Vibration Amplitude Measurement Research Articles

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.

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.

Relationship between Casing Pressure and Non-Synchronous Vibration in an Axial Compressor

The relationship between aerodynamic forcing and non-synchronous vibration (NSV) in axial compressors remains difficult to ascertain from experimental measurements. In this work, the relationship between casing pressure and blade vibration was investigated using experimental observations from a 1.5-stage axial compressor under off-design conditions. The wavenumber-dependent auto-spectral density (ASD) of casing pressure was introduced to aid in understanding the characteristics of pressure fluctuations that lead to the aeromechanical response. Specifically, the rotor blade’s natural frequencies and nodal diameters could be directly compared with the pressure spectra. This analysis indicated that the rotating disturbances coincided with the first bending (1B) and second bending (2B) vibration modes at certain frequencies and wavenumbers. The non-intrusive stress measurement system (NSMS) data showed elevated vibration amplitudes for the coincident nodal diameters. The amplitude of the wavenumber-dependent pressure spectra was projected onto the single-degree-of-freedom (SDOF) transfer function and was compared with the measured vibration amplitude. The results showed a near-linear relationship between the pressure and vibration data.

Enhancing the Elastohydrodynamic Lubrication and Vibration Behavior of Rolling Bearings Using a Hybrid Bio-Grease Blended with Activated Carbon Nanoparticles

In recent years, bio-lubricants have received a growing interest for industrial applications. Still, a full-scale implementation in machinery lubrication requires a thorough evaluation of their performance through tribological and operational tests to stand upon their performance. Additionally, the promising outcomes achieved by nanoadditives in improving the performance of synthetic lubricants have prompted research efforts to identify suitable nanoadditives for bio-grease. This paper introduces a bio-grease from a hybrid vegetable oil and glycerol monostearate as a thickener for the lubrication of rolling bearings. Activated carbon nanoparticles (ACNPs) as nanoadditives were synthesized, characterized, and incorporated into the bio-grease at concentrations of 0.5, 1, and 2% by weight. Tribo-tests were conducted on these bio-grease blends, and running tests were carried out using 6006 ball bearings on a custom test rig. Throughout a 30-min test run under a radial load of 10% of the bearing’s dynamic load rating, mechanical vibrations and power consumption were measured and analyzed for each bearing. The bio-grease with ACNPs exhibited a substantial reduction in wear scar diameter (WSD) and coefficient of friction (COF), achieving improvements of up to 73.6 and 65%, respectively, in comparison to lithium grease. Furthermore, the load carrying capacity was enhanced by 200%. The study revealed a strong correlation between measured vibration amplitudes and the viscosity of the bio-grease. The absence of high frequency resonant bands in vibration spectra indicated that the test grease samples satisfied the conditions of elastohydrodynamic lubrication, and these findings were corroborated through calculations of the minimum oil film thickness.

Optical coherence elastography and its applications for the biomechanical characterization of tissues.

The biomechanical characterization of the tissues provides significant evidence for determining the pathological status and assessing the disease treatment. Incorporating elastography with optical coherence tomography (OCT), optical coherence elastography (OCE) can map the spatial elasticity distribution of biological tissue with high resolution. After the excitation with the external or inherent force, the tissue response of the deformation or vibration is detected by OCT imaging. The elastogram is assessed by stress-strain analysis, vibration amplitude measurements, and quantification of elastic wave velocities. OCE has been used for elasticity measurements in ophthalmology, endoscopy, and oncology, improving the precision of diagnosis and treatment of disease. In this article, we review the OCE methods for biomechanical characterization and summarize current OCE applications in biomedicine. The limitations and future development of OCE are also discussed during its translation to the clinic.

Исследование амплитудной и фазовой ошибок датчика-опоры при ультразвуковой сварке пластмасс

The paper presents a technique making it possible to evaluate amplitude and phase errors of the magnetoelastic support sensor used in the plastics ultrasonic welding. Measurement of the support sensor vibration amplitude allows monitoring alterations in the basic physical properties of the polymer being welded, i.e. its temperature and thickness. The support sensor operation dynamic mode is described. It is established that evaluating measurement errors with the proposed method in manufacture of any support sensor of different design makes it possible to accurately determine its performance with parameters of the polymer material ultrasonic welding process. The problem of evaluating accuracy of the magnetoelastic support sensor operation used in the welding process was considered. The support sensor amplitude and phase errors during ultrasonic welding were studied. A magnetoelastic sensor was designed and developed ensuring improved accuracy in measuring the support vibrations amplitude during the polymer material ultrasonic welding. The experiments carried out confirmed clear relationship between the support vibrations amplitude and heating of the welded samples, their thickness and properties during the ultrasonic welding.

Vehicle-Mounted Pavement Health Monitoring System Based on a Spring-Guide-Assisted Triboelectric Sensor.

The present pavement health monitoring is limited by a professional staff patrol. Herein, a vehicle-mounted pavement health monitoring system (VPHMS) based on a spring-guide-assisted triboelectric sensor (S-TES) is proposed, which uses the vibration generated by vehicles passing through uneven pavements to monitor the pavement damage. The VPHMS consists of S-TES, the integration module, and the terminal display module. The designed S-TES has high stability and can achieve a high linear vibration amplitude measurement within 90 mm. Moreover, the integration module is used to process signals and transmit wireless data transmission. The terminal display module is used to receive signals and display the measurement results on the screen. When a vehicle equipped with VPHMS is driven over uneven pavements, the system can accurately monitor the potholes and upheavals on the pavement in real time. This work has significant application value in fields such as pavement health monitoring and intelligent transportation.

Super-sensitivity full-field measurement of structural vibration with an adaptive incoherent optical method

Full-field measurements of structural vibrations have been achieved by incoherent optical methods with video cameras such as digital image correlation and optical flow. In contrast to coherent optical methods such as scanning laser vibrometers, incoherent optical methods are low-cost and easy to set up. However, the sensitivity (minimum measurable displacement) of incoherent optical methods is generally lower than that of coherent optical methods. Typically, the sensitivity of incoherent optical methods is essentially limited by the finite bit depth of the digital camera due to the quantization with round-off errors. Quantitatively, this theoretical sensitivity limit is determined by the bit depth B as δp=1/(2B−1) [pixel] which corresponds to a displacement causing an intensity change of one gray level. Fortunately, natural dithering may be leveraged to overcome the quantization and exceed the sensitivity limit, achieving super-sensitivity.In this work, we first study the mechanism of the sensitivity limit induced by the quantization and the critical limitation of existing super-sensitivity methods in the full-field measurement of structural vibration. Addressing such a limitation, we present a general adaptive weighted averaging method with dithering, achieving super-sensitivity incoherent optical measurement of full-field deformational vibration of flexible structures. Specifically, both spatial and temporal samplings of the pixels are leveraged simultaneously to adaptively identify the motion (deformation) shape of the structure by principal component analysis (PCA) of spatiotemporal pixel intensities. Then, the identified deformation shape is used to perform a deformation-shape-weighted averaging over spatial pixels with dithering, revealing the sub-sensitivity displacement while retaining spatial resolution at full field. Numerical simulations and laboratory experiments are performed for principle explanation and method validation. Particularly, we derive a mathematical model of the minimum measurable vibration amplitude A∗ for the developed super-sensitivity method, which is found to be determined by the number of spatial pixels for averaging Ns and the noise level σn in the imaging system. Thus, this work provides, for the first time, a rigorous quantification of the sensitivity of incoherent optical measurement for structural vibration, and a new quantitative method to achieve super-sensitivity full-field measurement of structural vibration.

Investigation on Measurement of Vibration Amplitude by Torsional Resonant Column Apparatus

Investigation on Measurement of Vibration Amplitude by Torsional Resonant Column Apparatus

Modelling and vibration control of magnetorheological-based polishing tool for robotic polishing process

The instability of the polishing force in the robot polishing process causes vibration of the polishing tool and degrades surface quality. Controlling vibration is essential for enhancing machining quality during high-precision polishing. This paper presents a magnetorheological (MR)-based polishing tool and vibration control method for improving the stability and reducing the vibration during machining. Firstly, a polishing end-effector with MR-based damper and magnetic spring mechanism is designed, the damping and stiffness model are built, the vibration dynamic model is established, and the vibration characteristics are theoretically analyzed. Multi-objective optimization is carried out to minimize the maximum frequency response value of polishing system. Then, a disturbance observer is designed to estimate the nonlinear cutting force and the stability is proved. To maintain normal contact force and reduce polishing tool vibration, a vibration controller based on polishing force with gravity compensation is proposed. The measured vibration amplitude and estimated cutting force are used as feedback in the controller to maintain the desired contact force. Finally, the polishing experiments are carried out to verify the feasibility of proposed strategy. The results show that the proposed method suppress the fluctuation of the polishing force and reduce vibration, the maximum vibration amplitude is reduced by 45% and the surface roughness is improved up 57.9%.

Quantitative STEM: A method for measuring temperature and thickness effects on thermal diffuse scattering using STEM/EELS, and for testing electron scattering models

In the last two decades, advances in the dark field detectors and microscopes of scanning transmission electron microscopy (STEM) have inspired a resurgence of interest in quantitative STEM analysis. One promising avenue is the use of STEM as a nanothermometric probe. In this application, thermal diffuse scattering, captured by a CCD camera or an annular dark field detector, acts as an indirect measurement of the specimen temperature. One challenge with taking such a measurement is achieving adequate sensitivity to quantify a change in scattered electron signal on the order of 1% or less of the full electron beam. Another difficulty is decoupling the thermal effect on electron scattering from scattering changes due to differing specimen thicknesses and materials. To address these issues, we have developed a method using STEM, combined with electron energy loss spectroscopy (EELS), to produce a material-specific calibration curve. On silicon, across the range 89 K to 294 K, we measured a monotonically increasing HAADF signal ranging from 4.0% to 4.4% of the direct beam intensity at a thickness-to-mean-free-path ratio of 0.5. This yielded a calibration curve of temperature versus full-beam-normalized, thickness-normalized HAADF signal. The method enables thermal measurements on a specimen of varying local thickness at a spatial resolution of a few nanometers. We demonstrated the potential of the technique for testing electron scattering models by applying single-electron scattering theory to the data collected to extract a measurement of the mean atomic vibration amplitude in silicon at 294 K. The measured value, 0.00738 ± 0.00002 nm, agrees well with reported measurement using X-rays.

SMALL DIGITAL VIBROMETER

During scientific studies of the operation of ultrasonic equipment in modern technological processes, it is necessary to measure the amplitude of the mechanical vibration of the working tool, which at high frequencies has significant technical complexity. Knowing the magnitude of the amplitude of ultrasonic vibration makes it possible to precisely dose the amount of energy necessary to obtain a high-quality processing product, as well as for constant repeatability of the results of the equipment. Known foreign vibrometers are purposefully produced for specific conditions of use and are characterized by complexity, bulkiness and high cost, which is an obstacle to wide use. Therefore, the purpose of this work is to develop a low-cost, small-sized vibrometer for measuring the amplitude of ultrasonic emitters. For this, a capacitive measurement method with frequency modulation of the carrier frequency is used, which is characterized by high sensitivity and resistance to external interference. This vibrometer consists of two parts: a vibration sensor with an electronic converter of a high-frequency signal into a constant voltage proportional to the vibration amplitude, and a power supply unit and digital signal processing and indication of the amplitude in μm. The vibrometer sensor is mounted on a hinged tripod for ease of installation in any plane at a distance of ≈1 mm from the tested surface. The vibrometer is powered by a 220V network. The vibrometer is equipped with microprocessor processing and indication of the results of measurement of the vibration amplitude, as well as control and indication of the gap between the vibration sensor and the tested surface and stabilization of the amplitude readings when this gap varies within 0.7...1.2 mm. The vibration amplitude measurement range is 0...99 μm, with a resolution of 1 μm. The vibration frequency range is 5...50 kHz. The analog signal from the output of the vibrosensor can be used in the ultrasound generator feeding the piezoelectric transducer as a feedback signal to stabilize the amplitude of the mechanical vibrations of the emitter at the required level.

A Ring-Shaped Curved Deformable Self-Powered Vibration Sensor Applied in Drilling Conditions

Because of their low flexibility, traditional vibration sensors cannot perform arbitrary bending adjustments when facing curved surfaces and other complex working conditions during the drilling process; therefore, this research proposes a ring-shaped vibration sensor (RSV−TENG) that can deform freely in the bending direction, and which can be used in working conditions where the inner bending angle of the drill pipe changes greatly. Test results show that the vibration frequency measurement range is from 4 Hz to 16 Hz, with a measurement error less than 4%, the vibration amplitude measurement range is less than 20 mm, with a measurement error less than 5%, the output voltage and current signal are 120 V and 60 nA, respectively, when three RSV−TENGs are connected in parallel, and the maximum output power is 6 × 10−7 W when the external resistance is 106 Ω. Compared with traditional downhole sensors, this sensor has self-powered and self-sensing functions, eliminating the shortcomings of battery and cable power supply; in addition, this sensor can be installed in the drill pipe space with different curvature radii, so it is more suited to complex and changeable downhole working conditions.

Investigation of passive acoustic emissions during powder mixing in a V-blender

Powder mixing is a complex process and a critical step in production across various industries. Passive acoustic emissions provide a promising potential for inline powder mixing monitoring. Vibrations from these emissions were measured during rotations of a V-blender using glass beads as a model solid as well as starch granules. Vibration profiles were correlated to specific phases of particle motion within the revolving V-shells. The phase, labeled Feature #1b, associated with particle collisions of the V-shell lid with attached accelerometer provided the largest measured vibration amplitudes and most reliable and relevant information on particle movement. After wavelet filtering to remove large-scale vibrations of the V-shell, the optimal information extraction method was identified as the average of the 50 highest amplitudes within the Feature #1b phase. An example illustrating the mixing of two size ranges of granules shows the potential of this monitoring method for pharmaceutical powder mixing in V-blenders. • Passive acoustic emissions are measured by a sensor on the lid of a V-blender. • Passive acoustic emissions from collisions reflect particle size and flow. • The largest emission amplitudes occur from collisions with the V-blender lids. • The 50 largest emissions amplitudes allow a mixing profile to be estimated.

Low-Cost Portable Device Design for Preventive Maintenance of Rotating Systems

In the present work, the technological development of a low-cost acquisition device is proposed that allows the simultaneous measurement of vibration amplitude in acceleration and the temperature variable, and that through Bluetooth communication, the parameters are acquired by a cellphone. The data stored in the mobile device will be used for the development and/or improvement of predictive maintenance plans in medium and small companies, whose internal budget does not allow the acquisition of specialized vibration equipment. Finally, the developed App makes it easier for maintenance personnel with minimal knowledge of vibration analysis and thermography to acquire and analyze data insitu and/or offline, using 2D graphing

Non-Linear Regression Models with Vibration Amplitude Optimization Algorithms in a Microturbine.

Machinery condition monitoring and failure analysis is an engineering problem to pay attention to among all those being studied. Excessive vibration in a rotating system can damage the system and cannot be ignored. One option to prevent vibrations in a system is through preparation for them with a model. The accuracy of the model depends mainly on the type of model and the fitting that is attained. The non-linear model parameters can be complex to fit. Therefore, artificial intelligence is an option for performing this tuning. Within evolutionary computation, there are many optimization and tuning algorithms, the best known being genetic algorithms, but they contain many specific parameters. That is why algorithms such as the gray wolf optimizer (GWO) are alternatives for this tuning. There is a small number of mechanical applications in which the GWO algorithm has been implemented. Therefore, the GWO algorithm was used to fit non-linear regression models for vibration amplitude measurements in the radial direction in relation to the rotational frequency in a gas microturbine without considering temperature effects. RMSE and were used as evaluation criteria. The results showed good agreement concerning the statistical analysis. The 2nd and 4th-order models, and the Gaussian and sinusoidal models, improved the fit. All models evaluated predicted the data with a high coefficient of determination (85–93%); the RMSE was between 0.19 and 0.22 for the worst proposed model. The proposed methodology can be used to optimize the estimated models with statistical tools.

Simplified parametric modeling to predict vibration attenuation provided by on-grade slabs

When measured vibration amplitudes at the proposed site for a highly sensitive facility exceed the maximum allowable for the sensitive equipment, mitigation measures must be integrated into the design that will reduce the vibration amplitudes to meet the requirements. Past studies have shown that thick concrete slabs supported on a well-engineered subgrade can effectively reduce ground borne vibrations at certain frequencies. Predicting the vibration performance of a new slab-on-grade can be a significant challenge, however, as the performance is highly dependent upon the site soil conditions and nature of the vibration sources impacting the location, as well as structural characteristics. Large and detailed three-dimensional finite element analysis models of the site conditions and proposed structure are often used for this type of assessment, however development of such a model requires significant time and cost to develop accurately. This presentation discusses a proposed an alternative simplified parametric modeling technique using two-dimensional plane strain modeling. This technique can be utilized in combination with real-world data to predict the relative benefit of various slab thicknesses and design features such as structural breaks. The paper will include multiple comparisons between predicted results using this methodology and field measurement results.

Monitoring the Impact of the Large Building Investments on the Neighborhood

The article presents the concept of monitoring buildings and infrastructure elements located near large construction investments (the construction of high-rise buildings of the Oak Terraces housing estate in Katowice and the construction of a tunnel under the roundabout in Katowice along the intercity express road DTŚ). The impacts include deep excavation, lowering of the groundwater level over a large area, and dynamic influences related to the use of impact methods of soil improvement. The presented monitoring includes observation of the groundwater level with the use of piezometers, geodetic measurements of settlement and inclinations, as well as the measurement of vibration amplitudes generated during the works involving shocks and vibrations. It was also important to observe the development of cracks on the basis of a previously made inventory of damage. The results of the monitoring allow corrections to be made in the technology of works (e.g., reduction of vibration amplitudes, application of additional protections at excavations, etc.) or the use additional safety measures. Currently, there are also monitoring systems used during the operation of completed facilities.

Image processing technology in high frequency vibration direction and amplitude measurement

In recent years, with the development of computer software and hardware and artificial intelligence technology, photoelectric imaging equipment has gradually developed in the direction of digitization and intelligence. This paper mainly studies the application of image processing technology in the measurement of high-frequency vibration direction and amplitude. According to the corresponding relationship between the vibration blur image and the still image in the frequency spectrum, the image is preprocessed. This article adopts the traditional camera calibration method, which uses a special standard template to calibrate the internal and external parameters of the camera. The three-dimensional search algorithm is used to analyze and compare the recognition images of the left and right cameras in each state, and finally calculate the internal and external parameters of the camera. The data shows that the fundamental frequency is about 4.9 Hz, and the fundamental frequency order basically fluctuates around 16. The calculated amplitudes are 0.89, 0.93 and 0.99μm, respectively. The results show that the image processing technology can restore image edge details to a certain extent, suppress noise, and effectively shorten the matching time between feature points.

Design and experimental study of longitudinal-torsional ultrasonic transducer with helical slots considering the stiffness variation

The ultrasonic transducer employing helical slots to generate longitudinal-torsional (L&T) ultrasonic vibration is popular in the field of hard and brittle material machining. However, the design approach for this type of L&T ultrasonic transducer is not well established. An improved design model combining equivalent circuit theory and material parameter equivalent method based on stiffness variation was proposed in this study. The structure parameters of the transducer can be obtained according to given resonance frequency and nodal position. The model can further predict electrical characteristics and mechanical responses under specific excitation. For the preliminary verification of this theoretical model and the optimization of the transducer, finite element analyses were carried out to investigate the influences of slot structure parameters on dynamic performances in terms of resonance frequency, frequency separation, and amplitude of L&T vibration. After that, a prototype was manufactured according to the design results, and the measurements of impedance curve and vibration amplitude were conducted. The experimental results indicate that this prototype resonates at 24,920 Hz with an effective electromechanical coupling coefficient of 0.19. Meanwhile, the vibration amplitude in longitudinal direction is 8.1 μm and that in tangential direction is 5.6 μm under 70-V sinusoidal voltage excitation, which are consistent with the theoretical design and simulation results. Furthermore, machining tests demonstrate that surface roughness reduction and surface quality improvement can be gained by adopting this L&T ultrasonic transducer, compared to using the longitudinal vibration transducer. The proposed design approach was validated and this study can provide guidelines for the design of L&T ultrasonic transducer for rotary ultrasonic machining (RUM).