Vibration Transmission Research Articles

Direct measurement for hand-transmitted vibration of human fingers-hand-arm system in the zero-gravity environment

This paper proposes a direct measurement method to obtain the mechanical impedance and vibration transmissibility of the fingers-hand-arm system when operating power tools based on zero-gravity environment simulations. A hand-transmitted vibration measurement system with a suspension device for zero-gravity simulation is first built. The two-step dynamic measurement method is used to measure the dynamic force and acceleration of fingers and palm directly. The forearm and upper arm’s acceleration is also measured using the two-step dynamic measurement method. Based on eliminating the effect of the handle’s effective mass on the mechanical impedance, the mechanical impedance and vibration transmissibility of the human fingers-hand-arm system during the actual operation of the power tool are calculated by using the measured data, and the biodynamic response characteristics of the fingers-hand-arm system at different frequencies are analyzed. The results show that, under the condition of the ISO standardized operating posture (ISO 10819, 2013), the mechanical impedance and vibration transmissibility curves obtained by direct measurement of 21 subjects have remarkable consistency respectively. Compared with the experimental data in the gravity environment, the mechanical impedance and the vibration transmissibility obtained based on the zero-gravity simulation are more consistent with the working conditions of the on-orbit maintenance power tools.

The research of vibration localization under strong disturbances using modal analysis methods

Abstract Vibration localization is a typical feature of aperiodic structures. This work investigates the vibration localization of framed cylindrical shells with a high disturbance degree. First, the spring oscillator system is considered an example to reveal the general law governing how high disturbance degree influences the vibration transmission in a structure. Then the strong localization coefficient is calculated using the modal analysis method. Finally, the conclusions of the one-dimensional systems are applied to the two-dimensional structures based on the passband approximation equivalent method to derive the strong localization coefficient of the aperiodic ring-ribbed cylindrical shell. This study realizes quantitative calculation of the vibration localization coefficient under high disturbance degree. The results of this work provide theoretical support for reducing the vibration transmission performance of a structure by increasing the degree of disturbance.

Design of new anti-vibration gloves for workers: ongoing research and preliminary results

Abstract Powered hand-held tools such as drillers, chainsaws, blowers, etc. cause hand-arm vibration syndrome. Common anti-vibration gloves cannot attenuate the vibrations at low frequencies and satisfy workers due to a lack of dexterity and grip strength. Therefore, the study presents a new glove based on an absorber to reduce vibration transmission at low frequencies. The new gloves and the passive absorbers are affordable and made of simple components, rubber rods, and violin strings with different sizes are the base of the used absorbers to attenuate the range of working frequencies. To predict the effectiveness of the fabricated gloves, the study performed experiments using non-expensive tools. A smartphone and a credible Android application (IDynamics) are utilized to measure the response in the wrist when using an air blower 450 W in specific working conditions. Additionally, the study builds a simple test rig to carry out the effect of the new gloves on the dexterity. Accordingly, the suggested low-cost gloves achieve a 50% acceleration reduction at the wrist approximately to the bare hand or any current anti-vibration gloves that are specified for the higher frequencies only.

In plane mechanical properties of hexagonal V-chiral and Tri-chiral metamaterials

The reasonable design of man-made multifunctional metamaterials with advanced mechanical and physical properties that are not found in nature is both challenging and important. In this paper, novel chiral structures are designed by adding V- and Tri- chiral elements to the typical hexagonal honeycomb substrate, so as to realize the modulation of in plane mechanical properties. Finite element simulations show that the Poisson's ratio of the hexagonal V-chiral structure is negative when the strain is greater than 0.4, and that of the hexagonal Tri-chiral structure is always negative. Quasi-static compression tests show that the introduction of chiral properties results in a stronger load-bearing capacity, and the hexagonal Tri-chiral structure has a stronger energy absorption (EA) and specific energy absorption (SEA) capability. A parametric study is carried out by means of FEM, by adjusting the geometrical parameters of the proposed structures, the performance in terms of energy absorption and compressive stiffness can be improved. Subsequently, Bloch-Floquet theorem is employed for the dispersion relations of the chiral metamaterials and the results show that compared to conventional hexagonal honeycomb, chiral metamaterials are able to generate band gaps in a lower frequency range. Numerical simulation results show that the bandwidth of the proposed novel chiral metamaterials can be tuned through a reasonable selection of hexagonal edge length, wall thickness and radius. Experimental investigations are conducted to test the vibration transmission rate of Structure Ⅲ, and the results prove that the structure is capable of vibration suppression in the target frequency band range. Finally, by filling Structure Ⅲ with steel columns, the structure generates band gaps in the lower frequency range, hence the application of this chiral metamaterial is broadened.

Mitigation of Force and Vibration Transmission by the Hifim Jump Sled during Repeated Jumping in Microgravity

Mitigation of Force and Vibration Transmission by the Hifim Jump Sled during Repeated Jumping in Microgravity

Longitudinal Vibration Transmission Suppression for Propeller-Shaft System by a Lever-Type Isolator with Negative Stiffness

Longitudinal Vibration Transmission Suppression for Propeller-Shaft System by a Lever-Type Isolator with Negative Stiffness

Characterization of elastic wave propagation in high-speed railway tracks considering temperature effects

This study establishes a three-dimensional infinite-length periodic ballasted track model, considering the effect of coupling between bending and torsion and the impact of sleeper width. The GPWE method is employed to investigate the energy bandgap structure of the track. The results show three vertical bending wave bandgaps below 1500 Hz: 0–109 Hz, 110–167 Hz, and 1081–1126 Hz. The node responses from a hammer impact experiment are used in the WSM to calculate the frequency dispersion curves, which confirms the validity of this model. The model is then utilized to analyze the influence of rail temperature forces and temperature-dependent fastener stiffness on the vibration transmission characteristics of the track within a temperature range of −35°C to 25°C. As temperature increases, the starting and cutoff frequency values and the width of bandgaps both decrease nonlinearly and later stabilize, with the width of the Bragg bandgap showing a significant reduction of 83%. The vibration attenuation rate in the bandgap gradually increases and finally stabilizes, especially above 15°C, while the vibration transfer characteristics are not significantly affected by temperature.

Evaluation of vibration behavior at different sensing positions on gearboxes

Monitoring systems for rolling contacts in machinery are widespread. There are multiple solutions in various applications like Health Usage Monitoring Systems (HUMS) for Helicopters and smart bearings from different manufacturers. The number of solutions and possibilities is rising. This paper outlines how the vibrational behavior depends on the measuring position outside and inside the gearbox. The effect of the sensor location is evaluated by examining different locations close to the main excitation of gearboxes—the loaded tooth contact—as well as positions on the gearbox housing. Based on the results, recommendations for an optimal sensor position for gear vibration monitoring are given by considering the efforts of sensor integration. The results can be used to select sensors with the lowest cost to support the widespread gear vibration monitoring.Important locations for health monitoring are the gear meshes inside the gearbox. Due to the requirement of high power density, a compact design is mandatory. This does not allow for sensor application close to the gear meshes but only on the outside of the gearbox. An impediment of signal quality and less chance of early damage detection is the consequence. Hence, efforts have been made to directly integrate multiple sensors inside the gear body without negatively impacting the package.For the investigation of the vibration transmission behavior, an FZG gear test rig is selected. These standardized test rigs are approved and established all around the world for the creation and evaluation of various gear failure data. The presented test rig has been modified to be able to sense vibration in the gear wheel, at the gear wheel, and on the gearbox housing to evaluate different sensor positions and vibration sensors for their suitability on vibration measurement.

Modelling of railway ballast as a poro-elastic medium and its effects on sleeper sound radiation

Conventional railway track is laid in a layer of coarse stones known as ballast. Due to the gaps between the stones, the railway ballast behaves as a porous acoustic material, with absorptive properties that are important for the noise produced by the railway system. Sound radiated by the bottom of the sleepers may also be transmitted through the ballast. Moreover, during a train pass-by the ballast can vibrate, which may contribute to the radiated noise. To consider all three effects simultaneously, the ballast is treated here as a poro-elastic medium. To obtain the properties of the ballast as a porous medium, transfer function measurements are performed in a vertical impedance tube to determine the surface impedance and absorption coefficient of different depths of reduced scale ballast. The complex wavenumber is also determined through transfer function measurements within the ballast in the vertical tube. Porosity and flow resistivity are determined by non-acoustic measurements, and the Johnson-Champoux-Allard model for porous materials is then fitted to the measured wavenumbers, allowing the remaining parameters to be determined. Comparison is made with the measured impedance and normal incidence absorption coefficient. The model is then used to predict the diffuse field absorption coefficients of both the reduced scale ballast and full-size ballast, which are compared with measurements, showing acceptable agreement. Finally, the effects on the sleeper radiation of introducing the poro-elastic ballast model are estimated and the sensitivity of the results to a practical range of ballast properties is assessed. The ballast vibration increases the sleeper radiation at low frequency, and especially between 120 and 280 Hz. This is caused by the structural vibration of the ballast driven by the sleepers, which has a resonance around 250 Hz. The acoustic velocity within the ballast is 180° out of phase with the structural velocity, and this leads to a small reduction in the sound radiation around 100 Hz. These effects could not be predicted using a surface impedance model for the ballast. Compared with the effect of the ballast vibration and sound transmission, the absorption of the ballast has a much smaller influence on the sleeper radiation.

Analysis of Train-Induced Vibration Transmission and Distribution Characteristics in Double-Layer Metro Depot

Analysis of Train-Induced Vibration Transmission and Distribution Characteristics in Double-Layer Metro Depot

Diversity of solitonic wave structures to the M‐truncated dynamical system in ultrasound imaging

The utilization of ultrasound imaging has become extensively prevalent and well‐established in clinical practice. The fundamental technologies that serve as the foundation for various applications in the field include transducers, beam shaping, pulse compression, tissue harmonic imaging, contrast agents, methodologies for quantifying blood flow and tissue motion, and three‐dimensional imaging. This article focuses on the examination of ultrasonic propagation, which involves the transmission of mechanical vibrations within the molecules or particles of a material. It quantifies the velocity of sound propagation in the medium of air. The third‐order nonlinear M‐fractional Westervelt model has been used as a governing model in the imaging process for securing the different wave structures. The recently developed computational methods have been applied in this study. The different wave structures are secured in various forms of solitary wave solutions including bright, dark, and combo solitons. In the domains of medical imaging and therapy, the investigation of sound wave propagation and high‐amplitude phenomena is facilitated by the utilization of wave structures. The effectiveness of these solutions extends to acoustic cavitation, acoustic levitation, underwater acoustics, and facilitating the process of ultrasonic propagation in tissue. Ultrasound imaging technologies currently find application in the medical field, enabling the visualization and examination of internal human tissue. This technology exhibits a wide array of applications in the fields of industry and medicine. A representation of the graphs is produced using the appropriate parametric values. The results suggest that the chosen approaches exhibit effectiveness, viability, and adaptability when implemented in complex systems in various fields, with particular emphasis on ultrasonic imaging.

A concave X-shaped structure supported by variable pitch springs for low-frequency vibration isolation

Based on the known X-shaped structure, a concave X-shaped structure (CXSS) featuring custom-designed variable pitch springs (VPS) is proposed. This design aims to enhance the displacement range of the quasi-zero stiffness (QZS) system and improve its performance in isolating low-frequency vibrations. The CXSS is obtained by merging two semi-X-shaped structures. The negative stiffness property of the concave structure can be improved by utilizing the motion limitations of the mechanical structure. Of particular concern is the VPS, it can provide nonlinear restoring force and variable stiffness by self-adjusting the effective number of coils. This special spring is suitable to neutralize the negative stiffness of the concave structure, enabling a wider range of QZS properties than linear springs and magnets. The average error between the practical and theoretical restoring force of the VPS is less than 10 %. Based on a special compression coefficient, the objective-load design method (OLDM) is proposed to obtain the stiffness conditions implementing QZS properties against rated mass. The stiffness obtained by the OLDM is considerably accurate. Under this condition, the vibration transmissibility is about 0.45 at 3.5 Hz and 0.1 at 14 Hz, which is lower than that of the unmatched load and stiffness coefficients. Compared with the X-shaped structure, the proposed structure has better low-frequency vibration isolation performance with a natural frequency of about 2 Hz. The vibration transmissibility is about 0.2 at 5 Hz and is about 0.1 at 10 Hz. Pulse excitations with an amplitude of 16 g can be attenuated to about 0.51 g through the CXSS compensated by VPS. It is convenient and efficient to implement QZS properties using the VPS to compensate negative stiffness.

The study on mechanical properties of the vibration isolator

First of all, the working principle of vibration reduction of the vibration isolator is briefly introduced. The vibration isolator adopts the design ideal of no formant and adopts a damping locking mechanism in the resonance region to solve the problem of vibration amplification of the system. The purpose of vibration attenuation is to use small damping in the attenuation region. Then, through the numerical simulation calculation method, it can be obtained that the isolator has a good vibration isolation effect under different effects of shock and impact, and the effective rate is about 90%, which fully guarantees the structural safety of the test equipment. Finally, according to an example, a model is established to study the influence of equipment weight and center of gravity design deviation on the natural frequency and natural frequency point vibration transmission efficiency of the equipment. Through analysis, it can be found that in the case of no abnormality of the equipment, the frequency is changed in the range of 1∼160 Hz, and the ratio of the system response to excitation is not more than 2, which meets the design requirements.

Performance evaluation of Meliadubia/Polypropylene composite crates for tomatoes packaging under simulated vibration

This research work proposes the substitution of plastic crates used for packaging fruits/vegetables with composite crates, aiming to minimize environmental issues. Vibration is a crucial factor contributing to package and product damage. In this study, tomato fruits were chosen to analyze the impact of vibration on product quality. The research primarily focuses on evaluating the performance of two newly developed wood plastic composite packaging crates namely 20 %Meliadubia/80 %Polypropylene (20 %MPPC) and 30 %Meliadubia/70 %Polypropylene (30 %MPPC) under simulated vibration in the laboratory as per ISO 13355 standard. The mechanical damage on packed tomatoes was quantified and the results were compared with those of Polypropylene crates (PPC) and commercial crates such as Reusable Plastic Crates (RPC) and Wooden Crates (WC). The results of this study revealed there were no damages on 20 %MPPC and 30 %MPPC crates, and the best protective performances for tomatoes were exhibited in 20 %MPPC, 30 %MPPC, and PPC. These packaging crates were found to reduce vibration transmissibility in the top crate by 50 % to 70 %, consequently minimizing further mechanical damage to tomatoes. Therefore, the composite crates were identified as a more suitable replacement for commercial packaging crates used for packaging fruits/vegetables, addressing environmental concerns related to packaging material and reducing the wastage of fruits/vegetables in transit.

Influence of contact characteristics of joint surface on vibration performance of the giant magnetostrictive transducer

The giant magnetostrictive transducer is a transducer device that realizes magneto-mechanical energy conversion. Each mechanical component is connected by the joint surface to realize the transmission of ultrasonic vibration energy. To ensure the efficient transmission of energy, the influence of the contact characteristics of the joint surface on the output stability of the transducer is studied. According to the contact conditions between the mechanical joint surfaces of the giant magnetostrictive ultrasonic transducer (GMUT), the key factors affecting the mechanical vibration performance of the ultrasonic system are obtained by analyzing the vibration transmission characteristics of the joint surfaces. The influence of different joint surface contact characteristics (JSCT) on the amplitude–frequency curve of the transducer is analyzed by the ANSYS software. Simulations and experiments have been conducted to verify the predicted results. As the preload force increases, the natural frequency of the transducer increases, but the growth rate decreases. The natural frequency of the double-rod GMUT with a small joint surface area is slightly higher in the optimal output mode shape, while its amplitude is significantly larger. The optimal prestress for the GMUT with different-sized joint surfaces is 3–5 MPa. This paper acquires the JSCT under a high-frequency vibration condition, reveals the influence of the joint surface on the mechanical output performance of the GMUT, and can provide a theoretical basis for the design and analysis of the rotary ultrasonic vibration processing system.

Design of low-frequency circular metastructure isolators with high-load-bearing capacity

Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads, due to the inherent contradiction between the high-static and low-dynamic stiffness of these structures. Although the challenge can be effectively addressed by introducing a negative stiffness mechanism, the existing structures inevitably have complex configurations. Metastructures, a class of man-made structures with both extraordinary mechanical properties and simple configurations, provide a new insight for low-frequency vibration isolation technology. In this paper, circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration, including a single-layer isolator and a double-layer isolator, and their static and dynamic characteristics are studied, respectively. For the static characteristic, the force–displacement and stiffness–displacement curves are obtained by finite element simulation; for the dynamic characteristic, the vibration transmissibility curves are obtained analytically and numerically. The result shows that the circular nonlinear single-layer isolator has excellent low-frequency isolation performance, and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg, compared with a similar circular linear isolator. These static and dynamic properties are well verified through experiments. Our work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.

Finite element simulation analysis of vibration transmission characteristics of double shell based on ANSYS

Ship noise contains a large number of low-frequency line spectrum features. It is difficult to distinguish where they come from and even more difficult to identify the ship’s target types using the line spectrum. Therefore, research on ship targets’ vibration transmission characteristics and radiation noise is of great importance for underwater target recognition. From the perspective of underwater acoustic target recognition, this article establishes a simplified finite element model of the double shell using ANSYS, calculates the displacement response of the double shell under harmonic loads, and conducts modal analysis, harmonic response analysis, and transient dynamic analysis, which verifies the consistency of vibration between the inner shell and outer shell. Marine experimental data show that the low-frequency line spectrum of ship noise is related to the vibration frequency of ship main engines. It may be caused by diesel engine vibration transmitted through ship hull vibration and can be used as an auxiliary feature for underwater acoustic target recognition.

Mechanisms of multi-bandgap inertial amplification applied in metamaterial sandwich plates

The design concept of integrating locally resonant metamaterials with sandwich plates has demonstrated promising prospects in the development of lightweight, load-bearing structures endowed with excellent capabilities for noise and vibration attenuation. However, achieving low-frequency vibration attenuation in the locally resonant metamaterial sandwich plates remains a challenging task that frequently requires the inclusion of additional centralized mass or heavy local resonators. This study proposes a novel multi-bandgap metamaterial sandwich plate with the lever-type inertial amplification mechanism (LIA-MMSP) for achieving the low-frequency vibration attenuation. Compared with the metamaterial sandwich plates incorporating multi-frequency local resonators (LR-MMSP) with equivalent additional mass, the LIA-MMSP exhibits the ability to achieve lower-frequency multiple bandgaps. The theoretical dynamic model is employed to elucidate the underlying mechanism behind the generation of multiple bandgaps at lower frequencies in the LIA-MMSP. The vibration attenuation performances of the LIA-MMSP are analyzed through both the finite element method and experiment study. The effect of various parameters on the vibration transmission characteristics of the LIA-MMSP is studied. The results show that the boundary frequencies of the LIA-MMSP are precisely one of the lever ratios of the LR-MMSP. By altering the lever ratio within the LIA-MMSP, precise fine-tuning and optimization of the low-frequency multiple bandgaps are achievable. When the attached mass is constrained, increasing the lever ratio enables the achievement of lower bandgaps. In addition, as the eigenfrequency of the primary lever-type IA resonator fp and secondary lever-type IA resonator fs decrease, both the first attenuation zone (AZ1) and the second attenuation zone (AZ2) of the LIA-MMSP shift towards lower frequencies. However, as fp decreases, the width of AZ1 expands, and the minimum accelerations within the AZs decrease even further. Moreover, a normalized comparison provides validation of the exceptional performance of the proposed LIA-MMSP in terms of lightweight design, as well as its ability to achieve low-frequency broadband vibration attenuation.

Damping Optimization Method of Combine Harvester Frame Undergoing Multi-Source Excitation

The complex mechanical system of a rice combine harvester not only has various excitation sources, but also, the vibration transmission path between each working device and the vibration contribution characteristics to the frame are not clear, so it is difficult to perform a reduction vibration design for the sharp vibration of the rice combine harvester frame. Therefore, based on the comparison and improvement of multiple classical transfer path analysis methods, this paper analyzed the vibration transfer characteristics and transfer characteristics of each harvester by the discrete time matrix method and operating path method. In the Experimental section, through the vibration characteristic experiment firstly, this paper obtained the power spectrum variation and the most needed optimized path in the transmission path of each device under each operating condition. Secondly, through frame simulation analysis under the exciting force, we obtained the vibration damping areas that needs to be optimized. Finally, the damping optimization experiment connected with the vibration characteristic experiment, and the excitation force simulation analysis was performed. The results of the damping optimization experiment displayed that the maximum change value of the vibration acceleration of the cutting table decreased from 7.862 m·s−2 to 3.522 m·s−2, decreasing by 55.2%, and the peak amplitude of the multipoint test in the cab was 5.4, 5.3, 1.7 and 2.0 μm, respectively, which was significantly reduced, so the optimization effect was significant. This study provides theoretical support for the vibration reduction optimization of a rice combine harvester frame.

Experimental and Numerical Investigation of the Use of Ultrasonic Waves to Assist Laser Welding.

This study evaluates the enhancement of laser welding using ultrasonic waves aimed at reorganising the intermetallic position in such a fashion that leads to increased mechanical properties of welds in battery pack assemblies for electric vehicles. The experiment employed 20 kHz and 40 kHz High-Power Ultrasound Transducers (HPUTs) in both contact and contactless modes. A simplified experimental configuration is suggested to represent conditions similar to those found in electric vehicle battery pack assemblies. Measurements of vibration transmission to aluminium alloy 1050 plates revealed more than a 1000-fold increase in acceleration amplitude in contact mode compared to contactless mode. The 20 kHz transducer in contactless mode demonstrated superior performance, showing a 10% increase in load and 27% increase in extension compared to welding without ultrasonic assistance. On the other hand, the 40 kHz transducer, while still improved over non-ultrasonic methods, showed less pronounced benefits. This suggests that lower-frequency ultrasonic assistance (20 kHz) is more effective in this specific context. The study explores ultrasonic assistance in laser welding copper (Cu101) to aluminium alloy 1050 using 20 kHz and 40 kHz HPUTs, showing that both transducers enhance microstructural integrity by reducing copper homogenisation into aluminium, with the 20 kHz frequency proving more effective in this context. A numerical simulation was conducted to evaluate the transmission of pressure into the molten pool of the weld, correlated with the vibration results obtained from the 20 kHz transducer. The numerical simulation confirms that no cavitation is initiated in the molten pool area, and all improvements are solely due to the ultrasonic waves.