Vibration Attenuation Characteristics Research Articles

Study on Vibration Characteristics of Piers and Foundation Sites in Seasonal Frozen Soil Areas under Train Load

In order to study the vibration characteristics of railway piers and different foundation sites in seasonal frozen soil region under train load, the piers and foundation sites of Tieling-Siping of Harbin-Dalian high-speed railway were tested on site, and the vibration attenuation characteristics of different sites and different seasons were analysed using numerical simulation method. The results show that the vibrations in the Y and Z directions are amplified on the side of piled soil-filling in both freezing and non-freezing seasons, when the distance R from the bottom of pier is less than 0.8m. But the vibration is amplified only in Z direction on the side of non-piled soil-filling. In the freezing season or in the non-freezing season, when R is between 1 and 2m, the vibration attenuation speed on the side of piled soil-filling is obviously lower than that on the side of non-piled soil-filling. When R is larger than 3m, the vibration attenuation of three directions is not affected by the piled soil-filling or not. Whether on the side of piled soil-filling or non-piled soil-filling, the vibration attenuation speed in freezing season is lower than that in non-freezing season.

Flexural wave band gaps and vibration attenuation characteristics in periodic bi-directionally orthogonal stiffened plates

Vibrations in ship and offshore structures owing to various ocean environmental loads and excitations of power systems become increasingly serious. In this paper, the flexural wave propagation and vibration attenuation characteristics in periodic bi-directionally orthogonal stiffened plates are investigated. The dispersion relations and the displacement fields of the eigenmodes of infinite periodic bi-directionally orthogonal stiffened plates are calculated by using the finite element method in combination with Bloch periodic boundary conditions. Numerical results show that periodic bi-directionally orthogonal stiffened plates can yield complete and directional flexural wave band gaps, in which the propagation of flexural vibrational waves is prohibited and flexural vibration suppression is dramatically achieved. With the introduction of bi-directionally orthogonal stiffeners, the flexural wave and vibration energy is confined in the four corners of the plate owing to the scattering effect of the bi-directionally orthogonal stiffeners. The transmission spectra for a finite periodic stiffened plate are numerically and experimentally achieved to verify the existence of the flexural wave band gaps and vibration suppression characteristics. Furthermore, the effects of geometrical parameters on the flexural wave vibration band gaps are carried out. The flexural wave band gaps and vibration attenuation properties can be artificially modulated by changing the geometrical parameters of periodic bi-directionally orthogonal stiffened plates.

Research on vibration reduction of multiple parallel gear shafts with ISFD

The vibration reduction methods for reducing the complexly coupled vibrations in multiple parallel gear shafts using integral squeeze film damper (ISFD) is studied in this paper. A multiple parallel gear system with three involute spur gears is built, and experiments are carried out to compare the vibrational characteristics of the gear system with rigid support and ISFD elastic damping support. The experimental results show that the ISFD support can reduce the shock vibrations of the multiple parallel gear shafts with excellent vibration attenuation characteristics due to damping. ISFD elastic damping support can inhibit the vibrations in a wide frequency range during the gear transmission, which can guarantee a smooth transition between multiple parallel gear shafts over a range of operating speeds.

Dynamic response and pile-soil interaction of a heavy-haul railway embankment slope reinforced by micro-piles

We investigated the dynamic characteristics and pile-soil interaction of a heavy-haul embankment reinforced by micro-piles. First, the vibration of a heavy-haul railway under a C80 train was tested. Based on the acceleration test, the dynamic response characteristics were further studied using a model test and 3D numerical simulation, which were verified via comparison with the field test. Finally, by integrating the model test and numerical simulation results, the influence of the pile length, pile diameter and pile spacing on the dynamic behavior of the embankment was analyzed, and the vibration-attenuation characteristics and dynamic soil-arching effect were discussed.

Test verification of a seat-cabin system vertical dynamic model for high-grade fork lift trucks

The seat-cabin system of fork lift trucks has a great influence on ride comfort. On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck, a seat-cabin system vertical dynamic model was created. The vertical dynamic responses of the model under the random irregularities excitation were calculated. The calculated responses including the seat dynamic response and the cabin dynamic responses at the four corners are very close to the field measurement data and the relative deviations of the (root mean square) RMS acceleration responses are all less than 6.0%. The results show that the vertical dynamic model is acceptable and can truly describe the basic mechanical behavior of the seat-cabin system. The model provides a good basis for investigating the relations between the dynamic parameters and the vibration attenuation characteristics of the seat-cabin system to further improve ride comfort.

Vibration attenuation of spacecraft in the presence of parametric and unmodeled dynamics uncertainties using collocated and noncollocated control: A comparative study

µ-control synthesis offers the advantage of maintaining robust performance and stability in the presence of plant uncertainties. Expressions relating the 2-norm of the vector of regulated outputs and closed-loop modal damping to the weights used for µ-control synthesis are derived in this paper. By using these expressions, the amount of damping added to each mode can be controlled individually while maintaining equal importance for each controlled mode. Hence, the selection of weights for synthesizing a suitable µ-controller is greatly simplified. Furthermore, a comparative study of µ-controllers designed by the proposed procedure and positive position feedback (PPF) controllers designed by analytically derived optimal parameters is also presented. The techniques are compared for their vibration attenuation, energy utilization, and stability characteristics, in the presence of parametric and unmodeled dynamics uncertainties. Results for both time domain and frequency domain simulations are presented. As in some cases (sandwich plate structures etc.) the noncollocation of actuator/sensor becomes crucial for achieving good performance, the above-mentioned characteristics are evaluated for both collocated and noncollocated sensor locations.

Embedded Acoustic Black Holes for semi-passive broadband vibration attenuation in thin-walled structures

We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.

Experimental investigation on the defrosting performance of a finned-tube evaporator using intermittent ultrasonic vibration

When an air-source heat pump (ASHP) was operated in heating mode under certain ambient conditions, frost always accumulated on the fin surface of its outdoor coil. Frosting may increase the energy consumption and deteriorate the performance of the ASHP, and hence, periodic defrosting is necessary. In this study, a new defrosting method using intermittent ultrasonic vibration was investigated. First, the vibration attenuation characteristics of a double-row outdoor coil and the frost growth characteristics under different ambient conditions were determined. Next, the average frost thickness with and without the application of intermittent ultrasonic vibration was calculated using MATLAB software. Finally, the decrease in defrosting energy consumption, the increase in heating capacity, and the increase in the coefficient of performance were analysed. The experimental results indicate that intermittent ultrasonic vibration could effectively remove the frost accumulated on the fin surface, and the effective defrosting area of an single ultrasonic transducer was 0.165m2 for a double-row finned-tube evaporator on which an ultrasonic transducer with a rated power of 50W and resonant frequency of 40kHz was applied. The defrosting energy consumption of the ASHP unit with ultrasonic vibration was 3.14–5.46% lower than that without ultrasonic vibration, whereas the heating capacity increased by 2.2–9.03% and the COP increased by 6.51–15.33%. In addition, the thermal comfort of the indoor side was clearly improved.

Research of a Dynamic Vibration Absorber with Tunable Resonant Frequency and its Vibration Attenuation Characteristics

In order to improve working frequency band and damping effect of a dynamic vibration absorber, a new kind of dynamic vibration absorber is presented. Its resonant frequency could be real-time adjusted by adapting the stiffness of the spring. The vibration attenuation characteristics are analyzed theoretically and numerically. According to simulation analysis, effects of geometrical parameters are researched and optimum geometric parameters are determined. The damping effect was simulated in a flat structure, the results show that the working frequency band and damping effect of the DVA are both remarkable.

Vibration-reducing gloves: transmissibility at the palm of the hand in three orthogonal directions

Vibration-reducing (VR) gloves are commonly used as a means to help control exposures to hand-transmitted vibrations generated by powered hand tools. The objective of this study was to characterise the vibration transmissibility spectra and frequency-weighted vibration transmissibility of VR gloves at the palm of the hand in three orthogonal directions. Seven adult males participated in the evaluation of seven glove models using a three-dimensional hand–arm vibration test system. Three levels of hand coupling force were applied in the experiment. This study found that, in general, VR gloves are most effective at reducing vibrations transmitted to the palm along the forearm direction. Gloves that are found to be superior at reducing vibrations in the forearm direction may not be more effective in the other directions when compared with other VR gloves. This casts doubts on the validity of the standardised glove screening test.Practitioner Summary: This study used human subjects to measure three-dimensional vibration transmissibility of vibration-reducing gloves at the palm and identified their vibration attenuation characteristics. This study found the gloves to be most effective at reducing vibrations along the forearm direction. These gloves did not effectively attenuate vibration along the handle axial direction.

The Dividing Frequency Bands Prediction Method Based on Bornitz Model for Train-Induced Environmental Vibration and its Application

The frequency component of ground vibration induced by train is complex. The propagating attenuation characteristics of ground vibration are dependent on frequency. A new prediction method based on Bornitz model for predicting the train-induced ground vibration is presented in this paper. This approach divides the frequency component into many small frequency bands according to one-third-octave. Then it predicts the vibration acceleration level VAL of each frequency bands based on Bornitz model respectively. Finally, the predicted value of Z-vibration level VLZis computed by the predicted value of VAL and the corresponding frequency-weighting value C. The traininduced ground vibration was measured and predicted in Chengdu-Dujiangyan railway. The results of comparing the predicted value of VLZ with the measured value show that the prediction value of VLZ is 3.8dB less than the measured value in the prediction point of 25m away from the railway, where the vibration strength occur rebound. In other five prediction points the ground vibration predicted value are 1.3~3.1dB more than measured value. This study shows that using the prediction method presented in this paper for predicting train-induced ground vibration has good accuracy on the whole.

Vibration suppression analysis of FGM shells with higher order shear deformation theory

Analytical solutions of functionally graded material (FGM) shells with embedded magnetostrictive layers are presented in this study. These magnetostrictive layers are used for vibration suppression in the functionally graded shells. Higher order shear deformation theory is employed to study the vibration suppression characteristics. The exact solution for the FGM shell with simply supported boundary conditions is based on the Navier solution procedure. Negative velocity feedback control is used. The parametric effect of the location of the magnetostrictive layers, material properties, and control parameters on the suppression effect are investigated in detail. Higher order shear deformation theory has significant influence on the prediction of the vibration response of thick shells. Further, it is found that the shortest vibration suppression time is achieved by placing the actuating layers farthest from the neutral plane, that the use of thinner smart material layers leads to better vibration attenuation characteristics, and that the vibration suppression time is longer for a smaller value of the feedback control coefficient. A list of symbols can be found starting on page 54.

Response of Test House to Vibroseis Vibrations and Environmental Forces

In response to public concerns about the damage potential of vibroseis vibrations from seismic exploration, Fina Oil and Chemical Company (now Total E&P USA, Inc.) sponsored full-scale testing of a typical residence. The test house was vibrated by four vibroseis trucks on both soil and asphalt surfaces at declining separation distances. Ultimately, the vibrators were 13 feet (4.0 m) from the front porch and 10 feet (3 m) from the front sidewalk. Peak particle velocities of the ground motions were about 1 in./second (0.4 cm/second) at the house foundation. As expected, the responses of the superstructure were strongly dependent on the frequencies of the ground motions. No damage to the house of any kind was produced by these vibrations, even though the vibrators were operating at 90% maximum output. Tests were also conducted away from the house to explore the vibration intensities and attenuation characteristics of the ground motions generated. The resulting vibrations were compared to previous work and found to be consistent with those results. Changes in crack width and associated weather-induced changes in temperature, humidity, and other environmental factors were recorded every 2 hours for 1 year. Environmental effects are known to produce larger crack responses than vibrations that conform to common standards and regulated limits, a fact demonstrated again in this case. Response motions in the house were also recorded during common household activities, including hammering nails, slamming doors, and use of the fireplace. In the vicinity of the input forces, some of these activities generated greater response than did the vibroseis excitation.

Centrifugal modelling of subway-induced vibration

In a congested urban situation between subway lines and facilities requiring noise and vibration free conditions, it is necessary to estimate the propagated subway-induced vibration. The attenuation characteristics of subway-induced vibration in the ground may not be fully understood because of a number of influencing factors, and it is appropriate to investigate the attenuation under a clear ground condition with known boundary conditions. This paper describes the development of a centrifugal model test system, simulating the subway-induced vibration, experimental results, including contour of vibration acceleration level and comparisons between experimental observations and field measurements. It was found that the attenuation of subway-induced vibration in the ground becomes larger as frequency becomes higher. Bomitz’s formula is applied to estimate the attenuation and it was found that the values of material damping coefficient α are almost the same in the acceleration level of 15 to 62 g, which are consistent with those obtained by field measurements at 14 sites in and around the Tokyo area.

Vibration suppression of FGM shells using embedded magnetostrictive layers

Analytical solutions of functionally graded material (FGM) shells with embedded magnetostrictive layers are presented in this study. These magnetostrictive layers are used for the vibration suppression of the functionally graded shells. The first-order shear deformation shell theory (FSDT) is employed to study the vibration suppression characteristics. The exact solution for the FGM shell with simply supported boundary conditions is based on the Navier solution procedure. Negative velocity feedback control is used. The parametric effect of the location of the magnetostrictive layers, material properties, and control parameters on the suppression effect are investigated in detail. It is found that (i) the shortest vibration suppression time is achieved by placing the actuating layers farthest from the neutral axis, (ii) the use of thinner smart material layers leads to better vibration attenuation characteristics, and, (iii) the vibration suppression time is longer for a smaller value of the feedback control coefficient.

Wave attenuation in periodic three-layered beams: analytical and FEM study

We study infinite composite beams with periodic simple supports and analyze their vibration attenuation characteristics. In the literature single spans of such beams have been studied for determining their loss factors. Such loss factor information is insufficient for determining attenuation in the periodic or multi-span case. Here, we directly derive propagation constants as a function of frequency. Two distinct cases are investigated in detail. The first is a three-layered periodic beam with a continuous central visco-elastic layer. The second is a periodic beam with visco-elastic inserts of finite extent. The former is analytically tractable and yields insight, while the latter has better structural properties for practical applications. The continuous layer case is studied using several different beam theories. The case with inserts is studied for several different configurations using FEM. Dependence of attenuation characteristics on size, location, and number of inserts is presented. This study provides insights that will be useful for designing visco-elastic inserts for vibration attenuation in periodic structures.

A method for reducing adaptor misalignment when testing gloves using ISO 10819.

International standard ISO 10819 was established in order to quantify the vibration attenuation characteristics of anti-vibration gloves. One problem that exists with the standard is possible misalignment of the palm adaptor that is placed underneath the test glove. If the adaptor becomes misaligned, the measured glove transmissibility will be lower than the actual value. A tri-axial accelerometer was installed in the adaptor and was used as the basis for providing visual feedback of the adaptor alignment to the test subjects. The objective of this study was to test the hypothesis that adaptor misalignment could be reduced by providing feedback to the test subjects. Eight male volunteers (mean age 24.8 yr) were used in the study. Each subject performed two sets of tests: the standard ISO 10819 glove test and the modified version. Three different anti-vibration gloves were tested. Glove transmissibility and adaptor misalignment were calculated for each glove. A three-way analysis of variance was used to analyze the results. A comparison of the two testing methods showed that the modified glove testing method did reduce misalignment significantly, which, in turn, resulted in an increase in the measured glove transmissibility. The proposed method greatly improved the standard deviation of transmissibility and made the test results more consistent.

Vibration control of laminated composite plates using embedded smart layers

Analytical solutions and finite element results of laminated composite plates with smart material layers embedded in them are presented in this study. The third-order plate theory of Reddy is used to study vibration suppression characteristics. The analytical solution for simply supported boundary conditions is based on the Navier solution procedure. The velocity feedback control is used. Parametric effects of the position of the smart material layers, material properties, and control parameters on the suppression time are investigated. It has been found that (a) the minimum vibration suppression time is achieved by placing the smart material layers farthest from the neutral axis, (b) using thinner smart material layers have better vibration attenuation characteristics, and, (c) the vibration suppression time is larger for a lower value of the feedback control coefficient.

A Method for Measuring the Vibration Attenuation Characteristics of Resilient Tool Wrap Materials in a Shipyard Production Environment

A Method for Measuring the Vibration Attenuation Characteristics of Resilient Tool Wrap Materials in a Shipyard Production Environment

A Method for Measuring the Vibration Attenuation Characteristics of Resilient Tool Wrap Materials in a Shipyard Production Environment

To determine the relative effectiveness of several resilient tool wrap materials in reducing the vibration of a pneumatic hand grinder extensively used in a shipyard production environment, a testing situation was developed to closely simulate the production process. Data from the unwrapped tool and a similar tool wrapped with a variety of resilient materials was collected in twenty 2-minute trials in the performance of a standardized task. Instead of using the ANSI S3.34-1986 recommended handheld metal plate as the triaxial accelerometer mount, a clamped accelerometer mount was designed and used. This served to constrain the variability found to exist with a handheld mount, where hand pressure can vary during the measurement period, thus influencing the measured vibration levels. Data analysis was performed in accordance with ANSI S3.34-1986. Vibration attenuation resulting from the use of various tool wrap materials is presented both for the ANSI weighted 5–1400 Hz range and for the unweighted 5–5000 Hz range, as recommended by the National Institute for Occupational Safety and Health. Details regarding the design and use of the clamped accelerometer mount are given to assist health professionals in the measurement of hand-arm vibration in a production environment and in the hope that others will further explore this in situ research methodology.