Experimental study on electro-magneto-mechanical coupling behavior of smart materials

New experiment systems, which are controlled by an industrial PC (computer) and can offer electromechanical or electromagnetic coupling loads, were designed and established. Automatization skills and technologies of measurement have been developed and the software was produced to monitor the testing process and to deal with the acquired data. The experimental difficulties and technical problems, such as insulation, discharge, electric breakdown and so on, have been well resolved. The constitutive experiments on piezo/ferroelectrics under coupling loads were first carried out. To eliminate the internal bias field, an impacting poling approach was developed. The effects of poling direction on the toughness of PZT-5 were investigated by means of three-point bending tests. Moir6 interferometry was applied to measure the domain transformation at crack tip in ferroelectric ceramics under coupling loads. The tests of electric fatigue on ferroelectric specimens with through pre-cracks were firstly conducted. The integrated curves of fatigue crack growth were obtained. Experimental phenomena, such as two types of crack growth mechanisms, fatigue crack closure, electric breakdown and so on, have been discovered and studied. To improve the fracture of the brittle ferroelectric ceramics, the PZT/MgO nano-composites were prepared. The experimental investigation on 0-3 and 1-3 piezocomposites was also carried out and novel experimental data were obtained. Several ferromagnetic materials were used to investigate magneto-mechanical coupling behavior, such as electrolytic nickel, Ni6, Manganese-Zinc ferrite ceramics, Terfenol-D, NiMnGa. The characteristic curves of ferromagnetic materials have been measured, including the hysteresis loops, the magnetostriction curve and stress-strain curve. To analyze the effects of magnetic field on toughness, three-point bending tests and Vicker's indentation tests were performed too.