Search

The localization of shaking forces acting on an operating machine is an important step to identify vibration and noise sources. The forced vibration response of a linearly vibrating structure is assumed to be linear. However, the energy distribution of a linearly vibrating structure contains “coupled terms” in the modal decomposition of the vibration energy density function. These coupled energy terms represent the cross-modal energy density associated with the exciting force of a dynamic structure under forced vibration. In this research, it is proved analytically that the high-order cross-modal energy densities of a linear dynamic structure are highly correlated to the location of the external exciting force. Using this finding, a new force localization index based on the high-order cross-modal energy densities of a dynamic structure is proposed and tested. Numerical tests on uniform and step beam structures under force excitation with different frequencies and locations have been carried out to test the effectiveness of the proposed force localization method. It is found that the proposed force localization method works well on vibrating beam structures. Experiments are carried out to verify the proposed force localization method.

Creation of downhole sources of elastic vibrations for the implementation of vibrowave enhanced oil recovery methods is an urgent task of mining engineering. The paper substantiates the expediency of using an electromagnetic linear drive of a downhole vibration source to generate axial shock pulses. A mathematical model is proposed that describes the dynamics of movement of the striker of electromagnetic impact unit under the action of traction forces of coils, friction forces and aerodynamic resistance, taking into account the elastic constraints at the end of the lower and upper working strokes of the striker. Theoretical dependences of striker displacement and speed on time, obtained using the developed model, are presented, and their high convergence with the experimental data is shown. The mathematical model of electromagnetic impact unit can be used to optimize its parameters, as well as to design new standard sizes of vibration sources that meet the requirements of the oil and gas industry.

There are some studies in the literature in order to make the interpretation of human tissues having different characteristics. Some of these studies focused on the evaluation of human face tissues. Vibration signals generated from vocal cords have been used in these studies about human face tissues. However, any study using the vibration signals recorded by applying the external vibration source having fixed frequency value is not available in the literature. In this study, it is aimed to investigate the frequency characteristics of the vibration signals recorded from the human face. These signals obtained from nine different regions on the faces of subjects are analysed using frequency characteristics. In the analysis stage, median and maximum frequency values are calculated and evaluated. So, the softness and hardness interpretation about these regions on the face can be made and the frequency ranges of these regions can be determined. As a result, it is observed that low-frequency signals are dominant in hard regions and high-frequency signals are dominant in soft regions.

Indonesia merupakan salah satu negara dengan gunungapi terbanyak di dunia. Rangkaian gunungapi membentang dari Pulau Sumatera, Jawa, Bali dan Nusa Tenggara. Dari kepulauan di Laut Bdana sampai bagian utara Pulau Sulawesi merupakan daerah gunungapi terpanjang di dunia. Indonesia memiliki 129 gunungapi aktif, 70 buah diantaranya berancaman dan 500 buah tidak aktif. Sejak tahun 1800, paling tidak telag tercatat 600 kali letusan oleh 70 gunungapi di Indonesia. Karena itu, Indonesia dapat dikatakan sebagai negara yang rawan bencana, terutama ancaman bencana gunung berapi. Pengamatan, pemantauan, pencatatan, penyebaran informasi dan peringatan tanda bahaya terhadap aktivitas gunungapi menjadi salah satu fokus dalam penanggulangan bencana gunungapi. Untuk mendukung hal tersebut diperlukan instrumentasi deteksi aktivitas vulkanik gunungapi. Salah satu instrumentasi yang digunakan untuk memantau aktivitas gunung berapi Gunung Merapi adalah Real-time Seismic Amplitude Measurement (RSAM). RSAM adalah sistem yang menyediakan pengukuran kontinu dari amplitudo seismik rata-rata absolut dari jumlah stasiun seismik. RSAM menempati peran strategis dalam memantau aktivitas seismik gunung berapi terutama pada saat krisis sebelum letusan. Dalam penelitian ini, perancangan sistem RSAM menggunakan sensor geophone untuk mendeteksi getaran seismik. Frekuensi tes yang diberikan dalam penelitian ini termasuk 10 Hz, 30 Hz, dan 50 Hz. Sistem yang telah dirancang bangun dapat mendeteksi frekuensi dengan baik sebagaimana dibuktikan bahwa semakin besar frekuensi uji maka semakin banyak output grafik yang dihasilkan. Selain itu, besaran yang dihasilkan juga semakin besar. Pada frekuensi 10 Hz, magnitudo yang dihasilkan adalah 0,997, pada 30 Hz magnitudo yang dihasilkan 1,559 sedangkan pada 50 Hz magnitudo yang dihasilkan adalah 1,962. Sistem RSAM yang dirancang bangun menghasilkan amplitudo yang memiliki hubungan linier dengan besarnya getaran sumber disediakan..

Vibrations propagating through the soil into the building can not only be harmful to the building structure or cause its accelerated wear, but can also effect on the vibrational comfort in the rooms. They can also be annoying for residents and building users, and in extreme cases can lead to sleep disorders, headaches and neurotic conditions. Especially vibrations from the low frequency range from 5 to 25 Hz are undesirable, because there are resonance frequencies of human internal organs in this frequency range. The human perception of vibrations in buildings, despite many researches made in the past, despite standards and requirements in this area, is still a topic not fully understood mainly due to the subjective nature of the perception of vibrations by various people. It is widely known that the type of transport vibration source has an impact on human perception. Vibrations generated by above-ground sources are more felt on the upper floors as opposed to vibrations generated from the underground. In this paper three types of transport vibrations are analyzed on one chosen building located in Warsaw. Human perception of vibration is evaluated according to two methods: root mean squared (RMS) and vibration dose value (VDV).

Harvesting energy from ambient vibration sources is challenging due to its low characteristic amplitude and frequencies. In this purpose, this work presents a compact hybrid vibration converter based on electromagnetic and magnetoelectric principles working for a frequency bandwidth and under real vibration source properties. The combination of especially these two principles is mainly due to the fact that both converters can use the same changes of the magnetic field for energy harvesting. The converter was investigated using finite element analysis and validated experimentally. Results have shown that a frequency bandwidth up to 12 Hz with a characteristic resonant frequency at 24 Hz and a power density of 0.11mW/cm3 can be reached.

When a high-power vibrating roller compact the subgrade, the vibration wave will quickly propagate along the surface of the subgrade and generate hazards to surrounding environment and structure. To study the vibration propagation rules of the roller, the vibration acceleration of the high-power vibrating roller was measured on the surface of the rock subgrade, coarse-grained soil subgrade and fine-grained soil subgrade. The respective relations between vibration acceleration and the distance from a vibration source in the vertical, horizontal radial and horizontal circumferential direction have been discovered. The research results show that the vibration peak frequency generated by the vibrating roller on the subgrade approximates vibration frequency. The vibration effective influence distance varies from 10m to14m, and the horizontal radial vibration is greater than that of vertical and horizontal circumferential direction. The vibration of the rock subgrade attenuates the most slowly and propagates the most remotely.

The movement and mechanical characteristics of oil-tea camellia fruit coupling with flower simultaneously during the harvest period were studied to provide an indispensable theoretical guideline for the mechanized picking machine. The mechanical properties of Camellia oleifera were obtained by investigating its flowers and fruits, and the vibration harvesting of Camellia oleifera was studied by using dynamic vibration device. The i-Speed3 high-speed camera was used to record the harvesting process, and the image analysis and calculation were carried out by its own Control-Pro software. The results showed that different varieties of Camellia oleifera had different flowering periods, ranging from 30 to 55 days; their weight also varied among varieties; there was no inevitable relationship between the binding force (pulling force and torque) of fruit stalks and their varieties, locations and diameter of fruit stalks. More importantly, during the vibration process, the fruit peeling speed is related to the vibration source clamping position and vibration parameters. Under the condition of short clamping distance and high frequency and low amplitude, the fruit is more likely to fall off.

Vibration assessment criteria for cosmetic building damage are specified in terms of peak velocity thresholds. For masonry buildings, these thresholds are relatively low compared to vibration levels generated by various sources in the built environment. Therefore they will be exceeded numerous times over the lifetime of most buildings. These exceedances are important when one tries to establish or disprove a causal relation between building damage and a vibration source. Despite the relevance of this information, little is known about the number of times velocity thresholds for cosmetic building damage are exceeded in the built environment. The vibration data collected over a period of more than 5 years in 326 buildings, mostly constructed in masonry and randomly distributed over the Province of Groningen, allowed for a unique opportunity to gain insight. First of all, to determine the number of times these thresholds were exceeded, and secondly to make a comparison between shallow earthquakes and other sources. The number of exceedances and the return period were determined for a set of thresholds (i.e. 0.3, 1, 3, 5, 10, and 20 mm/s), which align with peak velocity thresholds typically encountered in vibration assessment guidelines and standards. The results obtained over a 1 year period with very low seismic activity (only earthquakes with M < 2.0) show that the velocity thresholds for cosmetic damage to masonry buildings (i.e. 1, 3, and 5 mm/s) were exceeded on average less than once a month for 80% of the building sensors. For buildings with a large number of exceedances of these thresholds, the most important sources appear to be traffic, construction work, and hits near the sensor. A subset of 59 building sensors was selected, for which the full operational period of about 5 years was analysed to determine the contribution of earthquakes to the threshold exceedances. Less than 1% of the 1 mm/s exceedances measured by the 59 sensors over their full operational period were caused by earthquakes. Only for building with few exceedances (less than 8), the relative influence of induced earthquakes on the number of exceedances is significant (between 30 and 50%).

We analyze temporal variations in the travel times of both P and S waves (Vp and Vs) for 14 months at Toyohashi (central Japan) with a continuously operating vibration source that could efficiently produce both P and S waves. Seismic waves produced by the source, which is called the accurately controlled routinely operated signal system (ACROSS), are recorded by three nearby seismic stations, and the travel time variation at each station is estimated using the transfer function calculated from the recorded data. Long-term variations in Vp and Vs are observed and can be interpreted by the change in fluid saturation and crack density of the subsurface rocks. The variation in fluid saturation and crack density are consistent with that in the groundwater level, which is measured at the station nearest to the ACROSS. Short-term responses to rainfalls are observed at the station nearest to the ACROSS system; the interpretation of the changes in crack density and saturation is inconsistent with the ground water observation, partly owing to the initial response to rainfall. This can be interpreted as an air–water mixture within pores or cracks on a fine scale.

This study investigated the localization ability of an impulse vibration source outside the body in two-dimensional space. We tested whether humans can recognize the direction or distance of an impulse vibration source when using their hand to detect spatiotemporal vibrotactile information provided by the propagated vibrational wave from the source. Specifically, we had users put their hands on a silicone rubber sheet in several postures. We asked users to indicate the position of the vibration source when a location on the sheet was indented. Experimental results suggested that the direction of the impact vibration source can be recognized to some extent, although recognition accuracy depends on hand posture and the position of the vibration source. The best results were achieved when the fingers and palm were grounded and a vibration source was presented around the middle fingertip, and the directional recognition error in this case was 6 degree. In contrast, results suggest it is difficult to accurately recognize the distance of the vibration. The results of this study suggest a new possibility for directional display where vibrotactile actuators are embedded at a distance from the user's hand.

Arachnids including sand scorpions and spiders use their tactile sense organs, called basitarsal compound slit sensilla (BCSS), to detect their prey. The sense organs consisting of mechanoreceptors are located at or near joints in the cuticle, and they can sense a vibrational signal caused by prey movement. The nocturnal sand scorpion Paruroctonus mesaensis has a distinguished capability of finding their prey only with these tactile senses. The sand scorpions show their orientation behaviour of positioning themselves directly towards their prey and then run into the prey when there is a vibration disturbance caused by the prey. According to the biological researches (Brownell & Farley, 1979, Brownell, 1984), it is presumed that the sand scorpions respond to Rayleigh waves, surface waves of sand, to detect the direction of a vibration source and possibly longitudinal vibrations to estimate the distance. Especially, the time delay between arrival of a vibration signal at the BCSS sense organs is an important cue to determine the direction of their prey (Brownell & Farley, 1979). The central nervous system should process stimulus-locked neuron firings of the sense organs on their eight legs to induce the orientation behaviour. How the nervous system is organized to handle the orientation behaviour is still an open question. Only a few studies explain this behaviour mechanism. Stuerzl et al. (2000) introduced a neuronal mechanism to support the orientation behaviour of scorpions, and it is based on the difference of the arrival time of stimulus signals produced at sense organs on their legs. They argued that the brain of sand scorpions receives sensor signals from mechanoreceptors on their eight legs and processes an inhibition mechanism among a set of command neurons projected from the sense organs on each leg. This inhibitory interaction leads to more accumulated firings of the command neurons near the prey source and less firings at the opposite sides. The accumulated neuron firings thus form a tuning curve for a specific resource direction. Then the distribution of neuron firings can vote to determine the resource direction. In fact, arachnids have sensory projections to the central nervous system for each leg (Babu & Barth, 1989, Anton & Barth, 1993). Previously Brownell and Farley (1979) suggested that eight command neurons (or eight clusters of neurons in the brain) accumulate neuron firings from mechanoreceptors on the eight legs of scorpions, respectively and also interact each other with triad inhibitions. According to the triad inhibition hypothesis, early arrival of vibration stimulus to mechanoreceptors on a leg excites the corresponding command O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg

Ground vibrations induced by large flood discharge from a dam can damage surrounding buildings and impact the quality of life of local residents. If ground vibrations could be predicted during flood discharge, the ground vibration intensity could be mitigated by controlling or tuning the discharge conditions by, for example, changing the flow rate, changing the opening method of the orifice, and changing the upstream or downstream water level, thereby effectively preventing damage. This study proposes a prediction method with a modified frequency response function (FRF) and applies it to the in situ measured data of Xiangjiaba Dam. A multiple averaged power spectrum FRF (MP-FRF) is derived by analyzing four major factors when the FRF is used: noise, system nonlinearity, spectral leakages, and signal latency. The effects of the two types of vibration source as input are quantified. The impact of noise on the predicted amplitude is corrected based on the characteristics of the measured signal. The proposed method involves four steps: signal denoising, MP-FRF estimation, vibration prediction, and noise correction. The results show that when the vibration source and ground vibrations are broadband signals and two or more bands with relative high energies, the frequency distribution of ground vibration can be predicted with MP-FRF by filtering both the input and output. The amplitude prediction loss caused by filtering can be corrected by adding a constructed white noise signal to the prediction result. Compared with using the signal at multiple vibration sources after superimposed as input, using the main source as input improves the accuracy of the predicted frequency distribution. The proposed method can predict the dominant frequency and the frequency bands with relative high energies of the ground vibration downstream of Xiangjiaba Dam. The predicted amplitude error is 9.26%.

Machine-induced vibrations and their control represent, for several reasons, a crucial design issue for buildings, and especially for industrial facilities. A special attention is required, at the early design stage, for the structural and dynamic performance assessment of the load-bearing members, given that they should be optimally withstand potentially severe machinery operations. To this aim, however, the knowledge of the input vibration source is crucial. This paper investigates a case-study eyewear factory built in Italy during 2019 and characterized by various non-isolated computer numerical control (CNC) vertical machinery centers mounted on the inter-story floor. Accordingly, the structure started to suffer for pronounced resonance issues. Following the past experience, this paper reports on the efficiency of a coupled experimental-numerical method for generalized predictive and characterization studies. The advantage is that the machinery features are derived from on-site experiments on the equipment, as well as on the floor. The experimental outcomes are then assessed and integrated with the support of Finite Element (FE) numerical simulations, to explore the resonance performance of the floor. The predictability of marked resonance issues is thus analyzed, with respect to the reference performance indicators.

Requirement of oil and gas industry in increasing of rate of hydrocarbon extraction from deposits contributes to development of science-based methods of oil production increasing. Vibrowave impact to productive seam is related to such methods. This impact can be effectively carried out with hole seismic signal sources. In the work results of study of load-bearing element of hole electro-magnetic pulse source are represented. Objective of the work is the study of static and dynamic strains of casing pipe, determination of values of pressure pulses at modified load-bearing element during its work with electro-magnetic striking center. Values of static and dynamic strains of casing pipe under the action of thrust force are experimentally determined. The values are located in flexible zone and make 1mm at the static load and from 0.35 up to 0.6mm at the pulse load. As the results of tests of vibration source prototype, dependence of pulse pressure value at load-bearing element on voltage of striking center supply under the pressure of preliminary pumping 20MPa is obtained. Pulse amplitude raises proportionally voltage in the range from 14.2 MPa up to 19.7 MPa. Experiments with increasing of pumping pressure in the range from 20 MPa up to 27 MPa have shown that ratio of pulse value to pumping pressure linearly reduces when voltage of striking center supply is constant. Obtained results are scientific basic for designing of load-bearing elements destined for work at pulse impact transfer mode.

The article describes a project proposed to determine the epicenter of a future short-focus earthquake tens of hours before and to reduce the magnitude of an impending catastrophic earthquake. It focuses on developing a physical model to determine the conditions necessary for the start of an earthquake, for a method based on the registration of flows of mercury vapor in the gas rising from the Earth. This model gives an explanation of why an earthquake precursor appears so early (such a long period of time can range from a few to hundreds of hours). Normally, the characteristic times of an earthquake precursor for seismic methods are tens of seconds. The project is based on the physical and mathematical models of an earthquake. The derived formula for the time of the precursor of a future earthquake allows us to explain and to describe the time increase for the precursor, depending on the magnitude of the earthquake. The method of reducing the magnitude of an impending catastrophic earthquake is based on the proposed physical model of the onset of an earthquake and is implemented by the action of a vibration source in the region of the detected earthquake epicenter. The proposed system should save citizens, lives from future short-focus earthquakes.

This paper investigates the responses of cohesive sediment to mechanical vibration by experimental observation, containing: (1) the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration to the vibration source; (2) the soil pressure distribution in the near field centered in an artificial columnar vibration source. Under the mechanical vibration with a frequency of 200 Hz and an amplitude of 1.15 mm, the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment were measured in the sediment of four different depositing conditions. Results of the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment in the near field responding to artificial vibration source are exhibited and discussed. It is found that, excited by the sinusoidal vibrator, the soil pressure presents a response of statistical sinusoidal fluctuation with the same frequency to the vibration source. In the sediment of lower initial yield stresses, the soil pressure distribution distinctly tends to firstly increase and then decrease with distance. The amplitude of the soil pressure is attenuated exponentially with distance.

In the paper, modeling of the effect of road vibrations on displacements in the slide zone, taking into account impulse waves is presented. The analysis was carried out for an area in which landslide movements occurred in 2010. The analysis concerning the influence of the vibration source’s speed was carried out. The influence of the generated load on the values of vertical displacements created in the slide zone was analyzed. Loads from moving trucks have been included in the form of kinematic impact. Numerical simulations were carried out using a program based on the Finite Element Method.

To study the influence of annular trenches on a vibration isolation area, the depth, width, vibration source distance, and central angle of the trench are analysed as research variables, and a contour diagram of the amplitude reduction ratio is drawn based on an outdoor test of the trench. Taking an area with an amplitude reduction ratio less than 0.40 as the evaluation index of the effective vibration isolation area, the effects of the above geometric parameters on the vibration isolation area are analysed. Limited to the test conditions of this paper, the results show that the depth, vibration source distance, and deep width ratio are the important factors affecting the effective vibration isolation area; with the increase of the above parameters, the effective vibration isolation area increases significantly, but the area increase rate decreases gradually. The width has a relatively little effect on the effective vibration isolation area. When the ratio of depth to width is from 7.05 to 9.15, and the width reaches 0.23 times the Rayleigh wavelength, the annular trench can have a good effective vibration isolation area. When the central angle of the trench is less than 90°, a discontinuous effective vibration isolation area will form in the vibration isolation region. The selection of the central angle of the trench is related to the frequency. With the same trench size, the effective vibration isolation area decreases as frequency decreases. In addition, the effect of distance depth ratio on the effective vibration isolation area presents a fluctuation. When the ratio of distance to depth is from 1.21 to 2.05, a good effective vibration isolation area can be obtained and it is reasonable.

With the rapid development of subway systems, the negative environmental impacts of vibration induced by subways has gradually become a research hotspot. For the purpose of developing predictive models of vibration and designing effective vibration mitigation systems, continuous field dynamic measurements were conducted simultaneously in a subway tunnel, ground, and building in eastern China, the most prosperous region in China. The characteristics of vibration transmission and attenuation induced by subway were analyzed by statistical analysis of large amounts of measurement data. The results showed that most prominent and visible attenuation of vibration is from the track to the ballast bed in the tunnel, where the ground-borne vibration would quickly decrease exponentially with distance. The results also showed that the measured attenuation value of indoor vibration was approximate 0.76 dB on average between each floor. Moreover, the decay ratio of the vibration increased with the increase in the frequency range. Based on these findings, construction gauge of 20&ndash, 25 m outside of the tunnel is recommended. In addition, reducing the vibration source excitation intensity is the most effective vibration isolation method, especially by track structural transformation.

We design a kind of vertical vibration experiment bench with small vibration source and large load, and demonstrate that the support spring has no influence on the vibration transmissibility. The spring parameters are designed based on the resonance characteristic of the spring, and the transfer plate is simulated and optimized by Workbench and Hyperworks. The experiment bench makes the large load can be vibrated under the excitation of small vibration source, which provides a reference design for the vibration isolator and other equipment that need to carry out the large load vibration experiment.

The contribution deals about determination of vibration source and mechanical system by using Short Time Fourier Transformation. To understand the degradation mechanisms in a machine would be required to perform dynamic analysis to identify the source of vibration and their interactions. To excitation of measured object we used run-up and shut down expected rotational excitation source in the system. After performing the measurement has been carried out with determining the interaction between the natural frequencies of the system and excitation frequency. Since it was present for more than one excitation source, the effect of the first was characterized by the independent variable and the second excitation source as the measurement parameter. Based on the measurements can also be adjusted by controlling operating modes of the excitation source.

Traditional researches concerning the damping mechanisms of materials are limited to the phases and structures of materials, ignore the damping-related characteristics of the vibration source and of the materials themselves, and thus have great one-sidedness. This paper combines vibration science and material science on the basis of the models of mechanical vibration. Based on summarizing existing damping mechanisms, it proposes three mechanisms of damping: wave-type, particle-type and molecular force-type. By considering the macroscopic morphology of materials and the structures of molecules composing materials, it provides a guideline for preparing damping materials and studying their performance. Drawing on various research results, it also presents some inference based on available theories, creates a new perspective for researching damping mechanisms, and thus it is of high reference value for future research.

The vibration prediction model of the key vibration source points of a vehicle platform is studied. Starting from the analysis of the factors affecting the vibration response and the correlation analysis, the key factors affecting the vibration response of the same vehicle structure are sorted out. The vibration prediction model of the key vibration source points is established by using neural network, and using the measured data to verify the accuracy of the vibration prediction model of the cabin section I, cabin II and cabin III of the platform. The results show that in the frequency range of 1∼500Hz, the maximum error of root mean square of cabin I is 2.75dB, that of cabin II is 2.3dB, and that of cabin II is 2.97dB.

Preservation of historical buildings is a main challenge in civil engineering field. One of the main concerns in this regard is metro induced vibration received by historical structures. There is a need to evaluate effectiveness of vibration mitigation measures in preservation of monumental buildings. The most widely used method of reducing metro vibrations is changes in the structure of the vibration source (not sufficiently investigated in the literature). In response to this need, effectiveness of track stiffness reduction in mitigation of vibration was investigated in this research. Comprehensive field tests were conducted in the Iranian metro lines. The track stiffness as well as the induced vibrations were measured. It was shown that track stiffness has noticeable role in the track levels of vibration, and in turn in metro vibration reduction. The amounts of vibration reduction were derived as a function of track stiffness reduction.

Using UDEC discrete element numerical simulation software and a cosine wave as vibration source, the whole process of rockburst failure and the propagation and attenuation characteristics of shock wave in coal-rock medium were investigated in detail based on the geological and mining conditions of 1111(1) working face at Zhuji coal mine. Simultaneously, by changing the thickness and strength of immediate roof overlying the mining coal seam, the whole process of rockburst failure of roadway and the attenuation properties of shock wave were understood clearly. The presented conclusions can provide some important references to prevent and control rockburst hazards triggered by shock wave interferences in deep coal mines.

The propagation of acoustic emission (AE) signal in waveguide is quite important for AE-based prediction of dynamic disasters in coal rocks. In this study, based on some relevant theories in wave mechanics, the elastic mechanical model of one-dimensional (1D) waveguide was firstly established, and the relationship between AE source signal and the signal at the waveguide’s receiving end was derived. On the basis of theoretical analysis, numerical simulation and laboratory test schemes were designed; additionally, using the standard vibration source method, AE response in different sizes of waveguides were investigated, the effects of waveguide size of waveguide were concluded, and the application conditions of the established theoretical model were clarified. Numerical simulation results fit well with the laboratory test results. Meanwhile, the effects of the sensor’s installation method on the propagation rules of AE signal were examined and appropriate installation method was determined.

An optical approach to determine the hydration level in human skin is presented. The approach is based on temporal tracking of back-reflected secondary speckle patterns generated while illuminating the tested area with a laser and applying periodic vibrations to the surface via a controlled vibration source (CVS). This approach has already been tested successfully for other biomedical parameters such as sensing vital signs, hematology and hemodynamic processes in the body. In this paper we examine and adjust this optical technique with the aim of measuring human skin moisture. We compare the suitability and accuracy of our optical method to the commercially available device for skin moisture measurements, the Corneometer CM 825 (by Courage + Khazaka, Cologne, Germany). Preliminary experiments showing the method's suitability for hydration measurements are presented, may lead to more accurate results that may upgrade the control of the cosmetic industry as well as identifying symptoms of moisture-related skin diseases.

In this paper, a method for predicting vibrations due to an electromagnetic force from among the other types of vibrations that occur in an electric motor is proposed. Among electromagnetic forces, the forces applied in the radial direction were separated into their spatial and temporal harmonic components for developing the vibration-prediction method. Each separated radial force densities acts as a vibration source and generates vibrations combined with the mechanical characteristics of the motor. The separation of vibration sources makes it possible to predict the magnitude of the vibration velocity occurring in the motor. This enables optimal motor design considering vibration. To this end, a description explaining the characteristics of electromagnetic vibrations that occur in an eight-pole nine-slot permanent magnet synchronous motor has been provided in this paper as an example. In addition, the proposed method was verified by comparing the obtained vibration velocity with that obtained through electromagnetic-vibration coupled analysis.

The engineering structures which based on laminated composites, have a high probability of unexpected damage development during services. The damage formations must be monitored from the beginning before it headed towards structural failure which could result in substantial damage. This lead to the necessity of Structural Health Monitoring (SHM) system to be installed during the construction of laminated composite structures. However, an understanding of damage area detection and damage characteristics is essential, before a SHM system can be integrated into the structures. This article presents the effects of propagating wave propagation through an existing damage on composite plates. Theoretically, a propagating wave that started from any source will vary when crossing an area with damage. This study shows a high frequency wave propagation (kHz range) show different reactions when passing through the damaged area, compared with the low frequency wave propagation. Results of the study will lead to good damage detection method, which utilizing the available vibration source; especially for the condition monitoring of thin laminated composite structures.

A novel vibration source separation and identification method using the denoising source separation (DSS) technique is proposed for the mixed mechanical vibration signals from engines in ships. Denoising source separation enables us to extract the source signals from the mixed signals without prior knowledge of sources and their mixing mode, and thus the important source information extracted by DSS can be used to monitor or actively control engine noises. Different denoising functions such as energy, skew, kurtosis, and tangential functions in DSS are applied to both simulation studies and experimental data to evaluate their separating performances. The tangential function provides the best outperformance with both numerical study and engineering application. In addition, the effectiveness of the proposed DSS method is validated by correlation analysis and the frequency marker tracking method.

In an increasingly urbanized areas transport vibration source are closer and closer to the receiver which is a building. At the same time residents requirements for comfort in rooms are higher. In this paper influence of transport vibrations from various types of trams on human perception was tested and analysed. Measurements were made in Cracow on 11 buildings located near tramway. Human perception were investigated according to ISO and Polish standard. Basic RMS method and additional VDV method were applied because of high crest factor of recorded signal. Results of both methods were compared.

The ultrasonic longitudinal-torsional vibration used in manufacturing technology can be produced from a vibration source containing diagonal slits. The diagonal slits act as a vibration converter that can produce longitudinal-torsional vibration in conjunction with a longitudinal vibration source. The diagonal slits are generally located on the circumference of a cylindrical vibration source. However, the ultrasonic vibration sources used for ultrasonic vibration-assisted manufacturing technology come in various shapes other than cylindrical. Therefore, we investigate a vibration source with diagonal slits in two facing surfaces, which can be used for vibration sources of various shapes. In this study, we investigate the vibration characteristics of an ultrasonic vibration source coupled with a square prism rod containing diagonal slits and assess whether it can produce longitudinal-torsional vibration. From the results, we find that the vibration source has a resonance frequency of 38.6 kHz. When the vib...

The location of a vibration source within a machine is sometimes found to have a significant impact upon the machine's radiated sound power. Radiation mode analysis is known to be a powerful tool for interpreting and predicting sound radiation from a vibrating object since radiation modes are independent of a structure's surface vibration. However, knowledge of the radiation modes alone cannot be used directly to understand the relationship between vibration source location and sound power radiation. Previously, it was suggested that the radiation mode concept could be extended to understand the relationship between the sound power and the driving force distribution by combining a structure's mobility matrix and its radiation modes to form force radiation modes (frad-modes). It was demonstrated by simulation that the radiated sound power can be reduced by choosing the driving force location to be at or near the nodes of the force radiation modes. Here, to further validate the usefulness of the force radiation mode concept, the acoustic transfer vectors and the mobility matrix of a thin steel strip mounted in a rigid baffle were first measured. Then, the force radiation modes were calculated by using the experimental data and it was confirmed that the force radiation modes can serve as a practical guide for choosing a vibration source location that minimizes the radiated sound power, especially at low frequencies.

A new stiffness identification method for a high-rise building is proposed when the building includes an unknown vibration source at the top. By performing limit manipulation, the ratios between shear stiffness coefficients of consecutive stories can be obtained from the floor acceleration data and the ratios of the rotational stiffness to the shear stiffness (SR stiffness ratio). The level of stiffness coefficients can be determined to satisfy the recorded lowest natural frequency and the SR stiffness ratios can be obtained to satisfy the compatibility of higher-order natural frequencies. The validity of the proposed method is examined through actual recorded data.