Vibration Source Research Articles

Multi-directional reconfigurable ultra-low frequency vibration energy harvester

Abstract Converting vibrational energy from the environment into electrical energy more efficiently has been one of the key research topics of this century. The majority of vibrations observed in the natural environment occur at low frequencies and are not fixed in direction. This work presents a design of a piezoelectric vibration energy harvester supported by an elastic rod (R-PVEH), which allows for multidirectional responses to capture vibrational energy. The distinctive configuration of the structure allows for a reduction in vibration attenuation in the presence of low-frequency, unstable excitation. Further, in instances where a complex vibration source is present, multiple units can be reconfigurable to achieve a higher and more stable voltage output. The device can output an average voltage of 15.2 V in response to horizontal low-frequency vibrations of 0.3 Hz, representing a 193.3% increase compared to the conventional cantilever beam structure. The device is expected to be employed in multidirectional low-frequency scenarios such as ocean wave energy harvesting.

Investigation on Micro-Vibration Test and Image Stabilization of a High-Precision Space Optical Payload

With the advancement of space exploration and optical communication toward deep space, the high-precision evaluation and image stabilization of space optical payloads under micro-vibration have become increasingly critical. To address these challenges and ensure sub-micro-radian pointing accuracy for high-precision space optical payloads (HPSOPs), this paper proposes a high-precision micro-vibration testing scheme and a two-stage image stabilization system. The micro-vibration testing scheme is based on an automated quasi-zero stiffness suspension device (AQZSSD), which enhances testing sensitivity and environmental disturbance resistance, ensuring the accuracy of the results. The two-stage image stabilization system integrates three bipod vibration isolation legs (BVILs) and a decoupled fast steering mirror (FSM), extending control bandwidth and achieving comprehensive vibration suppression. Micro-vibration testing and image stabilization experiments were conducted under disturbances from multiple vibration sources. Experimental results demonstrate that the AQZSSD introduces disturbances below 0.4 Hz, confirming its quasi-zero stiffness characteristics in alignment with theoretical predictions. Furthermore, the line-of-sight (LOS) jitter root mean square (RMS) value is reduced from 1.253 μrad to 0.276 μrad, achieving sub-micro-radian stability. Additionally, due to the coupling effect of the micro-vibration response, the collaborative testing results were found to be lower than the linear superposition of individual sources. This work offers critical theoretical and technical support for the development of HPSOPs, with potential applications in future space missions and advanced optical technologies.

Structural Health Assessment of a Reinforced Concrete Building in Valparaíso Under Seismic and Environmental Shaking: A Foundation for IoT-Driven Digital Twin Systems

Structural health monitoring is vital for the safety and longevity of infrastructure, particularly in seismic zones. This study focuses on identifying the dynamic properties of a reinforced concrete building in Chile’s Valparaíso region. Using an experimental approach, the study compares ambient vibration records, seismic events (moment magnitude > 4), and data collected during adjacent construction activities. Force-balanced accelerometers were used for vibration measurements. The analysis employs the Stochastic Subspace Identification with Covariances (SSI-COV) method within an operational modal analysis framework to extract the building’s modal parameters without requiring artificial excitations. This technique effectively identifies modal characteristics under different vibration sources, making it suitable for evaluating the structural condition under diverse loading conditions. The findings reveal the building’s modes and frequencies, offering critical insights for maintenance and management of infrastructure. Little to no variations were observed in the identified frequencies of the building when working with different types of input data. These data support the integration of real-time IoT systems for continuous monitoring, providing a foundation for future digital twin applications. These advancements facilitate early deterioration detection, enhancing resilience in seismic environments.

Fluid-induced vibration response characteristics of the oxygen pump volute

The oxygen pump constitutes a crucial and intricate component within liquid rocket engines, serving as a primary source of engine vibration. This study delves into the unsteady fluid-induced excitation loading, considering the interplay between gap flow and main flow. The findings are validated through testing on a liquid rocket engine. Modal characteristics of the oxygen pump under varying liquid mediums are examined. The Rayleigh damping parameter is determined, accounting for the frequency characteristics of fluid-induced excitation, thereby establishing a comprehensive transient dynamic model. Subsequently, the transient dynamic response of the volute in an oxygen pump to unsteady fluid-induced excitation is analyzed, unveiling both time-domain and frequency-domain vibration response characteristics. The analysis methodology is corroborated through comparison with the statistical distribution of test results. Notably, the vibration response of the oxygen pump volute predominantly exhibits frequency doubling of rotational speed, with prominent occurrences observed at the 12X and 18X frequencies.

Toward a Consistent Framework for Describing the Free Vibration Modes of the Brain.

Frequency-domain analysis of brain tissue motion has received increased focus in recent years as an approach to describing the response of the brain to impact or vibration sources in the built environment. While researchers in many experimental and numerical studies have sought to identify natural resonant frequencies of the brain, limited description of the associated vibration modes limits comparison of results between studies. We performed a modal analysis to extract the natural frequencies and associated mode shapes of a finite element model of the head. The vibration modes were characterized using 2D plate deformation notation in the basic medical planes. Many of the vibration modes characterized are similar to those found in previous numerical and experimental studies. We propose this characterization method as an approach to increase compatibility of results between studies of brain vibration behavior.

Numerical simulation method for generating seismic waves by a simplified point source based on seismic-while-excavation in coal mine roadways

The advanced geological prediction of seismic-while-excavation (SWE) in coal mine roadways employs the noise vibrations generated during the construction process as the signal source. The excitation process of seismic waves derived from this noise source significantly differs from that associated with conventional pulse sources. Exploration of the characteristics and process involved in exciting seismic waves through excavation noise sources is undertaken. Initially, challenges posed by complex vibration sources during excavation are addressed, with analysis of signal characteristics derived from field data and consideration of the excavation environment. Investigation of the seismic wave excitation forms of these complex noise sources leads to a summary of their characteristics. The simplification of various excavation machinery into distinct forms of point sources facilitates theoretical analysis. Coupling the excitation processes of each point source and leading into virtual source theory of seismic record interferometry reconstruction results in a simplified point source time function of excavation noise sources. Analysis of the types and magnitudes of forces exerted by the cutting head during coal seam excavation, in conjunction with the operating mode of a boom-type roadheader, is conducted. A spatial loading method for the noise source is proposed, grounded in the components of the excited wavefield. The staggered grid finite difference algorithm is employed for numerical simulations. Comparison of synthetic seismic records with field-measured data validate the rationality and effectiveness of the simulated source term. A theoretical foundation for future investigations into the imaging and inversion of excavation noise sources is established.

Study on the vibration characteristics and influence range of buried dam pipeline

To alleviate water resource shortages and tensions and meet the water diversion needs of different river basins, buried (cross-dam) pipelines have become an essential component of water diversion projects. They are installed in levee projects in key river basins such as the Yellow River, Jingjiang River, and Beijiang River. Due to the complex engineering structure and multiple sources of vibration excitation, if vibrations propagate along the pipeline axis towards the surrounding levee, they could have an adverse impact on the stability and safe operation of the levee. To accurately identify the vibration and transmission characteristics of the buried pipeline dikes, determine its primary vibration sources, and clarify the propagation laws of pipeline vibrations within the levee, this study, based on prototype observation data and utilizing signal fusion processing technology, investigates the inherent vibration characteristics of the buried pipeline dikes from the perspectives of excitation, transmission, and response. At the same time, by introducing the “finite element-infinite element” theory, a coupled finite element-infinite element model is established for the pipeline, levee, anchor piers, support piers, foundation, and infinite half-space. This model is then used to analyze the site response induced by flow-induced vibration in buried pipeline levee structures. The results show that the primary vibration frequencies of the buried pipeline dike structure are the unit rotation frequency of 74.4 Hz and the blade vibration frequency of 24.8 Hz. These vibration sources originate from the pump unit and propagate outward along the pipeline axis. Using the transmission range of the vibration source as the basis for determining the vibration impact range, it was established that the horizontal vibration impact of the buried pipeline extends 10 m on either side of the pipeline axis, while the vertical vibration impact extends 7.5 m below the dike crest.

The impact of mechanical vibrations on pressure pulsation, considering the nonlinearity of the hydraulic valve

The article identifies some of the forces acting on hydraulic valves used in the civil and military vehicles. Particular attention was paid to the single-stage electrically controlled “on/off” hydraulic directional control valve. Special attention was focused on vibrations of hydraulic directional valve four ways, three positions (4/3) controlled by typical solenoids. Military vehicles can be a source of vibrations in low and high range of frequency. The spectrum of vibrations frequency is wide in this case. The value of the natural frequency of vibrations of the hydraulic directional control valve spool, whose body was affected by mechanical vibrations, was estimated. The paper shows that the natural vibrations of the directional control valve spool can coincide with the frequency of external vibrations acting on the valve from the ground. The mathematical description takes into account that when the spool is overdriven, the oscillating movement of the directional control valve spool is described by a model that takes into account the nonlinearity resulting from the fact that the spool is in the extreme position—it is a poor nonlinear mechanical system. The results of theoretical considerations were confronted with the results of experimental research. In addition, the presented modified model was used to assess the impact of the capacitance change on the value of the amplitude of pressure pulsations caused by the vibrations of the directional control valve spool.

Fault detection of a diesel engine through vibration source separation and deep learning

Fault detection of a diesel engine through vibration source separation and deep learning

Investigation of combustion-induced vibration sources in a diesel engine in the time-frequency domain using the wavelet analysis method and wavelet cross-correlation analysis method

Investigation of combustion-induced vibration sources in a diesel engine in the time-frequency domain using the wavelet analysis method and wavelet cross-correlation analysis method

Investigation into vibration propagation and attenuation characteristics of shield construction based on field measurement

Vibration caused by shield tunneling construction have adverse impacts on surrounding environment. To ascertain the influence of shield tunneling construction on ambient vibration, based on the shield tunnel project of Zhijiang Road in Hangzhou, the on-site vibration tests were carried out on the deep soil and surface during the excavation, and the vibration characteristics and vibration attenuation law during shield construction were investigated. The results show that the main frequency of vibration near the vibration source is wide, and the response components can be observed at 0–100 Hz. Under the filtering effect of the surface-covering soil layer, the high-frequency components of the vibration response are significantly attenuated, and the surface vibration is mainly distributed within 40 Hz. In the shield crossing, the deep measurement point is 5 dB higher than the vibration level of the same position on the surface. After the shield is pushed forward 20 m, the average attenuation of the surface vibration response is 10 dB, and the average attenuation of the deep vibration response is 12 dB.

The Role of Vibrations in Unmanned Aerial Vehicles Efficiency Measurement Techniques and Performance Effects

Vibrations in unmanned aerial vehicles (UAVs) significantly impact flight stability, sensor accuracy, and structural integrity, with common sources including propeller rotation, motor dynamics, and aerodynamic forces. Addressing these vibrations is essential to enhancing UAVs performance and operational durability. This paper examines both theoretical and experimental vibration analysis techniques such as frequency analysis, modal analysis, and finite element analysis as key tools for understanding and controlling vibration dynamics. Various strategies for vibration mitigation are explored, including structural optimization, flight control systems, and active/passive isolation systems, all aimed at improving stability and durability. By accurately identifying vibration sources and effects, along with applying effective engineering solutions, UAVs can achieve enhanced performance, extended operational longevity, and broadened applications in sectors requiring high precision and stability. Consequently, vibration mitigation emerges as a critical factor not only for performance improvement but also for the reliable deployment of UAVs technology in demanding environments.

In-field Verification of the Applicability of MEMS-IMU Accelerometers for Monitoring of Mining-induced Seismic Activity

Measurements of seismic activity induced by mining operations are a basic tool for assessing the level of dynamic load associated with the occurrence of tremors. Knowledge of the location of the source of vibrations and the nature of seismicity is the basis for the safe planning of operations and design of both underground and surface infrastructure. The key parameter influencing the quality and reliability of seismic measurements is the coverage density of the analysed area with measurement stations. Unfortunately, the cost of seismic networks using standard devices is so high that in most cases the density of the network is much lower than needed for a good resolution and low event detection threshold. A certain breakthrough in this area may be the introduction of cost-effective measuring devices based on MEMS technology. This study compares the seismic data collected with the use of MEMS-IMU accelerometers with standard accelerometers for field seismic monitoring. The basis for the comparison was the analysis of data recorded by both devices located on the same site for two months. The comparison was carried out in terms of the characteristics of seismic waveforms, their amplitude distribution, frequency characteristics and effective duration of vibrations. Based on the results of the analysis, it was shown that MEMS-IMU accelerometers can be successfully used to monitor seismicity induced by mining activities in the near wave field.

Monitoring of a Low-Order Even Radial Vibrational Circumferential Mode in a Round Hollow Cylinder

This paper presents a nondestructive testing method for assessing the structural integrity of cylindrical elements by monitoring a range of radial vibrational modes, with a specific emphasis on the so-called ovalling mode. The method involves exciting the cylinder with a single vibration source in the radial direction and measuring the response using two vibration sensors positioned diametrically on the cylinder's surface. The ovalling mode was extracted from the frequency response by adding the in-phase signals recorded by the sensors. Experiments conducted on a PVC pipe showed good agreement between the measured resonance frequency of the ovalling mode and its predicted value, calculated using the theory for thin cylindrical shells and Finite Element Method simulations. This research is an investigation into the potential and reliability of this nondestructive technique for detecting corrosion and strength-weakening defects in concrete building elements, steel pillars, and columns. The extent of the strength reduction can be determined by analyzing the change in the resonance frequency of the ovalling mode.

Study on vertical-torsional chatter under asymmetric conditions in tandem cold rolling

The vibrations generated by the rolling mills significantly impair the production quality and efficiency of cold tandem rolling. Considering that the main drive system constitutes one of the energy sources of vibration, this study integrates the vertical structure of the rolling mill with the torsional structure of the main drive system for a comprehensive analysis. This study establishes an asymmetric dynamic rolling force model that accounts for the structural asymmetry of the rolling mill, the asymmetric power transmission between the upper and lower connecting shafts of the main drive system, and the long-term wear and friction conditions of the mechanical equipment. Furthermore, this study accounts for the speed differential between the upper and lower work rolls induced by torsional vibrations. Based on these interdependent parameters, this study develops a rolling mill vibration coupling model to comprehensively assess stability. The validation of the model confirms its high accuracy. Variations in rolling torque under different roll speed ratios, friction coefficient ratios, and roll diameter ratios were analyzed, along with the impact of the cross-shear zone's proportion on system stability under key rolling parameters. Furthermore, changes in rolling torque, amplitude, and the cross-shear zone during unstable operating conditions were examined. Finally, the interaction between the vertical and torsional structures was studied, providing a theoretical foundation for optimizing process parameters and mitigating vibrations in the continuous cold rolling process.

Проекционный метод определения аномальных датчиков в задачах виброакустики

A common problem in measurements using a set of vibration sensors in vibroacoustics is the lack of an accurate signal model on the receivers. Such uncertainty can lead to processing algorithms errors and an incorrect solution to the inverse problem. Due to a malfunction, vibration sensors data can also be bad, deteriorating the quality of measurements. In practice, the search for such anomalous sensors is a non-trivial task. In this paper, an original method related to projection algorithms is proposed for this problem. It is shown that the proposed method allows detecting anomalous sensors of various types. The method main feature is using both numerical finite element model of the object and experimental data. The efficiency of the proposed method is demonstrated in the localizing vibration sources problem. The new method can be used in other applications where the inverse problem is solved using a numerical or analytical model.

A time-lapse multicomponent (9C 4D) seismic study at Vacuum Field, New Mexico, USA

In November and December 1995, the Reservoir Characterization Project (RCP) at the Colorado School of Mines acquired time-lapse multicomponent 3D surveys over the Central Vacuum Unit of Vacuum Field in Lea County, New Mexico. Two surveys were acquired — one before and one after the injection of 50 MMscf CO2 through a single wellbore into the San Andres Reservoir. The project determined that repeated multicomponent seismic surveys at the earth's surface can detect changes in bulk rock properties due to variations in reservoir pressures and fluid properties. Interpretation of the dynamic seismic response due to reservoir production processes over time provides an image of the relative permeability structure of the reservoir. Time-lapse multicomponent data were acquired using three-component geophones and vertically and horizontally actuated vibrator sources at the surface. A data processing flow was developed for time-lapse multicomponent 3D surveys. It uses surface-consistent processing algorithms and the source and receiver redundancy between initial and repeat surveys to derive surface-consistent corrections. Differences in S-wave polarization are measured between the initial and repeat surveys. S-wave data show sensitivity (through birefringence) to anisotropy caused by the orientation of fractures and low-aspect-ratio pore structure in a nonuniform stress field. The direction of fast S-wave polarization can be related to the direction of maximum horizontal stress and preferential permeability. Pore-pressure variations alter the effective stress. This varies the direction and intensity of open fractures and low-aspect-ratio pore structure within the current permeability structure of the reservoir, causing detectable changes in S-wave anisotropy. Anomalies in S-wave anisotropy, interpreted from time-lapse multicomponent 3D data, in conjunction with reservoir production data, are consistent with the fluid composition and pore-pressure changes associated with the CO2 injection program and reservoir processes in the survey area. Applications include monitoring hydrocarbon enhanced oil recovery; carbon capture, utilization, and storage; hydraulic stimulation; induced seismicity; and geothermal investigations.

Equivalent Load Identification and Verification in Frequency Domain for Liquid Rocket Engine

Accurately characterizing the dynamic load environment is vital for the structural optimization and fatigue life assessment of liquid rocket engines, but the difficulty in precisely measuring or identifying such distributed loads is substantial. This paper proposed a method to determine the equivalent concentrated loads of liquid rocket engines at main vibration sources using the direct inverse method in the frequency domain. Response verification is performed to confirm the effectiveness of the equivalent loads by assessing the consistency between responses due to them and actual distributed loads. A pumped liquid rocket engine is investigated for specific research. Responses from the hot-fire test are used to identify equivalent loads at three main vibration sources, which are the gas generator, turbine shell, and combustion chamber. The results indicate that the errors in responses induced by the equivalent loads and the actual distributed loads are generally within ±4 dB. To further validate the equivalent loads, an experiment is conducted, scaling and applying the equivalent loads to the rocket engine. The resulting responses, after amplification, align well with those obtained from the hot-fire test, confirming the validity of the proposed method. However, response verification errors escalate significantly when nonprimary sources are included in the equivalent locations.

Designing a vibration energy harvester for several directions of excitation in planar motion

Abstract Harvesting energy from a mechanical vibration source is always challenging and comes with drawbacks, especially when the vibration input changes direction very often. This research proposes a novel design to harvest energy from a planar mechanical vibration source no matter its direction of oscillation. To achieve this, a spiral beam with a tip mass is designed to be flexible to various directions of the vibration input in a horizontal plane, which is orthogonal to the direction of gravity. An approximate analytical investigation is first performed. Numerical simulations are then conducted using commercial FEA software and the results are in good agreement with the analytical approach. Numerical simulations show that the tip mass acts symmetrically in the plane, although the system is not geometrically symmetric. To experimentally validate the proposed configuration, a 3D-printed prototype device was manufactured and attached to a shaker, which induced a vibrating motion for the tests. A piezoelectric patch was attached to the curved beam to generate electrical energy and measurements of produced open-circuit voltages were taken for different directions of the exciting vibration.

Effect of operating conditions on the time-frequency characteristic of high-speed vehicle-turnout dynamic interaction using synchrosqueezed wavelet transform

Structural irregularities are a primary source of vibration when vehicles traverse turnouts. This study investigates their impact on the time-frequency characteristics of vehicle dynamic responses under varying operating conditions, focusing on the crossing zone of a No. 18 ballastless high-speed railway turnout. A vehicle-turnout coupled dynamic model incorporating rail flexibility is developed, and the time-frequency features of vehicle responses under different conditions are analysed. The results reveal that structural irregularities in the crossing zone lead to higher peak values and more pronounced high-frequency components (250–850 Hz) in vertical wheel/rail forces in the facing direction compared to the trailing direction. Furthermore, the vertical vibration acceleration of the point rail in the facing direction exhibits higher peak values, greater energy in dominant frequency components, and the emergence of a new dominant frequency band (70–150 Hz). Differences in vertical wheel/rail forces and point rail vertical vibration acceleration across vehicle types are primarily evident in the high-frequency range (above 150 Hz). Additionally, increasing speed amplifies dynamic response amplitudes, peak values, and vibration frequencies. This study provides critical insights into the dynamic response characteristics of turnouts under various conditions, offering a foundation for damage detection and operational assessment.