Vibrodiagnostic Methods Research Articles

Assessment of the Correlation between the Monitored Operating Parameters and Bearing Life in the Milling Head of a CNC Computer Numerical Control Machining Center

The present paper describes a study conducted at the request of the operator of machining center equipment. The operator observed undesirable indicators in terms of increased backlash and vibration of the milling head and poor quality of the machined surfaces. Vibration measurements and vibrodiagnostics were carried out before disassembling the milling head in the idle state. The bearings, lubricant, and friction regime were analyzed in the next step. The vibrodiagnostic methods used included VEL, ACC, EN2, EN3, and EN4, with recommended limits conforming to STN ISO 10816-3. The vibration values obtained indicated a problem with the bearings, exceeding the limit values. After disassembly of the bearings, abrasive wear, corrosion, and improper lubricant conditions were detected. Lubricant analysis showed the presence of abrasive and corrosive particles, indicating an unsatisfactory friction regime. Determining the optimum lubricant temperature and the effect on friction torque constituted other aspects of the study. Inspection of the bearing microgeometry confirmed unsatisfactory roundness. Furthermore, the assembly of tapered roller bearings with axial preload was analyzed with a focus on bearing stiffness, accuracy, and life. The results showed that preload improves shaft guidance accuracy and load distribution, promoting reliable operation and extending bearing life.

FEATURES OF DIAGNOSING ROLLING BEARINGS BY THE ENVELOPE METHOD

The article is devoted to the work on identifying defects of the surface crack type by the vibrodiagnostic method of non-destructive testing using the envelope method on the example of a rolling bearing. Used in the work rolling bearings with a set of various surface defects: a roller crack and an outer ring crack along the rolling surfaces. The rolling bearing was installed in a test bench, which simulated its regular operation, with a fixed outer ring and internal ring rotated at a constant frequency. The features of the detection of the following specific defects are established: a roller crack, a crack in the outer ring, etc., as well as the correspondence of the calculated frequencies of the bearing elements to the actual ones obtained during the research. The norm/rejection criteria were obtained in a numerical value in relation to specific types of defects, namely: weak, strong defects of the rolling elements and the outer ring of the rolling bearing. The features of detecting specific defects by the envelope method, that depends on the pressure on the outer ring and its spatial location relative to the defect, are experimentally established.

Phase-chronometric diagnostic system for main drive of rolling mill

At present at the diagnostic of metallurgical equipment state, expert methods of evaluation are prevailed which have subject character. To solve the problem of information-metrological support of rolling mill stand effectively, a phase-chronometric method was proposed, elaborated in N.E. Bauman Moscow State Technical University. It was shown that increase of quality of measuring diagnostical information is provided by transfer from amplitude to chronometric scale and means of its realization at relative errors about 5×10‒4 % at the industrial frequency. At the phase-chronometric method, precision measuring of time intervals, correspondent to the phases intervals of the working cycle is used, depending on characteristic features of motion of a mechanism elements. In contrast to vibro-diagnostic method, by using the phase-chronometric method, the change of operation mode of rolling equipment can be defined hundred times quicker. Cyclicity of a mechanism motion and minimal scattering of measurement results at accomplishing working cycle enable to reveal stable in time diagnostic features and individual quantitative parameters values, which characterize technical state of a rolling mill. The proposed phase-chronometric system consists of an angle sensor of position (incremental encoder), system of information collection and defining of time intervals and personal computer with application software. The system of information collection and defining of time intervals is realized based on a plate, functionally uniting high-stability pulse generator, scale convertor, counter, measuring pulse generator and chrono-comparator. The embedded systems to realize the phase-chonometric metod are simple and reliable in operation. To realize the phase-chronometric method, a mathematical model was elaborated, comprising a system of differential equations, describing interaction of the package of interrelated multi-mass torsion systems. It was showed that verified mathematical model enabled quickly to reveal defects in a rolling mill operation.

Kratkoročno predviđanje vibracionog ponašanja Fransis turbine nakon višedecenijske eksploatacije

Contemporary approaches in forecasting and preventing accidents, reducing the number and duration of downtimes, detecting and monitoring the failures in the real decades-long operating conditions of units in hydropower plants, are based on vibrodiagnostics. The multidisciplinary character of such approaches is reflected in the identification of certain vibrations in the hydro-aggregates, the application of various vibrodiagnostic methods, the quality assessment of measured data, as well as analysis and prediction based on artificial intelligence. The paper presents one of the possible approaches to solving the complex problem of predicting the behavior of a hydraulic turbine that has been in operation for more than half a century. An appropriate algorithm using artificial neural networks has been developed for short - term prediction of absolute and relative vibrations. The obtained results are presented depending on various operating conditions.

Vibrodiagnostic method of water pump control

The research aims to carry out comprehensive diagnostics and develop diagnostic systems for vertical pumping units. The article discusses the method of technical diagnostics of large vertical pumping units to ensure reliability during their operation. An assessment of the qualitative and quantitative changes in the parameters of their operating modes during wear is given, and a diagnostic system is proposed for monitoring these parameters.

RESEARCH OF FEATURES OF DEVELOPMENT OF BEARING DEFECTS ON THE BASIS OF WAVELET ANALYSIS

Today the vibrodiagnostic method achieves the highest efficiency and manufacturability for the operation of the technical condition of the technological equipment of the agro-industrial complex. At the same time, this method is one of the most modern methods of technical diagnostics, indicating the kinematic warehouses of diagnostic objects. Vibration analysis is a fundamental tool for diagnostic monitoring of bearings. The vibration signal of defective rolling bearings and its spectrum contain characteristic features by which it is possible to fairly correctly identify the type and location of the defect. At the moment the defective element passes through the loaded zone of the rolling bearing, a pronounced peak, an energy impulse, appears in the vibration. Thus, when a bearing with internal defects is operating, characteristic components appear in vibration - harmonics with natural frequencies, the numerical values of which can be calculated using theoretical formulas using the geometric dimensions of the bearing elements and the rotor speed of the mechanism. In a loaded bearing, four characteristic frequencies can be distinguished that are used for diagnostics - the frequency of the outer bearing cage, the frequency of the inner cage, the cage frequency and the rolling element frequencies. The complexity of the analysis of vibration signals of rolling bearings for the purpose of their diagnostics lies in the fact that the signs of a defective bearing are distributed over a wide range of frequencies, have low vibrational energy and are somewhat random in nature. In addition, the vibration signal is, of course, removed from the body of the equipment containing the bearing, and therefore contains not only information useful from the point of view of bearing diagnostics, but also noise - vibrations produced by other parts of the mechanism. The analysis of methods for diagnosing bearing defects based on wavelet analysis of their vibration signals allows us to single out the most promising direction, which consists in the fact that the bearing vibration signal is decomposed into coefficients using wavelet analysis, after which the most significant coefficients are selected from these coefficients.

Rail vehicle axle-box bearing damage detection considering the intensity of heating alteration

The article observes problems of detection of rolling bearing damages in rail vehicles. Two methods of bearing damage detection are examined – according to heating of axleboxes and by vibro-diagnostic manner. The disadvantage of vibro-diagnostic method is that a contact vibration sensor is used for vibration diagnostics, intervention into rail vehicle structure is required. The method according to heating of axle-boxes also has drawbacks. The same temperature value of axle-box in various conditions may characterize different bearing technical state. The Authors studied a possibility to use temperature change intensity parameters as the diagnostics criteria. Based on the examples of axle-box temperature measurement data, Authors developed and proposed a methodology for detecting axle-box bearings defects. The Authors suggest the use the method according to heating of axle-boxes. The given example proofs that the fact of the presence of their damages can be unambiguously identified by the intensity of temperature change of the axle-boxes.

Introduction to the Examination of Thin-Walled Structures Using the Vibrodiagnostic Method

Abstract The article presents a methodology of non-destructive diagnostic vibratory tests of welded plates with geometrical parameters that classify them into a group of thin-walled panels. On the basis of such plates, most ship constructions are created. In previous works, the authors dealt with the study of welded joints in plates with significant thicknesses and developed for them a number of methods for assessing the quality of welded joints. Vibrodiagnostics is a NDT method that allows the use of a variety of techniques and tools. It enables measurements to be made in both a contact and non-contact way depending on the requirements of the structure and the environment. Vibrodiagnostic method is one of the most modern NDT methods, which uses modern measurement tools and computer analysis of data. On the basis of the developed methods, the authors intend to verify their application to plates from real welded constructions, which will be performed in typical shipyard conditions by welders. Such tests are important due to their use for the construction of a real SHM ship construction monitoring system. These methods allow for the examination of the condition of ships’ structural plates and can detect defects in welded joints that prevent ships from operating under severe sea conditions. The article presents the laboratory stand, the sensor layout, results, and their initial analysis.

Concrete base influence on the increased vibrations level of the mill drive system elements - A case study

The paper presents the influence of concrete base cracks on the state and performance of mill electrical drive components based on vibration measurements taken at characteristic locations for the drive group. Measurements were performed before and after the reconstruction of the concrete base, under the full load of electrical drive, to demonstrate the negative impact of the existing and to verify the accuracy and advantage of the newly applied solution. Technical solution for repair and reconstruction of the supporting concrete structure of the mill drive group was derived from a detailed load analysis, subsequently identified cracks in the concrete, from the results of measured vibrations, as well as in accordance with discovered causes of the concrete base deterioration. The newly applied solution significantly reduced the level of vibration. Analysis of measurement results presented in the case study has once more verified the potential of vibration spectral analysis in terms of monitoring and diagnostics of problems in idustrial drive operation. Vibro-diagnostic method within proactive maintenance of industrial drives provides reliable early detection of malfunctions and accordingly better time and capacitive utilization of industrial resources, leading to significant economical benefits.

Diagnostic benchmarks on dynamic characteristics of thin-walled marine damaged structures

Abstract Among structural health monitoring (SHM) methods of thin-walled structures, a vibrodiagnostic method is one of the most promising. The accelerometer recorded responses provide diagnostic information that requires mathematical processing to extract the essential dynamic characteristics. The authors have been looking for new parameters - diagnostic benchmarks which can be applied to non-destructive, automatic testing of thin-walled marine structures (especially their welded joints) like ship hulls. All characteristics have been based on recorded data generated during the vibration tests of welded joints with and without failures. For this purpose, the authors proposed method based on: FFT windowing analysis, benchmark with using 2D or 3D time – frequency dynamic characteristics and the determination of damping decrement in function of time. The work presents the algorithm and exemplary results obtained from the application of proposed method to several selected sample plates with different type of welds.

Determination of Optimal Milling Modes by Means of Shock-Vibration Load Reduction on Tool and Peak-Factor Equipment

Vibrodiagnostics of metal-cutting machines is an efficient method to increase reliability of all elements of the technological system «machine tool-device-instrument-detail». The development of vibrodiagnostic methods is especially important for milling metal-cutting machines which operate in intermittent cutting mode and are exposed to shock-vibration loads. One of the trends in the development of metal cutting equipment is to increase its productivity by expanding the ranges of cutting modes. Increase in the combination of cutting modes leads to increased probability of coincidence of the natural frequencies of the equipment and the frequencies of the cutting process which in its turn leads to operation of the machine equipment elements under resonance conditions. In the article we provide the results of our research aimed to develop the method to reduce shock-vibration load on tool and peak-factor equipment of milling machine. In our research we developed the technique that makes it possible to measure not only the general level of vibration, but also other parameters used for vibrodiagnostics, for example, the value of the peak factor has been developed. The method includes the development of a principle layout and of a plan for a three-factor experiment, construction and analysis of vibrational and spectral diagrams of the milling process for the assignment of optimal modes that provide machine operating at lower level of shock-vibration loads. Based on the results of the work we have come to the conclusion that it is rather promising to use the peak factor in analysis of the milling machines reliability.

Optimization of vibro-diagnostic method for marine rotating pumps

Techno-economical optimization of vibro-diagnostic method implies defining of the minimal number of vibro-diagnostic information, which could be used for precise and definite diagnosis of broad spectra of failures or malfunctions with all types of rotating machines in standard use, including marine pumps. Economic optimization is done based on competitive advantage approach, but in coherence to technical aspect. Techno-economical optimization in this research is analysed more from the aspect of the optimization problem new formulation, then from the aspect of mathematical apparatus for solving the problem. In this case, the optimization is based on establishing the possibility of certain defect appearance at marine rotating machines and implementation of causal relations between diagnostic model and defined goal functions values.

Research into the causes of increased vibration levels on the diesel-electric generators set at the air traffic control: Belgrade Airport

The paper presents the research into the causes of increased vibration levels on the diesel-electric generators at the Air Traffic Control-Belgrade Airport. The types of diesel generating sets are of the 175 KVA No-Break type (no interruption in electricity supply). Diesel generators serve as a backup power source (duplex system) in case of interruption in the regular electricity supply from the city grid for the systems and devices of the Air Traffic Control at Belgrade Airport. One diesel generator is in continuous operation, while the second diesel engine serves as a backup power system. The determined vibrodiagnostic methods for evaluating the technical functioning of diesel generators are an integral part of the documentation for the maintenance and overhaul of the No-Break diesel-generating set.

Prevention of machine strength failures by vibrodiagnostic methods. 2. Study of vibrodiagnostics for preventing failure of certain gas-turbine engine parts and assemblies

Vibrations were measured in the frequency range up to i000 Hz, embracing several harmonics of engagement frequencies. Vibration converters type KD-13 and KD-14 (German Democratic Republic) were placed in areas accessible for installation on the engine body under operating conditions. Measurements were performed during operating schedules. Vibrations were recorded on magnetic tape, and analysis of the magnetic recordings was carried out by means of a harmonic analyzer $5-3. Spectrograms for mean square values of vibrational acceleration were recorded on paper by means of a PSG-101 (German Democratic Republic) self-recorder. For vibration analysis, use was also made of a selective microvoltmeter V6-4, measuring the level

Prevention of machine strength failures by vibrodiagnostic methods. Report 1

Prevention of machine strength failures by vibrodiagnostic methods. Report 1