A second-order output spectrum based method for detecting bolt-loosening fault in a satellite-like structure

2019 ◽  
Vol 26 (4) ◽  
pp. 157-165
Author(s):  
Quankun Li ◽  
Xingjian Jing
Keyword(s):  
Second Order ◽  
Bolted Joint ◽  
Output Spectrum ◽  
Engineering Structures ◽  
Local Tuning ◽  
Damage Indicator ◽  
Non Linear ◽  
Linear Behaviour ◽  
Novel Method ◽  
Bolt Loosening

Bolt-loosening faults frequently exist in industrial engineering structures since these bolted structures are often subjected to vibrations or the like in their service process. In this paper, a novel method based on the second-order output spectrum (SOOS) is proposed to detect potential bolt-loosening faults in a complex satellite-like structure. In this method, a general multi-degree-of-freedom (MDOF) model simulating bolt-loosening faults induced non-linearities and inherent boundary or material non-linearities by non-linear forces is built to describe the non-linear behaviour of the structure, and then a local damage indicator is derived for bolt-loosening fault detection through a local tuning approach (LTA) which tunes local structural properties. Results of experimental cases demonstrate that the state of bolted joint in the satellite-like structure with inherent non-linearities can be estimated by this novel SOOS based method effectively and reliably.

Fault diagnosis of bolt loosening in structures with a novel second-order output spectrum–based method

2019 ◽  
Vol 19 (1) ◽  
pp. 123-141 ◽  
Author(s):  
Quankun Li ◽  
Xingjian Jing
Keyword(s):  
Estimation Algorithm ◽  
Second Order ◽  
New Method ◽  
Spectrum Estimation ◽  
Output Spectrum ◽  
Damage Indicator ◽  
Restoring Forces ◽  
Bolt Loosening ◽  
A Chain ◽  
Detection And Localization

This article presents a novel second-order output spectrum–based method for detecting and localizing multiple bolt loosening faults in complex structures with a sensor chain. This new method is developed based on a recently developed nth-order output spectrum estimation algorithm using only proper data obtained from a chain of sensors. The properties of the second-order output spectrum transmissibility of the sensor chain along physical structures with bolts are studied systematically. In the new method, the noise effect on accuracy of the estimation of fault indicators is investigated as well. The new method also considers more general nonlinear restoring forces not only due to faults but also due to inherent nonlinearity in structure when deriving the properties of the second-order output spectrum transmissibility. Extensive simulation and experimental results demonstrate that the second-order output spectrum of the studied structure can be estimated efficiently, and the second-order output spectrum transmissibility can be used as an effective and reliable damage indicator for the detection and localization of multiple bolt loosening faults in complex bolted structures.

scholarly journals Analysis and simulations of a frequency synthesizer with internal and external noise sources

2006 ◽  
Vol 4 ◽  
pp. 175-178
Author(s):  
G. S. Sangha ◽  
M. H. W. Hoffmann
Keyword(s):  
Output Signal ◽  
Phase Plane ◽  
Frequency Synthesizer ◽  
External Noise ◽  
Second Order ◽  
Noise Sources ◽  
Novel Technique ◽  
Non Linear ◽  
Linear Behaviour

Abstract. In this paper, a novel technique to analyse the noise behaviour of a second-order-PLL based synthesizer is demonstrated. Its non-linear behaviour is analyzed with independent noise-sources introduced at different points of the circuit. Phase plane trajectories will be used to demonstrate that noise sources at different locations in the loop produce qualitatively different contributions to the output signal of the synthesizer.

First and Second Order Elastoplastic Analyses of Thin-Walled Metal Members using Generalized Beam Theory

2018 ◽  
Author(s):  
Miguel Abambres
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Cross Section ◽  
Beam Theory ◽  
Second Order ◽  
Flow Rule ◽  
Non Linear ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalized Beam Theory

Original Generalized Beam Theory (GBT) formulations for elastoplastic first and second order (postbuckling) analyses of thin-walled members are proposed, based on the J2 theory with associated flow rule, and valid for (i) arbitrary residual stress and geometric imperfection distributions, (ii) non-linear isotropic materials (e.g., carbon/stainless steel), and (iii) arbitrary deformation patterns (e.g., global, local, distortional, shear). The cross-section analysis is based on the formulation by Silva (2013), but adopts five types of nodal degrees of freedom (d.o.f.) – one of them (warping rotation) is an innovation of present work and allows the use of cubic polynomials (instead of linear functions) to approximate the warping profiles in each sub-plate. The formulations are validated by presenting various illustrative examples involving beams and columns characterized by several cross-section types (open, closed, (un) branched), materials (bi-linear or non-linear – e.g., stainless steel) and boundary conditions. The GBT results (equilibrium paths, stress/displacement distributions and collapse mechanisms) are validated by comparison with those obtained from shell finite element analyses. It is observed that the results are globally very similar with only 9% and 21% (1st and 2nd order) of the d.o.f. numbers required by the shell finite element models. Moreover, the GBT unique modal nature is highlighted by means of modal participation diagrams and amplitude functions, as well as analyses based on different deformation mode sets, providing an in-depth insight on the member behavioural mechanics in both elastic and inelastic regimes.

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