scholarly journals Fretting Fatigue Damage Nucleation and Propagation Lifetime Using a Central Point Movement of Power Spectral Density

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Thanh Q. Nguyen ◽  
Hieu C. Doan ◽  
Luan C. Vuong ◽  
H. Nguyen-Xuan ◽  
Nhi K. Ngo
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Fatigue Damage ◽  
Fretting Fatigue ◽  
Central Point ◽  
Reference Source ◽  
Forced Circulation ◽  
New Approach ◽  
Power Spectral ◽  
Different Levels

This paper presents a new perception in evaluating fretting fatigue damage nucleation and propagation lifetime under periodically forced circulation. A new approach, which is proposed in this paper, is to measure the change of the central point of power spectral density (CP-PSD) in different structural stiffness degradation stages. A notable aspect of this study lies in the combination between vibration amplitude and forced frequency of the fatigue-causing factors in beam structures. Additionally, it is found that randomization of the first phase from 0 to 2π yields more accurate modelling of the fatigue phenomenon. Results show that the CP-PSD parameter is significantly more sensitive compared to the regularly damage-evaluating parameters such as natural frequency, eigenvalues, or stress value. This reflects different levels of fatigue cycle effect on the structure in the experiment. At the same time, CP-PSD also categorizes the degradation level on different points on the structure under the periodically forced circulation. In addition, this paper also quantifies the relation between the changes of CP-PSD and each fatigue state. Results of this research will be a reference source to evaluate the lifespan of the structure by experimental methods.

Condition Monitoring of Fatigue Cracks in Machinery Blades

2005 ◽  
Vol 36 (11) ◽  
pp. 18-23
Author(s):  
L. Gelman
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Crack Detection ◽  
Traditional Approach ◽  
Fatigue Cracks ◽  
Diagnostic Features ◽  
New Approach ◽  
Numerical Examples ◽  
Power Spectral ◽  
The Fourier Transform

A novel generic approach to fatigue crack diagnostics in machinery blades is proposed and employed. The approach consists of simultaneously using two new diagnostic features: the real and imaginary parts of the Fourier transform of vibroacoustical signal generated from a blade. This approach is more generic than traditional approach based on the power spectral density; the power spectral density is a particular case of the proposed approach. Numerical examples are given based on the processing of signals generated using a nonlinear model of a blade. The signals generated are the resonant vibroacoustical oscillations of cracked and uncracked blades under narrowband vibration excitation. The numerical examples show that the crack detection is more effective when using the new approach than when using the power spectral density approach. The presented experimental results are matched with the numerical results. The proposed approach offers an effectiveness improvement over the traditional approach based on power spectral density.

scholarly journals Generation of Two Correlated Stationary Gaussian Processes

Mathematics ◽  
2021 ◽  
Vol 9 (21) ◽  
pp. 2687
Author(s):  
Guo-Qiang Cai ◽  
Ronghua Huan ◽  
Weiqiu Zhu
Keyword(s):  
Spectral Density ◽  
Stochastic Processes ◽  
Power Spectral Density ◽  
Series Expansion ◽  
Gaussian Processes ◽  
Linear Filters ◽  
Advantages And Disadvantages ◽  
Power Spectral ◽  
Stationary Gaussian Processes ◽  
Different Levels

Since correlated stochastic processes are often presented in practical problems, feasible methods to model and generate correlated processes appropriately are needed for analysis and simulation. The present paper systematically presents three methods to generate two correlated stationary Gaussian processes. They are (1) the method of linear filters, (2) the method of series expansion with random amplitudes, and (3) the method of series expansion with random phases. All three methods intend to match the power spectral density for each process but use information of different levels of correlation. The advantages and disadvantages of each method are discussed.

scholarly journals Numerical study of the relation between chosen statistical parameters of input stresses and cumulative fatigue damage provided rainflow decomposition

2019 ◽  
Vol 254 ◽  
pp. 02006
Author(s):  
Milan Sága ◽  
Ondrej Štalmach ◽  
Mária Blatnická ◽  
Marian Handrik ◽  
Zuzana Ságová
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Fatigue Damage ◽  
Numerical Study ◽  
Statistical Moments ◽  
Statistical Parameters ◽  
Material Parameters ◽  
Numerical Tests ◽  
Power Spectral ◽  
Cumulative Fatigue Damage

The aim of the article is to present a series of numerical tests of the cumulative fatigue damage solution under assumption of random stress input. It is realised study of the influence of the statistical moments or power spectral density on the cumulative fatigue damage using well-known rainflow method. The distribution of the cumulative fatigue damage is determined for pre-defined material parameters.

Comparing Random Vibration Inputs: Power Spectral Density (PSD) Versus Root Mean-Square Acceleration (Grms)

2003 ◽  
Author(s):  
Ivan Straznicky
Keyword(s):  
Spectral Density ◽  
Root Mean Square ◽  
Power Spectral Density ◽  
Fatigue Damage ◽  
Random Vibration ◽  
Mean Square ◽  
Vibration Effect ◽  
Operating Environments ◽  
Power Spectral ◽  
Magnitude Difference

Many defense programs have vibration requirements for electronics which are often specified as random vibration input. Often, this input is based on measurements taken at the locations of interest for the spectrum of vehicle operating environments. The resulting specification is typically several power spectral density, or PSD, curves with associated durations. The root mean square acceleration, or Grms, can be readily calculated for each PSD curve. Grms values are sometimes used to compare different PSD curves for severity. However, this can be misleading. The impacts of two different random vibration inputs, with the same Grms value, can be very different. By calculating fatigue damage values for various components on a circuit card assembly subjected to these inputs, it can be shown that equal Grms values do not result in equal damage. In fact, there can be two orders of magnitude difference in component damage values. This means that Grms values are very poor indicators of random vibration effect, and should not be used for comparison purposes.

Simple Method for Evaluation of Fatigue Damage of Structures in Wide-Band Random Vibrations

1994 ◽  
Vol 208 (1) ◽  
pp. 65-68 ◽  
Author(s):  
J J Kim ◽  
H Y Kim
Keyword(s):  
Spectral Density ◽  
Frequency Domain ◽  
Power Spectral Density ◽  
Fatigue Damage ◽  
Time Domain ◽  
Wide Band ◽  
Simple Method ◽  
Density Data ◽  
Power Spectral ◽  
The Time Domain

The note describes a simple method for evaluation of fatigue damage of structures in wide-band vibrations from response power spectral density data in the frequency domain. The method is applied to three sample cases and the results are compared with those of the damage calculation in the time domain.

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