Nonlinear vibrations and heating phenomena of cracks in metal plates excited by intensive ultrasonic pulses.

Abstract

When thin metal plates are excited by intensive ultrasonic pulses, nonlinear vibration phenomena are observed in experiments. As the plates contain cracks, the frictional heating of both faces of the crack appears under the excitation of the ultrasonic pulses. Based on the experimental conditions, a finite element modeling is established and transient dynamic analyzes are performed to explore the generation mechanism of the nonlinear vibrations including superharmonics, subharmonics, and chaotics, as well as the heating phenomena of the cracks. A piezoelectric‐thermal analogy method is used to simulate the high‐power ultrasonic transducer excitation, and a contact‐impact algorithm is used to simulate the dynamical interaction between the ultrasonic horn and plate as well as between both sides of the cracks. By analyzing the vibration velocity waveforms, vibration frequency spectra, and contact force waveform, it can be found that the waveform distortion of the intermittent contact forces between the horn ...