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.

scholarly journals Vehicle response on kinematic excitation

2018 ◽  
Vol 211 ◽  
pp. 13001
Author(s):  
Veronika Valašková ◽  
Jozef Melcer
Keyword(s):  
Spectral Density ◽  
Frequency Domain ◽  
Power Spectral Density ◽  
Engineering Problem ◽  
Kinematic Excitation ◽  
The Road ◽  
Power Spectral ◽  
Road Profile ◽  
Vehicle Response ◽  
On The Road

The vehicle - roadway interaction is actual engineering problem solved on many workplaces in the world. At the present time preference is given to numerical and experimental approaches. Vehicle designers are interested in the vibration of the vehicle and the forces acting on the vehicle. Civil engineers are interested in the load acting on the road. Solution of the problem can be carried out in time or in frequency domain. Road unevenness is the main source of kinematic excitation of the vehicle and therefore the main source of dynamic forces acting both on the road and the vehicle. The offered article deals with one of the possibilities of numerical analysis of the vehicle response in frequency domain. It works with quarter model of the vehicle. For the selected computational model of the vehicle it quantifies the Frequency Response Functions (FRF) of both force and kinematic quantities. It considers the stochastic road profile. The Power Spectral Density (PSD) of the road profile is used as input value for the calculation of Power Spectral Density of the response. All calculations are carried out numerically in the environment of program system MATLAB. When we know the modules of FRF or the Power Response Factors (PRF) of vehicle model the calculation of vehicle response in frequency domain is fast and efficient.

Experimental and Theoretical Studies of the Fractal Scaling Parameter and the Lateral Scale Dependence of the Asperity Interference

2007 ◽  
Author(s):  
Shao Wang ◽  
Yi Hui Leong
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Numerical Scheme ◽  
Surface Profile ◽  
Density Data ◽  
Fractal Scaling ◽  
Scaling Parameter ◽  
Power Spectral ◽  
Surface Profiles ◽  
The Difference

The fractal scaling parameter was released in a recent study from its artificially assigned constant value to become a measurable parameter for simulated surface profiles. In the present study, this concept was extended to develop schemes for determining the fractal scaling parameter from experimental power spectral density data. The difference in the trends of peaks has been observed between experimental power spectral density data and those of the Weierstrass-Mandelbrot function. A modified W-M function was proposed based on a peak splitting behavior of the power spectrum. To verify a relationship between the interference and lateral length scale for asperities, which is commonly assumed in fractal modeling, a numerical scheme was developed to truncate measured surface profiles for finding asperity interferences for microcontacts of various sizes. This relationship was confirmed by the favorable results from a comparison of the power values obtained from truncation of a surface profile to those obtained by using the fast Fourier transform. A numerical scheme was developed to generate random power spectral density curves and fractal surface profiles for given values of the fractal scaling parameter.

scholarly journals Time-resolving the COVID-19 outbreak using frequency domain analysis

2020 ◽  
Author(s):  
Keno L. Krewer ◽  
Mischa Bonn
Keyword(s):  
Steady State ◽  
Severe Acute Respiratory Syndrome ◽  
Spectral Density ◽  
Frequency Domain ◽  
Time Domain ◽  
Case Fatality ◽  
Frequency Domain Analysis ◽  
Time Domain Data ◽  
Current Outbreak ◽  
The Time Domain

AbstractDifficulties assessing and predicting the current outbreak of the severe acute respiratory syndrome coronavirus 2 can be traced, in part, to the limitations of a static description of a dynamic system. Fourier transforming the time-domain data of infections and fatalities into the frequency domain makes the dynamics easily accessible. Defining a quantity like the “case fatality” as a spectral density allows a more sensible comparison between different countries and demographics during an ongoing outbreak. Such a case fatality informs not only how many of the confirmed cases end up as fatalities, but also when. For COVID-19, knowing this time and using the entire case fatality spectrum allows determining that an outbreak had entered a steady-state (most likely its end) about 14 days before this is obvious from time-domain data. The lag between confirmations and deaths also helps to estimate the effectiveness of contact management: The larger the lag, the less time the average confirmed person had to infect people before quarantine.

Research and analysis of the wheeled vehicle load spectrum editing method based on short-time Fourier transform

2019 ◽  
Vol 233 (14) ◽  
pp. 3671-3683
Author(s):  
Zongkai Liu ◽  
Chuan Peng ◽  
Xiaoqiang Yang
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Fatigue Damage ◽  
Time Domain ◽  
Short Time Fourier Transform ◽  
Load Spectrum ◽  
Statistical Parameters ◽  
Original Spectrum ◽  
The Time Domain ◽  
Short Time

The measured uniaxial-head load spectrum in the road simulation test has a large number of useless small loads. When applying the measured load spectrum directly, it will take a lot of time. This paper designs a comprehensive road spectrum measurement system to collect data and proposes a method for editing the uniaxial-head acceleration load spectrum using short-time Fourier transform to speed up the reliability test process and reduce time costs. In this method, the time domain and frequency domain information of the signal is obtained by short-time Fourier transform. The concept of accumulated power spectral density is proposed to identify the reduced load data, and the relative fatigue damage is used as the pass criterion. The length of the edited spectrum is only 66% of the original spectrum through the above-mentioned editing method and retains the relative damage amount of 91%. Finally, through the analysis of time domain, frequency domain, and fatigue statistical parameters, it demonstrates that the short-time Fourier transform–based acceleration load spectrum edition method could achieve a similar fatigue damage to the original spectrum in a shorter time.

Time-Domain Simulation of High-Speed Railway Track Irregularity

2014 ◽  
Vol 587-589 ◽  
pp. 1039-1042
Author(s):  
You Fu Du ◽  
Chu Yang Chen ◽  
Xiang Na Li
Keyword(s):  
Spectral Density ◽  
Density Function ◽  
Power Spectral Density ◽  
Time Domain ◽  
High Reliability ◽  
Spectral Density Function ◽  
Superposition Method ◽  
Power Spectral Density Function ◽  
Power Spectral ◽  
Track Irregularity

It was more convenient to describe track irregularity by the spatial frequency.The conventional frequency-domain transfer function can not effectively solve the vibration equation when anlysis of the vibration response to structure of vehicle-track dynamic coupling system, the time domain numerical integration must be used to solve it.The trigonometric series superposition method can be used to convert track irregularity spectrum into time domain frequency power spectral density function, and then turn the simulated irregularity samples into spectral density by the Inverse Fast Fourier Transform (IFFT), which compared with the theoretical spectral density to test the reliability of the sample. The results show that the simulated sample have the same characteristics with the given power spectral density function, which demonstrate the high reliability of this sample and it can be used as the external excitation of the locomotive vehicle system.

Sign in / Sign up

Export Citation Format

Share Document