As part of the research colloquium for final theses, doctoral candidates and post-doctoral students, we cordially invite you to a lecture:

Dr.-Ing. Stefan Descher:

"Thermomechanical analysis of strain recovery in shape memory alloys under variable non-isothermal conditions"

This research work was carried out in cooperation with Dr.-Ing. Philipp Krooß and Felix Ewald M.Sc. from the Institute of Materials Engineering of the Faculty of Mechanical Engineering.

Tuesday, 28.05.2024, at 16.30 in room 3516, Mö 7

We look forward to seeing you there!

Abstract

A major reason for the application of shape memory alloys (SMAs) is to make use of the one-way effect. It allows recovering plastic strains that are mechanically brought into the material by thermal activation due to heating. The underlying process is a phase transformation from a martensitic phase (M) to an austenitic phase (A) that occurs in a certain temperature range. It resets the change of microstructure that was introduced mechanically, and therefore, e.g., allows making use of restoring strains. A popular application of SMAs are actuators, often found in aviation and automotive industry, or as smart reinforcements in novel materials of civil engineering. As found out in the preceding thermodynamic studies of the present work, latent heat effects play a key role in this activation process. The heat sink caused by the M-A phase transformation during activation causes an interface of transformation to move through the material. This highly depends on the local heating rate, that is reached during activation. To further study this behavior, in the present work, mechanical coupling is realized. Studies are carried out for a characteristic non-isothermal tension test, as it is performed to record stress-strain-temperature curves. For this purpose, the M-A phase transformation is described by a phenomenological evolution equation, which is solved together with the Cauchy-Fourier equations using the Finite Element Method.