Vibration Measurements Research Articles

Camera-Based Dynamic Vibration Analysis Using Transformer-Based Model CoTracker and Dynamic Mode Decomposition.

Accelerometers are commonly used to measure vibrations for condition monitoring in mechanical and civil structures; however, their high cost and point-based measurement approach present practical limitations. With rapid advancements in computer vision and deep learning, research into tracking the motion of individual pixels with vision cameras has increased. The recently developed CoTracker, a transformer-based model, has demonstrated excellence in motion tracking, yet its performance in measuring structural vibrations has not been fully explored. This paper investigates the efficacy of the CoTracker model in extracting full-field structural vibrations using cameras. It is initially applied to capture the dense point movements in video sequences of a cantilever beam recorded using a high-speed camera. Subsequently, modal analysis using delay-embedding dynamic mode decomposition (DMD) is conducted to extract modal parameters including natural frequencies, damping ratios, and mode shapes. The results, benchmarked against those from a reference accelerometer and the Finite Element Method (FEM) result, demonstrate CoTracker's high potential for general applicability in structural vibration measurements.

FDS-MOMEDA: optimization-blind deconvolution in finite high-dimensional spaces for extracting pulse signal in rolling bearing fault diagnosis

Rolling bearing fault diagnosis is crucial for ensuring the safe and reliable operation of mechanical equipment. Detecting faults directly from measurement signals is challenging due to severe noise and interference. Blind deconvolution (BD), as a preferred method, effectively recovers periodic pulses from the measured vibration signals of faulty bearings. This study introduces a simulated annealing-based BD approach to enhance the pulse signal components reflecting faults in vibration signals measured on rolling bearings. This method iteratively searches for the optimal coordinates in a high-dimensional orthogonal optimization space, where the optimal coordinates reflect the combination of the inverse filter coefficients. Compared to the generalized spherical optimization space used in the ‘Optimization-Blind Deconvolution’ method in previous works, the proposed finite high-dimensional optimization space helps overcome the problem of inverse filter coefficient convergence, allowing for the design of inverse filters without limit of its shape. To better accommodate the cyclostationarity characteristics of bearing signal measured in reality, the proposed method employs a target vector that allows for uncertainty in pulse occurrence instants, thus overcomes challenges introduced by pseudo-periodic phenomena resulting from bearing slippage. Numerical simulations and experimental results on real bearing vibration signals confirm that the proposed method can design more flexible filters to enhance pulse-like patterns in signals, effectively utilize limited filter resources. Its capacity to tolerate inaccurate fault period estimates, high background noise, and pulse randomness enables it to effectively address vibration measurement signals in real-world scenarios.

Rotational and vibrational temperatures of transient atmospheric glow plasma

Plasma ignition can significantly improve the efficiency and performance of combustion devices through the enhancement of combustibility limits. Investigating plasma development for fundamental experimental flame conditions (i.e. spherical flame experiments) can provide insight into how plasma thermalizes the combustible mixture and, therefore a better understanding of flame development in future experimental studies. This study observed an ignition system designed to produce spherical flames in quiescent gas inside a constant-volume combustion chamber. Rotational and vibrational temperature measurements of dry atmospheric air glow plasma are reported. Measurements were taken for a transient discharge with currents less than 0.5 A. The electrode wire geometry and discharge variation resulted in an ellipsoid-shaped kernel and plasma region with an abnormal glow discharge. The measured temperatures were compared to the conductive thermal kernel boundary observed with Schlieren imaging. Maximum rotational and vibrational temperatures of 3000 K and 10 000 K, respectively, were observed near the anode electrode for a 0.5 A current. The temperature decreased with the axial distance from the anode, while a constant temperature was observed in the radial direction. Lower currents resulted in a smaller temperature, with minimum measured rotational and vibrational temperatures of 1500 K and 5000 K, respectively. The results were compared with available experimental literature and the variation observed was a result of the transient nature, which resulted in hysteresis in temperature vs discharge current measurements.

A Comprehensive Review on Low-Cost MEMS Accelerometers for Vibration Measurement: Types, Novel Designs, Performance Evaluation, and Applications

Maintenance of mechanical elements is considered to be the most crucial task in industry and affects the economics, predominantly. There are many techniques available for fault diagnosis and condition monitoring of rotatory machine elements and one of the popular tools is vibration monitoring. Analyzing vibrations would be useful in supervising equipment/machine components in an attempt to detect the significant change which is the cause of growing failures or faults. Broadly speaking, it comes under prognostics and health monitoring (PHM) and prevents unexpected failure and costly repair. Proficient predictive monitoring and on-board recognition of failures is a need of the Fourth Industrial Revolution. Several types of vibration analyzers and sensors are commercially available, however, their total budget is not affordable. This motivates reviewing the suitability of low-cost sensors for vibration monitoring. An inclusive review of a variety of applications wherein microelectromechanical system (MEMS)-based accelerometer is used is presented in this paper. This would support an open-design movement for creating open.

Radial vibration measurement of rotating shaft using constant density fringe pattern and line scan camera

The radial vibration signals of the rotor can provide abundant information about the health condition of the machine. In this paper, a simple vision-based measurement system is proposed to simultaneously measure two-dimensional displacements in radial directions for the rotating shaft, where the system consists of a constant density fringe pattern (CDFP), a line scan camera (LSC), and a lens. The CDFP should be installed around the surface of the rotating shaft to make the density of the fringe constant along the shaft axis, while the shaft axis is vertical to the optical axis of the LSC but not parallel to the line-array sensor of the LSC. Therefore, the density of the fringe imaged on the LSC is not constant because of the modulation of the circular surface of the shaft, and the distribution of the fringe density on the LSC is a U-shaped curve. Thus, the shaft centreline orbit can be tracked by the lowest point of the density distribution curve (DDC) of the fringe. Then, an efficient and accurate parameterized instantaneous frequency estimation method is employed to estimate the DDC of the fringe, because the variable density fringe can be regarded as an amplitude-modulated and frequency-modulated nonstationary signal whose instantaneous frequency function is equivalent to the DDC. Experimental results verify the feasibility and effectiveness of the proposed method by comparing it to the eddy current sensors.

Interferometric-scale full-field vibration measurement by a combination of digital image correlation and laser vibrometer

Digital Image Correlation (DIC) is a crucial noncontact full-field optical measurement method used in various fields. However, in practical applications, DIC is affected by systematic and random noises, leading to experimental resolutions lower than theoretical ones. In this study, we proposed a laser Doppler vibrometer guided DIC to perform vibration measurements. 3D-DIC obtains a sequence of out of displacement field initially. A three-dimensional frequency domain collaborative filtering (3D-FDCF) method that utilizes Laser Doppler vibrometer (LDV) single-point data to assist in processing of the displacement field sequence pixel-wise is adopted. The 3D-FDCF method combines lowpass filtering in the spatial frequency domain with LDV-guided bandpass filtering in the temporal frequency domain. The effectiveness of the 3D-FDCF method is demonstrated through a comparison among DIC data, the filtered DIC data, and continuously scanning LDV data. The experiment results demonstrate the 3D-FDCF method's capability in measuring vibration amplitudes of several hundred nanometers with the size of a test sample of about 100 mm × 100 mm, supporting the statement of interferometric scale full-field vibration measurement by DIC with the guidance of the LDV data.

Analysis of hot spots and trends in rolling bearing fault diagnosis research based on scientific knowledge mapping

As a key component of mechanical equipment, real-time monitoring and diagnosis of rolling bearings play a critical role in ensuring the stable operation of equipment and the safety of operators. In order to present the current status and trends of fault diagnosis research on rolling bearings more intuitively, the scientific knowledge mapping was used to visualize and analyze the relevant literature in the article. The results show that the number of publications in this area of research has grown significantly in recent years, with China, India, the United States, and England having contributed significantly. The journals such as MECHANICAL SYSTEMS AND SIGNAL PROCESSING, MEASUREMENT, and JOURNAL OF SOUND AND VIBRATION have played an important role in disseminating cutting-edge technologies in this field. In addition, the exploration of modern methods based on data-driven and artificial intelligence, as well as their application to real-world problems, are gradually becoming the focus of research. Through summarising and analysing, the application of modern data processing techniques, the development of more efficient and practical intelligent fault diagnosis techniques, and the close integration of laboratory research and practical applications will become future research trends.

Structural intensity in thin plates and beams under transient and stationary forces using time-resolved, full-field optical slope measurements

Structural intensity, or structure-borne intensity or power flow, was introduced in the 1970s and implemented at that time using contact sensors like accelerometers. Point and contactless measurement methods removed added mass and sensor size constraints. Time-resolved and full-field vibration measurement techniques now open new perspectives for the estimation of structural intensity, but these prospects also come with many challenges. In this work, we study the applicability of optical deflectometry measurements to calculate the structural intensity in thin plates or beams under transient and stationary loadings. Since deflectometry directly provides slope fields, a slope formulation of structural intensity is proposed and evaluated. The effect of various parameters like frame rate (sampling frequency) and spatial resolution is studied from a numerical point of view on a simply-supported plate. Experimental results are then presented on a simply-supported plate and on a cantilever beam. Numerical and experimental results allow identifying the main challenges related to the implementation of structure intensity estimation using full-field and time-resolved data.

Influence of Subsoil and Building Material Properties on Mine-Induced Soil–Structure Interaction Effect

Soil–structure interaction (SSI) refers to the dynamic interaction between a structure and the surrounding soil on which it rests. The behavior of the soil can significantly affect the response of the building structure. In the context of civil engineering and structural analysis, SSI becomes particularly important when considering the response of structures to dynamic loads such as earthquakes or so-called paraseismic loads, e.g., mining tremors. Several factors contribute to SSI. Soil and building structure material properties, foundation type, and loading conditions are the most important parameters. The article concerns SSI in the case of mining rock bursts in Poland. The influence of changes in site material conditions and building material properties on the SSI phenomenon was investigated. A few variants of different properties of typical construction materials (brick, reinforced concrete, and cellular concrete) in the case of selected representative building structure were considered. The subsoil material properties from the wide range were also taken into account. Numerical three-dimensional finite element method (FEM) analysis was applied. The adopted models of the soil-structure system were verified by data from in situ experimental vibration measurements. A significant influence of the subgrade material and the building structure material on the SSI was demonstrated.

In-situ measurement of subway train-induced vibration and noise of steel spring floating slab with MEMS-based sensing units

The concrete floating slab, as a widely-used measure to reduce the subway-induced vibration and noise, can deteriorate with the accumulation of trainload. To monitor the dynamic performance of the floating slab during operation, this study develops a lightweight sensing unit based on microelectromechanical systems (MEMS). This sensing unit, which can be easily mounted on the concrete slab, enables synchronous monitoring of vibration and noise at different sampling frequencies with a very low power consumption. With the advantage of easy installation, the sensing units are mounted on various concrete slabs and tunnel walls to collect massive vibration and noise data. With the monitoring data, the dynamic performance and vibration reduction capability of the floating slab can be assessed. A case study is conducted on two floating slab sections: one section has a floating slab with a potential defect on its shear hinge and the other has a normal floating slab. The monitoring results show that: (1) the train condition has a significant effect on the amplitude of the track-side vibration; (2) the train-induced noise data last longer than vibration data during the passage of trains; (3) for the floating slab with shear hinge defect, the vibration levels at edge points are much higher than that in the middle. Through the monitoring test, the performance of the MEMS-based sensing unit and its adaptability in subway circumstances are verified.

High-Pressure Polymorphism in Silver Ferrite Delafossite, AgFeO2.

The delafossites are a class of layered metal oxides that are notable for being able to exhibit optical transparency alongside an in-plane electrical conductivity, making them promising platforms for the development of transparent conductive oxides. Pressure-induced polymorphism offers a direct method for altering the electrical and optical properties in this class, and although the copper delafossites have been studied extensively under pressure, the silver delafossites remain only partially studied. We report two new high-pressure polymorphs of silver ferrite delafossite, AgFeO2, that are stabilized above ∼6 and ∼14 GPa. In situ X-ray diffraction and vibrational spectroscopy measurements are used to examine the structural changes across the two phase transitions. The high-pressure structure between 6 and 14 GPa is assigned as a monoclinic C2/c structure that is analogous to the high-pressure phase reported for AgGaO2. Nuclear resonant forward scattering reveals no change in the spin state or valence state at the Fe3+ site up to 15.3(5) GPa.

Determination of Optimal Machining Parameters Based on Roughness and Vibration Measurements of Pieces Produced by Whirling on a Lathe Machine

Worms can be produced using special machines or standard lathes equipped with a whirling thread-cutting device. A blank is placed on the mandrel and tightened using the three-jawed chuck of the standard lathe. If the workpiece diameter is excessively large, passage through the driven pulley is not possible, and the workpiece cannot be supported. Therefore, a new tool holder for whirling devices is needed. During the whirling process, vibrations in the form of machine velocity amplitudes were measured. After whirling was complete, roughness values were calculated. Using numerical procedures of Wolfram Mathematica 10, vibration peaks were extracted, from which frequencies and maximum amplitudes were determined. The data were then inputted into Design Expert, and the rotational speed and amount of separated material were optimized. The results of the study showed that the quality of the processed surface did not improve with processing in two passes of the tool. The measured vibration amplitudes on the lathe carrier and thread whirling attachment increased with cutting speed at the same cutting depth, whereas the quality of the machined surface was best at the smallest and largest cutting depths.

Sound pressure level determination around the transformer using coherent and incoherent analytical summation methods

In this paper, coherent and incoherent analytical summation methods from elementary sound sources on the transformer’s tank are presented. They aim to determine a one-third-octave spectrum of sound pressure levels (SPL) in points around the transformer. Each part of the transformer’s surface is treated as a separate plane source so the analytical calculation can be applied to find SPL in the surroundings. Reflections from the ground are also considered by putting an image of the plane sources on the other side of the reflecting plane and adding its contributions to the total pressure in the desired points. Grid-like vibration measurements of vibration velocity on the tank surfaces are used as input parameters. Vibrations and sound pressure levels are measured to validate the method on the 5 MVA transformer experimental object. The SPL around the transformer in short-circuit (SC) and open-circuit (OC) tests is measured in the semi-anechoic chamber to compare it with theoretical results. By analyzing the results, the coherent calculation with reflection provided the most accurate results. In the SC operating condition, the normalized root mean square error (NRMSE) is 17.2%, and in the OC operating condition, it is 10.9%. The novelty of the presented method is that it considers complicated transformer geometry where each surface is calculated as a separate noise source. It calculates noise at a distance from the elementary vibration sources, considering phase and reflection from the hard ground, and provides detailed noise maps that can be used for noise modeling around the substations.

Field measurement of track vibration induced by full-load and empty-load condition in curve section of underground metro line

In order to compare the differences in vibration before and after wheel re-profiling and assess the vibration impact of train under full-load and empty-load condition, the field vibration measurement was conducted on an underground metro track components (including rail, sleeper, and track-bed) by using a specific testing car. The results indicate that wheel re-profiling is effective in reducing track vibration, within the frequency range of 31.5–1250 Hz, the vibration acceleration levels of the track after wheel re-profiling were notably lower than those prior to re-profiling and the vibration acceleration levels of the rail, sleeper, and track-bed decrease by 4.7 dB, 6.6 dB, and 6.7 dB, respectively. In the frequency domain, the characteristic peak frequencies of the three track components, whether under full load or empty load, align closely with the frequencies associated with track irregularities. Full-load condition primarily affects the vibration acceleration at lower frequencies, with minor influence on higher frequencies. The vibration acceleration levels of all three track components are higher under full load than empty load. Additionally, under full-load condition, the transmission loss from the rail to the sleeper increases, while the transmission loss from the sleeper to the ballast remains nearly constant. The results of vibration acceleration levels obtained from routine vehicle operations validate the limited impact of axle load on track components vibration.

Underwater radiated noise from small craft in shallow water: Effects of speed and running attitude

Underwater radiated noise from marine vessels is a growing problem, with a large body of evidence now showing the detrimental impact this is having on marine life. Whilst most of the discussion currently focusses on the impact of large vessels, recent evidence shows that small vessels can dominate the soundscape in shallow coastal waters. In this study, acoustic trials are carried out on two small vessels: a pilot boat and a rigid inflatable boat (RIB) across a wide speed range. The average source levels range from 156–173 dB for the pilot boat and 164–166 dB for the RIB (re1μPam). The engine noise is dominant for the RIB across the speed range, and it is further shown that the heading relative to the prevailing waves is a bigger determining factor for noise levels than speed. In upper sea state 3, the overall sound level is up to 6 dB higher when in head waves compared to following waves. Acoustic measurements are combined with onboard vibration measurements to provide further insights into the relationship between noise and vibration. Analysis of this data shows the vessel running attitude plays a key role in determining how much noise is transmitted into the water.

A novel mirror-assisted method for full-field vibration measurement of a hollow cylinder using a three-dimensional continuously scanning laser Doppler vibrometer system

A novel general-purpose three-dimensional (3D) continuously scanning laser Doppler vibrometer (CSLDV) system was recently developed by the authors to measure 3D vibration of a structure with a curved surface. As a non-contact system, it can avoid the mass-loading problem in 3D vibration measurement using triaxial accelerometers. In previous studies, the 3D CSLDV system was used to measure 3D full-field vibration of a turbine blade with a curved surface and identify its operating deflection shapes (ODSs) and mode shapes. The 3D CSLDV system had the same level of accuracy as that with a commercial 3D scanning laser Doppler vibrometer system, but can measure many more points in much less time than the latter. However, the 3D CSLDV system can be limited by its field of view, which is a common problem for optical-based measurement devices. Moving the 3D CSLDV system to different positions to measure different parts of a test structure is not practical during 3D CSLDV measurement, since the system has to be re-calibrated once it has been moved, which can be time-consuming and introduce measurement errors. This work proposes a novel mirror-assisted testing methodology for 3D CSLDV measurement that aims to measure vibration of difficult-to-access areas of a structure without moving the 3D CSLDV system during the test, and stitch ODSs of its different parts together to obtain its panoramic 3D ODSs. The proposed methodology includes a novel scan trajectory design method that uses virtual areas of the structure behind the mirror to conduct continuous and synchronous scanning of three laser spots, and a novel velocity transformation method that uses virtual positions of three laser heads behind the mirror to stitch ODSs of different parts of the structure together. To demonstrate the proposed methodology, 3D CSLDV measurement is conducted on an aluminum hollow cylinder specimen, which has difficult-to-access areas such as its side and back surfaces, with the assistance of the mirror to obtain its panoramic 3D ODSs corresponding to its first two modes. Comparison between identified ODSs of the hollow cylinder specimen from the experiment and mode shapes from its finite element model is made and modal assurance criterion values are larger than 0.98.

Low-frequency vibration measurements in harsh environments using a frequency-modulated interferometer

Low-frequency vibration measurements in harsh environments are considerably challenging owing to strong background noise. In this study, a simple, high-dynamic-range, and high-precision vibration-measuring system using a frequency-modulated interferometer was proposed and validated. Harmonics with perfectly orthogonal phases were extracted directly from the interference signal, and noise with random frequencies was filtered using a synchronous detection method. The modulation index of the interferometer was controlled to remove the effect of Bessel functions; hence, a full-circle Lissajous diagram was obtained. The ratio of the two harmonics was used to determine the vibration; hence, the effects of intensity fluctuation and background noise can be neglected. The vibration measurement bandwidth was well controlled by controlling the modulation and cutoff frequencies of the bandpass filters. The best noise level of 1 nm/√Hz under harsh measuring conditions can be archived in the low-frequency range.

Numerical simulation and experimental analysis of foreign object impact on aero-engine fan rotor blade

The detection and identification of fan rotor foreign object impact events during the working process of aero-engines are crucial to the safety and security of aircraft flight. Through the numerical simulation method based on finite element and the foreign object impact test platform to simulate the process of real engine impact by foreign objects, the rule of fan rotor blade foreign object impact and the monitoring and identification method were studied. Meanwhile, aiming at the problems of high difficulty and low accuracy in identifying the impact of foreign objects on the fan by the airborne parameters and added vibration parameters, the non-contact vibration measurement method based on blade tip timing was used to obtain the blade vibration displacement under different fan speed, foreign matter mass and impact velocity. The numerical simulation and experimental results show that the change trend of the vibration displacement of the rotor tip of the fan is consistent with that of the numerical simulation. And with the increase of the foreign object projectile mass, the vibration displacement of the blade tip caused by the impact of the foreign object on the fan blade increases. In addition, the impact velocity of the foreign object has little effect on the vibration displacement of the blade tips after impact. Furthermore, the vibration displacement of the blade tip caused by the impact of foreign objects first increases and then decreases with increasing speed.

Research on bearing fault diagnosis based on laser vibrometer

As general components in machinery, rolling bearings are also fault prone components. And unexpected faults will bring immeasurable loss to economy, personnel, etc. Therefore, fault detection and diagnosis are of paramount importance. As the carrier of fault information, component response signal is the most concerned part in fault diagnosis researches. The detection methods for response signal can be divided into contact and non-contact detection. Compared with the contact detection, laser Doppler vibrometer has the advantage of no contact, no damage and dynamic measurement. Thus, this paper progresses theoretical and experimental researches on non-contact detection of bearing wear fault based on laser Doppler vibrometer. Firstly, the vibration measurement principle of laser Doppler vibrometer is analyzed in this paper. On account of the principle, the internal optical path and signal flow of the single point laser vibrometer is established and analyzed. Secondly, in order to carry out the non-contact detection test, an optical measuring system based on a single point laser vibrometer is built to collect signals. Also, a bearing wear fault simulated test rig is built to provide fault response signals. Based on the above built test devices, the detection tests of the intact and faulty bearings are carried out. Lastly, through the analysis of collected signals of bearings with wear of different parts in time domain and frequency domain, the characterizations of the corresponding fault are obtained so as to implement the fault diagnosis, which prove the effectiveness of laser vibration detection method for fault detection.

Hand-Arm-Vibrationsdosis und arbeitstechnische Voraussetzungen für die Berufskrankheit Nr. 2103 – Eine epidemiologische Fall-Kontroll-Studie

Hand-arm vibration dose and work-related requirements for occupational disease no. 2103 – An epidemiological case-control study Background: An epidemiological case-control study of dose-effect relationships between hand-arm vibration exposure and musculoskeletal disorders of occupational disease no. 2103 (BK 2103) was carried out in order to provide evidence-based recommendations for the recognition of BK 2103. Methods: Male cases and controls were recruited and standardised personal interviews were conducted between 1 January 2010 and 30 November 2021. In addition to leisure activities and comorbidities, work histories regarding the use of hand-operated and hand-held technical tools that can induce hand-arm vibrations were recorded in detail. To quantify the individual vibration exposure, a database of industrial hygiene measurements of vibration values of over 700 technical power tools was established (vibration register). The vibration measurements recorded in the database allows quantification of the daily dose and lifetime dose of the vibration exposure. The dose-effect relationships between hand-arm vibration exposure and musculoskeletal disorders as defined by BK 2103 were quantified for the various dose models using conditional logistic regression analyses. Results: In total, 209 cases and 614 controls were recruited. Compared to controls, cases suffered more frequently from gout, arm fractures, hip osteoarthritis, knee osteoarthritis, spinal osteoarthritis and trauma injuries or inflammatory conditions of the finger, elbow and shoulder joints. After adjusting for relevant confounders, the study analyses demonstrate consistent and statistically significant dose-effect relationships between hand-arm vibration exposure and musculoskeletal disorders as defined by BK 2103. A vibration dose of Dhv = 142.331 m2/s4 x day or Dhw = 38.724 m2/s4 x day is associated with a doubling of the risk of musculoskeletal disorders of the upper extremities as defined by BK 2103. Conclusions: These dose values serve as a guide and could also be applied in an assessment of the work-related requirements for the recognition of BK 2103. Sensitivity analyses indicate that an exposure duration with a defined threshold daily dose is not suitable for guiding the recognition of BK 2103. Keywords: hand-arm vibration – musculoskeletal disorders – dose-effect relationship – epidemiology – risk-doubling dose