Vibration Measurements Research Articles

Study on vibration response and isolation of substation structure under subway load excitation

This study takes the indoor substation adjacent to the elevated bridge subway line as the engineering background, investigates the structural vibration response law of the substation induced by the operation of the subway line through on-site vibration measurement, and proposes a novel nonlinear gas-spring quasi-zero stiffness isolator (NGS-QZSI) is proposed to reduce the structural vertical vibration and further reduce the safety distance. The software ABAQUS is used to establish a structure-equipment coupling numerical analysis model considering soil-structure interaction, and its effectiveness and accuracy are validated based on the measured results. The structural vibration response analysis is carried out under different vibration source distances, and a nonlinear gas-spring quasi-zero stiffness isolator is proposed to be employed for substation structural vibration isolation. The research results show that the substation structure under subway load excitation is dominated by vertical vibration, and its vibration response increases gradually with the increase of floor level. When the substation structure is less than 45 m from the subway line, the structural response exceeds the safety limit (12.5 μm/s) of the VC-C standard. With the vibration isolator attached, the structural vibration response is significantly reduced, with the peak and root mean square response controlled by more than 70 %. Particularly, the safe distance of the substation from the subway line is reduced from 45 m to 20 m. Moreover, the frequency domain result analysis indicates that the proposed nonlinear vibration isolator can effectively control the low-frequency vibration of the structure.

DInSAR–SBAS satellite monitoring of infrastructures: how temperature affects the “Ponte della Musica” case study

Continuous monitoring of the structural health of strategic structures and transport infrastructures plays a crucial role in providing an effective assessment of the safety conditions and in timely planning of the ordinary and extraordinary maintenance programme. Deformation monitoring and dynamic characteristic identification are some commonly used strategies for this purpose. One of the main challenges of recent years in the field of structural health monitoring is the use of data deriving from satellite interferometry, capable of providing information on structural deformations at a local and territorial scale. Despite the solidity and dependability of satellite-based methods for assessing ground deformation over time, when it comes to structural surveillance, there are certain circumstances under which satellites are incapable of accurately assessing displacements. This is particularly true for structures that are sensitive to temperature variations. The paper uses the “Ponte della Musica–Armando Trovajoli” in Rome as a case study to explore these aspects in more depth. This bridge has a steel arch structure with a prestressed concrete deck below it. It represents an example in which satellite differential interferometry does not allow obtaining useful information on displacement, at least for the most deformable portion of the deck, and therefore also on any pathological movements. This work proposes a 3D digital twin of the bridge, appropriately calibrated through experimental measurements of the environmental vibrations performed on the bridge. This will allow to evaluate the role played by thermal deformations related to air temperature variations and thus better understand the connection between physiological deformations and satellite limits.

Fast and accurate visual vibration measurement via derivative-enhanced phase-based optical flow

Visual vibration measurement using a digital camera is an emerging non-contact modality capable of enabling flexibility, high spatial resolution, and full field. However, the massive amounts of video data with vibration information (thousands of time-lapse images per measurement) to be handled lead to an actual bottleneck. This prevents the system from extracting the vibration information with high speed and fidelity. Here, a straightforward phase-based optical flow approach is proposed by introducing a derivative operation to perform vibration measurements in a more accurate and efficient manner, in contrast to the state-of-the-art phase-based visual method. This approach generates analytical signals by considering each raw gray image as the real part and its first-order derivative as the imaginary part. As a result, the physical vibration can be extracted from the phase variations of the analytical signals from one to the next. Numerical simulations and experiments are conducted to validate the effectiveness and accuracy of this simple but powerful approach. The results indicate that the proposed approach provides a significantly higher speed than current methods and a correlation coefficient of 99.2 % with the identification results.

Building Vibration Measurement and Prediction during Train Operations

Urban societies face the challenge of working and living in environments filled with vibration caused by transportation systems. This paper conducted field measurements to obtain the characteristics of vibration transmission from soil to building foundations and within building floors. Subsequently, a prediction method was developed to anticipate building vibrations by considering the soil and structure interaction. The rigid foundation model was simplified into a foundation–soil system connected via spring damping, and the building model is based on axial wave transmission within the columns and attached floors. Building vibrations were in response to measured input vibration levels at the ground and were validated through field measurements. The influence of different building heights on soil and structure vibration propagation was studied. The results showed that the predicted vibrations match well with the measured vibrations. The proposed prediction model can reasonably predict the building vibration caused by train operations. The closed-form method is an efficient tool for predicting floor vibrations prior to construction.

A Theoretical Methodology and Measurement of Dynamic Characteristics of Wind Turbines with Composite Bucket Foundations

A composite bucket foundation (CBF) is a new type of supporting structure in offshore wind engineering. Its huge transition part is the key difference compared to other offshore foundations. Firstly, the vibration measurement system of a wind turbine with the CBF is introduced. A finite element method (FEM) was developed, and the rigid deformation performance of the transition part was characterized. Then, to clarify the influence of the transition part brings to wind turbines with CBFs, a three-DOF theoretical model was established by simplifying the transition part as a rigid body. Horizontal and rotational foundation stiffness were considered to present the constraint effect below the mudline. Sensitivity studies were conducted on the parameters (including mass, moment of inertia and mass center height) of the transition part. Further, the vibration properties of the CBF structures under different operation load conditions were compared through the theoretical model and the in situ data. The results show that the relative errors between the theoretical model and FEM model are 3.78% to 5.03%, satisfying the accuracy requirements. The parameters of the transition part have varying degrees of influence on the natural frequency, foundation stiffness and vibration response of the wind turbines with CBFs. Compared to wind and 1P loads, the 3P load has a greater influence if the 3P frequency is close to the natural frequency of the wind turbine.

Exposure–response relationship between work-related hand–arm vibration exposure and musculoskeletal disorders of the upper extremities: the German hand–arm vibration study

ABSTRACT Objective. To quantify the exposure–response relationship between hand–arm vibration exposure and the risk of musculoskeletal disorders of the upper extremities (UMSDs), a case–control study was carried out among workers in the construction, mining, metal and woodworking industries. Methods. In total, 209 male cases and 614 controls were recruited. Cases were newly reported patients with UMSDs. Controls were a random sample of persons with compensable occupational injuries. Standardized personal interviews were performed among cases and controls by well-trained safety engineers. In addition to leisure activities and comorbidities, work histories of all participants were collected in detail. To quantify hand–arm vibration exposures, a database of vibration measurements of over 700 power tools was used. This database allows the detailed quantification of vibration exposures over time. A dose–response relationship between hand–arm vibration exposure and UMSDs was quantified by conditional logistic regression analyses. Results and conclusions. After adjusting for relevant confounders, statistically significant exposure–response relationships between cumulative hand–arm vibration exposure and UMSDs were established. A cumulative hand–arm vibration exposure of D hv (vibration total value in three measuring directions) = 142,300 (95% confidence interval [CI] [90,600–333,200]) m2/s4·day or D hw (vibration value in the direction along the forearm) = 38,700 (95% CI [25,400–80,900]) m2/s4·day is associated with a doubled risk of UMSDs.

Vibration and impact sound properties of hybrid steel-timber floor structures

Lightweight floor structures, such as timber or hybrid timber floors, face challenges associated with excessive vibrations and elevated levels of low-frequency impact sound. Especially here, accurate prediction of a floor’s vibration and acoustic behavior is essential. However, typical laboratory testing of building elements is costly and time-consuming. To reduce costs, in this study, adapted simulations are carried out on two types of hybrid steel-timber floor structures to evaluate vibrations and impact sound. The hybrid elements are made of laminated veneer lumber as the top and bottom layers and a trapezoidal steel component as the web. Vibration measurements are used in combination with Bayesian optimization to efficiently calibrate Finite Element models, which are subsequently utilized to quantify and validate the floor structures regarding vibrations and impact sound. The two types of cross-sections, i.e., closed and open, are investigated and compared. The impact sound pressure level computations reveal promising results in predicting the behavior of the hybrid structures. However, further countermeasures are required to fulfill vibration serviceability requirements.

Measurements of flow-induced vibration of a flexible splitter plate mounted on a cylinder in free stream flow

We experimentally study flow-induced vibration (FIV) of a thin, cantilevered, flexible plate attached on the lee side of a circular cylinder in a free stream airflow. The Reynolds number (ReD) based on the diameter of the cylinder was varied in the range of (4 × 103, 5×104). The plates of different lengths and the same span were tested with varying airflow velocities (U) in a wind tunnel. The reduced velocity (UR) based on the length and the second natural frequency of the plate was in the range of (1, 11). We describe the plate dynamics showing displacement, frequency, phase plane, amplitude spectral density (ASD), oscillation envelope, modal energy contribution, and flow structures. Based on the motion of the plate, three FIV regimes are observed, namely, initial excitation, transition, and lock-in. During lock-in, the plate attains self-sustained limit cycle oscillation. We observe the presence of small-amplitude higher harmonics in the ASD plot. The second mode is dominant around the onset of lock-in, while the first mode is dominant later in the lock-in regime. The dimensionless displacement increases with an increase in mass ratio (Ms) in the lock-in regime. With a decrease in Ms, the slope of the dimensionless frequency with UR increases. To explain measurements, we develop a wake oscillator model (WOM) in which the plate and fluctuating lift force are modeled as an Euler–Bernoulli cantilever beam and van der Pol oscillator, respectively. The coupled WOM qualitatively and quantitatively predict the measured amplitude and frequency response, respectively, in the lock-in regime.

Design and Prototyping of a Combined Sensor for Vibration and Temperature Measurement in High-Temperature Environments

Design and Prototyping of a Combined Sensor for Vibration and Temperature Measurement in High-Temperature Environments

Unraveling the solvent stability on the cathode surface of Li-O2 batteries by using in situ vibrational spectroscopies.

In aprotic lithium-oxygen (Li-O2) batteries, solvent properties are crucial in the charge/discharge processes. Therefore, a thorough understanding of the solvent stability at the cathode surface during the oxygen reduction/evolution reactions (ORR/OER) is essential for the rational design of high-performance electrolytes. In this study, the stability of typical solvents, a series of glyme solvents with different chain lengths, has been investigated during the ORR/OER by in situ vibrational spectroscopy measurements of sum frequency generation (SFG) spectroscopy and infrared reflection absorption spectroscopy (IRRAS). The structural evolution and decomposition mechanism of the solvents during ORR/OER have been discussed based on the observations. Our results demonstrate that superoxide (O2-) generated during the ORR plays a critical role in the stability of the solvents.

Chirp Noise Analysis in Laser Doppler Vibration Measurement and Its Suppression Methods

Chirp Noise Analysis in Laser Doppler Vibration Measurement and Its Suppression Methods

Non-coincidence detection of fiber optic circulators based on Hertz-level frequency-shifting heterodyne interferometry

The fiber optic circulator in the form of point diffraction is a key component for coupling fiber optical path and spatial optical path in a laser Doppler vibration measurement system. The coupling efficiency and other performance parameters of fiber optic circulator are great significant for improving measurement accuracy and working distance of vibration measurement system. The conventional circulator coincidence detection methods include energy monitoring method and far-field coincidence monitoring method, which cannot be used to quantitatively analyze the fiber mismatch factors. Therefore, the consistency of the circulator coupling efficiency cannot be guaranteed. To solve these problems, a phase detection technology based on Hertz-level frequency-shifting heterodyne interferometry is proposed. The interferometry phase information is used to calculate the relative spatial positions of optical fibers, and this technology performs quantitative detection in the fiber alignment process. The interference wavefront formed by relative spatial positions of optical fibers is simulated and validated experimentally. The curves of coupling efficiency and wavefront PV value versus different kinds of alignment errors are simulated and analyzed. By fitting the interference wavefront with the Zernike polynomials, the correspondence between different kinds of alignment errors and Zernike coefficients is obtained. The value of Z2 (Zernike coefficient) can be used as the basis for judging whether there is transverse displacement in the Y direction. Similarly, Z3 corresponds to the transverse displacement in the X direction, Z4 corresponds to the longitudinal displacement in the Z direction and Z5 corresponds to the optical axis angle. Through this correspondence relationship, the quantitative separation and analysis of fiber mismatch factors are realized. The experimental results show that the accuracy of this method for measuring lateral displacement is better than 1μm. According to the phase diagram obtained from the experiment, Zernike coefficient fitting is performed. The lateral displacement deviation, longitudinal displacement deviation, and angular deviation are calculated by the coefficients of Z2 to Z5. The fiber adjustment mechanism corrects the transverse displacement deviation. It provides a new detection method for realizing fiber alignment and mismatch correction. Compared with the existing detection methods, the phase detection method based on Hertz-level frequency-shifting heterodyne interferometry solves the quantification problem of fiber coincidence adjustment. This method has the advantages of high measurement accuracy, compact detection structure and composition, and low detection cost. This method has great potential applications in the fields of optical fiber and spatial optical device alignment, optical system aberration detection, and planar wavefront detection.

Directionally Effect Observation in Topographical Site-Effects at Feden-Sema Range (Guelma-Northern Algeria) from Ambient Vibration

The Eocene Feden-Sema Range is a topographical structure located in the complex area of Mechtat El-Ababsia (Guelma) characterized by topographical site effects from an experimental investigation using earthquake and ambient vibration. The structure has its maximum orientation toward the south and a half-circular shape. To study the directionality effects caused by this structure, two profiles of ambient vibration measurements were carried out on the maximum axe and through the range of 12 points. The analysis of the horizontal over vertical spectral ratio indicated that the fundamental frequency, f0, of the topographical structure is constant and around 3.0 Hz in all measurement points. The ambient vibration analysis in the 0.1–20 Hz frequency domain showed that f0 is strongly related to the polarization or directionality, where the maximum amplification is obtained at 45° azimuth from the north with an amplitude of 3.5 times compared to 0° at 2.5 times. The obtained result is of great importance in showing that the topographical site effects are not free from the directionality influence in the ground motion, which must be taken into consideration in the case of building construction orientation.

Enhanced Video Motion Magnification Utilizing Envelop Shift for Vision-Based Vibration Measurements

Enhanced Video Motion Magnification Utilizing Envelop Shift for Vision-Based Vibration Measurements

Identifying Unbalance in Forced Draft Fan Using Vibration Measurement Methods

The Forced Draft (FD) Fan is a component in a power plant that serves as a supplier of secondary air to assist combustion within the boiler. The Forced Draft Fan has a motor coupled to an impeller, where this component often experiences imbalance with very high vibration values. The imbalance can affect performance and decrease the efficiency of the Forced Fan. Special maintenance in the form of balancing is required to reduce vibration values according to ISO 10816-3 standards so that the Forced Draft Fan can operate safely. In one power plant, there was a Forced Draft Fan experiencing unbalance on the impeller side. In this study, the highest vibration value for the Forced Draft Fan was found at the MOH point, measuring 4.75 mm/s, and after balancing, the vibration value decreased to 0.82 mm/s.

Wind turbine gearbox multi-scale condition monitoring through operational data

Since wind is expected to play a crucial role on the worldwide electricity production scenario, the reliability of the turbines is attracting attention of both industry and academia. New techniques for efficient condition monitoring of key components can be fundamental to optimising the performance and maintenance of a large fleet of turbines. The gearbox and bearings are the most critical mechanical components as they are responsible for a large proportion of the downtime of a wind turbine over its lifetime. However, the monitoring of wind turbine gearboxes is challenging due to the non-stationary nature of the operation and the lack of noise-free vibration measurements. In the present work, a new approach for efficient long to short term monitoring of wind turbine gearboxes has been developed based on real data. An turbine drivetrain failure was used as a test case to develop a new approach based on the use of multi-scale data sources. On the one hand, SCADA (Supervisory Control And Data Acquisition) data were used for general monitoring of the condition of the machine component on long to medium term time scales, while on the other hand, high resolution, triggered event data collected by a CMS (Condition Monitoring System) were used to refine the diagnosis and prognosis of the fault on a shorter time scale. Even though triggered spot events are very difficult to manage, the results show that the use of multi-scale high resolution CMS data can be fast and useful in fault diagnosis to classify a target machine with a healthy reference one. In the present work, the one-class SVM (Support Vector Method) was used for novelty detection. The approach, when applied to all available time scales, can be very precise in detecting the faulty machine and can therefore be proposed as a fast detection approach requiring less data compared to the classical data-driven regression normal behaviour model developed with continuously available SCADA data.

Vibration Measurement of Small Scaled Model Tank Using Conductive Ink

Vibration Measurement of Small Scaled Model Tank Using Conductive Ink

Predicting Axial Stress State In Continuously Welded Rail Using Impulse-Generated Vibration Measurements

Continuously welded rails are connected without stress relief joints and, thus, thermally induced rail movement is constrained, which can result in the development of excessive axial stress and risk of rail failure. Nondestructive testing (NDT) methods that estimate in-place rail stress state or rail neutral temperature are desired. Some methods have been developed, but none satisfy the requirements for ideal monitoring in practice. We propose an NDT technique based on impulse-generated vibration, seeking high-frequency rail vibration resonances whose frequency maintains a consistent correlation with rail axial stress/strain across different temperatures, stress states, and rail support conditions. Rail temperature, axial strain, and vibration data were collected from an active Class 1 commercial rail line over a period of nearly two years. The frequencies of four consistent and clear resonance modes of the rail were monitored. One of the identified modes demonstrates a unique linear relation with axial strain across a range of temperatures and stress states at each of the two measurement locations. The developed linear relations were used to predict in-place strain and rail neutral temperature with acceptable accuracy across all the measurement data, although each test location exhibits a unique relation.

Robot Collisions Classification Based on Variational Mode Decomposition of Vibration Measurements

Robot Collisions Classification Based on Variational Mode Decomposition of Vibration Measurements

Exploring Modal Analysis Technique for Identifying Proper Assembly of ECFM in Vertical Centrifugal Pumps of Fast Reactor

Vertical centrifugal pumps are provided in fast reactors for circulating the primary coolant and flow measurements in these pumps are done using Eddy Current Flow Meters (ECFM). ECFM is an assembly of Outer and Inner Guide Tube (IGT) and a probe that needs replacement after every five years of operation. IGT is a nine meter long, slender component that requires blind insertion through intermittent supports in the pump’s stationary portion. IGT, being flexible, may miss out on its supports during assembly, leading to errors in flow measurement, undesired flow-induced vibration, and stresses. In-situ vibration measurements were conducted to ensure proper assembly of the IGT. The experimental results were then compared with analytical ones obtained using finite element based models to confirm the number of supports acting on IGT. This paper describes the experiments and related analyses, with the help of which vibration characteristics of ECFM assembly are understood and a conclusion on the state of IGT supports is reached.