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The lining cavities in tunnels have strong concealment and pose significant risks, seriously affecting tunnel operational safety. Therefore, it is necessary to develop efficient and high-precision detection techniques for tunnel lining cavities. In this study, concrete slabs with different parameter cavities were selected as the research object, and experiments on remote detection using Laser Doppler Vibrometry were conducted. During the experiments, the vibration parameters of the concrete surface were measured for cavities of varying sizes and depths, filled with different materials, and under different detection distance conditions. The vibration differences between the defective and healthy parts were analyzed using the spatial spectral entropy algorithm. The results showed that for cavities with side lengths of 200mm, depths of 50mm, and filled with hollow wooden boxes, the maximum velocity amplitudes of the surface concrete were 10.68, 3.55, and 4.01 times higher than those of the healthy parts, respectively. Moreover, at the same frequency, larger cavity areas and shallower depths resulted in greater surface vibration amplitudes. The vibration amplitudes of the surface with hollow wooden box filling were higher than those with foam polystyrene board filling. With increasing detection distance, the overall surface vibration velocity of the cavities was higher at a distance of 3 m from the laser probe compared to 5 m, indicating the ability to quantitatively describe the apparent vibration characteristics of concrete cavities under different parameters. This study demonstrates the significant effectiveness of laser Doppler vibrometry in remote detection of lining cavities in tunnels. [ABSTRACT FROM AUTHOR]

In this paper, the thermomechanical buckling and vibration analysis are investigated for carbon nanotube‐reinforced composite sandwich doubly curved shells (CNCSDS) under the action of both thermal loads and in‐plane compressive loads. Based on the von‐Karman non‐linear kinematic relations, First Order Shear Theory, and Hamilton's principle, the vibration and stability equations for CNCSDS under thermomechanical loads are deduced. For obtaining the critical thermomechanical buckling load and vibration frequency, an exact method is adopted. Subsequently, the results are validated by comparing with the finding in published literature and simulation results. At last, the influence of system parameters on critical thermomechanical buckling load and vibration frequency is studied and displayed graphically. Meanwhile, some new results about thermomechanical buckling and vibration analysis of CNCSDS are proposed for the first time. Highlights: Thermomechanical buckling and vibration of carbon nanotube‐reinforced composite sandwich doubly curved shells was studied.Vibration and stability equations under thermomechanical loads was deduced.The change rules of thermomechanical buckling load and frequency were obtained. [ABSTRACT FROM AUTHOR]

With the advancement of industrial automation, vibrational energy generated by machinery during operation is often underutilized. Developing efficient devices for vibration energy harvesting is thus essential. Triboelectric nanogenerators (TENGs) based on spring and cantilever beam structures show considerable potential for industrial vibration energy harvesting; however, traditional designs often fail to fully harness vibrational energy due to their structural limitations. This study proposes a triboelectric nanogenerator (TENG) based on a crank-rocker mechanism and a spring cantilever structure (CR-SC TENG), which combines a crank-rocker mechanism with a spring cantilever structure, designed for both energy harvesting and self-powered sensing. The CR-SC TENG incorporates a spring cantilever beam, a crank-rocker mechanism, and lever amplification principles, enabling it to respond sensitively to low-frequency, small-amplitude vibrations. Utilizing the crank-rocker and lever effects, this device significantly amplifies micro-amplitudes, enhancing energy capture efficiency and making it well suited for low-amplitude, complex industrial environments. Experimental results demonstrate that this design effectively amplifies micro-vibrations and markedly improves energy conversion efficiency within a frequency range of 1–35 Hz and an amplitude range of 1–3 mm. As a sensor, the CR-SC TENG's dual-generation units produce output signals that precisely reflect vibration frequencies, making it suitable for the intelligent monitoring of industrial equipment. When placed on an air compressor operating at 25 Hz, the first-generation unit achieved an output voltage of 150 V and a current of 8 μA, while the second-generation unit produced an output voltage of 60 V and a current of 5 μA. These findings suggest that the CR-SC TENG, leveraging spring cantilever beams, crank-rocker mechanisms, and lever amplification, has significant potential for micro-amplitude energy harvesting and could play a key role in smart manufacturing, intelligent factories, and the Internet of Things. [ABSTRACT FROM AUTHOR]

This research aims to study the mechanical behavior of the materials most commonly used in crankshaft manufacturing by designing a four-piston crankshaft, analyzing the stresses and displacements resulting from the applied load, and determining vibration frequencies. Additionally, this study examines the thermal behavior of the crankshaft. For this purpose, a three-dimensional model of the crankshaft was designed using CATIA V5 R18 software, and finite element analysis was subsequently performed using ANSYS 2019 R1 software under static, dynamic, and thermal conditions with four different materials in various orientations. To verify the effectiveness of the proposed design, it was compared with a reference design in terms of stresses and displacements. This study also explores improvements in crankshaft geometry and shape. The results indicate that selecting the appropriate material for the working conditions and optimizing the geometry and shape enhance engine performance and reduce the crankshaft's weight by 20%. The findings were validated by comparing the designs, which support increased productivity and improved durability. [ABSTRACT FROM AUTHOR]

Saturated sand foundations are susceptible to liquefaction under dynamic loads. This can result in roadbed subsidence, flotation of underground structures, and other engineering failures. Compared with the traditional foundation reinforcement technology, enzyme-induced calcium carbonate precipitation technology (EICP) is a green environmental protection reinforcement technology. The EICP technology can use enzymes to induce calcium carbonate to cement soil particles and fill soil pores, thus effectively improving soil strength and inhibiting sand liquefaction damage. The study takes EICP-solidified standard sand as the research object and, through the dynamic triaxial test, analyzes the influence of different confining pressure (σ3) cementation times (CT), cyclic stress ratio (CSR), dry density (ρd), and vibration frequency (f) on dynamic strength characteristics. Then, a modified dynamic strength model of EICP-solidified standard sand was established. The results show that, under the same confining pressure, the required vibration number for failure decreases with the increase in dynamic strength, and the dynamic strength increases with the rise in dry density. At the same number of cyclic vibrations, the greater the confining pressure and cementation times, the greater the dynamic strength. When the cementation times are constant, the dynamic strength of EICP-solidified sand decreases with the increase in the vibration number. When cementation times are 6, the dynamic strength of the specimens with CSR of 0.35 is 25.9% and 32.4% higher than those with CSR of 0.25 and 0.30, respectively. The predicted results show that the model can predict the measured values well, which fully verifies the applicability of the model. The research results can provide a reference for liquefaction prevention in sand foundations. [ABSTRACT FROM AUTHOR]

Accurately determining the natural frequency of coal-containing geological structures is crucial for preventing mine dynamic disasters and utilizing vibration waves to break coal and enhance its permeability. Based on the modal theory of rock, vibration models of coal-containing geological structures, including layering and fractures are established. By analysis, the undamped vibration equation and its characteristic equation for both the layered coal system and the fractured coal system are derived. Subsequently, the Lanczos method is employed to solve the system's vibration modes using ABAQUS. The effects of the layering position, layering thickness, layering physical properties, crack width, and crack length on the natural frequency and vibration response of coal-containing geological structures are investigated. The results indicate that when a single influencing factor is altered, the displacement response distribution of the coal body vibration system with geological structures remains essentially the same, and these single influencing factors have a minimal impact on the vibration displacement of the coal-containing geological structure. The natural frequency of the system decreases exponentially as the distance between the layering and the geometric center of the coal system with geological structures increases. The presence of layering in the coal system with geological structures significantly reduces the system's natural frequency. The natural frequency of the coal system with geological structures increases in a power function manner as the layering elastic modulus increases. Conversely, the natural frequency decreases with an increase in crack length. When the change ranges of crack width and bedding thickness are the same, the natural frequency of the fractured coal body system exhibits more significant changes. The natural frequency of the coal system with geological structures initially decreases and then increases as bedding thickness and crack width increase. The trend in the natural frequency changes and the position of the extreme point are related to the ratio of the elastic modulus and density of the geological structure. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have attracted considerable attention as nanomechanical resonators because of their exceptional mechanical properties and nanoscale dimensions. In this study, a novel CNT-based probe is proposed as an efficient nanoforce sensing nanomaterial that detects external pressure. The CNT probe was designed to be fixed by clamping tunable outer CNTs. By using the mobile-supported outer CNT, the position of the partially clamped outer CNT can be controllably shifted, effectively tuning its resonant frequency. This study comprehensively investigates the modeling and vibration analysis of gigahertz frequencies with loaded CNTs used in sensing applications. The vibration frequency of a partially clamped CNT probe under axial loading was modeled using continuum mechanics, considering various parameters such as the clamping location, length, and boundary conditions. In addition, the interaction between external forces and CNT resonators was investigated to evaluate their sensitivity for force sensing. Our results provide valuable insights into the design and optimization of CNT-based nanomechanical resonators for high-performance force sensing applications. [ABSTRACT FROM AUTHOR]

In the current paper, hygro-thermo-magnetically induced vibrations of small-scale viscoelastic tubes containing flow with a spin motion under gravity and tangential loads are analyzed by including surface effects. The dynamic equations are derived in the framework of the modified nonlocal elasticity theory (NET) and Rayleigh beam model. The Galerkin method and Laplace transformation are implemented to solve model equations. Vibration frequencies, stability boundaries, and Campbell diagrams of the system are acquired. Impacts of influential parameters such as scale rotary inertia factor, scale parameter, viscoelastic materials, gravity and tangential loads, flow and spin velocities, geometrical properties, and environmental conditions on the stability of the structure are examined. Also, the obtained results are compared for the Rayleigh and Euler-Bernoulli (EB) beam models. The golden results of this work are that by fine-adjusting the scale parameter and magnetic intensity in the system, destructive effects of hygro-thermal loads can be dampened. Besides, the increment of the rotary inertia factor and nanotube thickness induces destabilizing effect on the system. [ABSTRACT FROM AUTHOR]

Many buildings during their operational period incur damage of different origin: man-made, natural, operational, etc. Dynamic tests are performed for detailed assessment of the technical condition of buildings and structures in accordance with the regulatory documents for general analysis of the building damage state. In a large number of papers, the results of comparison of full-scale tests and numerical analysis using finite element method are presented. When analyzing the results, it can be concluded that the dynamic method is reliable, but has several limitations. The advantage of the dynamic method of building damage assessment is the possibility to adjust finite element models in software systems taking into account results obtained from in-situ tests, which allows to obtain more accurate results for the assessment of bearing capacity under seismic loading. To examine the effect of damage to buildings on their seismic resistance, an experiment with corrosiondamaged reinforced concrete columns was performed. The result of the first stage of the experiment is the assessment of the change in dynamic characteristics (eigenfrequency, vibration decrement, vibration damping coefficient, etc.) of reinforced concrete column specimens subjected to corrosion damage.

In order to investigate the effects of transportation pavement grade on the quality and softening metabolism of winter jujube, this study simulated the actual transportation conditions of winter jujube on high, medium, and low road surfaces through setting vibration frequencies of 4, 10 and 20 Hz on a vibration test bench. The effects of transport vibrations on nutrient composition, softening metabolism, and polysaccharide content in winter jujube were evaluated. Additionally, the shelf life quality of winter jujube was evaluated at room temperature (25.0±1.0 ℃). Results showed that winter jujube appeared earlier decay, hardness decline was accelerated and red index increased with the increase of vibration frequency. The respiration intensity of winter jujube fruit in the vibration treatment groups increased. Throughout the shelf life, the respiratory intensity of the 20 Hz treatment consistently showed a higher level, thereby accelerating the physiological activity of the fruit and leading to substantial consumption of total soluble solids (TSS) and ascorbic acid (AsA). The activities of polygalacturonase (PG), pectin methylesterase (PME), and cellulase (Cx) were enhanced under vibration treatment. The degradation of cell wall polysaccharide components such as protopectin, cellulose and hemicellulose was accelerated, and the content of water-soluble pectin was increased, resulting in softening of winter jujube. Additionally, the content of water-soluble pectin increased, leading to the softening of winter jujube. Low frequency vibration (4 Hz) has minimal impact on the shelf life quality of winter jujube, making it suitable for long-distance transportation. Conversely, high frequency vibration (10, 20 Hz) could expedite quality deterioration and reduce the shelf life of winter jujube.

Context: Whole-body vibration (WBV) training improves muscle strength and balance. Few studies have focused on the effects of WBV frequencies below 30 Hz. We aimed to investigate the effect of low-frequency WBV training on muscle activity, fatigue recovery, and oxygen consumption (VO2). Design: Prospective single-group, repeated-measures study. Methods: In this controlled laboratory setting study, 20 healthy adults (age 23.26 [1.66] y) performed half squats at 0, 4, 6, 8, 12, 16, 20, 24, and 30-Hz WBV. Muscle activity was evaluated using the root mean square and peak electromyography amplitude of 6 muscles (iliocostalis, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius) obtained via surface electromyography. VO2 was measured during the squats using a gas analyzer, and fatigue recovery was evaluated using measurements of lactate after the squats and after a recovery period. Statistical significance was set at P < .05, and analysis of variance was conducted to determine differences in muscle activity, fatigue, recovery, and VO2, with post hoc analyses as appropriate. Results: Of the 6 muscles measured, the muscle activity of the gastrocnemius alone significantly increased from 0 Hz at 4, 8, 12, 16, 24, and 30 Hz based on the root mean square values and at 4, 8, 12, and 30 Hz based on the peak electromyography amplitude values. There were no significant differences in the other muscles. There were no significant differences in VO2 or in lactate levels. Conclusions: Low-frequency WBV during squat exercises significantly increased the activity of the gastrocnemius medialis only at specific frequencies in healthy young adults. Low-frequency WBV is safe and has the potential to increase muscle activity. [ABSTRACT FROM AUTHOR]

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vibration-assisted cutting is a promising technique widely utilized to enhance machining efficiency and achieve superior material finishes compared to traditional cutting methods. However, the underlying mechanism of how vibration impacts material properties and deformation requires an in-depth understanding. In this study, molecular dynamics (MD) simulations were employed to investigate the atomic-scale effects of vibration on copper. The result reveals significant changes in the mechanical behaviours of copper under different cutting conditions. The high-frequency vibration of the cutting tool introduces a notable temperature rise to the workpiece, which is considered beneficial for improving the material removal efficiency. Additionally, the cyclic loading of the tool assists in reducing cutting forces and polishing the machined surface to enhance the surface integrity. Furthermore, the analysis of dislocations and defects suggests that vibration effectively prevents large-scale lattice deformations and visible cracks, thereby enhancing surface finish. This research provides insights into the role of vibration in improving cutting processes and surface quality. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: Sowing Rapeseed. The direct sowing of rapeseed requires shallow tillage for stubble removal, which can cause significant vibrations that impact the seed metering device, thereby affecting the quality of seeding. This study focuses on a double-row hole-wheel-type seed metering device on the 2BYG-220 type combined rapeseed planter. Initially, vibrations experienced by the seed drill during field operations were measured and analyzed, revealing that the vibration frequencies during field operations predominantly ranged between 0 and 25 Hz. Consequently, an eccentric wheel–return-spring-type vibration seed metering test rig was designed, manufactured, and set up. By swapping out the eccentric wheel on the test rig, the amplitude was mainly concentrated within 3 mm. The test results indicate that amplitude had a minimal impact on the performance of the double-row hole-wheel-type rapeseed seed metering device, whereas vibration frequency had a more significant effect. When the vibration frequency was between 0 and 10 Hz, the seed metering device maintained a stable output between 7.6 and 8.2 g/min, with minimal impact from vibrations: the coefficient of variation for seeding uniformity ranged between 35.81% and 44.58%, indicating stability and good uniformity. However, when the vibration frequency ranged from 10 to 24 Hz, the output of the seed metering device decreased rapidly and exhibited a linear relationship with frequency changes, with a determination coefficient (R2) of 0.92376. The coefficient of variation for seeding uniformity increased rapidly and also showed a linear relationship with frequency changes, with a determination coefficient (R2) of 0.87973. Vibrations with frequencies greater than 10 Hz had a considerable impact on the performance of the seed metering device. [ABSTRACT FROM AUTHOR]

For fragile products, packaging requires cushioning protection to prevent irreversible damage from accidental falls, transportation impacts, and other causes. The new polyurethane foam (PUF) material demonstrates superior cushioning and vibration isolation performance in practical applications, effectively minimizing damage from vibrations. Drop and vibration experiments were conducted on packages comprising novel PUF, expandable polyethylene, ethylene–vinyl acetate copolymer foam, and bracelets. Results verify that the new PUF material outperforms in cushioning and vibration isolation, as observed from the acceleration response. Furthermore, a random vibration analysis of a packaging unit involving different thicknesses of PUF materials and bracelets reveals the enhanced vibration isolation effect within a specific thickness range. The vibration results of the bracelet's outer packaging align closely with finite element simulation results, validating the effectiveness of designing and optimizing the outer packaging. Through finite element simulation, deeper understanding and prediction of the bracelet's vibration response under various conditions is achieved, facilitating optimized packaging design for better protection and vibration damping. [ABSTRACT FROM AUTHOR]

Cable force estimation of the suspenders is of tremendous significance for the safety and condition evaluation of arch bridges. The modern suspender cable structure widely used nowadays calls for an efficient and robust estimation method accounting for the cable bending stiffness, complex boundary conditions, intermediate dampers, and variable suspender segments. To estimate the tension force in arch bridge suspenders, this paper proposes an exact analytical method that can simultaneously consider the aforementioned factors for the first time. Based on a generalized suspender cable model including all these factors, the transcendental equation for cable force calculation was obtained from the determinant of a 4 × 4 matrix derived using the transfer matrix method. Due to the low dimensionality of the matrix, the transcendental equation size is largely reduced. This allows rapid cable force calculation without requiring complicated numerical iteration algorithms. A dimensionless parametric analysis was conducted to investigate the impact of various factors on the frequency parameter of the suspenders. Subsequently, the efficacy of the proposed method was verified, and an extensive estimation error analysis was performed using finite elements. Moreover, the method was applied to four real-world bridges with measured vibration frequency available. The results showed that the method can accurately estimate the tension force in suspenders with flexural rigidity, arbitrary boundary conditions, and any number of intermediate dampers and nonuniform segments. The proposed method can also be used for suspender cable force estimation of other cable-supported bridges, such as suspension bridges. [ABSTRACT FROM AUTHOR]

The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated. The effects of the control and interface parameters on the system's stability are analyzed. The frequency range of self-excited vibrations is investigated from the energy point of view. The phenomenon of self-excited vibrations is elaborated with the phase trajectory. The corresponding control strategies are briefly analyzed with respect to the vibration mechanism. The results show that when the levitation objects collide with the mechanical interface, the system's vibration frequency becomes larger with the decrease in the collision gap; when the vibration frequency exceeds the critical frequency, the electromagnetic system continues to provide energy to the system, and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state. [ABSTRACT FROM AUTHOR]

Using Tokuda's improved linear combination operator method and variational technique, the expression of the polaron effective mass in a parabolic quantum well is derived. Due to the spin-orbit interaction, the effective mass ratio of polaron splits into two branches. The dependence of the effective mass ratio on the vibration frequency, the spin-orbit coupling parameter, and the velocity is discussed by numerical calculation in the presence and absence of phonon. The effective mass ratio of polaron is an increasing function of vibration frequency. The absolute value of the spin splitting effective mass ratio increases with the increase in the spin-orbit coupling parameter and decreases with the increase in velocity. Due to the heavy hole characteristic of spin-orbit interaction, the spin splitting effective mass ratio is negative. The effective mass ratio is larger in the presence of a phonon than in the absence of a phonon, and the effective mass ratio splitting distance is independent of the phonon. [ABSTRACT FROM AUTHOR]

Copyright of Light Industry Machinery is the property of Light Industry Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article discusses the design and the optimization of converters for converting vibration energy into electrical energy by using the vortex interaction of flows. Given the global need to transition to renewable energy sources in response to climate change, this research focuses on improving the structural efficiency of vibrational energy converters. By using a laboratory setup with a regular structure of transducers, the effect of the ratio of the width of the contact area of the transducer to the width of the free end on the amplitude and frequency of oscillations has been studied. Based on the results of the research, the optimal width ratio that maximizes vibration energy output while ensuring material efficiency and structural strength has been determined. The findings show that a minimum contact zone width not only reduces material costs, but also increases vibration energy output, which is key to the efficiency of energy conversion processes. Mathematical calculations of the vibration movements of converters based on experimental data provide a reliable basis for predicting performance and guiding design improvements of future installations. This study contributes to the broader field of renewable energy technologies by offering a detailed analysis of the parameters affecting the efficiency of vibrational energy converters. [ABSTRACT FROM AUTHOR]

The results of experimental studies on the creation of highly efficient designs of vibration-isolating compensators for pipelines with liquid are considered. It is noted that the only way to evaluate the effectiveness of various compensators in reducing vibration at different frequencies currently is to compare their transient vibration stiffness or transient mechanical impedance, which were measured on special stands at a given frequency. The stiffness of the compensator increases significantly with increasing frequency vibrations. Hazardous frequencies may vary between piping systems. For this reason, it is impossible to set an integral criterion for the effectiveness of a vibration-isolating compensator, similar to static stiffness. The results of measurements carried out on a special stand on the transitional vibration stiffness of a new design compensator with thin-layer rubber-metal elements (TRME) are presented. The rigidity decreased by 10 or 100 times or more in the frequency range from 50 to 800 Hz relative to the rigidity of a serial compensator based on rubber cord casing (RCC), including in the presence of water inside it. It has been experimentally shown that the vibration-isolating ability of the same compensator as part of a pipeline system, determined by the value of the dynamic force transmitted by the compensator to the pipeline from the pump, significantly depends on the presence of water in them and its flow, which is not taken into account in known methods. The results of testing compensators with RCC and TRME with a bore diameter of 80 mm as part of a stand with a ring pipeline system, a pump, systems for monitoring the flow of the working fluid, vibrations, pressure pulsations, and dynamic (vibration) forces transmitted by the compensators to the pipeline are presented. In a stand with pipelines, the efficiency of vibration-isolating compensators with TRME is still 10 and 100 times higher than compensators with RCC in the absence of water and decreases by an order of magnitude in the presence of water without its flow when the pump is vibrated by a vibrator. Efficiency decreases even further if water flows through expansion joints and pipelines while the pump is running. [ABSTRACT FROM AUTHOR]

Under unstable wind loads, the wind turbine tower, as a supporting component of the horizontal axis experiences inevitable vibration. To explore the vibration characteristics of the tower, a vehicle test platform is established to measure the vibration acceleration component signals at different heights of a 300W small horizontal axis wind turbine tower. The results show that specific vehicle vibration test equipment can accurately test the vibration characteristics and laws of small wind turbine towers. The main vibration form of the tower is low frequency, with noticeable axial vibration at the top and lateral vibration in the middle of the tower due to aerodynamic load from natural wind. These findings can be used as a valuable reference for the safety and reliability design of the whole machine and the low-frequency vibration status monitoring of wind turbines. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon nanotubes (CNTs) have attracted considerable attention as nanomechanical resonators because of their exceptional mechanical properties and nanoscale dimensions. In this study, a novel CNT-based probe is proposed as an efficient nanoforce sensing nanomaterial that detects external pressure. The CNT probe was designed to be fixed by clamping tunable outer CNTs. By using the mobile-supported outer CNT, the position of the partially clamped outer CNT can be controllably shifted, effectively tuning its resonant frequency. This study comprehensively investigates the modeling and vibration analysis of gigahertz frequencies with loaded CNTs used in sensing applications. The vibration frequency of a partially clamped CNT probe under axial loading was modeled using continuum mechanics, considering various parameters such as the clamping location, length, and boundary conditions. In addition, the interaction between external forces and CNT resonators was investigated to evaluate their sensitivity for force sensing. Our results provide valuable insights into the design and optimization of CNT-based nanomechanical resonators for high-performance force sensing applications.

Accidental boiling liquid expansion vapour explosions (BLEVEs) caused by the bursting of liquified petroleum gas (LPG) tank inside a tunnel can induce vibrations of its surrounding geological media and threaten the stability of adjacent tunnels and structures. Therefore, it is essential to understand the characteristics of vibrations induced by LPG BLEVEs inside the tunnel for the safety design of its adjacent structures. Owing to the difficulty in effectively predicting the LPG BLEVE loads, the current practice usually employs equivalent methods, e.g., the TNT-equivalency method, in LPG BLEVE load predictions for structural response analysis, which may lead to inaccurate response predictions. This study compares ground vibrations induced by a BLEVE inside an arched road tunnel with those induced by its equivalent TNT explosion via high-fidelity numerical simulations. The results demonstrate that the frequency of BLEVE-induced vibrations is lower than that induced by the TNT explosion at the same scaled distance. The intensity of LPG BLEVE-induced vibrations at relatively small-scaled distances is lower than that of TNT explosion-induced vibrations at the same scaled distance, but becomes higher after a certain scaled distance because of the relatively low attenuation rate. In addition, parametric analysis is conducted to evaluate the effects of various factors on the characteristics of LPG BLEVE-induced ground vibrations. It is found that the surrounding rock type, the rock porosity, and the cover depth of the tunnel have more significant influences than the concrete grade of the tunnel lining. The recommendation for the tunnel design is also given based on the intensity and frequency characteristics of BLEVE-induced vibrations.

This article discusses the modal behavior of elastically constrained beams under various types of foundations and provides insights into the effects of different factors on the eigenfrequencies of beams. Numerical and analytical techniques, specifically the Galerkin finite element method (GFM) and the separation of variables, are utilized to determine the eigenfrequencies and mode shapes of beams. Modal analysis of Timoshenko, shear, Rayleigh, and Euler-Bernoulli beams that are elastically constrained and resting on Winkler, Pasternak, and Hetényi foundations, considering non-classical boundary conditions, is included in the study. The effects of factors such as flexural rigidity, transverse modulus, and Winkler foundation constant on natural frequencies of different beam models are investigated. The proposed method efficiently converges to the exact solution without shear locking in the stiffness element. The results demonstrate that the natural frequencies of the beam rise because of the shear layer, flexural rigidity, and foundation constant. Furthermore, the Hetényi elastic foundation affects the natural frequency of the beam, depending on the relative values of beam stiffness and foundation stiffness. Additionally, incorporating both shear deformation and rotary inertia has a greater impact on the eigenfrequencies of Euler-Bernoulli beams compared to incorporating only one of these effects. The findings of this work provide valuable insights into the behavior of beams under different foundation conditions and have potential applications in the design and optimization of structures incorporating beams, thereby enhancing the understanding of beam analysis.

This study aims to reduce the violent vibration for the high reliability of the integrated machine for straw return and residual film recycling. A vibration characteristic analysis was carried out to optimize the structural parameters. The modal characteristics of the frame were solved using the Lanczos algorithm on the ANSYS software, in order to obtain the modal frequencies and shapes. The equivalent vibration mechanics model was used to establish the vibration model of the machine. Newton's second law was adopted to analyze the model force. The vibration program of the simulation was constructed to solve the vibration parameters using Matlab/Simulink. A series of measurements of point locations were used to verify the vibration of the machine. The test was also carried out in the conditions of no-load and field harvesting. Some sensors were installed and connected to the YND Data Acquisition Instrument. Vibration data was collected with the time and frequency domains. The results showed that the 1st and 2nd order natural frequencies of the frame were 39.001 and 39.076 Hz, respectively. The modal vibration pattern was that the side panels oscillated back and forth along the y-axis. The vibration intensity under field harvesting was higher than that under no-load conditions. The measurement point 3 vibration amplitudes in the two conditions were 34.93 and 22.36 m/s², respectively, where the difference in the vibration amplitude was 12.57 m/s². The maximum was found in the measurement point 3 of the Y, and Z directions in field harvesting, as well as the measurement point 5 in the X direction of the amplitude. The continuous operation of the stripping device increased the vibration intensity of the machine with less reliability in the field harvesting under the straw crushing device. The straw-crushing device and the stripping device were the main components that contributed to the machine's vibration. The effective values of vibration acceleration were 2.92 and 2.64 m/s², respectively, after test and simulation. The relative error of 9.6% fully met the requirements of mechanical simulation. The spectrum analysis showed that the machine vibration frequency was mainly for the fundamental frequency of the tractor power output shaft, as well as the fundamental frequency and frequency multiplier of the straw crushing device. The large vibration intensity was measured at point 3 of the X, Z directions, and point 1 of the Z direction. There were weld cracks and bolt loose. The measured vibration frequency appeared at 36.13 Hz close to the first two orders of the frame's natural frequency. The modal vibration pattern was easy to stimulate the local resonance in the range of excitation frequency. The orthogonal experiment was adopted to optimize the frame with the thickness of the side plate, the thickness of the main connecting beam tube wall, and the width of the secondary support beam as the object variables, while the 1st and 2nd orders of the frame's natural frequency as the indicators. The optimal parameters were achieved, where the thickness of the side plates was 12.0 mm, the tube wall thickness of the main connecting beam was 6 mm, and the width of the secondary support beam was 70 mm. The 1st and 2nd natural frequencies were 50.700 and 53.322 Hz, respectively, which were higher than the maximum limit of the excitation frequency in the straw-crushing device of 46 Hz. Thus the resonance was effectively avoided. The improved model was verified to significantly reduce the vibration intensity of each measurement point, with a 48% amplitude of the maximum reduction. The transmission of vibration intensity was also significantly weakened, indicating the effective optimization. This finding can provide the theoretical reference for the vibration analysis and structural optimization of the residual film recycling machine. [ABSTRACT FROM AUTHOR]

Mechanized agriculture is the foundation of large-scale agriculture. However, in current mechanized corn cultivation, the cleaning efficiency during the cleaning phase is poor due to design defects, which in turn reduces its yield. Therefore, this study proposed an optimization of the corn screening device based on high-precision aerodynamic models. 3D modeling was used to explore the parameter optimization of the corn cleaning devices from an aerodynamic point of view, and certain improvements were made to the fish scale sieve structure. The results indicated that the cleaning efficiency was related to airflow velocity, vibration frequency, and the opening of the fish scale sieve. The optimal wind speed was 16 m/s, and the separation efficiency currently was 94.27%. The optimal vibration frequency was 8 Hz, and the separation efficiency currently was 97.24%. The optimal opening of the fish scale sieve was 26 mm, at which point the screening efficiency reached 100%. The optimized fish scale sieve reduced blockage by 63.7% compared to the traditional fish scale sieve, and ultimately achieved an impurity content of 1.4% with an improvement of 81.3%. In summary, the optimization plan proposed by this research can effectively improve the cleaning efficiency of corn and promote agricultural production and efficiency. [ABSTRACT FROM AUTHOR]

The solidification characteristics of commercially pure aluminum with and without vibration were investigated using experiments and numerical simulation methods. The results showed that the vibration condition is beneficial to the filling flow. The changes of melt flow and temperature field were studied and compared with those obtained without a mechanical vibration field. The existence of the mechanical force causes the melt velocity to be accompanied by abrupt fluctuations at different positions of the melt. However, the ending time of vibration solidification is slightly longer than that without applying mechanical vibration field. The application of mechanical vibration significantly refines the grain size, thereby increasing tensile strength and elongation. With the increase in vibration frequency, the solidification structure of the alloy is refined and then coarsened. It is, therefore, found that the optimal mechanical vibration frequency is 30 Hz. The present study can provide guidance for engineering practice in the vibration field. [ABSTRACT FROM AUTHOR]

It is shown that the vibration transfer and working medium pressure pulsations through vibration-isolating pipeline junctions of various plants may increase by two or three orders of magnitude with an increase in the vibration frequency and in the presence of incompressible working fluid. The results of research of the found physical models that determine this phenomenon are presented. The experimental results for a spatial three-component broadband active vibration-protection system (AVS) for vibration damping beyond the vibration isolation junction with liquid are considered. An experimental plant scheme for studying the simultaneous spatial active damping of dynamic forces, vibrations and pressure pulsations downstream from the junction has been given. Calculated dependences of the maximum efficiency of considered AVS on frequency are obtained. Efficient active damping of forces is shown to be attainable in an open loop without feedback. While damping in an open loop at the experimental plant, the efficiency of active damping of dynamic forces is obtained in three directions up to 10 dB or more in the frequency range from 5 to 800 Hz (more than seven octaves). The analysis of scientific publications reveals the uniqueness of this result. In this case, there are no zones of negative efficiency outside the active damping frequency range, which appear while using other methods of active damping. [ABSTRACT FROM AUTHOR]

Graphene has excellent mechanical properties and vibration frequency is an important mechanical property. In this paper, the effects of doping elements and doping concentrations on the vibration characteristics of graphene nanoribbons were investigated by molecular dynamics simulation. The vibration characteristics are influenced by the doping element, depending on the bond structural difference in bond structure between doping atoms and carbon atoms. The vibration frequencies of Nitrogen (N)-doped and Nitrogen–Nitrogen (N–N)-doped graphene nanoribbons are slightly lower than those of pure graphene nanoribbons. However, the vibration frequencies of Sulfur (S)/Phosphorus (P)-doped and Sulfur–Sulfur (S–S)/Phosphorus–Phosphorus (P–P)-doped graphene nanoribbons are significantly lower than those of pure graphene nanoribbons. In addition, with the increase of S (P) doping concentration, the vibration frequency of monolayer graphene nanoribbons decreases gradually. [ABSTRACT FROM AUTHOR]

In this study, we sought to characterize the effect of water vibration frequency stress on crimson snapper (Lutjanus erythropterus) survival to determine an optimal transportation speed. To achieve this, we used a transport tank (25 cm × 17 cm × 16 cm) to simulate the transport process. After 8 h at five different vibration frequencies (D1 = 75 rpm, D2 = 105 rpm, D3 = 135 rpm, D4 = 165 rpm, and D5 = 195 rpm), the pH and dissolved oxygen (DO) levels in the tanks decreased; ammonia nitrogen levels (NH4-N) and temperature (T) increased with increasing density; and significant changes in oxidative stress biomarkers, digestive enzymes, and ATPase levels were observed in crimson snapper fry. The enzyme activity increased and reached the maximum value at 195 rpm. The experimental results suggested that during the actual transport, when using transport tanks, the length of the transport time was less than 8 h, and setting the vibration frequency for transportation at 135 rpm was more appropriate, that is, a speed of 50 km/h for transporting crimson snapper fry. [ABSTRACT FROM AUTHOR]

The research mainly focuses on the fatigue strength characteristics of 6061-T6 aluminum alloy fillet welds under different vibration frequencies. Firstly, by introducing Stress Life Curve (S-N Curve) and Probability Stress Life Curve (P-S-N Curve), the external vibration stress effects of the main load-bearing points in the stress environment of welded joints are analyzed. Subsequently, a vibration test control system is designed to analyze the relationship between vibration frequency and fatigue strength through nominal stress analysis and hot spot stress analysis. The research findings revealed that under the nominal stress analysis method, the P-S-N fitting curve showed a declining trend with an increase in fatigue life for stress variation curves with survival rates of 50 %, 95 %, and 97.7 % at vibration frequencies of 57.5 Hz, 67.5 Hz, and 77.5 Hz. At the same survival rate stress conditions, the fatigue life variation formed by resonance frequency was smaller, and the fatigue life in the resonance state was relatively lower. There is a certain correlation between vibration frequency and fatigue strength, with resonance frequency corresponding to relatively low fatigue life. This research result helps to reveal the fatigue behavior of 6061-T6 aluminum alloy fillet welds under different vibration stresses, providing a reference for the structural safety design of aluminum alloy components. [ABSTRACT FROM AUTHOR]

This article is devoted to the development of a dynamic vibration absorber as a system in which an air spring moves between guides of a given shape perpendicular to their axis of symmetry. The shape of the guides is determined from the condition that the characteristic of the dynamic absorber is linear, which is equivalent to a spring with a given stiffness. The main disadvantage of most modern dynamic absorbers is that they are effective when operating only at a certain frequency of the driving force acting on a protected object. With a small change in this frequency, the amplitude of the protected object can increase many times over. This article proves that, by changing the designed pressure in the air spring of the proposed absorber, it is possible to get a given stiffness, at which it is effective at different frequencies of the driving force. [ABSTRACT FROM AUTHOR]

The direct sowing of rapeseed requires shallow tillage for stubble removal, which can cause significant vibrations that impact the seed metering device, thereby affecting the quality of seeding. This study focuses on a double-row hole-wheel-type seed metering device on the 2BYG-220 type combined rapeseed planter. Initially, vibrations experienced by the seed drill during field operations were measured and analyzed, revealing that the vibration frequencies during field operations predominantly ranged between 0 and 25 Hz. Consequently, an eccentric wheel–return-spring-type vibration seed metering test rig was designed, manufactured, and set up. By swapping out the eccentric wheel on the test rig, the amplitude was mainly concentrated within 3 mm. The test results indicate that amplitude had a minimal impact on the performance of the double-row hole-wheel-type rapeseed seed metering device, whereas vibration frequency had a more significant effect. When the vibration frequency was between 0 and 10 Hz, the seed metering device maintained a stable output between 7.6 and 8.2 g/min, with minimal impact from vibrations: the coefficient of variation for seeding uniformity ranged between 35.81% and 44.58%, indicating stability and good uniformity. However, when the vibration frequency ranged from 10 to 24 Hz, the output of the seed metering device decreased rapidly and exhibited a linear relationship with frequency changes, with a determination coefficient (R2) of 0.92376. The coefficient of variation for seeding uniformity increased rapidly and also showed a linear relationship with frequency changes, with a determination coefficient (R2) of 0.87973. Vibrations with frequencies greater than 10 Hz had a considerable impact on the performance of the seed metering device.