Effects of cyclic and seismic loading on the superelastic behaviour of shape memory alloys
Shape memory alloys(SMAs)are metallic smart materials.Phase changes of the atomic grid structure allows them hysteretic energy dissipation without irreversible deformation.This superelastic behaviour makes SMA an attractive alternative to conventional anti-seismic devices.For this purpose,numerical material models are necessary,which can predict the dynamic behaviour of SMA accurately.Existing constitutive models of SMA revealed significant discrepancies regarding the seismic response.For the development of a precise constitutive model,authors propose a separated investigation of the effects of strain amplitude and excitation frequency.For this purpose,the authors conducted uniaxial tensile tests on nickel titanium(NiTi)wires.This study involved quasi-static,harmonic and seismic excitations.Both trained and untrained NiTi wires were investigated with 0.127 and 0.200 mm diameters and 150 mm length at an excitation frequency range of 0-4 Hz and a strain amplitude range of 0-6%.This paper presents some of the experimental data,which revealed the strain amplitude and excitation frequency effects.The results show that at a constant excitation frequency an increase in the strain amplitude yields,besides the expected increase of stress-strain level,a further significant change in the critical transformation stresses.Consequently,the hysteresis area circled by the stress-strain curves increases with the increasing strain rate.On the other hand,at a constant strain amplitude an increase in the excitation frequency initiates a decrease of the hysteresis area with the increasing strain rate.This non-conformity between strain rate and hysteresis area reveals the necessity of a separated consideration of the strain rate as strain amplitude and excitation frequency.Accordingly,for a precise constitutive model,authors propose in this paper also a numerical improvement,which considers the strain amplitude effects during a dynamic excitation.A comparison with the experimental data shows that the improved model calculates the superelastic hysteresis more realistically.
Shape memory alloys superelasticity constitutive material model seismic behaviour experimental investigations
A.Kaup O.Altay J.Wang S.Klinkel
Department of Civil Engineering,RWTH Aachen University,Aachen,Germany State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing,China
国际会议
The 7th World Conference on Structural Control and Monitoring(7WCSCM)(第七届结构控制与监测世界大会)
青岛
英文
1064-1074
2018-07-22（万方平台首次上网日期，不代表论文的发表时间）