Papers by Keyword: Dynamic Property

Abstract: The viscoelastic and creep and recovery behaviors of a carbonyl iron (CI)-water-based magnetorheological fluid (MRF) were studied under dynamic and constant loading conditions. The feature of MR fluid is to change from liquid to semi-solid state just in a few milliseconds after applying a magnetic field. ThereforeMR fluid is a kind of smart material whose rheological properties change with step-change in a magnetic field. We prepared MR fluids comprising CI 65 wt%, water 35 wt %, bentonite 3 wt %, and oleic acid 1 wt %. Because bentonite with nanosized fills the voids between the CI particles, it was used with oleic acid to enhance the MR response of the CI/water suspension. The strain amplitude tests reveal that MR fluid behaves as a viscoelastic material in the LVE range and a transition of fluid occurred from linear viscoelastic to non-linear viscoelastic behavior at the critical strain of 0.1%. Its storage moduli confirmed a steady plateau region for the entire angular frequency range, suggesting the well-known solid-like behavior of the MR suspension. The creep and recovery result signified that as the magnetic field increased, the instantaneous creep strain contributions decreased dramatically.

Abstract: Microstructure evolution and compression property of Ti-10V-2Fe-3Al titanium alloy were studied in this paper. Solution treatments were performed at temperature ranging from 710°C to 830°C and some followed by aging treatment. Ti-10V-2Fe-3Al alloys with α+β phase show higher mechanical properties compared with single β phase alloy. With the increase of solution temperature, the content of equiaxed α phase decrease. Consequently, the strength of the alloy increases while the plasticity drops down. The highest yield strength value of 1668 MPa was obtained in the sample treated by 770°C solution treated for 2 hours then water quenched and followed by 520°C aging for 8 hours then air cooled. The stress induced martensite α'' phase appeared after SHPB dynamic compression in the sample solution treated at 830°C.

Abstract: Bearings of small turbo machines support high speed rotors rotating with the frequency over 1 [kHz]. Such bearings are often supported with O-rings made of soft materials like rubber to attenuate high frequency oscillations. Dynamic properties of rubber supporters have been measured experimentally for individual dimensions, but the universal prediction of dynamic properties for various frequencies is difficult not only because rubbers exhibit nonlinearity against its strain, but because O-ring supporters deform heterogeneously. For the precise prediction, it is necessary to investigate the viscoelasticity of rubber under various deformations and frequencies. Such properties can be measured by the standard shear vibration non-response method of ISO 6721-6 (JIS K 7244-6). However this is applicable only to low frequency range under 100 [Hz] because of the limitation of resonance frequency of the load cell. In this research, based on BERM (Base Excitation Resonant Mass) method, a new method was developed to measure the complex shear modulus at high frequencies up to 1 [kHz] of rubber sheets under homogeneous shear deformations. In the presented method, the force is calculated from the acceleration of the mass instead of the direct measurement by a load cell. Hence accurate measurement became possible even in the range beyond the resonance frequency of a load cell. The measured shear storage modulus G’ and shear loss modulus G” of deformed rubber were presented.

Abstract: It is one of focus topics that metro vibration affects foundations and environments. Assumed that crumb rubber mortar can be injected into foundations to form separate vibration layerbecause crumb rubber mortar is with better ductility and properties of vibration resistance,the layer decreases the effect of transportation load on foundation. Different diameters and volumes of rubber power were joined into the mortar to form rubber mortar by experiments. Then their flow degree and strenghth were measured and compared with ordinary mortar. The result shows that the rubber with smaller diameters can improve flow properties of mortar. When the volume inserting is ten percent of total sand volume, the flow property is best. The rubber mortar with best flow property was conserved for twenty-eight days. The damp property and impact resistant were determined under metro dynamic load. The experiment found that when the volume inserting is twenty percent of total volume, the damp value was improved twenty percent with twenty-five percent of absorbing energy and better separate vibration property. Therefore, the separate vibration layer can largely reduce the effect of vibration from metro and decrease the settlement of foundations of metro.

Abstract: The paper presents an assessment methodology for comparable evaluation of a Spar and a Barge support with multi-megawatt OWT. Stability and hydrodynamic performance of both two floaters are checked by SESAM software. Taking consideration of rotational excitation frequencies of the OWT and primary wave excitations, reasonable engineering attributes of the structures are derived. The attributes are applied in multi-criteria decision making method-TOPSIS combining with environmental and economic attributes for benchmarking relatively better solution. The outcome of the study would contribute towards a more informed decision making process for the most suitable configuration of a new floating support structure for large wind turbine at deeper water.