Use of Bispectrum Analysis to Inspect the Non-Linear Dynamic Characteristics of Beam-Type Structures Containing a Breathing Crack

The object of this study is the dynamics of hazardous parameters of the gas environment during the ignition of materials. The problem that was solved is the early detection of fires in the premises. The research results indicate the nonlinear nature of the dynamics of hazardous parameters of the gas environment in the absence and presence of materials ignition. It was established that the bispectrum amplitude, in contrast to the amplitude spectrum of the hazardous parameters of the gas medium, contains information on the reliable detection of fires. As such information, the value of the positive dynamic amplitude range of bispectrum is used. It was established that during the ignition of alcohol, the positive dynamics of the amplitude bispectrum of all dangerous parameters of the gas medium change. Significant changes are characteristic of smoke density (from 1 dB to 30 dB) and temperature (from 1 dB to 70 dB). The dynamic range of amplitude bispectrum for CO concentration is increased from 30 dB to 70 dB. Paper ignition was found to reduce the dynamic range of the amplitude bispectrum for smoke density from 40 dB to 20 dB. At the same time, the dynamic range of amplitude bispectrum for carbon monoxide concentration and temperature increases to 60 dB. The ignition of wood causes an increase in the dynamic range of the amplitude bispectrum relative to the concentration of carbon monoxide from 40 dB to 60 dB, and the temperature – from 30 dB to 40 dB. It was established that when textiles are ignited, the range of dynamics of the amplitude bispectrum for temperature increases from 10 dB to 60 dB. The results indicate that the dynamic characteristics of the amplitudes of the bispectrum of the gas medium can be used in practice for the early detection of fires in the premises

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“…The third-order spectrum is often referred to as a bispectrum. An estimate B(f1, f2) of the bispectrum, following [52], will be defined as…”

Section: Substantiation Of the Study Of The Amplitude Spectrum Of The...mentioning

confidence: 99%

Peculiarities of amplitude spectra of the third order for the early detection of indoor fires

Поспелов¹,

Rybka

Savchenko

et al. 2022

EEJET

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“…The concept can be used to localise cracks and elucidate the mechanism needed for the generation of higher harmonics by 'breathing' cracks. Cui et al [41] used bispectrum analysis to detect 'breathing' cracks by studying the nonlinear dynamic properties of cracked beams. K. Wang et al [42] developed a twodimensional analytical model to interpret the modulation mechanism of a breathing crack to guide ultrasonic waves.…”

Section: Methods Of Closed Crack Detection In Structurementioning

confidence: 99%

“…Bispectrum analysis was used by Cui et al [41] to examine the nonlinear dynamic properties of cracked beams in order to identify 'breathing' cracks. Their approach causes the first harmonics, which appear to be hidden, to dominate higher harmonics.…”

Section: Future Researchmentioning

confidence: 99%

Nonlinear Vibration Analysis of Beam and Plate with Closed Crack: A Review

Tewelde

Krawczuk

2022

Acta Mechanica Et Automatica

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The effect of nonlinearity is high sensitivity in damage detection, especially for closed cracks and delamination. This review illustrates the results of several researchers dealing with nonlinear effects caused by the closure of cracks in the structure, i.e., beam and plate structures. Early detection of damage is an important aspect for the structure and, therefore, continuous progress is being made in developing new and effective methods that use nonlinear effects for early detection of damage and barely visible cracks, i.e., closed cracks and delamination, as well as for the determination of crack size and location. After analysing various methods, the merits, drawbacks and prospects of a number of nonlinear vibration methods for structural damage detection are discussed, and recommendations are made for future researchers.

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“…The approaches are based on the combination of the acoustic and magnetic methods and have been developed and used since the 1980s. The architecture in the meaning of construction often utilizes the Barkhausen's effect in NDT, mainly for state checking of steel ropes and rods (can be viewed as 1D geometry); planar elements (can be viewed as 2D geometry) are monitored only for the purpose of elastic-strength properties and potential spreading of cracks [56].…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Magnetic Fields in Diagnostics of Low-Speed Electrical and Mechanical Systems

et al. 2021

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The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, or generators. Identification of causalities of device failure processes with near magnetic field is one of the suitable NDT methods improving sustainability of systems. The measurements presented in the article were performed with the VEMA 04 fluxgate vector magnetometer with the DC-250 Hz bandwidth and 2 nT sensitivity. Postprocessing of the results was performed in the means of standard methods of discrete Fourier Transform, spectrogram creation and Wavelet Transform. The article presents data gathered during the measurement of a pair of extraction fans with power of 140 kW each and maximum revolutions up to 740 rev/min controlled by frequency converters and a single semi-Kaplan water power plant with 400 kW peak power at 1005 rev/min maximum generator speed. The measurements were performed before and after repairs of one of the ventilators in the ventilation system at 60% and 100% of maximal output power. The rotating magnetic fields of the fan electromotor stator, fan rotor revolutions, rotor slip frequency and ball-bearing frequencies were identified in frequency spectrums in the distance of 700 mm from fan electromotor axis in both cases. During the measurements on the semi-Kaplan turbine, the changes in states of mechanical and electrical components of the machine were monitored in the magnetic fields with increase of the power in the range of 0–95%, before and after phasing to the electrical grid. Standard processing methods, Discrete Fourier Transform, spectrograms and Discrete Wavelet Transform were used. In the spectrograms of the measured magnetic fields, the 1st–4th harmonics of the turbine shaft, generator shaft and also their side frequencies were identified. Significant changes of magnetic fields in time were identified in the area of 60–95% power. With the help of the Wavelet, transform intervals were identified where it is desirable to operate the turbine. The analyses of magnetic fields measurements performed on the power plant were compared with vibro-diagnostic principles.

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Use of Bispectrum Analysis to Inspect the Non-Linear Dynamic Characteristics of Beam-Type Structures Containing a Breathing Crack

Cited by 23 publications

References 34 publications

Peculiarities of amplitude spectra of the third order for the early detection of indoor fires

Peculiarities of amplitude spectra of the third order for the early detection of indoor fires

Nonlinear Vibration Analysis of Beam and Plate with Closed Crack: A Review

Low-Frequency Magnetic Fields in Diagnostics of Low-Speed Electrical and Mechanical Systems

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