scholarly journals Discussion of “On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Frequency Domain” (Moussa, W. A., and Abdelhamid, A. N., 1999, ASME J. Pressure Vessel Technol., 121, Aug., pp. 241–245)

2001 ◽  
Vol 123 (2) ◽  
pp. 259-261 ◽  
Author(s):  
K. T. Truong,
Keyword(s):  
Frequency Domain ◽  
Pressure Vessel ◽  
Dynamic Stresses ◽  
Vibration Measurements

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Frequency Domain

1999 ◽  
Vol 121 (3) ◽  
pp. 241-245 ◽  
Author(s):  
W. A. Moussa ◽  
A. N. AbdelHamid
Keyword(s):  
Frequency Domain ◽  
Minimum Distance ◽  
Exciting Force ◽  
Vibration Measurement ◽  
Dynamic Stresses ◽  
Vibration Measurements ◽  
Pipe Model ◽  
Translational Vibration ◽  
Related Risk

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a harmonically loaded pipeline structure is used to establish the validity of the technique in the frequency domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

scholarly journals On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Frequency Domain

1998 ◽  
Author(s):  
Walied A. Moussa ◽  
Amr N. AbdelHamid
Keyword(s):  
Frequency Domain ◽  
Minimum Distance ◽  
Exciting Force ◽  
Vibration Measurement ◽  
Dynamic Stresses ◽  
Vibration Measurements ◽  
Pipe Model ◽  
Translational Vibration ◽  
Related Risk

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of Finite Element Method (FEM) and field measurement vibrations at selected points. Numerical simulation of a harmonically loaded pipeline structure is used to establish the validity of the technique in the frequency domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

Multiharmonic Forced Response Analysis of a Turbine Blading Coupled by Nonlinear Contact Forces

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Christian Siewert ◽  
Lars Panning ◽  
Jörg Wallaschek ◽  
Christoph Richter
Keyword(s):  
Frequency Domain ◽  
Nonlinear Equations ◽  
Forced Response ◽  
Vibration Response ◽  
Contact Forces ◽  
Dynamic Loads ◽  
Response Analysis ◽  
Dynamic Stresses ◽  
Nonlinear Contact ◽  
Turbine Blading

In turbomachinery applications, the rotating turbine blades are subjected to high static and dynamic loads. The static loads are due to centrifugal stresses and thermal strains whereas the dynamic loads are caused by the fluctuating gas forces resulting in high vibration amplitudes, which can lead to high cycle fatigue failures. Hence, one of the main tasks in the design of turbomachinery blading is the reduction in the blade vibration amplitudes to avoid high dynamic stresses. Thus, coupling devices like underplatform dampers and tip shrouds are applied to the blading to reduce the vibration amplitudes and, therefore, the dynamic stresses by introducing nonlinear contact forces to the system. In order to predict the resulting vibration amplitudes, a reduced order model of a shrouded turbine blading is presented including a contact model to determine the nonlinear contact forces. To compute the forced response, the resulting nonlinear equations of motion are solved in the frequency domain using the multiharmonic balance method because of the high computational efficiency of this approach. The transformation from the time domain into the frequency domain is done by applying Galerkin’s method in combination with a multiharmonic approximation function for the unknown vibration response. This results in an algebraic system of nonlinear equations in the frequency domain, which has to be solved iteratively in order to compute the vibration response. The presented methodology is applied to the calculation of the forced response of a nonlinear coupled turbine blading in the frequency domain.

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Time Domain

1999 ◽  
Vol 121 (1) ◽  
pp. 37-41 ◽  
Author(s):  
W. A. Moussa ◽  
A. N. AbdelHamid
Keyword(s):  
Time Domain ◽  
Minimum Distance ◽  
Exciting Force ◽  
Vibration Measurement ◽  
Dynamic Stresses ◽  
Vibration Measurements ◽  
Pipe Model ◽  
Related Risk ◽  
The Time Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a randomly loaded pipeline structure is used to establish the validity of the technique in the time domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

Stochastic Response of Piping Systems With Flexible Supports

1996 ◽  
Vol 118 (1) ◽  
pp. 109-114 ◽  
Author(s):  
H. O. Soliman ◽  
T. K. Datta
Keyword(s):  
Frequency Domain ◽  
Cross Sections ◽  
Equations Of Motion ◽  
Response Analysis ◽  
Piping System ◽  
Dynamic Stresses ◽  
Support Points ◽  
Flexible Supports ◽  
Piping Systems ◽  
Support Excitation

A frequency domain spectral analysis of piping systems with flexible supports is presented for uniformly modulated nonstationary support excitations. The support points are idealized by spring-dashpot arrangements. The equations of motion of the resulting nonclassically damped, multipoint excitation system are written and solved in terms of the absolute displacements of the dynamic DOF. This facilitates a direct computation of the dynamic stresses induced at various cross sections of the pipe segments. The method of analysis provides a quasi-stationary response based on the assumption that the modulating function varies slowly with time; the exact response analysis in frequency domain for such systems with nonstationary support excitation is difficult to determine. Using the method of analysis presented, the response of a piping system is obtained for a set of important parametric variations related to the flexibility, damping, and excitation of the supports.

scholarly journals Identification of Rub and Unbalance in 320 MW Turbogenerators

2003 ◽  
Vol 9 (2) ◽  
pp. 97-112 ◽  
Author(s):  
N. Bachschmid ◽  
P. Pennacchi ◽  
A. Vania ◽  
G. A. Zanetta ◽  
L. Gregori
Keyword(s):  
Power Plant ◽  
Frequency Domain ◽  
Theoretical Background ◽  
Fault Identification ◽  
Vibration Measurements ◽  
Rotating Speed ◽  
Model Based ◽  
First Case ◽  
Identification Technique ◽  
Fossil Power Plant

This article presents two experiences of applying a model-based fault-identification method to real machines. The first case presented is an unbalance identification in a 320 MW turbogenerator unit operating in a fossil power plant. In the second case, concerning a machine of the same size but from a different manufacturer, the turbine has been affected by a rub in the sealings. This time, the fault is modeled by local bows. The identification of the faults is performed by means of a model-based identification technique in a frequency domain, suitably modified in order to take into account simultaneous faults. The theoretical background of the applied method is briefly illustrated and some considerations are also presented about the best choice of the rotating speed set of the run-down transient to be used for an effective identification and about the appropriate weighting of vibration measurements at the machine bearings.

scholarly journals Analysis of composition of linear acceleration body structure of vehicle during the gear changing

2018 ◽  
Vol 19 (6) ◽  
pp. 678-681
Author(s):  
Krzysztof Prażnowski ◽  
Dawid Drabik
Keyword(s):  
Frequency Domain ◽  
Human Body ◽  
Commercial Vehicle ◽  
Linear Acceleration ◽  
Vehicle Body ◽  
Body Structure ◽  
Vibration Measurements ◽  
Vibration Intensity ◽  
Intensity Index ◽  
Gear Change

The article presents and discusses the results of vibration measurements of a commercial vehicle body during a gear change. Data obtained during road tests were analyzed in the frequency domain and evaluated for the vibration intensity index affecting the human body.

scholarly journals Crack Classification of a Pressure Vessel Using Feature Selection and Deep Learning Methods

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4379 ◽  
Author(s):  
Manjurul Islam ◽  
Muhammad Sohaib ◽  
Jaeyoung Kim ◽  
Jong-Myon Kim
Keyword(s):  
Feature Selection ◽  
Frequency Domain ◽  
Pressure Vessel ◽  
High Pressures ◽  
Early Stage ◽  
Pressure Vessels ◽  
Crack Identification ◽  
Hybrid Features ◽  
Time Frequency ◽  
Highly Effective

Pressure vessels (PV) are designed to hold liquids, gases, or vapors at high pressures in various industries, but a ruptured pressure vessel can be incredibly dangerous if cracks are not detected in the early stage. This paper proposes a robust crack identification technique for pressure vessels using genetic algorithm (GA)-based feature selection and a deep neural network (DNN) in an acoustic emission (AE) examination. First, hybrid features are extracted from multiple AE sensors that represent diverse symptoms of pressure vessel faults. These features stem from various signal processing domains, such as the time domain, frequency domain, and time-frequency domain. Heterogenous features from various channels ensure a robust feature extraction process but are high-dimensional, so may contain irrelevant and redundant features. This can cause a degraded classification performance. Therefore, we use GA with a new objective function to select the most discriminant features that are highly effective for the DNN classifier when identifying crack types. The potency of the proposed method (GA + DNN) is demonstrated using AE data obtained from a self-designed pressure vessel. The experimental results indicate that the proposed method is highly effective at selecting discriminant features. These features are used as the input of the DNN classifier, achieving a 94.67% classification accuracy.

scholarly journals Contribution to the analysis of grinder vibrations using condition monitoring procedures based on vibration measurements

2021 ◽  
Vol 1199 (1) ◽  
pp. 012025
Author(s):  
V Dekýš ◽  
M Čilíková ◽  
M Gavlas ◽  
P Novák ◽  
A Sapietová ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Condition Monitoring ◽  
Chip Formation ◽  
Hardened Steel ◽  
Grinding Wheel ◽  
Vibration Measurements ◽  
Cbn Grinding Wheel

Abstract The article deals with the vibration of the workpiece on the grinder using a cBN grinding wheel. The workpieces were made of hardened steel with a hardness of 62 HRC and ceramics: Al2O3, SiC, Si3N4, and ZrO2/Y2O3. Grinding was performed at different infeed rates during 5 consecutive passes. Up and down grinding were also evaluated. Measured realizations of the acceleration of the workpiece during grinding were processed in the time and frequency domain and compared with each other. We consider acceleration patterns to be diagnostic signals that will help to understand the process of chip formation during grinding as well as the process of damaging parts made of the tested materials.

Correction to "The analysis of slug tests in the frequency domain" (WRR 25(11), pp. 2388-2396

1990 ◽  
Vol 26 (8) ◽  
pp. 1863-1863
Author(s):  
Paul Marschall ◽  
Baldur Barczewski
Keyword(s):  
Frequency Domain ◽  
Slug Tests
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