scholarly journals Extraction of Features due to Breathing Crack from Vibration Response of Rotated Blades considering Tenon Connection and Shroud Contact

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Faming Yang ◽  
Yongmin Yang ◽  
Haifeng Hu ◽  
Fengjiao Guan ◽  
Guoji Shen ◽  
...  
Keyword(s):  
Dry Friction ◽  
Online Monitoring ◽  
Vibration Response ◽  
Lumped Parameter Model ◽  
Breathing Crack ◽  
Online Identification ◽  
Bladed Disk ◽  
Lumped Parameter ◽  
Frequency Domains ◽  
Coupling Force

Cracks are common failures of aeroengine rotated blades. Online monitoring of rotated blades through their vibration to identify cracks early in various working conditions is significant for operational safety. Breathing crack is a practical form of early cracks and results in nonlinear vibration response. Tenon connection and shroud contact are common structures in aeroengine rotated blades, which can also lead blades to vibrate nonlinearly and seriously interfere online identification of early cracks. Thus, it is important to extract vibration features due to breathing crack considering these two structures. Firstly, a blade with tenon and shroud is simplified and a lumped parameter model of the bladed disk is built. Then, dry friction and coupling force on a blade are analyzed and dynamics equations of the lumped parameter model are established. Next, the stiffness of the blade trunk with a breathing crack is analyzed. Finally, the vibration response of blade trunks with the occurrence of breathing crack is analyzed in time and frequency domains by numerical simulation. Effective features due to breathing crack for online identification are extracted. 2x components of spectrums can be the criterion to judge whether breathing crack occurs. Besides, by comparing the changes in vibration amplitudes with 1x component peaks of spectrums, the cracked blade trunk can be distinguished. These findings can provide important theoretical guidance for online identification of early cracks in aeroengine rotated blades.

scholarly journals Investigation of vibration characteristics for bladed-disks with dry friction nonlinearity

2018 ◽  
Vol 207 ◽  
pp. 04009
Author(s):  
Tianyuan Liu ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Dry Friction ◽  
Normal Load ◽  
Frequency Domain Analysis ◽  
Friction Model ◽  
Load Level ◽  
Vibration Characteristics ◽  
Lumped Parameter Model ◽  
Qualitative Assessment ◽  
Bladed Disk ◽  
Harmonic Equation

This paper focuses on the vibration characteristics of the bladed-disk subjected to the dry friction damping under periodic excitation. Firstly, the multi-harmonic equation basing on the frequency-domain analysis is established to predicate the steady response of the bladed-disk. Then, the algorithm to solve the nonlinear multi-harmonic balance equation is given step by step. In the numerical simulation, a simplified lumped parameter model of a turbine bladed-disk as well as the elastic Coulomb friction model between the root and disk contacting surfaces are applied. The normal load level of the friction interfaces, which are the focal points of the bladed-disk design, is analysed for the nonlinear vibration characteristics of the blades. The results show that vibration response of bladed-disk is affected significantly by normal load, and there exists an optimal value of the normal load under the operating condition of the turbomachinery, which can provide a qualitative assessment for the design practice of friction dampers.

Two-Dimensional Thermal Model of Asperity Heating in a Disk Pair in Dry Friction Between Two Rough Surfaces

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
A. Elhomani ◽  
K. Farhang
Keyword(s):  
Heat Generation ◽  
Dry Friction ◽  
Rough Surfaces ◽  
Frictional Heating ◽  
Heat Rate ◽  
Lumped Parameter Model ◽  
Disk Brake ◽  
Braking System ◽  
Lumped Parameter ◽  
Rate Formulation

In this paper, a formulation for the rate of heat generation due to the contact of one asperity with asperities on a second surface is proposed. A statistical approach is used to obtain the heat generation rate due to one asperity and employed to develop the equation for generation of heat rate between two rough surfaces. This heat rate formulation between the two rough surfaces has been incorporated into the 2D lumped parameter model of disk pair in dry friction developed by Elhomani and Farhang (2010, “A 2D Lumped Parameter Model for Prediction of Temperature in C/C Composite Disk Pair in Dry Friction Contact,” ASME J. Therm. Sci. Eng. Appl., 2(2), p. 021001). In this paper, the disk brake is viewed as consisting of three main regions: (1) the surface contact, (2) the friction interface, and (3) the bulk. Both surfaces of the disk brake are subjected to frictional heating. This model is considered to be a necessary step for simulating the aircraft braking system that consists of a stack of multiple disks.

Influence of Friction Dampers on Torsional Blade Flutter

1986 ◽  
Vol 108 (2) ◽  
pp. 313-318 ◽  
Author(s):  
A. Sinha ◽  
J. H. Griffin ◽  
R. E. Kielb
Keyword(s):  
Dry Friction ◽  
Fluid Velocity ◽  
Supersonic Flows ◽  
Degree Of Freedom ◽  
Lumped Parameter Model ◽  
Single Degree Of Freedom ◽  
Friction Dampers ◽  
Single Degree ◽  
Lumped Parameter ◽  
Blade Flutter

This paper deals with the stabilizing effects of dry friction on torsional blade flutter. A lumped parameter model with single degree of freedom per blade has been used to represent the rotor stage. The well-known cascade theories for incompressible and supersonic flows have been used to determine the allowable increase in fluid velocity relative to the blade. It has been found that the effectiveness of friction dampers in controlling flutter can be substantial.

The Effect of Group Number and Group Coupling Stiffness on Vibration Response Localization in Tuned Grouped Blade-Disk

2012 ◽  
Vol 226-228 ◽  
pp. 124-128
Author(s):  
Ai Lun Wang ◽  
Hui Long ◽  
Qiang Huang ◽  
Qian Jin Wang
Keyword(s):  
Structural Parameters ◽  
Vibration Response ◽  
Lumped Parameter Model ◽  
Vibration Equation ◽  
Vibration Localization ◽  
Lumped Parameter ◽  
Group Number ◽  
Coupling Stiffness

The group number and group coupling stiffness are important structural parameters of the grouped blade-disk. This work examines how the group number and group coupling stiffness affect the vibration response localization of tuned grouped blade-disk. The lumped parameter model of the grouped blade-disk was established, and the vibration equation was derived. The vibration response localization factors of tuned grouped blade-disks were obtained at the different group number and group coupling stiffness, and the effects of group number and group coupling stiffness on vibration response localization was analyzed. The results show that the vibration localization appears in the tuned grouped blade-disk and the degree of vibration response localization reduces with the increasing of group number and group coupling stiffness. The results can help to completely reveal the localization mechanism of the grouped blade-disk

Dynamic Analysis and Multi-Object Optimization of the Forced Torsional Vibration for Vehicular Multi-Stage Planetary Gears

2011 ◽  
Vol 86 ◽  
pp. 263-267 ◽  
Author(s):  
Hui Liu ◽  
Zhong Chang Cai ◽  
Chang Le Xiang ◽  
Ming Zheng Wang
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Torsional Vibration ◽  
Vibration Response ◽  
Resonance Vibration ◽  
Lumped Parameter Model ◽  
Lagrange Method ◽  
Planetary Gears ◽  
Multi Stage ◽  
Lumped Parameter

On the basis of lumped parameter model and the Lagrange method, the model of powertrain was built. Resonance vibration response and non-resonance vibration response were calculated respectively in time domain and frequency domain, characteristics of forced torsional vibration in steady–state were concluded. Comparability and difference of response of parts in different stage were explained. Multi-object optimization was applied to reduce vibration.

Theoretical Study of the Vibration Suppression on a Mistuned Bladed Disk Using a Bi-periodic Piezoelectric Network

2018 ◽  
Vol 35 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Lin Li ◽  
Pengcheng Deng ◽  
Jiuzhou Liu ◽  
Chao Li
Keyword(s):  
Vibration Suppression ◽  
Robustness Analysis ◽  
Forced Response ◽  
Lumped Parameter Model ◽  
Modal Assurance Criterion ◽  
Vibration Localization ◽  
Bladed Disk ◽  
Lumped Parameter ◽  
Random Mistuning ◽  
Response Amplification

AbstractThe paper deals with the vibration suppression of a bladed disk with a piezoelectric network. The piezoelectric network has a different period (so called bi-period) from that of the bladed disk and there is no inductor in it. The system is simulated by an electromechanical lumped parameter model with two DOFs per sector. The research focuses on suppressing the amplitude magnification or reducing the vibration localization of the mistuned bladed disk. The dynamic equations of the system are derived. Both mechanical mistuning and electrical mistuning have been taken into account. The Modified Modal Assurance Criterion (MMAC) is used to evaluate the vibration suppression ability of the bi-periodic piezoelectric network. The Monte Carlo simulation is used to calculate the MMAC of the system with the random mistuning. As a reference, the forced responses of the bladed disk with and without the piezoelectric network are given. The results show that the piezoelectric network would effectively suppress amplitude magnification induced by mistuning. The vibration amplitude is even smaller than that of the tuned system. The robustness analysis shows that the bi-periodic piezoelectric network can provide a reliable assurance for avoiding the forced response amplification of the mistuned bladed disk. The amplified response induced by the mechanical mistuning with standard deviation 0.2 can be effectively suppressed through the bi-periodic piezoelectric network.

scholarly journals Effects of Crack on Vibration Characteristics of Mistuned Rotated Blades

2017 ◽  
Vol 2017 ◽  
pp. 1-18 ◽  
Author(s):  
Hailong Xu ◽  
Zhongsheng Chen ◽  
Yongmin Yang ◽  
Limin Tao ◽  
Xuefeng Chen
Keyword(s):  
Natural Frequency ◽  
Vibration Amplitude ◽  
Crack Detection ◽  
Vibration Characteristics ◽  
Lumped Parameter Model ◽  
Crack Model ◽  
Breathing Crack ◽  
Vibration Localization ◽  
Lumped Parameter ◽  
Amplitude Increase

Rotated blades are key mechanical components in turbine and high cycle fatigues often induce blade cracks. Meanwhile, mistuning is inevitable in rotated blades, which often makes it much difficult to detect cracks. In order to solve this problem, it is important and necessary to study effects of crack on vibration characteristics of mistuned rotated blades (MRBs). Firstly, a lumped-parameter model is established based on coupled multiple blades, where mistuned stiffness with normal distribution is introduced. Next, a breathing crack model is adopted and eigenvalue analysis is used in coupled lumped-parameter model. Then, numerical analysis is done and effects of depths and positions of a crack on natural frequency, vibration amplitude, and vibration localization parameters are studied. The results show that a crack causes natural frequency decease and vibration amplitude increase of cracked blade. Bifurcations will occur due to a breathing crack. Furthermore, based on natural frequencies and vibration amplitudes, variational factors are defined to detect a crack in MRBs, which are validated by numerical simulations. Thus, the proposed method provides theoretical guidance for crack detection in MRBs.

Vibration of Bi-Periodic Bladed Disk

2014 ◽  
Author(s):  
Peiyi Wang ◽  
Lin Li
Keyword(s):  
Vibration Suppression ◽  
Periodic Structures ◽  
Lumped Parameter Model ◽  
Modal Assurance Criterion ◽  
Nodal Diameter ◽  
Bladed Disk ◽  
Lumped Parameter ◽  
Generalized Force ◽  
The Difference ◽  
Modal Dynamics

The dynamic behavior of bi-periodic bladed disk has been studied systematically. Bi-periodicity in bladed disk means that two types of structural subassemblies, alternating in circumferential direction, make up the structure. Based on a lumped parameter model, the dynamic behaviors of mono- and bi-periodic structures were compared. The nodal diameter spectrum was proposed to compare the difference of modes between mono- and bi-periodic bladed disk. The modified modal assurance criterion was proposed to evaluate the vibration suppression ability of bi-periodic bladed disk. The results showed that the generalized force and infinity norm are two most effective factors in altering modal dynamics. At the end, an improved Monte Carlo simulation is performed to show the resonance attenuation ability of bi-periodic bladed disk with mistuning considered.

Nonlinear Dynamics Analysis of Mistuned Turbine Bladed Disks With Damped Shrouds

2017 ◽  
Author(s):  
Wei Zhao ◽  
Di Zhang ◽  
Lei Sun ◽  
Yonghui Xie
Keyword(s):  
Dry Friction ◽  
Normal Load ◽  
Forced Response ◽  
Vibration Response ◽  
Amplification Coefficient ◽  
Response Analysis ◽  
Friction Damping ◽  
Friction Forces ◽  
Bladed Disk ◽  
The Impact

This paper deals with the real dynamics characteristics of a mistuned steam turbine bladed disk subjected to dry friction forces to better understand the nonlinear mistuning phenomenon. Normal load, which directly affects contact stiffness between interfaces, is chosen as the mistuning parameter. Based on Mindlin model, a forced response analysis of the finite element model of mistuned bladed disk with damped shrouds is performed in ANSYS. Compared with results of other simplified models, a real and complicated nonlinear behavior are observed here. A mass of qualitative analysis is also performed to assess the impact of the mistuning magnitude and excitation level on the vibration. The result shows that, vibration response of bladed disk is affected by excitation and mistuning level significantly. Local amplification coefficient of vibration response in the cases of different mistuning levels is obtained by introducing 10 random mistuned patterns. In addition, frequency splitting phenomena even appears at one of the blades by the contribution of high mistuning levels. According to the calculated results for different excitation levels, the curve of modal damping varying with response amplitude is gained. Lastly, rigidity mistuning is introduced and a combined analysis is performed to investigate the influence of friction damping mistuning on rigidity mistuning in the same 10 random mistuning patterns. The arrangement of dry friction damping mistuning also could be controlled to reduce the local vibration amplification originating from structure mistuning. However, further statistical investigations should be made to gain more information. (CSPE)

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