Research on probability statistics of train running safety indices based on pseudo-excitation method

2021 ◽  
pp. 095440972110459
Author(s):  
Zhou Zi-ji ◽  
Zhang Nan ◽  
Sun Qi-kai
Keyword(s):  
Extreme Value Distribution ◽  
Extreme Value ◽  
Driving Safety ◽  
Pseudo Excitation Method ◽  
Interaction Forces ◽  
Running Safety ◽  
Train Operation ◽  
Pseudo Excitation ◽  
Safety Indices ◽  
Excitation Method

In order to explore the random nature of high-speed railway train operation safety indices, the pseudo-excitation method, extreme value theory, and non-stationary harmonic superposition theory are used in this paper to study the statistics of train operation safety indices. The pseudo-excitation load formulation for track irregularity is obtained by the pseudo-excitation method, and the resulting non-stationary random vibration problem is transformed into a deterministic time history problem. The pseudo-excitation method is used to establish the dynamic equations of motion, and the separation iteration method is used to solve the equations, so as to obtain the power spectral density of the wheel-rail interaction forces. The wheel-rail interaction forces are obtained by using a modulation function and the harmonic superposition method. By fitting an extreme value distribution, the maximum values of the train running safety indices are explored. The proposed numerical approach is validated experimentally using the data from a 24.6 m long simply supported concrete bridge by studying the extreme value distributions of driving safety indices. Additional numerical simulation are conducted for varying train speeds and bridge spans. The results show that the Gumbel distribution can fit the extreme value of driving safety parameters for different speeds and different bridge span lengths. It is observed that the higher the speed, the sharper the extreme value distribution of train running safety indices, and the larger the train running safety index values corresponding to 99.87% confidence level. The corresponding extreme values at the 99.87% confidence level are greater than the maximum value of each time-domain sample.

Dynamic Reliability Evaluation by First-Order Reliability Method Integrated with Stochastic Pseudo Excitation Method

2020 ◽  
pp. 2150024
Author(s):  
Siyu Zhu ◽  
Tianyu Xiang
Keyword(s):  
Random Variable ◽  
Random Excitation ◽  
Pseudo Excitation Method ◽  
First Order Reliability Method ◽  
Dynamic Reliability ◽  
First Order ◽  
Reliability Method ◽  
Uncertain Structure ◽  
Pseudo Excitation ◽  
Excitation Method

The stochastic pseudo excitation method (SPEM), which is based on the principle of pseudo excitation method (PEM), is introduced to represent the randomness of dynamic input in which the amplitude of excitation is adopted as a random variable. Based on the mathematic definition of power spectral density, a physical interpolation of the SPEM is discussed. Even if one random variable is involved in calculation, the effects of the uncertainties are required to be investigated. The SPEM offers a simple but quite effective way to solve the dynamic reliability problem. Through integrating the new algorithm into first-order reliability method (FORM), the dynamic reliability of uncertain structure subjected to random excitation is studied. A linear oscillator with three types of white noise is adopted to verify the SPEM for dynamic reliability of linear random vibration analysis. Also, the accuracy and efficiency of SPEM to handle the multi-degree-of-freedom structure is investigated in this paper.

Simultaneous optimization of control parameters and placements of piezoelectric patches for active structural acoustic control of shell structures under random excitation

2020 ◽  
Vol 31 (9) ◽  
pp. 1204-1219
Author(s):  
Jingjuan Zhai ◽  
Linyuan Shang ◽  
Guozhong Zhao
Keyword(s):  
Simulated Annealing Algorithm ◽  
Simultaneous Optimization ◽  
Continuous Variables ◽  
Control Cost ◽  
Pseudo Excitation Method ◽  
Acoustic Control ◽  
Pseudo Excitation ◽  
Excitation Method ◽  
Element Method ◽  
Structural Acoustic Control

Simultaneous optimization of multiple parameters of an active structural acoustic control system under random force excitation is presented in this article. A method integrating the pseudo excitation method, finite element method, and boundary element method is proposed to analyze the random acoustic radiation. The active structural acoustic control of randomly vibrating structures is developed using the velocity feedback control scheme with the help of the pseudo excitation method. The acoustic design optimization model is proposed, in which the auto power spectral density of sound pressure is taken as the objective function and the placements of actuators/sensors as well as control gains are assigned as design variables. Taking into account the operational efficiency and control cost, the number of actuators/sensors and the total actuation energy are considered as constraints. A simulated annealing algorithm is employed for the optimization problem with discrete and continuous variables coexisting. Numerical examples are given to demonstrate the effectiveness of the proposed methods and the programs, and several key factors on the optimized designs are also discussed.

Random Vibration Analysis for Centrifugal Compressor Impellers With Unsteady Aerodynamic Excitations

2016 ◽  
Author(s):  
Yuefang Wang ◽  
Yan Liu ◽  
Xuejun Wang ◽  
Hongkun Li ◽  
Daren Jiang
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Centrifugal Compressor ◽  
Random Vibration ◽  
Pressure Field ◽  
Pseudo Excitation Method ◽  
Vibration Problem ◽  
Power Spectral ◽  
Pseudo Excitation ◽  
Excitation Method

Dynamic response of impeller of centrifugal compressor is studied considering pulsating pressure field on blades due to unsteady flow conditions. The aerodynamic forces on the blades are modeled as random load whose spectral characteristics are determined through computational fluid dynamic simulations in the time domain. The dynamical response in the unsteady case is solved as a random vibration problem in the frequency domain which provides useful power spectral density displacement and stress for early stage of impeller design. A semi-open impeller mounted with 19 blades is modeled using three dimensional solid finite elements. The random vibration problem of the impeller is solved through the Pseudo-Excitation Method considering spatial variance of the pressure field. A user-defined module is developed based on harmonic analysis to generate the auto power spectral density and variance of displacement and stress at 200 nodes. It is demonstrated that solving a random vibration problem through the Pseudo-Excitation Method is faster than the commonly adopted multiple-step transient analysis. It is concluded that evaluating the structural integrity of impeller solids in the regime of random vibration is a feasible and efficient approach at the early design stage of compressors.

Random Vibration Analysis for Impellers of Centrifugal Compressors Through the Pseudo-Excitation Method

2015 ◽  
Vol 12 (04) ◽  
pp. 1540002 ◽  
Author(s):  
Yuefang Wang ◽  
Sujing Wang ◽  
Lihua Huang
Keyword(s):  
Time Domain ◽  
Random Vibration ◽  
Structural Integrity ◽  
Centrifugal Compressors ◽  
Pseudo Excitation Method ◽  
Transient Stress ◽  
Aerodynamic Pressure ◽  
Pseudo Excitation ◽  
Excitation Method ◽  
Stress Analyses

Impellers of centrifugal compressors are generally loaded by fluctuating aerodynamic pressure in operations. Excessive vibration of the impellers can be induced by unsteady airflows and lead to severe fatigue failures. Traditional transient stress analyses implemented in time domain generally require multiple load-step, very time-consuming computations using input of temporal pneumatic force previously obtained from Computational fluid dynamics (CFD) analyses. For quick evaluation of structural integrity of impellers, it is necessary to develop random vibration models and solution approaches defined in frequency domain. In this paper, the Pseudo-Excitation Method (PEM) is used to obtain power spectral density of three-dimensional, dynamic displacement and stress of impellers. A finite element model of an unshrouded impeller of a centrifugal compressor is generated based on the result of unsteady CFD analysis. Compared with the direct transient stress analyses in time domain, the pseudo-excitation method provides accurate and fast estimation of dynamic response of the impeller, making it an applicable and efficient method for analyzing random vibration of impellers.

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