Papers by Keyword: Dynamic Mechanical Analyzer

Abstract: Earthquakes, wind buffeting, ocean waves， noise vibration and explosion are all harmful to people’s life. For controlling the vibrations, one way is by improving the material damping capacity. Effects of improving the damping properties of cement based material by adding polymer, fiber and interfacial modification have been admitted. Whereas the relationship of the influence of the dosage of polymer to the damping functions and the changes of damping behaviors at different frequency, temperature environment have received much less attention. Furthermore, ethylene-vinyl acetate (EVA) which used as one of the mainly modified has been widely applied in various aspects such as improving ductility, impermeability and mechanical properties. However, the ability of EVA modification in cement on improving the damping capacity has received less attention. The main objective of this paper is to research the damping behavior of EVA modified cement pastes at different frequencies, temperatures and polymer contents by dynamic mechanical analyzer. Experimental results showed that damping property of EVA modification in cement was dramatically increased. For a certain EVA modified cement paste, tanδ slightly increases with the frequency increases and a sharp peak was found at the glass transition temperature. The SEM images indicated that there was a morphological difference in the plain cement paste and EVA modified cement paste.

Abstract: Earthquakes, wind buffeting, ocean waves， noise vibration and explosion are all harmful to people’s life. For controlling the vibrations one way is by improving the material damping capacity. Effects of improving the damping properties of cement based material by adding polymer, fiber and interfacial modification have been admitted. Whereas the relationship of the influence of the dosage of polymer to the damping functions and the changes of damping behaviors at different frequency, temperature environment have received much less attention. The main objective of this paper is to research the damping behavior of SBR modified cement pastes at different frequencies, temperatures and polymer contents by dynamic mechanical analysis Experimental results showed that the damping behaviors of low P/C ratio cement paste is close to a typical elastic cementitious material and higher P/C ratio resulted in higher damping behaviors. For a certain SBR modified cement paste, Tanδ slightly decreases with the frequency increases and a sharp peak was found at the glass transition temperature. The SEM images indicated that there was a morphological difference in the plain cement paste and SBR modified cement paste.

Abstract: Crystal structures and shape memory properties of Ti-rich Ti52Ni23Cu25 (at.%) ribbon annealed at 450°C for 10 min and 1 h were investigated by X-ray diffraction and dynamic mechanical analyzer. As-spun ribbon was full amorphous and its crystalline peak temperature is 455.4°C. The annealed ribbon is crystallized with strong preferential (110)-B2 orientation. It shows a well-defined shape memory effect and the transformation hysteresis for the annealed ribbon under an external load in the range of 3-9 N is about 38.5°C. With annealing time increasing from 10 min to 1 h, the maximum of transformation strain under the external stress decreases from 1.93% to 1.7%. The temperature dependence of the external stress increases from 0.3 N/°C to 0.43 N/°C. The residual plastic strain is up to about 0.4% at a load of 9 N.

Abstract: Damping capacity and storage modulus of cold-rolled and annealed Ti50Ni50 SMA are systematically investigated by DSC and DMA tests. The specimens annealed at 500 oC for 1 ~ 72 h and annealed at 650 oC for short time can all reach a high tan δ value and a deep storage modulus minimum during B2→R transformation. This reveals that the occurrence of R-phase can strongly soften the storage modulus and thus promote the damping capacity of Ti50Ni50 SMA. The specimens anneaed at 650 oC for longer time have a lower tan δ value due to the diminishing of R-phase formation. Therefore, a good damping capacity associated with a significant softening storage modulus can be acquired by suitably control the annealing conditions of cold-rolled Ti50Ni50 to generate adequate of R-phase premartensite.