Abstract
The effects of breathing behaviour on the dynamic response and crack growth are studied through a cracked cantilever beam. The main goal is to reveal the coupling mechanism of dynamic response and crack growth by employing a plain single-degree-of-freedom (SDOF) lumped system with the breathing crack stiffness and friction damping. The friction damping loss factor is derived by using Coulomb friction model and energy principle. Natural frequency, dynamic stress, dynamic stress intensity factor (DSIF), and crack growth are analyzed by case studies in the end. Results indicate that not only does the stiffness oscillates during crack growth corresponding to the physically open and closed states of the crack, but also stiffness and friction damping oscillate nonlinearly with crack growth. This behaviour induces not only nonlinear dynamic response but also nonlinear crack growth. It provides an approximate description of the nonlinearities introduced by the presence of a breathing crack. Therefore, it can be employed to improve the prediction precision of the crack identification and crack growth life of a cracked cantilever beam.
Highlights
Cantilever beam-like structures such as aircraft wings, engine blades, and rocket bodies are widely used in the aerospace engineering field
According to whether the crack is in the opening or closing state during working time, the crack model is classified into two types: open crack models or breathing crack models
That is why most of the recent studies about the dynamic response and crack growth mainly focus on the breathing cracked beams
Summary
Cantilever beam-like structures such as aircraft wings, engine blades, and rocket bodies are widely used in the aerospace engineering field. Will the crack depth increase and will the microslip of the crack surfaces that are produced when the closure effect is considered for a vibrating beam In this case, the friction force between the crack surfaces is introduced by the normal pressure forces. When a cracked beam works in a resonance condition, the friction damping will play a very important role in the dynamic response and crack propagation This scenario happens frequently in equipment and structures. The present work is to analyze the first mode frequency of the cracked beam by the mentioned two stiffness models and Galerkin method, to derive a friction damping model for a breathing crack by energy principle and Coulomb friction model, and to discuss the dynamic stress response, stress intensity factor, and crack growth with friction damping loss factor included by case studies in the end
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