Crack detection using nonlinear output frequency response functions

2007 ◽  
Vol 301 (3-5) ◽  
pp. 777-788 ◽  
Author(s):  
Z.K. Peng ◽  
Z.Q. Lang ◽  
S.A. Billings
Keyword(s):  
Frequency Response ◽  
Crack Detection ◽  
Response Functions ◽  
Output Frequency ◽  
Frequency Response Functions

scholarly journals Dynamics Analysis of Active Variable Stiffness Vibration Isolator for Whole-Spacecraft Systems Based on Nonlinear Output Frequency Response Functions

2020 ◽  
Vol 33 (6) ◽  
pp. 731-743
Author(s):  
Kefan Xu ◽  
Yewei Zhang ◽  
Yunpeng Zhu ◽  
Jian Zang ◽  
Liqun Chen
Keyword(s):  
Frequency Response ◽  
Energy Absorption ◽  
Absorption Rate ◽  
Vibration Isolation ◽  
Variable Stiffness ◽  
Response Functions ◽  
Vibration Isolator ◽  
Output Frequency ◽  
Frequency Response Functions ◽  
Vibration Transmissibility

AbstractIn order to improve the harsh dynamic environment experienced by heavy rockets during different external excitations, this study presents a novel active variable stiffness vibration isolator (AVS-VI) used as the vibration isolation device to reduce excessive vibration of the whole-spacecraft isolation system. The AVS-VI is composed of horizontal stiffness spring, positive stiffness spring, parallelogram linkage mechanism, piezoelectric actuator, acceleration sensor, viscoelastic damping, and PID active controller. Based on the AVS-VI, the generalized vibration transmissibility determined by the nonlinear output frequency response functions and the energy absorption rate is applied to analyze the isolation performance of the whole-spacecraft system with AVS-VI. The AVS-VI can conduct adaptive vibration suppression with variable stiffness to the whole-spacecraft system, and the analysis results indicate that the AVS-VI is effective in reducing the extravagant vibration of the whole-spacecraft system, where the vibration isolation is decreased up to above 65% under different acceleration excitations. Finally, different parameters of AVS-VI are considered to optimize the whole-spacecraft system based on the generalized vibration transmissibility and the energy absorption rate.

The Nonlinear Output Frequency Response Functions of One-Dimensional Chain Type Structures

2009 ◽  
Vol 77 (1) ◽  
Author(s):  
Z. K. Peng ◽  
Z. Q. Lang
Keyword(s):  
Frequency Response ◽  
Type Systems ◽  
Practical Case ◽  
Dimensional Chain ◽  
Response Functions ◽  
Output Frequency ◽  
Frequency Response Functions ◽  
One Dimensional ◽  
Nonlinear Component ◽  
Chain Type

It is well-known that if one or a few components in a structure are of nonlinear properties, the whole structure will behave nonlinearly, and the nonlinear component is often the component where a fault or an abnormal condition occurs. Therefore it is of great significance to detect the position of nonlinear components in structures. Nonlinear output frequency response functions (NOFRFs) are a new concept proposed by the authors for the analysis of nonlinear systems in the frequency domain. The present study is concerned with investigating the NOFRFs of nonlinear one-dimensional chain type systems, which have been widely used to model many real life structures. A series of important properties of the NOFRFs of locally nonlinear one-dimensional chain type structures are revealed. These properties clearly describe the relationships between the NOFRFs of different masses in a one-dimensional chain type system, and allow effective methods to be developed for detecting the position of a nonlinear component in the system. The results are an extension of the authors’ previous research studies to a more general and practical case, and have considerable significance in fault diagnosis and location in engineering systems and structures.

A novel analysis method for fault diagnosis of hydro-turbine governing system

2017 ◽  
Vol 231 (2) ◽  
pp. 164-171 ◽  
Author(s):  
Xin Xia ◽  
Wei Ni ◽  
Yingjun Sang
Keyword(s):  
Fault Diagnosis ◽  
Frequency Response ◽  
Experimental Studies ◽  
Response Functions ◽  
Output Frequency ◽  
Frequency Response Functions ◽  
Hydro Turbine ◽  
Identification Method ◽  
Governing System ◽  
Diagnosis Method

The fault diagnosis of hydro-turbine governing system is important to the operation of the hydropower station and the stability of the power grid. In order to improve the diagnostic accuracy and efficiency, a novel fault diagnosis method based on nonlinear output frequency response functions and a novel identification method of nonlinear output frequency response functions have been proposed and applied to the problem of hydro-turbine governing system fault diagnostics. First, the nonlinear model of hydro-turbine governing system is built. And the fault diagnosis principles based on nonlinear output frequency response functions are also introduced. Then, the disadvantages of the traditional identification method are discussed, and a novel identification method is proposed for nonlinear output frequency response functions according to the operation characteristic of hydro-turbine governing system. Finally, simulation verification and experimental studies have been presented to demonstrate the accuracy and efficiency of the proposed fault diagnosis method. The results indicate that the proposed method is simple and practical for fault diagnosis of hydro-turbine governing system.

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