Dynamics modeling and experimental modal analysis of bolt loosening for lightning rod

Chen, Guoda; Chen, Yang; Chen, Yijie; Ji, Shiming

doi:10.21595/jve.2019.20918

Cited by 6 publications

(3 citation statements)

References 30 publications

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“…In [72], the authors demonstrated that the first-order phase difference parameter is susceptible to the looseness of the bolts on the plate joint of the wind turbine tower. In [73], a finite element simulation is used to analyze rod flange-bolt structure unit (FBSU). Authors in [74] developed a simple method to assist bolt tightness by measuring natural frequency and damping ratio during the hammer test.…”

Section: Diagnostics Of Bolted Joints Loosening In Structuresmentioning

confidence: 99%

Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

Krot,

Shiri,

Dąbek

et al. 2023

Materials

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The condition-based maintenance of vibrating screens requires new methods of their elements’ diagnostics due to severe disturbances in measured signals from vibrators and falling pieces of material. The bolted joints of the sieving deck, when failed, require a lot of time and workforce for repair. In this research, the authors proposed the model-based diagnostic method based on modal analysis of the 2-DOF system, which accounts for the interaction of the screen body and the upper deck under conditions of bolted joint degradation. It is shown that the second natural mode with an out-of-phase motion of the upper deck against the main screen housing may coincide with the excitation frequency or its higher harmonics, which appear when vibrators’ bearings are in bad condition. This interaction speeds up bolt loosening and joint opening by the dynamical loading of higher amplitude. The proposed approach can be used to detune the system from resonance and anti-resonance to reduce maintenance costs and energy consumption. To prevent abrupt failures, such parameters as second natural mode frequency, damping factor, and phase space plot (PSP) distortion measures are proposed as bolt health indicators, and these are verified on the laboratory vibrating screen. Also, the robustness is tested by the impulsive non-Gaussian noise addition to the measurement data. A special diagram was proposed for the bolted joints’ strength capacity assessment and maintenance actions planning (tightening, replacement), depending on clearance in the joints.

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Section: Diagnostics Of Bolted Joints Loosening In Structuresmentioning

confidence: 99%

Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

Krot,

Shiri,

Dąbek

et al. 2023

Materials

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“…A combination of FEA with vibration and impedance responses measurement of wind turbine tower for bolts loosening detection is given in [77]. FEM simulation is used in [78] for a lightning rod flange-bolt structure unit (FBSU) analysis. The authors in [79], considering a bolt as an axially stressed and clamped at both ends beam, proposed a simple method to determine the bolt tightness by natural frequencies and damping ratios in hammer impact tests, in particular, the first transverse natural frequency [80].…”

Section: Diagnostics Of Bearing Supports and Bolts Looseningmentioning

confidence: 99%

Vibration-Based Diagnostics of Radial Clearances and Bolts Loosening in the Bearing Supports of the Heavy-Duty Gearboxes

Krot

Korennoi

Zimroz

2020

Sensors

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The problem solved in this research is the diagnosis of the radial clearances in bearing supports and the loosening of fastening bolts due to their plastic elongation (creep) or weak tightening using vibration signals. This is an important issue for the maintenance of the heavy-duty gearboxes of powerful mining machines and rolling mills working in non-stationary regimes. Based on a comprehensive overview of bolted joint diagnostic methods, a solution to this problem based on a developed nonlinear dynamical model of bearing supports is proposed. Diagnostic rules are developed by comparing the changes of natural frequency and its harmonics, the amplitudes and phases of shaft transient oscillations. Then, the vibration signals are measured on real gearboxes while the torque is increasing in the transmission during several series of industrial trials under changing bearings and bolts conditions. In parallel, dynamical torque is measured and its interrelation with vibration is determined. It is concluded that the radial clearances are the most influencing factors among the failure parameters in heavy-duty gearboxes of industrial machines working under impulsive and step-like loading. The developed diagnostics algorithm allows condition monitoring of bearings and fastening bolts, allowing one to undertake timely maintenance actions to prevent failures.

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“…Common lightning rod structures are composed of interconnected circular steel rods with varying diameters, forming slender and elongated structures with high flexibility. Wind loads can easily induce frequent and intense vibrations in such flexible structures, leading to component brittleness, cracks, and potential fractures at the joints of lightning rod segments [1][2][3]. Under the action of wind loads, circular steel rod structures not only experience vibrations in the windward direction but also exhibit regular vortex shedding in low wind speeds, resulting in transverse wind-induced vibrations.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of the Flow Field around a Cylindrical Lightning Rod

Guo,

Liu,

Wang

et al. 2024

SDHM

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As an important lightning protection device in substations, lightning rods are susceptible to vibration and potential structural damage under wind loads. In order to understand their vibration mechanism, it is necessary to conduct flow analysis. In this study, numerical simulations of the flow field around a 330 kV cylindrical lightning rod with different diameters were performed using the SST k-ω model. The flow patterns in different segments of the lightning rod at the same reference wind speed (wind speed at a height of 10 m) and the flow patterns in the same segment at different reference wind speeds were investigated. The variations of lift coefficient, drag coefficient, and vorticity distribution were obtained. The results showed that vortex shedding phenomena occurred in all segments of the lightning rod, and the strength of vortex shedding increased with decreasing diameter. The vorticity magnitude and the root mean square magnitudes of the lift coefficient and drag coefficient also increased accordingly. The time history curves of the lift coefficient and drag coefficient on the surface of the lightning rod exhibited sinusoidal patterns with a single dominant frequency. For the same segment, as the wind speed increased in a certain range, the root mean square values of the lift coefficient and drag coefficient decreased, while their dominant frequencies increased. Moreover, there was a proportional relationship between the dominant frequencies of the lift coefficient and drag coefficient. The findings of this study can provide valuable insights for the refined design of lightning rods with similar structures.

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Dynamics modeling and experimental modal analysis of bolt loosening for lightning rod

Cited by 6 publications

References 30 publications

Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

Vibration-Based Diagnostics of Radial Clearances and Bolts Loosening in the Bearing Supports of the Heavy-Duty Gearboxes

Numerical Simulations of the Flow Field around a Cylindrical Lightning Rod

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