elastocaloric effect, shape memory materials, Ni-Ti, fatigue, strain
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Year: 2018
• Number of pages: Str. 295-307
• Numbering: Vol. 150
• PID: 20.500.12556/RUL-127889
• UDC: 621.56(045)
• ISSN on article: 1359-6454
• DOI: 10.1016/j.actamat.2018.03.032
• COBISS.SI-ID: 15964187
• Publication date in RUL: 28.06.2021

Record is a part of a journal

• Title: Acta materialia
• Shortened title: Acta mater.
• Publisher: Elsevier Science
• ISSN: 1359-6454
• COBISS.SI-ID: 16852229

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.
• Licensing start date: 22.03.2018

Secondary language

• Language: Slovenian
• Keywords: elastokalorični učinek, zlitine z oblikovnim spominom, Ni-Ti, utrujanje, deformacije

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: Z2-7219
• Name: Od elastokaloričnega efekta do učinkovite hladilne naprave