Vibration Method Research Articles

Workpiece vibration in feed direction assisted electrochemical cutting using tube electrode with inclined holes

Electrochemical cutting using tube electrode with inclined holes is a machining method that directly and obliquely injects electrolyte into the machining gap through inclined jet-flow holes on the sidewall of a tube electrode, allowing the electrochemical cutting of a workpiece. To improve the machining efficiency and accuracy of this cutting technique, a method of workpiece vibration in feed direction–assisted electrochemical cutting is proposed in which workpiece vibration rapidly and periodically changes the machining gap. The near-instantaneous increases in the machining gap promote the renewal of electrolyte and the removal of electrolytic products. At the same time, the electrochemical reaction time under the nonuniform flow field caused by the inclined downward injection of electrolyte is reduced. The flow field simulation of electrolyte in machining gap indicates that the near-instantaneous increases in the machining gap can improve the flow velocity of electrolyte. The effect of the vibrational amplitude and frequency on the machining result is investigated by cutting slit experiments. Compared with that of electrochemical cutting without workpiece vibration in feed direction, the average feed rate of electrochemical cutting assisted by workpiece vibration with amplitude of 0.1 mm and frequency of 1.5 Hz can be increased by 50%, and the width difference between the upper and lower end of the slit is reduced from 115.56 to 49.6 μm. The machining efficiency and machining accuracy of electrochemical cutting using tube electrode with inclined holes are improved. Finally, an array slice structure is fabricated on a stainless steel block with a cross-section of 10 mm × 10 mm at average feed rate of 6 μm/s using a vibrational amplitude and frequency of 0.1 mm and 1.5 Hz, respectively.

Polyethylene Migration from Food Packaging on Cheese Detected by Raman and Infrared (ATR/FT-IR) Spectroscopy.

For multiple years, food packaging migration has been a major concern in food and health sciences. Plastics, such as polyethylene, are continuously utilized in food packaging for preservation and easy handling purposes during transportation and storage. In this work, three types of cheese, Edam, Kefalotyri and Parmesan, of different hardness were studied under two complementary vibrational spectroscopy methods, ATR-FTIR and Raman spectroscopy, to determine the migration of low-density polyethylene from plastic packaging to the surface of cheese samples. The experimental duration of this study was set to 28 days due to the degradation time of the selected cheese samples, which is clearly visible after 1 month in refrigerated conditions at 4 °C. Raman and ATR-FTIR measurements were performed at a 4–3–4–3 day pattern to obtain comparative results. Initially, consistency/repeatability measurement tests were performed on Day0 for each sample of all cheese specimens to understand if there is any overlap between the characteristic Raman and ATR-FTIR peaks of the cheese with the ones from the low-density polyethylene package. We provide evidence that on Day14, peaks of low-density polyethylene appeared due to polymeric migration in all three cheese types we tested. In all cheese samples, microbial outgrowth started to develop after Day21, as observed visually and under the bright-field microscope, causing peak reverse. Food packaging migration was validated using two different approaches of vibrational spectroscopy (Raman and FT-IR), revealing that cheese needs to be consumed within a short time frame in refrigerated conditions at 4 °C.

Heat capacity, density, surface tension, and contact angle for polyalphaolefins and ester lubricants

Thermophysical properties of lubricants are important to understand which ones are appropriated for the industrial conditions expected. Thermophysical properties of two different families of lubricants were analysed: polyalphaolefins (PAO6, PAO20, PAO32 and PAO40) and four ester-based lubricants. Specific heat capacity, density, surface tension, and contact angle were experimentally determined over a broad temperature range through methods such as μDSC, U-tube vibration, drop volume, and sessile drop method, respectively. A clear difference between the two families was observed due to their structure and composition, grouping by nature. Ester-based lubricants showed lower specific heat capacity but higher surface tension and density than polyalphaolefins. PAO6 clearly has the lowest density and surface tension and presents the highest specific heat capacity of all lubricants, and together with trimethylolpropane trioleate, TMPTO, presents the best wettability. Heat capacity values were used to test the validity of two predictive methods.

Investigation of Experimental and Statistical (Respond Surface Method and Grey Relational Analysis) of Surface Roughness, Vibration and Enerrgy consumption Values of Titanium Alloy During Machining

This study aims to explain the interaction between the results measured in the turning operation. For this purpose, Ti 6Al-4V alloy workpiece was machined on CNC lathe. Surface roughness (Ra), vibration and energy consumption values were determined by turning. Experimental results were analyzed statistically. Response surface method (RSM) and grey relational analysis were used statistical analysis. In RSM analysis, regression equations, ANOVA, contour graphs, pertubation graphs, real and prediction graphs, % contribution graphs, most significant factor, optimum parameters, it is determined that the effective parameter in surface roughness, vibration and energy consumption is feed rate. Grey relational analysis steps and results are examined.

Integration of vibration and optical techniques for watermelon firmness assessment

Fruit firmness is one of the key quality indices of fruit at different stages of the food supply chain. In this study, a new detection system based on the acoustic vibration method and visible/near-infrared (Vis/NIR) spectroscopy was developed to evaluate watermelon firmness. To diminish the influences of the shape index and white peel thickness on the second resonance frequency (f2), a multiple linear regression model was established by the finite element analysis (FEA) method to optimize the measured f2 to the modified second resonance frequency (f0) of a single-tissue watermelon. Besides, the machine vision system was designed to obtain the real white peel thickness and shape index. And the peel thickness was non-destructively predicted by Vis/NIR spectroscopy. In addition, a new puncture probe with ten cylinders was developed to determine the destructive firmness of the whole watermelon. The flesh firmness (FF) of watermelon was selected as an output variable in the prediction models due to its high correlation coefficients with vibration parameters. Regarding the acoustic vibration method, better prediction performance of FF was obtained in a back propagation neural network (BPNN) model by using the modified elasticity index (EI0), the peak width at half height (w), the peak value at f2 (A) and the peak area (S) as input variables. The correlation coefficient of prediction (rp) and root mean square error of prediction (RMSEP) were 0.655 and 0.971 N. Considering the merits and limitations of acoustic vibration method, a low-level data fusion method was applied to combine the vibration and Vis/NIR spectrum data to acquire more comprehensive firmness information. The successive projections algorithm (SPA)-BPNN model using 13 spectrum features achieved better prediction results than other prediction models (rp = 0.841, RMSEP = 0.932 N). It was found that the integration of vibration and optical techniques could be an effective approach to provide more detailed information about watermelon firmness.

Progress and applications of acoustic black holes

<p indent=0mm>The problem of vibration and noise has always been one of the difficulties in the development of society. Therefore, the innovation of vibration and noise reduction methods has never stopped. In recent years, the introduction of acoustic black holes to manipulate flexural waves has become a hot topic in the field of vibration and noise. In this review, the acoustic black hole is defined as a kind of structure which can converge the flexural wave by changing the geometric parameters or material properties. In the absolute ideal case, the flexural wave velocity gradually decreases to zero in the acoustic black hole region. Acoustic black hole structures, as a new kind of flexural wave manipulation technique, can effectively reduce the propagation speed of flexural waves in the structure, thus reducing the reflection at the end of the boundary and forming a region with high energy density. Therefore, it has a broad application prospect in vibration reduction, noise reduction, fluctuation control and energy recovery. Different from the composite structure of vibration reduction and noise reduction in the past, the acoustic black hole has some certain advantages in practical application because of its simple structure, material and preparation process. Up to now, a great deal of theoretical modeling and experimental research has been carried out on the structural form of acoustic black holes, and some certain research results have been obtained. This review first introduces the origin, basic definition and principle of acoustic black holes, then introduces the theoretical calculation and experimental research methods, including frequency domain methods (semi-analytical method, Gauss expansion method, geometric acoustics method, transfer matrix method, finite element method, unit decomposition finite element method, spectral element method, and finite difference method) and wave-number domain method. Additionally, the laser ultrasonic scanning technology is emphasized in the experimental research. Next, the four main functions of acoustic black holes are classified and described, which are vibration reduction, noise reduction, fluctuation control and energy recovery, and the research status and existing problems of each application direction are summarized. The application of acoustic black holes in vibration reduction and noise reduction is becoming more and more comprehensive, and its applications in wave regulation and energy recovery are emerging in recent years. As a new research direction, the basic theory and practical application of acoustic black holes still need to be widely studied further. The breakthrough points include: (1) The acoustic vibration coupling mechanism of acoustic black holes and the matching with functional materials need to be further clarified; (2) the nonlinear wave behavior in acoustic black holes needs to be further improved; (3) according to different engineering scenarios, the bearing integrated design method of acoustic black hole composite structures is developed; (4) theoretical modeling and application development of imperfect acoustic black hole structures. The development of acoustic black holes is also a supplement and broadening to the related research of vibration and noise reduction. From the perspective of social development needs, the related research of acoustic black holes has potential applications in the independent research and development of functional structures and materials.

Effects of Stick-Slip in Behavior of Structures with Friction Damper under Near-Field Earthquakes

The present study is an attempt to investigate structures equipped with friction dampers under the influence of near-field earthquakes based on Stribeck friction behavior of velocity function. At present, the cyclic behavior of friction dampers in structural design engineering software is simple and based on the Coulomb friction force that is independent of velocity, which should be estimated and considered in terms of Stribeck velocity-dependent friction. Their sliding and vibration methods, including displacement, velocity, and acceleration, are calculated using numerical analysis and differential equation. For this purpose, the representative of the near-field records affects the structure with Stribeck frictional behavior of velocity function as a pulse of Ricker wavelet stimulation. The response of the structure is evaluated in the transition phase from impending motion with a friction coefficient of μs to kinetic motion with μk and vice versa, which makes the poor results of previous simplifications more accurate. Due to the nonlinear behavior of the damping force, programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in OpenSees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis.

On the symplectic superposition method for free vibration of rectangular thin plates with mixed boundary constraints on an edge

A novel symplectic superposition method has been proposed and developed for plate and shell problems in recent years. The method has yielded many new analytic solutions due to its rigorousness. In this study, the first endeavor is made to further developed the symplectic superposition method for the free vibration of rectangular thin plates with mixed boundary constraints on an edge. The Hamiltonian system-based governing equation is first introduced such that the mathematical techniques in the symplectic space are applied. The solution procedure incorporates separation of variables, symplectic eigen solution and superposition. The analytic solution of an original problem is finally obtained by a set of equations via the equivalence to the superposition of some elaborated subproblems. The natural frequency and mode shape results for representative plates with both clamped and simply supported boundary constraints imposed on the same edge are reported for benchmark use. The present method can be extended to more challenging problems that cannot be solved by conventional analytic methods.

A magnetic control method for large-deformation vibration of cantilevered pipe conveying fluid

A magnetic control method for large-deformation vibration of cantilevered pipe conveying fluid

Π-Stacking in Heterodimers of Propargylbenzene with (Fluoro)phenylacetylenes.

The heterodimers of propargylbenzene (PrBz) with phenylacetylene (PHA) and monosubstituted fluorophenylacetylenes (FPHAs) were investigated using electronic and vibrational spectroscopic methods. The vibrational spectra in the acetylenic C–H stretching region show a marginal shift (0–4 cm–1) upon dimer formation, which suggests minimal perturbation of the acetylenic group. The M06-2X/aug-cc-pVDZ calculations indicate that the π-stacked structures are the most stable, followed by other structures. In general, structures incorporating aromatic C–H···π interactions are much higher in energy. The appearance of the spectra and the energy considerations clearly indicate the preference for the π-stacked structures. Furthermore, the observed trend in the stabilization energies for heterodimers with the three FPHAs is inversely proportional to the dipole moments of FPHAs. On the other hand, the absence of any clear trends in the electrostatic component of the interaction energy is attributed to the presence of the methylene group in PrBz.

Research of the process of obtaining capillary-porous materials from metal powders for heat pipes

Heat pipes are designed to effective removing heat from heating elements and reducing the temperature of various devices. Heat pipes with capillary porous structures are designed to operate under conditions of unfavorable gravity forces. Their main advantages are their high heat transfer capacity, as well as the ability to retain the coolant in a capillary-porous structure under dynamic power loads. The purpose of this work is to study the process of obtaining capillary-porous materials from metal powders for heat pipes with increased efficiency of using the vibration molding method. The article substantiates the relevance of creating heat pipes from metal powders. The information about the influence of the contact angle, surface tension and capillary pressure on the heat transfer capacity of a heat pipe is provided. It is shown that for the efficient operation of the heat pipe it is necessary to create such a capillary structure of the porous material, which could simultaneously provide a high speed of movement of the coolant and its rise to a given height. The above requirements can be satisfied by creating a capillary structure using powder metallurgy methods by optimizing the distribution of pore sizes. In this case, the most promising method seems to be the method of molding when applying a vibration to a mold with a powder. It is possible to obtain the required pore distribution in this way by choosing the correct particle size, shape and vibration parameters. This makes it possible to ensure the packing of particles in size, which affects their packing density, pore size, tortuosity and length of pore channels. The distribution of the maximum pore sizes over the thickness of the samples obtained from powders of various granulometric composition with the use of vibration has been investigated. As a result, a process was developed for obtaining capillary structures by the method of vibration molding of metal powders, depending on the size of the powder particles, the amplitude and frequency of vibration. It is shown that this method can provide a given pore distribution of the capillary structure for heat pipes, which makes it possible to increase their heat transfer capacity.

Deterioration characteristics of cement-improved loess under dry-wet and freeze-thaw cycles.

The effects of cement dosage, compaction coefficient, molding method (vertical vibration method and static pressure method), and dry-wet and freeze-thaw cycles on the mechanical strength of cement-improved loess (CIL) were studied to reveal its strength degradation law under dry-wet and freeze-thaw cycles. Results show that when using the vertical vibration molding method, the strength degradation effect of CIL can be improved by increasing the cement dosage and compaction coefficient; however, it is not obvious. Under the action of dry-wet cycle, damages, such as voids and cracks of CIL, develop continuously. Further, the strength deteriorates continuously and does not decrease after more than 15 dry-wet cycles. Therefore, the dry-wet cycle degradation system is selected by considering the most unfavorable conditions. In the process of freeze-thaw alternation, the pores and fissures of CIL develop and evolve continuously and the strength deteriorates continuously under the joint influence of water and low temperature. The strength tends to become stable after more than 12 freeze-thaw cycles. According to the safety principle, the deterioration coefficient of the freeze-thaw cycles is 0.3.

The Combination of Vibrational Spectroscopy and Chemometrics for Analysis of Milk Products Adulteration.

Milk products obtained from cow, goat, buffalo, sheep, and camel as well as fermented forms such as cheese, yogurt, kefir, and butter are in a category of the most nutritious foods due to their high contents of high protein contributing to total daily energy intake. For certain reasons, high price milk products may be adulterated with low-quality ones or with foreign substances such as melamine and formalin which are added into them; therefore, a comprehensive review on analytical methods capable of detecting milk adulteration is needed. The objective of this narrative review is to highlight the use of vibrational spectroscopies (near infrared, mid infrared, and Raman) combined with multivariate analysis for authentication of milk products. Articles, conference reports, and abstracts from several databases including Scopus, PubMed, Web of Science, and Google Scholar were used in this review. By selecting the correct conditions (spectral treatment, normal versus derivative spectra at wavenumbers region, and chemometrics techniques), vibrational spectroscopy is a rapid and powerful analytical technique for detection of milk adulteration. This review can give comprehensive information for selecting vibrational spectroscopic methods combined with chemometrics techniques for screening the adulteration practice of milk products.

APPLICATION OF VIBRATION EFFECTS IN BIOFUEL PRODUCTION

The considered effective way of processing by-products of biofuel production. The increase in the productivity of the technological line is achieved through the introduction of new vibration equipment for the primary purification of raw glycerin. This study proposes a new approach to determine the efficient operation of a new machine, which is useful for the purification of glycerol based on the combinatorial process of centrifugation and vibration separation. The mathematical mechanical-rheological evaluations are developed based on the experimental results. Has been proposed to evaluate the rheological characteristics of raw glycerin purification based on the experimental testing. A compression device has been used to determine the value of the unilateral deformation of this material, which allows simulating a condition of a material at various technological modes of processing. In this study, the changes of material properties under centrifugation and vibration separation processes in a vibrocentric machine have been investigated. At a choice of optimum technological parameters of processing of food masses by means of vibration methods of rheology are widely applied. In particular, the interaction of the working body of the machine with the treated environment. In order to find the optimal parameters of the technological regime, the process was considered comprehensively from the standpoint of mechanics and rheology. The methods of mechanics describe the interaction of the working body with the treated environment as a mechanical object; rheology, in turn, allows you to reveal the internal processes in the environment. The system under study can be attributed to the elastic-viscous medium, which is described by a phenomenological model consisting of interconnected elastic and viscous elements.

HHT-Based Detection Method of Cutter Abnormal Vibration in Spiral Surface Machining

Background:: Cutter abnormal vibration occurs frequently during the spiral surface machining process, and it results in low quality of the finished surface. In order to suppress cutter abnormal vibration effectively, it is necessary to detect abnormal vibration as soon as possible, but the analysis and processing of the cutter abnormal vibration signal in spiral surface machining are difficult because of its complicated components and non-linear non-stationary characteristics. In this paper, a detection method of cutter abnormal vibration signal based on Empirical Mode Decomposition (EMD) and Hilbert–Huang Transform (HHT) is proposed to be applied in spiral surface machining. Method:: First of all, EMD of the cutter vibration signal in the spiral surface machining is performed to obtain a series of Intrinsic Mode Function (IMF) components in different frequency bands. Secondly, the variation in the energy of each IMF component in the frequency domain and the correlation with the original signal are analyzed to obtain the IMF component with the largest amount of information on abnormal vibration symptom. Finally, the Hilbert transform is conducted on the IMF component to extract the symptom features of abnormal vibration. Results:: The Hilbert-Huang spectrogram obtained by Hilbert transform is a two-variable function of time and frequency, from which the frequency information at any time can be obtained, including the magnitude and amplitude of the frequency and the corresponding moments appearing, which can describe the time-frequency characteristics of the non-stationary non-linear signal in detail. Experimental results show that the HHT based method to analyze the cutter vibration signal in the spiral surface machining can extract the symptom of abnormal vibration quickly and effectively, and can detect cutter abnormal vibration rapidly. Conclusion:: The proposed method based on HHT in this paper is fundamentally different from the traditional signal time-frequency analysis methods, and has achieved good results in practical applications. This method could be successfully used in abnormal vibration detection, which could also provide basis and guarantee for the subsequent suppression of abnormal vibration.

Experimental study on mechanical properties of new biaxial compression wire rope isolator

<p indent=0mm>Wire rope isolator is widely used in the field of vibration isolation and shock resistance of naval equipment. To overcome the shortcomings of the poor tensile performance of the traditional wire rope isolator, a new biaxial compression wire rope isolator was designed, and the performance characteristics of the new biaxial compression wire rope isolators and spherical wire rope isolators were tested using vibration and shock test methods. By conducting a comparative experiment, the characteristics of the performance difference are studied. The frequency sweep test results show that the resonance peak of the spherical wire rope isolator is larger than that of the new one at the natural frequency. The fixed frequency test finds that the vibration performance of the new and the spherical wire rope isolator is not much different under different working conditions. The shock test results show that the shock isolation rate of the new biaxial compression wire rope isolator is above 82.5%, and the shock isolation rate in all working conditions is greater than that of the spherical wire rope isolation system, which effectively improves the tensile performance of the spherical wire rope isolator. The new biaxial compression wire rope isolator further improves the shock resistance of the vibration isolator on the basis of maintaining the original vibration isolation effect of the spherical wire rope isolator.

ВОЗДЕЙСТИЕ МЕХАНИЧЕСКИХ КОЛЕБАНИЙ НА ОБЛЕДЕНЕНИЕ ИСПАРИТЕЛЕЙ ВОЗДУШНОГО ТЕПЛОВОГО НАСОСА

The analysis of the reasons for the insignificant spread of air heat pumps in countries with a cold winter period is carried out. Problems arising in the heat exchanger of the outdoor unit of the heat pump during operation in heating mode are indicated. The existing methods of anti-icing of outdoor units are considered, and their effectiveness is demonstrated, taking into account the cost of electricity and the problem of utilizing condensate. The possibility of removing ice from evaporators of air heat pumps using the method of high-frequency mechanical vibrations has been investigated. Laboratory equipment has been designed and tested for experimental research of high-frequency oscillations in the structures of evaporators manufactured by an industrial method. The possibility of their use in heat pumps, where the fight against frostbite is carried out by the method of mechanical vibrations, is considered. Investigations of evaporators of air heat pumps with different types of coolant for removing ice by means of mechanical vibrations on the surface of the heat exchanger have been carried out. Methods of fastening piezoceramic emitters to evaporators of various designs are considered. A comparative analysis of the materials used in the design of evaporators, a comparison of their acoustic properties and thermal conductivity, and recommendations on the selection of material for further research to improve the efficiency of ice destruction from the surface of evaporators are given. Ways of increasing the degree of cleaning of evaporators from ice are identified, recommendations are given for further research on the use of mechanical vibrations to combat frostbite of heat exchangers in air heat pumps under conditions of operation at low ambient temperatures

Dynamic characteristics of a hydraulic curved pipe subjected to random vibration

In this paper, the effects of external random excitation on the dynamic characteristics of a hydraulic curved pipe are investigated. A random vibration motion equation of a curved pipe conveying fluid is determined using Hamilton's principle, in which the fluid-structure interaction (FSI) and the effect of shear deformation are taken into account. The finite element method (FEM) and discrete analysis method of random vibration (DAMRV) are employed to solve these equations. Then, the dynamic characteristics of a curved pipe with different vibration and fluid parameters under two types of supported modes are determined. The numerical results show that the dynamic characteristics of the curved pipe have significant influenced by different parameters. Moreover, the numerical and experimental results are found to have good consistency, which demonstrates that the proposed method can provide theoretical reference and technical support for the design and selection of curved pipes subjected to random vibration.

Obtaining mass normalized mode shapes of motorway bridges based on the effect of traffic movement

Ambient vibration testing has become a promising alternative for the forced vibration method due to its well-established practical advantages on bridge structures. However, because of the unavailability of the input data in output-only vibration tests, the extracted mode shapes are not mass normalized. Mass normalized mode shapes are essential in various modal analysis applications such as flexibility-based damage detection techniques. Mass change method was proposed to resolve this issue for Operational Modal Analysis (OMA); however, there are certain practical issues that limit the applicability of this method to real-world structures. In this paper, we propose to utilize the dynamic effects of the traffic movement over bridges as the required perturbation to the structure's modal properties. Numerous traffic conditions are considered, and uncertainty analyses are performed to evaluate the suitability of the loads in different traffic scenarios. Furthermore, a numerical case study is conducted on Hafez Bridge in the city of Tehran, Iran. Actual traffic conditions are simulated using the traffic micro-simulation method, and vehicle forces and masses are applied to the finite element model of the bridge using the equivalent nodal forces method. OMA is conducted in the time domain, and modal parameters are extracted using the Stochastic Subspace Identification method. Finally, it is shown that using the proposed framework, not only the modal scaling factors are estimated with satisfying accuracy, but also the practical difficulties of the conventional mass change method such as bridge shutdowns are eliminated.

Effects of Fe Addition on the Phase Transformation Internal Friction in Ni-Al-Based Alloys

The influences of chemical compositions on the internal friction of phase transformation were investigated for the quenched Ni-Al-based alloys. The internal friction measurements were completed using a low-frequency mechanical spectrum apparatus through forced vibration method. It was shown that the chemical compositions have the great influences on the internal friction of phase transition for the oil-cooled Ni-Al-based alloys. The peak-temperature of internal friction is lowered, and the peak-height is increased and the peak-width is narrowed when Fe content is elevated. The reducing of the peak-temperature is attributed to the increase of stability of γ phase due to the addition of Fe. The changes of the parameters of the peak are also related to the Aleq(equivalent Al) contents.