Mechanical properties and theoretical modeling of self-centering shape memory alloy pseudo-rubber

Abstract

Pounding between adjacent components and structures has become an important cause of structural damage or even collapse under large excitations such as earthquakes and ship collisions. Shock absorber devices (SAD) are often used to connect the separation gap to reduce the pounding force. However, some shock absorber devices may have residual deformation and need to be repaired or replaced after strong impact. A novel energy absorbing material with residual deformation self-recovery ability, martensitic nickel titanium (NiTi) shape memory alloy pseudo-rubber (SMAPR), is fabricated using three methods in this study. The mechanical properties of SMAPR at room temperature and deformation self-recovery ability of SMAPR material are investigated. After that, the deformation recovery ability of SMAPR specimens even with residual deformation is further tested through heating the specimens in a thermo-control stove. The subsequent mechanical properties after deformation recovery are further investigated to investigate whether degradation in mechanical properties occurs for all kinds of specimens. The experimental results indicate that SMAPR is a kind of material with good potential to develop novel shock absorber devices for engineering applications. Furthermore, theoretical modeling of SMAPR is conducted. Micro-variable-pitch springs in parallel and series, in parallel with a friction component, are employed to model the mechanical behavior of SMAPR. The hysteretic rules are presented and the parameters of this model are derived and identified. Finally, based on micro-variable-pitch springs (MVPS) in parallel and series, a parametric analysis is carried out and the effects of nominal densities, diameters of metal wires, diameters of micro-springs and generalized coefficients of friction of SMAPR are analyzed and discussed.

The mechanics of shape memory alloy metal rubber

“…Experimental results show that q lim % 0:15 [8][9][10][11]20], which sets a specific limit to the application of the constitutive model presented in this work. Below this limit value of the relative density the SMA-MR material has a very large porosity and does not exhibit a structural integrity under even moderate loading.…”

“…The actual load on the single coil can be decomposed along the two orthogonal directions (axial and tangential). [20], (b) friction pyramid cell [21], (c) helix cell [22][23][24].…”

“…The lead angle a in MR materials is usually quite small [8][9][10]20], therefore Eqs. (11) and (12) can be simplified as:…”

“…SMA-MR exhibits not only the characteristics typical of classical nickel-based metal rubber (nonlinear stiffness, large damping and transverse mechanical isotropy [8,16]) but also a temperature dependency and heat treatment effects due to the nitinol wires composing the microstructure [10,[18][19][20]. Quasi-static compression tests have shown the strong dependence of the SMA-MR mechanical properties upon its specific manufacturing parameters [17][18][19].…”

An analysis of pounding mitigation and stress waves in highway bridges with shape memory alloy pseudo-rubber shock-absorbing devices

“…The SMAPR exhibit the advantageous of strain hardening, large damping capacity, and corrosion resistance, which are suitable for the manufacture of the shock‐absorbing devices (SADs). Furthermore, SMAPR has excellent self‐recovery and repeatable capacity similar as the SMA material. In this study, the SMAPR were made from martensite NiTi (50 at% Ni) SMA wires with a diameter of 0.2 mm, as shown in Figure .…”