Çavdar, Özlem; Yıldız, Zeynep; Naghshineh, Ali Karimzadeh

High damping rubber isolators (HDRBs), which are popular in base isolation systems, extend the natural vibration periods of structures and increase the energy dissipation capacity of the systems. Thus, they can protect structures from damage that may occur in earthquakes. The difference between HDRBs and other elastomer bearings is the chemical formulation of the rubber used. The aim of this study is to prepare a new rubber mixture that is resistant to seismic loads and has good damping properties for HDRBs. In this direction, rubber mixtures were prepared with three different formulations. The mixture of ingredients used in this study is Natural Rubber (NR), Nitrile Butadiene Rubber (NBR), Carbon Black (CB), process oil, Zinc Oxide (ZnO), Stearic Acid (StA), coumaron resin, protective agent, sulfur and accelerators. Quadruple shear block specimens were produced with elastomers produced with mixtures. Dynamic tests were performed on these samples. Elastomer earthquake isolation bearings with a damping ratio of 6% or greater are classified as ‘highly damped’. In this study, values greater than 10% were obtained for damping ratio values at 100% shear stresses. Experimental and numerical analyses revealed that the damping values of the compounds developed with NBR-based formulations are at an acceptable level for highly damped isolators. In general, it was observed that the damping properties increased from 6% to 12%. Therefore, it is thought that the developed HDRB compounds can be used as elastomers in the construction of seismic isolators with high damping properties.

Mazlum, Ugur; Celik, Ilhan

Magneto-rheological (MR) materials can respond reversibly and quickly under the effect of an external magnetic field. MR materials contain micron-sized iron particles. These iron particles are typically dispersed in an elastomer or a liquid. These materials due to their properties constitute a kind of smart material in terms of engineering material. Such materials are used as isolators in various engineering applications, structures, and sound control subsystems. This study aimed to determine the mechanical properties for shear behavior of MR materials for under harmonic loading. Parameters such as matrix materials with different hardness values, powder types, magnetic field, frequency, and deformation were studied. The parameters related to the MR material itself were analyzed with the obtained data. The present study reveals that considering the sensitivity to magnetic field parameter, composite materials having the most suitable properties were produced with Shore 2 hardness value and SQ magnetic powder. It had been observed on increase about 200% at the rate of Shore A10 and A2 as a result of comparing the hardness scale. Also according to the powder rate while there was an increase on worth effect of relative MR, it is seen that the biggest increase had been in SQ powder with 199% worth. When looked some studies in literature, about comparing different hardness values such as matrix materials powder types etc. there aren’t any studies. The state of magnetic field thinks that features such as MR effect, Storage, and Loss modulus haven’t been examined yet.