Vibration Monitoring Method Research Articles

Handling the temperature effect in vibration monitoring of civil structures: A combined subspace-based and nuisance rejection approach

Monitoring the vibrations of a structure has been recognized as a useful monitoring approach. However, the temperature and other environmental factors are known to affect the way a civil structure vibrates. A vibration monitoring method based on a subspace residual and χ 2 -type global and sensitivity tests has been proposed by some of the authors. In this paper, an extended detection algorithm is presented, which rejects the temperature effect viewed as a nuisance parameter. Its relevance when applied to a simulated bridge deck example is investigated.

HANDLING THE TEMPERATURE EFFECT IN VIBRATION MONITORING OF CIVIL STRUCTURES: A COMBINED SUBSPACE-BASED AND NUISANCE REJECTION APPROACH 1

Monitoring the vibrations of a structure has been recognized as a useful monitoring approach. However, the temperature and other environmental factors are known to affect the way a civil structure vibrates. A vibration monitoring method based on a subspace residual and X2-type global and sensitivity tests has been proposed by some of the authors. In this paper, an extended detection algorithm is presented, which rejects the temperature effect viewed as a nuisance parameter. Its relevance when applied to a simulated bridge deck example is investigated.

Regular neutron noise diagnostics measurements at the Hungarian Paks NPP

The paper is devoted to the description of the regular neutron noise diagnostics measurements performed by KFKI AEKI at the four units of the Hungarian Paks NPP. Theoretical background, practical details and some results of the fuel assembly coolant flow surveillance measurements are outlined, emphasising their importance in practical plant operation. Control rod vibration monitoring methods and results are treated shortly, as well.

314 画像処理と TCP/IP 通信を用いた塔状構造物の遠隔セミアクティブ制振に関する一考察

Many vibration monitoring methods including remote monitoring are proposed for structural diagnostics or damage identification. And vibration control has been studied in order to maintain or improve structural performance. It is expected that the combination of remote vibration monitoring and vibration control have possibility to establish reasonable structural maintenance system. A low-cost remote displacement measuring system using PC camera and TCP/IP network is developed in this study. Property of the measuring system is examined in vibration measurement test. Moreover, semi-active vibration control experiments are performed on steel tower model by using proposed displacement system. From results of experiments, the remote vibration measuring system has basic applicability as sensor system of semi-active vibration control on tower structures.

Monitoring of Structural Vibration by Using Distributed PVDF Film Sensors.

In recent years, the new vibration monitoring methods using distributed continuous sensors have been actively developed in the field of smart sensors and actuators. PVDF film sensors have been mainly used for such purposes because they are less expensive and easy to handle. A lot of techniques have been reported so far, but they are not available for the structures whose boundary conditions are unknown. The authors propose the new approach using the PVDF films with the shape of appropriate Fourier series, which is applicable to the structure of arbitrary boundary conditions. Identification of the mode shape is simulated in the case of cantilever beam, which shows the availability of the proposed method. Furthermore, the experiment was carried out with the cantilever-like plate. The good agreements were obtained when compared with the calculated results.

Detecting Gear Tooth Breakage Using Acoustic Emission: a Feasibility and Sensor Placement Study

Vibration and debris monitoring methods are being increasingly used to detect gear tooth breakage. In this paper an alternate method of detecting gear tooth cracking is investigated. It is based on the phenomenon of acoustic emission (AE). The detectability of growing cracks using AE is established. Before this method can be used to detect crack growth in real systems, the transmissibility of these waves has to be studied. These waves have to propagate across a number of mechanical interfaces as they travel from the source to the sensor. The loss in strength of these waves at various interfaces commonly encountered in mechanical systems is studied in this paper.

Acoustic condition monitoring

For a number of years railroad wheels were used as test objects in developing acoustic signature monitoring techniques. This work will be reviewed as well as later laboratory studies using beams to determine the sensitivity of the method. Cracks and other defects can cause shifting and splitting of resonance frequencies, so that these changes can be used to indicate the presence of a defect. The limitation of the vibration monitoring method is that other conditions, such as uncertainties in the geometry of the test object, its surface conditions, and loading can also affect the vibration response, and it is necessary to distinguish the effects due to harmful conditions from those due to harmless ones. The sensitivity of the method is thus determined by the need to make this distinction. The concepts will be illustrated with experimental results from a test fixture for the case of a slotted steel beam, assuming that a slot can be used as a model for a crack. Some experiments with concrete beams will also be viewed.

A method for sensorless on-line vibration monitoring of induction machines

A method for sensorless on-line vibration monitoring of induction machines

Performance analysis of rotating machinery using enhanced cerebellar model articulation controller (E-CMAC) neural networks

For today's sophisticated machinery systems, on-line predictive maintenance has become a most reliable and cost effective method for machinery maintenance. An effective fault monitoring and diagnosis tool is able to recognize the characteristics, conditions, and developing trends of an operating machinery system, and is able to estimate fault severity of the system quantitatively. In order to meet the requirements, a new approach combining cerebellar model articulation controller (CMAC) neural networks and advanced vibration monitoring methods has been presented. A test rig consisting of two rotating hubs driven by a d.c. motor was used to produce different machine imbalance levels. A two-stage experiment is proposed. First, a CMAC network is trained with pre-defined imbalance conditions and a test data set is given to check the trained CMAC for imbalance severity prediction. Second, a CMAC network is trained by using a set of different imbalance levels and is then given an untrained condition to test the CMACs ability of imbalance severity interpolation. In addition, several potential capabilities of CMAC networks will be discussed and shown. The properties of the CMAC are notable. If implemented properly, CMAC can be used as an effective machinery condition monitor and fault severity estimation tool.

ART-based multiple neural networks for monitoring offshore platforms

A novel scheme using artificial neural networks to automate the vibration monitoring method of detecting the occurrence and location of damage in offshore jacket platforms is presented. A multiple neural network system is adopted which enables the problem to be decomposed into smaller ones, facilitating easier solution. An adaptive resonance theory (ART) neural network is used for damage diagnosis and its advantages and limitations are investigated. A comparison between a back-propagation network and an ART network is presented. The adaptability of ART for on-line monitoring is explored for possible adaptation to monitor offshore platforms in service. The system developed is tested using data from a finite-element analysis of a scale model of a jacket platform.

Detection and simulation of small trasverse cracks in rotating shafts

The detection of small transverse cracks in rotating shafts is difficult. An advanced vibration monitoring method is proved in laboratory tests. It bases on an angle dependent sampling of the vibrational data and the comparison with a reference signal of the undamaged rotor. A finite crack element is developed from a spatial finite element analysis and is used for numerical simulations of the dynamic behaviour of cracked rotors. The results of the numerical simulations are compared with experimental data.

Acoustic signatures: From natural to systems science

The interest in acoustic signatures began with the problem of detecting cracks in railroad wheels. When a wheel is struck with a hammer it produces a sound like that of a bell. If the wheel is cracked it sounds dissonant and muffled. By comparing sounds from the two members of a wheelset a measure of the difference in their mechanical properties is obtained. A fully automatic system was developed and installed on a Southern Pacific track in the 1980’s. The story of this undertaking is an object lesson in systems science. Recently beams have been used as test objects in an attempt to resolve certain basic questions in the science of the acoustic monitoring method. These questions will be illustrated with results from a test fixture with various beams. The limitation of the vibration monitoring method is that other conditions, such as uncertainties in the geometry of the test object, its surface conditions, and loading can also affect the vibration response, and it is necessary to distinguish the effects due to harmful conditions from those due to harmless ones. The sensitivity of the method is thus determined by the need to make this distinction. [Work supported by NSF Grant No. MSS-9024224.]

Suggested method for blast vibration monitoring : International Society for Rock Mechanics Commission on Testing Methods Int J Rock Mech Min SciV29, N2, March 1992, P143–156

Suggested method for blast vibration monitoring : International Society for Rock Mechanics Commission on Testing Methods Int J Rock Mech Min SciV29, N2, March 1992, P143–156

Sensitivity analysis for acoustic conditioning monitoring of beams.

Beams have been used to study the sensitivity of the vibration monitoring method of flaw detection. Cracks and other defects can cause shifting and splitting of resonant frequencies, so that these changes can be used to indicate the presence of the defect. The limitation of the vibration monitoring method is that other conditions, such as uncertainties in the geometry of the test object, its surface conditions, and loading, can also affect the vibration response, and it is necessary to distinguish the effects due to harmful conditions from those due to harmless ones. The sensitivity of the method is thus determined by the need to make this distinction. These concepts will be illustrated with experimental results from a test fixture for the case of a slotted beam, assuming that a slot can be used as a model for a crack. The effect of geometrical uncertainties, coatings of damping material, and loading can also be studied experimentally. It is possible to use Thomson’s theory to calculate the amounts of frequency changes due to a slot, so that the experimental results will be discussed in the light of this theory. [Work supported by NSF Grant No. MSS-9024224.]

Suggested method for blast vibration monitoring

This guideline is separated into three main sections. The first section, Character of Blast Excitation, defines the terminology necessary to describe blasting vibrations and the associated air over pressure. Importance of dominant frequencies of excitation and structural response is introduced here and is emphasized throughout the document. The second section, Measurement Techniques and Instrumentation, describes generic attributes of instruments necessary to measure time histories of the blast- induced disturbances. Special emphasis is placed on computerized systems. Guidance is given for the choice and deployment of instruments, both at the beginning and continuation of a project. The third section, Evaluation of Measurements, presents definitions of structural response. Explanation is given for the need of studies with immediate pre- and post-blast inspection to separate weather- and blast-induced response. Guidance is also given for monitoring response of rock masses and buried structures. (A)

Torsional vibration monitoring method and an apparatus for performing the same

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