Investigation on the characteristics of zero-frequency components in nonlinear ultrasonic waves

This study presents a systematic re-examination of zero-frequency component (ZFC) characteristics in nonlinear ultrasonic waves, with particular emphasis on rectangular pulse excitation scenarios. By combining theoretical analysis with finite-element simulations, we reveal that material nonlinearities substantially affect the waveform morphology of ZFC. Our results demonstrate that materials exhibiting bilinear stiffness nonlinearity (BSN) produce a distinct right-triangular ZFC profile, while those with weak quadratic nonlinearity (WQN) generate a flat-topped ZFC configuration. These findings not only provide critical insights for resolving long-standing controversies regarding ZFC waveform characteristics, but also establish ZFC analysis as a robust diagnostic methodology for identifying specific nonlinear constitutive behaviors in materials. The research advances the fundamental understanding of nonlinear wave propagation mechanisms and paves the way for novel applications in quantitative material characterization and precision damage assessment. This work provides critical insights for refining nonlinear ultrasonic measurement interpretation and introduces a promising paradigm for non-destructive evaluation techniques.