Base isolation technology has been widely theoretically and experimentally investigated, and it has also been verified through many severe earthquakes. Three dimensional (3-D) isolation technology was proposed several years ago, and the 3-D isolation theory has well developed till now. However, the development of 3-D isolation technology was deeply affected by the 3-D isolator devices. Many presented 3-D isolators are generally made up of complicated components, such as rubber, springs, dampers or theirs combinations. These isolators have some problem in certain extent, such as difficult fabrication process or little energy dissipation ability along the vertical direction. This paper presents a novel 3- D isolator which is made up of martensitic shape memory alloy wires through weaving, rolling, and punching. Mechanical properties of 3-D shape memory alloy pseudo-rubber isolator (SMAPRI) are investigated including compression, shear, and compression-shear loading with different frequencies and amplitudes. The mechanical behavior of isolators with different parameters is also compared. Accordingly, the mechanism resulting in the above differences is also analyzed. Experimental results indicated that 3-D SMAPRI has good mechanical properties and energy dissipation ability along both of horizontal and vertical direction. The fabrication process of the proposed 3-D isolator is relatively easy and the mechanism of isolation is clearer than the traditional 3-D isolators. Therefore, this new kind of 3-D isolator has good potentiality in both of seismic isolation for civil infrastructures and industrial isolation for important or precision equipment.
Stainless Steel Metallic Pseudo Rubber (SSMPR) and Shape Memory Alloy Metallic Pseudo Rubber (SMAMPR) are
novel porous materials with high elasticity and large restorable deformation, and they are also ideal material for three
dimensional isolators or Shock Absorber Devices (SADs). However, the theories on the constitutive model of metallic
rubber are seldom studied due to its complicated microstructure. A theory of contact micro-beams with equal section is
presented in this study, in which the friction between the metal wires in metallic rubber is considered according to
Coulomb's friction law. Firstly, the nonlinear rigidity of the micro-beams in the loading process is derived according to
the simplified mathematical model. Then, the parameters in the theoretic model are also determined through establishing
the relationship between the macro-structure and the micro-structure based on the law of mass conservation and the
probability theory. Especially, the number of contact points between the surfaces of the micro-beams is estimated
according to a mathematical function. Finally, combined with the finite element method, the results of normalized stress-strain
relationships under compression are obtained and compared with the experimental data.
Base isolation has been widely investigated and used in civil infrastructures all over the world. However, it still has some
problems need to be solved. For example, extra buffers are needed for some types of isolators to prevent them from
generating too large deformation. These buffers increase the cost of isolators and make them more complicated. In
addition, some isolators may have residual deformation and need to be repaired or replaced after large earthquake. This
also induces large cost. In order to develop novel isolators with self buffer and with residual deformation self-recovery
ability, two types of materials, stainless steel metallic pseudo-rubber (SS-MPR) and shape memory alloy metallic
pseudo-rubber (SMA-MPR), were fabricated and investigated in this study. Mechanical behaviors of these two materials
were investigated, together with deformation self-recovery ability of SMA-MPR material. Meanwhile, three types of
SMA-MPR specimens with various processing procedures were fabricated. Mechanical behavior of the SS-MPR and
SMA-MPR specimens under cyclic sinusoidal compression loadings with various loading frequencies were test. After
that, the three types of SMA-MPR specimens with residual deformation were put into a temperature controlled stove and
their deformation recovery ability were tested. In order to address if these SMA-MPR specimens still have stable
mechanical properties after deformation recovery, they were installed in the test machine and their stress-strain behavior
under cyclic sinusoidal loads were tested again. Experimental results indicated that both SS-MPR and SMA-MPR are
good potential material to develop novel seismic isolators for civil infrastructures.
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