SPECTRAL and FOCAL PARAMETERS of NORTHERN CAUCASUS EARTHQUAKES in 2015

The dynamic sources parameters of 29 earthquakes of the North Caucasus for 2015 with KR=9.5–11.4, determined from 38 S-wave amplitude spectra are analyzed. Records of four regional digital seismic stations, “Anapa”, “Kislovodsk”, “Makhachkala” and “Sochi”, located no more than 300 km from the sources are used. For the environment near these stations, the values of the frequency-dependent Q-factor, necessary for recalculating the station spectra to the focal ones. In 2015, the majority of earthquakes studied were located in the Eastern Caucasus. The dependence between log M0 and KR for this zone was constructed using together with the data for 2010–2014.

SOURCE PARAMETERS of CRIMEAN-BLACK SEA EARTHQUAKES in 2015

The spectral and dynamic source parameters (М0, r0, , , ησ, , u, Eu and Mw) of 16 Crimean earthquakes with КП=6.5–10.8, restored by amplitude spectra of compression and shear seismic waves recorded by digital regional seismic stations are analyzed. Approximation of the spectra and source parameters calculation is performed in the framework of the Brune dislocation model. The highest values of dynamic parameters (М0, r0, , , ησ, u, EU и Mw) are obtained for the earthquakes on June 13 and August 16 with h=11 km, h=7 km respectively and КП=10.8, which occurred in the Azov-Kuban and Kerch-Anapa areas. The radiation friction r for all earthquakes had a negative value, pointing to a complex slide of the rupture in the source. Within the whole energy range, the average value of the released stress did not exceed Δσ=8∙105 PA (8 bar) and apparent stress ησ <11∙105 PA (11 bar). For most 2015 earthquakes, the average M0 и r0 values were within the confidence intervals of long-term dependencies M0(КП), r0(КП). The values of r0 were evenly distributed concerning the regression r0(КП) and М0 is mostly located below the average according to М0 (КП). The maximum deviations of M0 from the long-term М0(КП) dependence were obtained for the most strong earthquakes on June 13 and August 16 with КП=10.8. These deviations can be associated with participation in average M0 of the "Sevastopol" station data which give low values of М0 and possible errors in determining the focal depths influencing the choice of environment velocity models to calculate М0. For the most strong earthquake of August 16 with Мw=3.8, which occurred in the Kerch-Anapa region, a solution of focal mechanism was obtained. The earthquake occurred under the action of horizontal latitudinal tensile forces. The type of movement in the source is an oblique normal fault. Both nodal planes have near-meridional (STKNP1=167°) and near-diagonal (STKNP2=336°) strike.

THE SEPTEMBER 2, 2015, КR=14.0, Mw=5.1, I0=7–8 TALLAY EARTHQUAKE at the NORTH-EASTERN FLANK of the BAIKAL RIFT

We consider September 2, 2015, Mw=5.1 Tallay earthquake occurred in the previously aseismic area of the North-Muya Ridge adjoining to the Muya-Kuanda basin from the north. Instrumental and macroseismic data on this seismic event are presented. Its seismic moment tensor is calculated from surface wave amplitude spectra. New data on strong ground motions are obtained within the north-eastern flank of the Baikal rift. The Tallay earthquake is found to be connected with seismogenic renewal of the second-order multidirectional faults activated in the rift stress field.

An algorithm to calibrate analytical models of multi-story buildings from vibration records

The common approach to develop analytical models of multi-story buildings from their vibration records is to match the modal properties identified from the records. However, the models developed by matching only the modal properties do not necessarily represent the real structure. In other words, more than one model can match the recorded motions. Moreover, modal properties do not give information on the distribution of stiffness and damping along the height of the building. In this study, an algorithm is developed to identify the dynamic characteristics of each story of multi-story buildings using the transfer-matrix formulation of the response. The building is considered as the superposition of 1-story structures, put one on top of the other. Starting from the top story and going downward, each story’s natural frequency and damping ratio are identified as it were a 1-story building. A key requirement for this approach is to have vibration records from every story. Since this is not typically the case, we utilize the so-called Mode Shape-Based Estimation (MSBE) method to estimate the vibration time histories at non-instrumented floors. Once vibration records are available at every floor, and starting from the top story, we can calculate the individual frequency and damping ratio of each story (i.e. as if it were a 1-story building) by minimizing the error between the recorded and estimated Fourier amplitude spectra (FAS) of the vibration records in that story. The analytical models calibrated in this way are more accurate, and the system identified is unique. Numerical examples are provided to show the application of the methodology.

Methods of Hidden Periodicity Discovering for Gearbox Fault Detection

It is shown that the models of gear pair vibration, proposed in literature, are particular cases of the bi-periodically correlated random processes (BPCRPs), which describe its stochastic recurrence with two periods. The possibility of vibration and analysis within the framework of BPCRP approximation, in the form of periodically correlated random processes (PCRPs), is grounded and the implementation of vibration processing procedures using PCRP techniques, which are worked out by the authors, is given. Searching for hidden periodicities of the first and the second orders was considered as the main issue of this approach. The estimation of the non-stationary period (basic frequency) allowed us to carry out a detailed analysis of the deterministic part, the covariance structure of the stochastic part, and to form, using their parameters, the sensitive indicators for fault detection. The results of the processing of the wind turbine gearbox vibration signals are presented. The amplitude spectra of the deterministic oscillations and the time changes of the stochastic part power for different fault stages are analyzed. The most efficient indicators, which are formed using the amplitude spectra for practical applications, are proposed. The presented approach was compared with known in literature cyclostationary analysis and envelope techniques, and its advantages are shown.

An Improved Method of Minimizing Tool Vibration during Boring Holes in Large-Size Structures

The paper presents a thoroughly modified method of solving the problem of vibration suppression when boring large-diameter holes in large-size workpieces. A new approach of adjusting the rotational speed of a boring tool is proposed which concerns the selection of the spindle speed in accordance with the results of the simulation of the cutting process. This streamlined method focuses on phenomenological aspects and involves the identification of a Finite Element Model (FEM) of a rotating boring tool only and validating it with a real object, while dispensing with discrete modelling of a completely rigid workpiece. In addition, vibrations in the boring process in all directions were observed, which implies a geometric nonlinearity of the process model. During the simulation, the values of the Root Mean Square (RMS) of the time plots and the dominant values of the “peaks” in the displacement amplitude spectra were obtained. The effectiveness of the method was demonstrated using a selected mechatronic design technique called Experiment-Aided Virtual Prototyping (E-AVP). It was successfully verified by measuring the roughness of the indicated zone of the workpiece surface. The economic profitability of implementing the method in the production practice of enterprises dealing with mechanical processing is also demonstrated.

Determination of the state and functioning of the equipment of rod well pumping units in the operation process by the parameters of the wattmetrogram

TARGET. The purpose of this work is to develop a method for diagnostics of equipment of sucker rod pumping units (SRPU) during operation according to the parameters of the wattmetrogram. A wattmetering module is used as a measuring element, the developed software in the MatLab software package serves as a tool for processing vibration signals. The technical condition of the sucker rod pumping unit is analyzed by the parameters of the wattmetrogram and the amplitude spectra of the object under study, formed using the fast Fourier transform procedure in the MatLab software environment.METHODS. The wattmetering method allows you to control the sucker rod-pumping unit during its operation under voltage. This control method is highly accurate, sensitive to developing defects, and allows the use of computer technologies for signal processing and analysis.RESULTS. The wattmetering method is fully disclosed. The construction of the spectrum is considered. The relationship between the wattmetrogram and the dynamogram has been established. The removal and evaluation of experimental data from the operating sucker-rod pumping unit during its operation was carried out. A wattmetrogram and a dynamogram were built, a spectrum was also built, which showed the presence of defects in this installation.CONCLUSION. This method of wattmetering with the MatLab software allows you to monitor the technical condition of the sucker rod pumping unit according to the amplitude-frequency characteristics of the wattmetrogram parameters.

Contactless laser control and measuring complex for determining the level of winding pressure and magnetic conductor of power transformer

TARGET. The purpose of this work is to develop a non-contact laser control and measuring complex (LCMC) for vibration control of the level of pressing of windings and magnetic circuit of a power transformer. A laser vibrometer is used as a measuring element, the developed software in the LabVIEW graphical programming environment serves as a tool for processing vibration signals. The technical condition of the power transformer is analyzed by the amplitude spectra of the vibration of the tank of the transformer under study, formed using the fast Fourier transform algorithm in the LabVIEW software.METHODS. The vibration control method makes it possible to control a power transformer during its operation under voltage, which makes it possible to move from a planned system of transformer repairs to a system for taking out for repair according to the current technical condition.RESULTS. The developed LCMC allows to carry out non-contact measurements of vibration parameters of a power transformer under voltage and to establish the current level of pressing of windings and magnetic circuit.CONCLUSION. The developed LCMC with software allows contactless control of the technical condition of the magnetic circuit and the windings of the power transformer according to the amplitude-frequency characteristics of the vibration parameters, as well as the use of statistical methods for processing and analyzing signals received from the transformer.

Contactless laser control and measuring complex for determining the level of winding pressure and magnetic conductor of power transformer

TARGET. The purpose of this work is to develop a non-contact laser control and measuring complex (LCMC) for vibration control of the level of pressing of windings and magnetic circuit of a power transformer. A laser vibrometer is used as a measuring element, the developed software in the LabVIEW graphical programming environment serves as a tool for processing vibration signals. The technical condition of the power transformer is analyzed by the amplitude spectra of the vibration of the tank of the transformer under study, formed using the fast Fourier transform algorithm in the LabVIEW software.METHODS. The vibration control method makes it possible to control a power transformer during its operation under voltage, which makes it possible to move from a planned system of transformer repairs to a system for taking out for repair according to the current technical condition.RESULTS. The developed LCMC allows to carry out non-contact measurements of vibration parameters of a power transformer under voltage and to establish the current level of pressing of windings and magnetic circuit.CONCLUSION. The developed LCMC with software allows contactless control of the technical condition of the magnetic circuit and the windings of the power transformer according to the amplitude-frequency characteristics of the vibration parameters, as well as the use of statistical methods for processing and analyzing signals received from the transformer.