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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.

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]

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]

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]

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]

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.

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.

The optimal process parameters of ultrasonic-assisted processing were studied to further improve the molding quality and mechanical properties of Ni60/WC-TiO2+La2O3 composite coating. A single-factor experiment was used to explore the influences of ultrasonic vibration frequencies on Ni60/WC-TiO2+La2O3 composite coating. The microstructure, elemental composition, phase composition, hardness, and wear resistance of the coating were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), an energy spectrometer, a microhardness meter, a friction and wear tester, and other equipment. Ultrasonic vibrations significantly improved the problems of pores in the coating, and the porosity was reduced from 0.13 to 0.014%. When the vibration frequency was 32 kHz in the experiment, the aspect ratio of the coating was optimized from 2.06 to 2.48, the dilution rate increased from 5.60 to 5.79%, the hardness increased from 960.25 to 988.45 HZ1.0, and the friction coefficient was reduced from 0.34 to 0.27. The coating performance was significantly improved, and the research results provide a reference for preparing excellent Ni60/WC-TiC+La2O3 composite coating. [ABSTRACT FROM AUTHOR]

A liquid launch vehicle is an important carrier in aviation, and its regular operation is essential to maintain space security. In the safety assessment of fluid launch vehicle body structure, it is necessary to ensure that the assessmentmodel can learn self-response rules from various uncertain data and not differently to provide a traceable and interpretable assessment process. Therefore, a belief rule base with interpretability (BRB-i) assessment method of liquid launch vehicle structure safety status combines data and knowledge.Moreover, an innovative whale optimization algorithm with interpretable constraints is proposed. The experiments are carried out based on the liquid launch vehicle safety experiment platform, and the information on the safety status of the liquid launch vehicle is obtained by monitoring the detection indicators under the simulation platform. The MSEs of the proposed model are 3.8000e-03, 1.3000e-03, 2.1000e-03, and 1.8936e-04 for 25%, 45%, 65%, and 84% of the training samples, respectively. It can be seen that the proposed model also shows a better ability to handle small sample data. Meanwhile, the belief distribution of the BRB-i model output has a high fitting trend with the belief distribution of the expert knowledge settings, which indicates the interpretability of the BRB-i model. Experimental results show that, compared with other methods, the BRB-i model guarantees the model's interpretability and the high precision of experimental results. [ABSTRACT FROM AUTHOR]

The marine and alluvial plains along the southeastern coast of China are widely distributed in sandy formations, including smaller sand lenses and interlayers. The interlayers of sand have a significant impact on the mechanical properties of soft clay. In this paper, a large number of undrained unidirectional and bidirectional cyclic loading tests for soft clay with sand interlayers were carried out by a dynamic triaxial test system. Test results show that, under unidirectional and bidirectional cyclic vibration, the area of the hysteresis loop decreases and the slope of the connecting line at both ends of the hysteresis loop increases with the increasing of frequency. For the same vibration frequency, the area of the bidirectional vibration hysteresis loop and the slope of the connecting line at both ends are smaller than that of the unidirectional cyclic vibration. Under the same dynamic stress ratio, cumulative axial deformation caused by unidirectional and bidirectional vibration increases with the increasing frequency. Under unidirectional vibration, dynamic elastic modulus decreases at first, and then increases with the increasing frequency. For the same frequency, dynamic elastic modulus of the sample increases with the increase in cycles. Due to the effect of radial cyclic stress, the curves of dynamic elastic modulus and damping ratio with frequency under bidirectional vibration are opposite to those under unidirectional vibration. [ABSTRACT FROM AUTHOR]

During the smelting process of the AOD furnace, the unbalanced reaction of material will lead to the occurrence of splashing. It will not only damage the smelting equipment but also seriously injure the personnel. In this study, first, the information of liquid level, audio information and vibration information are detected by multiple sensors respectively. Then the fused information is used to forecast the splashing. Finally, the multitasking fuzzy controller is used to suppress splashing. The results show that the method of forecasting and suppressing splashing can accurately forecast and achieve rapid suppression. Thus the efficiency of smelting can be improved. [ABSTRACT FROM AUTHOR]

When the traditional drill and blast method is applied to rock crushing projects, it has strong vibration, loud noise and dust pollution, so it cannot be used in densely populated areas such as urban public works. We developed a supercritical CO2 true triaxial pneumatic rock-breaking experimental system, and conducted laboratory and field tests of dry ice powder pneumatic rock-breaking. The characteristics of the blast-induced vibration velocity waveform and the evolution of the vibration velocity and frequency with the focal distance were analyzed and discussed. The fracturing mechanism of dry ice powder pneumatic rock breaking is studied. The research results show that: (1) The vibration velocity induced by dry ice powder pneumatic rock breaking decays as a power function with the increase of the focal distance; (2) The vibration frequency caused by dry ice powder pneumatic rock breaking is mainly distributed in 1–120 Hz. Due to the dispersion effect, the dominant frequency of 10–30 Hz appears abnormally attenuated; (3) The traditional CO2 phase change fracturing energy calculation formula is also applicable to dry ice pneumatic rock breaking technology, and the trinitrotoluene (TNT) equivalent of fracturing energy is applicable to the Sadovsky formula; (4) Dry ice powder pneumatic rock breaking is shock wave and high-energy gas acting together to fracture rock, which can be divided into three stages, among which the gas wedge action of high-energy gas plays a dominant role in rock mass damage.

To illustrate the vibration characteristics of a rotating pipe in flow, experiments were conducted for a pipe in flow, a rotating pipe in still water and a rotating pipe in flow. For the pipe in flow without rotation, the trajectory diagram is ‘8’ shaped. For the rotating pipe in still water, a multiple frequency component was induced, and a ‘positive direction whirl’ was found. For the flow and rotation, at a flow velocity of 0.46 m/s, the vibration is dominated by the combination of flow and rotation. With an increase in rotating frequency, the trajectory of the rotating pipe varies from an ‘8’ shape to a circular shape and the ‘reverse direction whirl’ is induced, which is different from ‘positive direction’ in still water. The vibration frequency ratio increases uniformly with flow velocity. At a flow velocity of 1.02 m/s, at which the frequency is close to the theoretical natural frequency, the vibration frequency ratio is f*≈1. Predominantly governed by vortex-induced vibration (VIV), the vibration behavior of a rotating pipe subjected to fluid flow conditions has been found to exhibit complete vanishing of whirl. The vibration characteristics of a rotating pipe in flow are studied by the experiments which is benefit for structural drilling design.

To reveal the action mechanism of vibration frequency in alfalfa opening compression, a self-developed vibration compression test system was used to evaluate the variation of compression force during alfalfa open compression. A faster vibration frequency yielded a smaller compression force required for compressing alfalfa into blocks. Compared with free vibration compression, vibration compression was beneficial to release the internal stress of alfalfa block, reduce the forming pressure, and stabilize the high density. In the range of test vibration frequency, when the frequency was 15 Hz, the residual internal stress release ratio of alfalfa block was the highest, and the stable density of alfalfa block was the largest. Considering the pressure and alfalfa block density comprehensively, the optimized vibration frequency was approximately 15 Hz.

Introduction: A hydraulic power injection machine is designed to use a driving screw to inject melted plastic into a specified mold. This machine can be found at an automotive spare parts factory. The cantilever-style heavy-duty screw injector is supported by one roller and secured at the end. An obvious need for vibration analysis on the roller support is essential. A mass spring damper model is proposed for deeply investigating the friction induced vibration mechanism for this injection system to well understand and analyze its vibration behavior. Purpose: A mechanical mode of two degrees-of-freedom (DOF) is designed to improve research on the dynamic features of the Plastic Hydraulic Injection System (PHIS) mechanism. Materials and methods: Experimental investigation and analysis of this mechanism are explored to obtain the instability speed and critical stick slip (SS) speed. The numerical imitation results of this work will help with the design and development of the PHIS mechanism. Conclusion: The stability of the system and SS behavior are next examined by determining the critical variability speediness and critical SS speed. A simulation study is carried out to evaluate the effect of various parameters of the system on its stability and on the behavior of the SS motion. [ABSTRACT FROM AUTHOR]

The seismic vulnerability assessment of existing structures is a well-known challenging task, due to a combination of several aspects. The use of analytical or finite element (FE) numerical models can offer robust support in this analysis but necessitates the accurate calibration of geometrical and mechanical input, with related uncertainties. In this paper, attention is focused on the identification of dynamic parameters, based on modal numerical analysis, of a 50-year-old, reinforced concrete, elevated water tank (EWT) characterised by a reservoir with a truncated cone shape. The structure is located in a high seismic region of northern Italy and presently necessitates retrofit plans to preserve its functionality. Based on the limited available experimental evidence and technical drawings, major efforts are spent for the numerical prediction of fundamental vibration modes and frequencies of the structure, which represent a first key step for seismic analyses, under various water-filling levels. To this aim, four different FE numerical strategies able to include both structural features and possible fluid–structure interaction (FSI) effects are developed. By progressively increasing the computational cost (and expected the accuracy of the solutions), FE models based on added-mass (M0 model), spring-mass (M1-DM or M1-DS models), or acoustic (M2 model) strategies are taken into account and combined with increasing detailing in geometrical description of the structure. Results from parametric modal analyses are discussed for the case-study EWT, in terms of computational cost, possible numerical limitations, accuracy of predicted frequencies/modal shapes, sensitivity to water-filling levels and operational configurations, with the support of several pieces of experimental evidence and consolidated analytical formulations for fundamental frequency estimations. [ABSTRACT FROM AUTHOR]

In particular environments, such as the Gobi Desert, the problems encountered in a project are complex, resulting in reduced stability of the anchoring system and multiple forms of failure. This paper takes the factors influencing the stability of sand anchors under vibration loads as the research background. Theoretical analysis and indoor model tests were used to study the load-bearing performance of sand anchors under vibration loads; in addition, a comparative analysis of this performance along with failure forms of sand anchor systems, various sand soil moisture contents, and vibration parameters was performed. The results of the study showed that as the water content becomes higher, the cohesive force of the sand decreases and produces a higher displacement in the water content, with most of the anchor solids becoming prone to fatigue failure. When the water content and vibration frequency remain stable and the vibration amplitude increases, the anchor rod is disturbed after the ultimate pullout bearing capacity forms a decreasing trend, with a decline rate of approximately 40%. By keeping the water content and vibration amplitude stable and changing the vibration frequency, the ultimate pullout capacity of the anchor does not change significantly, and the frequency reaches a certain level when it attains a compacting effect on the surrounding soil and thus has less influence on the anchor. The anchor pullout resistance bearing is most sensitive to the change in sand moisture content, more sensitive to the vibration amplitude, and less sensitive to the vibration frequency, but its correlation is not significant. [ABSTRACT FROM AUTHOR]

Purpose: A nondestructive, noncontact approach for the estimation of elastic parameters of fully clamped thin sheet is presented in current work. Frequency response of pulsed laser impulse excited clamped thin plate is used for the estimation of elastic parameters. Methods: Elastic parameters like Young's modulus, shear modulus and Poisson ratio of fully clamped thin square soda lime glass plate are determined by pulsed laser impulse excitation of vibrations. Initially, frequency response is recorded by measuring vibrations using quadrature Michelson interferometer. Then, finite element method (FEM) based simulations are performed in ANSYS Workbench for the identification of mode shapes for transverse modes of vibrations. Experimentally measured natural frequencies are compared with the modes of vibrations from FEM for the determination of elastic parameters. Materials: Soda lime glass fixed in an Aluminum holder. Results: The obtained values of parameters are in agreement with analytical calculations within 3% and Young's modulus measured by three point bending method within 1.5%. Effect of holder on the modes of vibrations of glass is found to be less than 2%. Conclusion: Both simulations and experimental results are matched iteratively and extra bending and twisting modes of holder are identified. Best fitted elastic parameters for results are further verified using other methods. Due to the noncontact nature of the pulsed laser excitation and laser-based measurements, current technique can easily be applied for the measurement of Young's modulus at in-situ harsh environments even at elevated temperatures. [ABSTRACT FROM AUTHOR]

The publication deals with the issue of ensuring the stability of an unmanned aerial vehicle flight by speed. An analysis of the physical essence of the process of ensuring the unmanned aerial vehicle stability by speed is presented. Attention is paid to the flight modes in which the operator (external pilot) may encounter difficulties in the practical piloting of the unmanned aerial vehicle. The possible causes of abnormal situations when flying the unmanned aerial vehicle at speeds close to the borderline low are analyzed. Possible actions of the operator (external pilot) to return the unmanned aerial vehicle to the operating speed range from the area of instability are considered. The article shows the features of stability and controllability of an unmanned aerial vehicle in a route flight mode. Attention is paid to the complexity of piloting and safety of flight in the second modes. The article demonstrates the method of determining the boundary between the first and second flight modes. The features of unmanned aerial vehicle management and ensuring stability in the first and second modes are shown. The issue of dynamic stability of the unmanned aerial vehicle is investigated. Numerical modeling of the longitudinal movement of the unmanned aerial vehicle in free, uncontrolled flight was carried out, trajectories for the unmanned aerial vehicle of the selected configuration with a change in speed and angle of inclination of the trajectory in time were obtained. Graphs of movement trajectories with changes in speed and height over time were constructed, graphs of transient processes were constructed for cases of stable and unstable flight modes. An analysis of the external factors that most affect the flight parameters in various conditions of unmanned aerial vehicle use was carried out. [ABSTRACT FROM AUTHOR]

The frame of corn harvester is prone to vibration bending and torsional deformation due to the vibration caused by field road bumps and fluctuations. It poses a serious challenge to the reliability of machinery. Therefore it is critical to explore the vibration mechanism, and to identify the vibration states under different working conditions. To address the above problem, a vibration state identification method is proposed in this paper. An improved empirical mode decomposition (EMD) algorithm was used to decrease noise for signals of high noise and non-stationary vibration in the field. The support vector machine (SVM) model was used for identification of frame vibration states under different working conditions. The results showed that: (1) an improved EMD algorithm could effectively reduce noise interference and restore the effective information of the original signal. (2) based on improved EMD - SVM method identify the vibration states of the frame with the accuracy of 99.21%. (3) The corn ears in grain tank were not sensitive to low order vibration, but had an absorption effect on high order vibration. The proposed method has the potential to be applied for accurately identifying vibration state and improving frame safety. [ABSTRACT FROM AUTHOR]

• A systematic experimental study to investigate the influence of vibration amplitude, frequency, and subsequent vibration-induced acceleration on oil recovery. • Image analysis-based methodology to quantify dislodgment effectiveness, representing a form of oil recovery, is developed. • Experimental observations demonstrate seismic vibrations' effect in dislodging an entrapped fluid. • The observed data serve as a reference tool for computational studies while implementing them in the reservoir simulations. The impact of seismic vibrational amplitude and frequency in dislodging an entrapped diesel globule in a pore model is experimentally studied. The effective change occurring inside a 3D printed pore model estimated from a systematic image analysis methodology is developed to represent the oil recovery. The pore model is subjected to sinusoidal vibrations with amplitudes ranging from 0.1 mm to 2 mm and frequencies ranging from 5 to 100 Hz. Dislodgment of entrapped diesel is observed for frequency values between 40 and 80 Hz with vibration amplitude above 0.5 mm. Even though increasing the vibration frequency increases the vibration-induced acceleration, the dislodgment of the entrapped fluid is not observed at higher frequencies. Smaller vibration amplitudes imparted by the shaker and a possible slip flow at the oscillating walls occurring at higher frequencies are reasoned for this observation. [ABSTRACT FROM AUTHOR]