Method for judging degree of looseness of bolt based on vibration mode information

Abstract

The invention discloses a method for judging degree of looseness of a bolt based on vibration mode information. The method comprises the following steps of firstly obtaining a freely attenuated vibration response signal by applying pulse excitation to the bolt connection structure; secondly realizing the multi-modal coupling feature separation on the vibration response signal based on a variational mode decomposition algorithm; thirdly calculating the frequency domain similarity index of each order of vibration mode component in two states; and finally judging the degree of looseness of the bolt connection structure according to the constructed index. The method is simple and practicable and is convenient for online non-destructive testing of the connection state of the bolt connection structure, is favorable for improving the judgment accuracy by judging the degree of looseness of the structure using the similarity index of the loose sensitive vibration mode component, and is beneficial to describe the change of vibration mode information caused by structural state changes and reflect the health status of the structure by constructing the detection index including frequency and amplitude information of the signal from the frequency domain, thereby having important engineering practical value.

Description

technical field [0001] The invention relates to a method for detecting the health state of a mechanical structure, in particular to a method for discriminating the degree of bolt looseness based on vibration mode information. Background technique [0002] Bolt connection is widely used because of its simple structure, easy assembly and disassembly, and reliable connection. When the bolt connection state becomes poor, the vibration increases under the external alternating load, which may cause the bolts to slip, separate or even loosen, and even lead to product failure and catastrophic accidents. Loosening, as one of the main failure modes of bolted connections, refers to the relative circumferential displacement of bolts and nuts as the use time increases, and the clamping force of bolts decreases. The failure sign is that the clamping force drops to a certain level and loses working ability. Therefore, effectively detecting the looseness of connecting structure bolts in a ...

AI Technical Summary

Problems solved by technology

[0003] At present, methods such as acoustic emission signals, guided waves, and piezoelectric impedance are commonly used to detect the bolt connection

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