Stress recovery behaviour of an Fe–Mn–Si–Cr–Ni–VC shape memory alloy used for prestressing

Abstract

This paper describes the stress recovery behaviour of an Fe-17Mn-5Si-10Cr-4Ni-1(V, C) (mass%) shape memory alloy used for prestressing of civil structures. The prestressing due to the shape memory effect was simulated by a series of tests with pre-straining of the material followed by heating and cooling back at constant strain. Different pre-strain and heating conditions were examined. Moreover, the response due to additional mechanical and thermal cyclic loading has been investigated. These results were used to predict the partial prestress loss in a structure due to variable loading during operation. Finally, a heating test at constant strain was performed after the cyclic loading to check the possibility of reactivating the prestress lost during an exceptionally high load.

Recovery stress formation in a restrained Fe–Mn–Si-based shape memory alloy used for prestressing or mechanical joining

“…Then the sample was heated to 160°C and cooled back to ambient temperature, keeping the strain constant. The pre-strain of 4% and the heating temperature of 160°C are the same values as the ones used in a previous study [9]. As discussed there, a higher pre-strain does not significantly increase the recovery stress and a higher temperature is undesirable in many applications.…”

“…In a previous study [9], the level of prestress which can be provided by the Fe-SMA has been investigated. In these tests, the strain was kept constant during heating and cooling, so that the shape recovery was completely converted into stress.…”

“…However, applications for large civil structures or structural elements have been limited by the high costs of raw materials and the processing, which usually requires high vacuum conditions. As an alternative, Fe-based SMAs (Fe-SMAs) such as Fe-Mn-Si-based alloys seem to be more favorable for this kind of application due to their lower costs [5][6][7][8][9]. In particular the alloy Fe-17Mn-6Si-10Cr-4Ni-1VC which has been developed previously by some of the present authors shows very http://dx.doi.org/10.1016/j.conbuildmat.2015.07.098 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.…”

“…promising properties with regard to potential commercial applications: high recovery stresses of up to 500 MPa after heating to only 130°C and without 'training', and production under standard air melting and casting condition [6][7][8][9]. In a previous investigation [9], the possible level of recovery stress and the influence of cyclic loading on the recovery stress were investigated.…”

“…In a previous investigation [9], the possible level of recovery stress and the influence of cyclic loading on the recovery stress were investigated. That study demonstrated that this Fe-SMA with 1% VC precipitates is very advantageous for applications where the formation of recovery stresses in restrained SMA elements is exploited.…”