Characterization of bullet fragment impact-generated stress waves on skin at varied angles
The helicopter skin is vulnerable to penetrated by fragmentation of explosive bombs during low-altitude operations,leading to different degrees of damage that impact flight safety and mission decision-making.In order to effectively support the impact monitoring of the skin,a stress wave characterization study is carried out for different damage levels caused by different angles of impact.This paper establishes a finite element model of skin impacted by bullet fragments and verify it through both simulation analysis and bullet fragment impact experiments.The goal is to obtain the stress wave signal generated by the bullet fragment impact.The study uses time-frequency analysis to analyze the main components of the impact stress wave signal,and determines the modal type and frequency range of the signal.This involves extracting the energy of the signal and the peak features of various wave packets and establishing the link between the stress wave signal characteristics and the angle of impact.The study reveals that stress wave signals created by impacts from different angles display unique patterns of three wave packet peaks.Furthermore,the signal energy significantly varies in different directions,gradually converging as the impact angle increases.These findings offer a reference point for monitoring bullet impacts on helicopters.
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