Dynamic Mechanical Properties Of Porous Metal Materials Filled With Magnetorheological Fluid

Porous metal materials have unique energy absorption characteristics and extensiveengineering applications. Under the low-speed impact with small kinetic energy, porousmetal material shows excellent cushion effect with long compression stroke. However,when under the high-speed impact with large energy, its impact and energy absorptioncharacteristics are not ideal enough. Therefore, it is necessary and significant to furtherimprove the energy absorption characteristics of the porous metal material, and to achievethe controllability and intelligence of energy-absorbing structure and material.In this thesis, by the means of experimental investigation combined with theoreticalanalysis, the energy dissipation, mechanical behaviors and energy absorption characteristicsof copper foam filled with magneto-rheological fluid （MRF） under the impact loadingwere studied. The main contents are as follows:1. By means of vacuum equipment, the specimens for copper porous materials filledwith magnero-rheological fluid were manufactured. Then, a series of quasi-staticcompression tests were conducted on the MTS testing machine. The results showed thatafter filling the magneto-rheological fluid, with the increase of the applied magnetic fieldintensity, the energy absorbed by filled composites will increase. However, when theintensity of the magneto-field is higher than0.2T, the effect of magneto-field becomes veryweak.2. Based on the low-impedance property of porous copper foam, using the splitHopkinson pressure bar (SHPB) experiments with two different materials of nylon andaluminum respectively, the dynamic compression characteristics of copper foam werestudied. The results showed that, compared to nylon bar testing method, the aluminum rodfour-wave method was also able to obtain a complete and effective dynamic compressionstress-strain curve of copper foam. Besides, the porous copper foam material is foundinsensitive to strain rate.3. A series of dynamic compression experiments of porous copper foam filled withMRF were conducted on the SHPB of nylon material rod. The results showed that the strainrate and pore size had a significant effect on dynamic energy absorption characteristic ofthe fluid-filled porous copper foam. Only within a certain impact loading range of strainrates, the dynamic energy absorption capacity of fluid-filled composites will be enhancedwith the increase of the applied magnetic field strength. 4. By considering the magneto-rheological fluid flowing within the pores of the porousmaterial, combined with static and dynamic experimental data, a contribution equationcontaining the strain rate and the magnetic field strength was derived. It is found that thisequation can describe the contribution of the magneto-rheological fluid on the porous metalmaterial strength at different dynamic loading speeds and magnetic field strength.