Detection of Damage in Lightning Masts and Loosening of Bolted Connections in Structures Using Changes in Natural Frequencies

2011 ◽  
pp. 63-78 ◽  
Author(s):  
K. He ◽  
W. D. Zhu
Keyword(s):  
Natural Frequencies ◽  
Bolted Connections

Detecting Loosening of Bolted Connections in a Pipeline Using Changes in Natural Frequencies

2011 ◽  
Author(s):  
K. He ◽  
W. D. Zhu
Keyword(s):  
Damage Detection ◽  
Natural Frequencies ◽  
Detection Method ◽  
Complex Geometry ◽  
Early Stage ◽  
Measurement Noise ◽  
Modeling Error ◽  
Bolted Connections ◽  
Bolted Connection ◽  
Stiffness Reduction

Loosening of bolted connections in a structure can significantly reduce the load-bearing capacities of the structure. Detecting loosening of bolted connections at an early stage can avoid failure of the structure. Due to the complex geometry of a bolted connection and the material discontinuity between the clamped components, it is difficult to detect loosening of a bolted connection using conventional non-destructive test methods. A vibration-based method that uses changes in natural frequencies of a structure to detect the locations and extent of damage can be used to detect loosening of bolted connections, since the method focuses on detecting a stiffness reduction, which can result from loosening of the bolted connections. Experimental and numerical damage detection using the vibration-based method was conducted to detect the loosening of the bolted connections in a fullsize steel pipeline with bolted flanges. With the recent development of a predictive modeling technique for bolted connections in thin-walled structures, an accurate physics-based finite element model of the pipeline that is required by the vibration-based damage detection method is developed. A trust-region search strategy is employed to improve the damage detection method so that convergence of the damage detection algorithm can be ensured for under-determined systems, and the robustness of the algorithm can be enhanced when relatively large modeling error and measurement noise are present. The location and extent of the loosened bolted connections were successfully detected in experimental damage detection using changes in the natural frequencies of the first several modes; the exact location and extent of the loosened bolted connections can be detected in the numerical simulation where there are no modeling error and measurement noise.

Detecting Loosening of Bolted Connections in a Pipeline Using Changes in Natural Frequencies

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
K. He ◽  
W. D. Zhu
Keyword(s):  
Damage Detection ◽  
Natural Frequencies ◽  
Detection Method ◽  
Complex Geometry ◽  
Early Stage ◽  
Measurement Noise ◽  
Modeling Error ◽  
Bolted Connections ◽  
Bolted Connection ◽  
Stiffness Reduction

Loosening of bolted connections in a structure can significantly reduce its load-bearing capacity. Detecting loosening of bolted connections at an early stage can prevent failure of the structure. Due to the complex geometry of a bolted connection and material discontinuity between clamped components, it is difficult to detect loosening of a bolted connection using conventional nondestructive test methods. A vibration-based method that uses changes in natural frequencies of a structure to detect locations and extent of damage can be used to detect loosening of bolted connections since the method focuses on detecting a stiffness reduction, which can result from loosening of bolted connections. Experimental and numerical damage detection was conducted to detect loosening of bolted connections in a full-size steel pipeline with bolted flanges using the vibration-based method. With the recent development of a modeling technique for bolted connections in thin-walled structures, an accurate physics-based finite element model of the pipeline that is required by the vibration-based damage detection method is developed. A trust-region search strategy is employed to improve the damage detection method so that global convergence of the damage detection algorithm can be ensured for underdetermined systems, and robustness of the algorithm can be enhanced when relatively large modeling error and measurement noise are present. The location and extent of loosened bolted connections were successfully detected in experimental damage detection using changes in natural frequencies of the first several elastic modes of the pipeline; the exact location and extent of the loosened bolted connections can be detected in numerical simulation where there are no modeling error and measurement noise.

Numerical Method for Hetero-Cavities Natural Frequencies’ Determination

2016 ◽  
Vol 10 (3) ◽  
pp. 141
Author(s):  
Fethi Maiz ◽  
Ridha Chouikh ◽  
Amenallah Guizani
Keyword(s):  
Numerical Method ◽  
Natural Frequencies

Tire Vibrations

1977 ◽  
Vol 5 (4) ◽  
pp. 202-225 ◽  
Author(s):  
G. R. Potts ◽  
C. A. Bell ◽  
L. T. Charek ◽  
T. K. Roy
Keyword(s):  
Natural Frequencies ◽  
Standing Waves ◽  
Resonant Mode ◽  
Mode Shapes ◽  
Resonant Vibrations ◽  
Resonant Frequencies ◽  
Radial Tire ◽  
Analysis Techniques ◽  
Thin Ring ◽  
Good Agreement

Abstract Natural frequencies and vibrating motions are determined in terms of the material and geometric properties of a radial tire modeled as a thin ring on an elastic foundation. Experimental checks of resonant frequencies show good agreement. Forced vibration solutions obtained are shown to consist of a superposition of resonant vibrations, each rotating around the tire at a rate depending on the mode number and the tire rotational speed. Theoretical rolling speeds that are upper bounds at which standing waves occur are determined and checked experimentally. Digital Fourier transform, transfer function, and modal analysis techniques used to determine the resonant mode shapes of a radial tire reveal that antiresonances are the primary transmitters of vibration to the tire axle.

A STUDY ON SLIP STRENGTH OF FRICTION TYPE HIGH STRENGTH BOLTED CONNECTIONS WITH PLASTICITY OF BASE AND SPLICE PLATE

2003 ◽  
Vol 68 (573) ◽  
pp. 201-208 ◽  
Author(s):  
Toshiro SUZUKI ◽  
Kikuo IKARASHI ◽  
Toshio MAKINO ◽  
Akira GEJO
Keyword(s):  
High Strength ◽  
Bolted Connections
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