Parametric Simulation Study of High-Energy Ultrasonic Nondestructive Assessment for Filler Dispersion in Nano-Modified

The insulation performance of the modified nanomaterials is critical to the safety and stability of the next-generation low-carbon power transmission system, while the dispersion of nanofillers in the dielectrics directly affects the electrical/mechanical/thermal properties. The existing methods for particle dispersion detection in solid polymeric materials are mainly microscopic imaging methods, however, they have a shortage of narrow detection areas and cannot evaluate the material dispersion as a whole. In this paper, we use high-power ultrasonic methods to measure the nonlinearity of different dispersive nanomaterials. To achieve accurate measurement and evaluation, quantitative optimization of excitation signal parameters is the key to high-power ultrasonic detection. Firstly, the nonlinear acoustic fluctuation equations of solid nanocomposite are derived based on the nonlinear acoustic theory. After that, a filler mass fraction of 1% with different agglomeration degrees was modeled and simulated to optimize the excitation ultrasonic parameters. The simulation results show that in the system of epoxy resin-silica particles (mass fraction 1%), the nanomaterial nonlinear coefficient increases by a maximum of 2% with the increase of particle agglomeration, and the dispersion decreases significantly; The optimal frequency range of the excitation signal is 0.1 MHz-5 MHz, and the optimal vibration amplitude is 70 nm. In this paper, the simulation studies accomplish parametric validation of the nonlinear model, preliminarily select the optimal frequency range for signal excitation, determine the optimal amplitude size of the excitation signal, and provide theoretical guidance for the optimal design of the high-energy ultrasonic measurement device.