Investigation of Dual-Frequency Excitation and the Influence of Excitation Phase on a Constrained Cantilevered Beam System

Many types of nonlinear phenomena have been studied in atomic force microscopy (AFM). As a tool for performing topographical measurements and material characterizations at the micro- and nano-scales, improving the understanding of the dynamic AFM system will impact many areas of research. The authors’ previous studies have shown that in dynamic AFM, with dual-frequency excitation, influence of attractive and repulsive interaction forces can be revealed by the presence of specific frequency components in the response. Motivated by the phenomenon predicted in the AFM system, a macro-scale test platform is used in this effort in order to qualitatively investigate the relationships between the dual-frequency excitation, interaction conditions, and the specific frequency components observed in the response. The experimental setup includes a base driven cantilever with a tip, a soft material as the sample and an electromagnet behind the sample to provide attractive interaction forces. The components in the experimental setup are characterized and the system is studied by using numerical and experimental methods. A thorough numerical and experimental study of the influence of the phase difference between the two frequency components in the excitation signal is investigated in this work.