Search

Free and fixed plate blade root states were simulated with finite element analysis to reveal the crack effect on the natural vibration frequency of the blade. Natural vibration frequencies are obtained for blades with different crack locations and lengths. The crack is found to reduce the blade stiffness and to affect its natural vibration frequency. The longer the crack, the greater the change of the stiffness, and the more the natural vibration frequency decreases. In the free state, the effect of the cracks of the same length on the natural vibration frequency is basically identical when it lies between the two nodal lines of first-order bending vibrations. The crack effect at a height of one-half the blade in the free state on natural frequencies is very close to that of the cracks of the same length at a height of one-eighth the blade in the fixed state. Practical guidelines for the detection of fracture cracks are given and the crack length and location were evaluated by frequency variations.

This study examines the effect of shear and rotatory inertia on the accuracy of the vibration method with additional mass (VAM). Bending vibration tests were performed for rectangular bars with a width of 30 mm, thicknesses ranging from 5 to 60 mm, and a length of 300 mm, small round bars with diameters in the range of 6–36 mm, and lengths of 150–300 mm, and cross beams for timber guardrails with and without a concentrated mass under a free–free condition. The estimation accuracy of the VAM and the effect of shear and rotatory inertia increased and decreased, respectively, as the length/thickness ratio of the rectangular bar and length/diameter ratio of the round bar increased. The estimation accuracy of the VAM decreased with an increase in the effect of shear and rotatory inertia, and it could be corrected. The range of the effect of shear and rotatory inertia for the sufficient estimation accuracy of the VAM was obtained.

This study examined whether or not weight, density, and Young’s modulus can be accurately measured by vibration test without weighing beams for timber guardrails. Bending vibration tests with and without the concentrated mass were performed on small clear round bars without the pith of spruce and cedar and on actual size round bars with the pith of cedar for the timber guardrail. The following results were obtained. The vibration method with additional mass could be applied to the round bar as well as the rectangular bar. It is possible that resonance frequency was decreased by the sawn split in the horizontal tapping. It is believed that the free ends condition is easier to realize than the fixed ends condition for cross beams for timber guardrails. The weight of the cross beam for the timber guardrail could be accurately estimated by the vibration method with additional mass under several testing conditions.

This work examines the effect of a method for generating bending vibration on the accuracy of a nondestructive and simple estimation of weight, density, and Young’s modulus through a vibration test without measuring specimen weight. The resonance frequencies with and without the concentrated mass generated by tapping the RT (radial tangential)-plane under the free-free condition were compared with those generated by the normal free-free bending vibration. The air-dried specimens and wet specimens in a drying process at 20 °C and 65% relative humidity were used and then their weight, density, and Young’s modulus were estimated by the vibration test. The appropriate resonance frequency of the bending vibration could be obtained by tapping the RT-plane. Generating bending vibration by tapping the RT-plane is effective for the application of the vibration method with additional mass to a drying process.

The pressure-dependent Raman spectra of synthetic alforsite, Ba5(PO4)3Cl, were investigated up to 34.9 GPa using a DAC at room temperature. During compression to greater than 20 GPa, new Raman active peaks of Ba5(PO4)3Cl were observed. The Raman frequencies of all observed bands for Ba5(PO4)3Cl alforsite increase continuously with increasing pressure. The quantitative analysis of PO4 internal vibrational pressure dependences for different Raman bands in alforsite shows that the ν3 anti-symmetric stretching modes have larger pressure coefficients (from 4.24 to 5.46 cm−1/GPa) whereas, the ν4 anti-symmetric bending vibrations have smaller pressure coefficients (from 1.16 to 2.04 cm−1/GPa). The external modes show larger pressure coefficients (from 4.71 to 5.54 cm−1/GPa). The PO4 internal modes in Ba5(PO4)3Cl alforsite give isothermal mode Gruneisen parameters varying from 0.147 to 0.488, which yields an average PO4 internal mode Gruneisen parameter of 0.314. On the other hand, the external modes give isothermal mode Gruneisen parameters from 1.583 to 2.030. The external modes mainly contribute to the bulk Gruneisen parameter since the bulk thermochemical Gruneisen parameter was determined as 1.44.

The objective of this study was to increase the estimation accuracy of the vibration method with additional mass (VAM). The wood specimen was divided into a cut end and a main body. The cut end was used in VAM. The estimation accuracy of VAM was increased by using the cut end as the additional mass. Hence, the cut end had completely adhered to the main body before cutting. The estimation accuracy reduced with decreasing specimen length. In order to maintain high estimation accuracy, the specimen length should not be too short. The estimation accuracy of the longitudinal vibration was higher than that of the bending vibration because the variation range of the resonance frequency due to end cutting of the longitudinal vibration was lower than that of the bending vibration.

Based on Jeffcott rotor model, the coupled bending-torsional rotor-bearing system with rub-impact under electromagnetic excitation for hydraulic generating set is established and the corresponding equation is given. The influence of excitation current, mass eccentricity and electromagnetic torque in the system is investigated by taking use of numerical method. The simulation results show that eccentricity is the crucial factor causing the changes of system dynamic characteristics, compared to the effect of torsional degree of freedom. And the larger the eccentricity is, the more obviously it affects the system responses. While the complicated dynamic behavior of bending vibration response can be restrained, due to the introduction of torsion motion, which has the property to suppress complex dynamic response of system, particularly, the inhibited and improved effect is more evident, as the eccentricity turns to be smaller. In addition, the unstable jumping phenomena of torsional response can be motivated by electromagnetic torque, which has to be taken seriously during the process of model establishment and dynamic analysis of system. From the global view of electromechanical coupling characteristics, the coupled bending-torsional vibration model with rub-impact under electromagnetic excitation can supply a more comprehensive reflection about the dynamic characteristics of system and provide useful reference with system state recognition and fault diagnosis.

The skew-symmetric problem of bending vibration of a thick-walled finite-length shell with sliding fixation of its ends is studied within the framework of the theory of elasticity. The boundary-value problem is reduced to an infinite system of singular integral equations of the second kind. The expressions for the amplitude value of relative circumferential stress are obtained as functions of the dimensionless wave number. On the basis of the developed analytic algorithm, we performed a numerical experiment and obtained a great amount of graphic data containing both the quantitative and qualitative characteristics of bending vibration of a thick-walled shell depending on its geometric parameters and Poisson’s ratio of the material of the shell.

The present work studied the very high-cycle fatigue (VHCF) test and fatigue properties of TC17 titanium alloy. The specimens for bending vibration were designed using the finite element method and the VHCF tests were conducted by using the ultrasonic fatigue testing system. The results indicated that there is no the fatigue limit for TC17 titanium alloy, and the S–N curve shows a continuously descending trend. The fatigue crack initiates at the specimen surface within the range of VHCF and the VHCF lives follow the log-normal distribution more closely.

Nanorods of one-dimensional (1D) trigonal selenium (t-Se) are synthesized using biomolecule substances for five different aging times (1 h, 2 h, 3 h, 1 day and 4 days) by precipitation method. XRD analysis indicates a shift of the (1 0 1) plane towards higher diffraction angle for 1 day aging time. It is observed that the crystallite size decreases with increase in aging time except for an aging period of 4 days. FTIR analysis confirmed that the presence of stretching and bending vibrations of Se–O in both synthesized and commercial selenium samples at 465, 668 and 1118 cm −1. The FESEM micrographs are evident for the changes of rod size as a function of aging time. It is observed that the optical band gap energy is increased with aging time up to 1 day, whereas it decreases in 4 days aging time.

A new approximate method for the determination of natural frequencies of a cantilever beam in free bending vibration by a rigid multibody system is proposed. Uniform Euler-Bernoulli cantilever beams with and without a lumped mass at the tips are considered. The modelling method consists of two steps. In the first step, the cantilever beam is replaced by lumped masses interconnected by massless flexible beams. In the second step, the massless flexible beams are replaced by massless rigid beams connected through revolute and prismatic joints with corresponding springs in them. Elastic properties of the massless flexible beams are modelled by the springs introduced. The method proposed is compared with similar ones in the literature.

A theoretical model of the phonon-mediated nuclear spin relaxation in H2O trapped by cryomatrices has been established for the first time. In order to test the validity of this model, we measured infrared spectra of H2O trapped in solid Ar, which showed absorption peaks due to rovibrational transitions of ortho- and para-H2O in the spectral region of the bending vibration. We monitored the time evolution of the spectra and analyzed the rotational relaxation associated with the nuclear spin flip to obtain the relaxation rates of H2O at temperatures of 5–15 K. Temperature dependence of the rate is discussed in terms of the devised model.

Analytical peculiarities of ultrasonic cavitators based on piezoceramic transducers with a radiative plate, which experiences bending vibrations, are analyzed. The acoustic dimensions of components of a sectional piezoelectric transducer used in the production process of contact ultrasonic treatment of a dry 1,120-mm wide cloth impregnated with a polymeric binder, are calculated.

The structure and vibrational spectra of twelve tautomers are calculated in the B3LYP/6-311+G(d,p) approximation and analyzed. Spectral manifestations of isomeric uracil transformations into one out of the twelve tautomeric forms and cis— trans- isomeric transformations of the tautomers themselves are considered. All tautomeric transformations are shown to be characterized by the presence of at least one vibration, whose frequency is different by ~ 100-200 cm-1 from a similar vibrational frequency of the precursor and also by a pronounced change in the intensity of bending vibrations of OH hydroxyl groups and stretching vibrations of CO bonds.

Room temperature Fourier transform IR and Raman spectra in the range 30–4000 cm−1 and 80–4000 cm−1 of Dy, Ho, Er and Lu phthalocyanide PcLn(OAc)-type complexes have been measured, respectively. The assignment of the bands observed has been made on the literature data. The molecular structure of the PcLnX-type derivatives has been discussed on the basis of the group theory taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of the LnN4O coordination polyhedron as well as whole PcLn(OAc) complex.

The basic relations of the thermomechanics of thin-walled viscoelastic plates with distributed piezoelectric sensors under monogarmonic mechanical loading are presented. To describe the thermomechanical behavior of materials, the concept of complex characteristics is used. Numerical and variational methods are used to study the forced resonant vibrations of viscoelastic plates with distributed piezoelectric sensors. The effect of dissipative heating on the readings of the sensors of a circular viscoelastic plate undergoing axisymmetric resonant bending vibrations is analyzed as an example

The basic equations for thin-walled thermoviscoelastic plates with distributed piezoelectric actuators under monoharmonic mechanical and electric loads are derived. The thermomechanical behavior of materials is described using the concept of complex characteristics. Variational methods of solving nonlinear problems of active damping of the bending vibrations of plates are considered. The effect of dissipative heating on the damping of the axisymmetric bending vibrations of a circular plate is examined as an example

The direct and inverse problems of the steady-state transverse vibrations of a cylindrical rod with a defect in the form of a cavity of small relative size are considered. An approach to determining the location and volume of the cavity of arbitrary shape is proposed. Results of computational experiments are analyzed.

With the motivation of discovering high-temperature superconductors, evolutionary algorithm is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH$_4$, new hydrides SnH$_8$, SnH$_{12}$ and SnH$_{14}$ are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin-hydrides are systematically investigated. I$\bar{4}$m2-SnH$_8$, C2/m-SnH$_{12}$ and C2/m-SnH$_{14}$ exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH$_4$ with T$_c$ of 52 K at 200 GPa. An interesting bent H$_3^-$ in I$\bar{4}$m2-SnH$_8$ and novel liner H$_4^-$ in C2/m-SnH$_{12}$ are observed. All the new tin-hydrides remain metallic over their predicted range of stability. The intermediate-frequency wagging and bending vibrations have more contribution to electron-phonon coupling parameter than high-frequency stretching vibrations of H$_2$ and H$_3$., Comment: 8 pages, 4 figures

We have used the density functional method (DFT) to calculate the geometric structure and the frequencies of even (gerade) vibrations of the Zn-phthalocyanine and Zn-phthalocyanine-d16 molecules, and we have refined the interpretation of the resonance Raman spectra and the fine-structure fluorescence spectra. We observed a dependence of the frequencies of both stretching and bending vibrations of the aza bridges on the nature of the central metal atom.

Useful structure characteristics of elastic cylindrical shells have led them to being widely applied in virtual projects, so it is important to conduct vibration research on the shells and find it’s a simpler corresponding compact calculation method. Utilising the input and transfer point mobility of a thin plate structure, a theoretical expression of the cylindrical shell's bending vibration responsewas deduced and numerical simulations were done to simplify the theoretical expression within an acceptable error margin, greatly reducing the amount of computations. Furthermore, whole vibration response distributions of the cylindrical shell were analyzed. It was found thathe vibration energy propagates in helical form under mono-frequency excitation, while under bandwidth frequency excitation, it attenuates around in term of fluctuation. The axial attenuation rate of the vibration energy is larger than the circumferential attenuation rate.

Viaduct roads have wide application in big cities with high traffic loads, in order to decrease traffic density and to connect subways to highways. Viaduct roads are constructed using steel structures instead of concrete ones in areas of earthquake risks. The low weight of steel structures however causes problems such as vibration and noise. There is increasing demand especially in populated areas to suppress vibration and noise on highway roads for reducing noise-related environmental pollution.

The vibrations and dissipative heating of an infinite viscoelastic beam under a moving load are studied on the basis of Timoshenko beam theory. The influence of transverse-shear strain and rotary inertia on the critical velocities of the moving load, the amplitude of bending vibration, and the temperature of dissipative heating is analyzed

This study was intended to detect nondestructively some defects such as knots and grain deviations in wood using modal analysis. The shapes of flexural vibration waves at the first mode generated by the tapping of wooden beams were determined using the transfer function. The wave shapes obtained were compared with the theoretical wave shape for a uniform material; and the possibility of detecting defects in wood was examined. The results are summarized as follows: (1) The shapes of flexural vibration waves at the first mode of wooden beams free of defects coincided almost completely with the theoretical wave shape. (2) The shapes of flexural vibration waves of wooden beams containing defects such as knots clearly differed from the theoretical wave shape, especially near the defect. (3) Based on these results, it should be possible to detect the presence of defects and to determine their location in wood.

The possibility is investigated for failure of long rods under face impact caused by the stability loss of longitudinal deformation. The formula is obtained for calculating the maximum tensile stress during bending under the action of prescribed duration and intensity.

We analyze the relations obtained earlier for the displacements and stresses components over a wide frequency range and derive expressions for the input admittance of a two-section planar transverse–longitudinal piezotransformer.

Quantitative dependences of the velocity of a moving domain boundary and sizes of magnetic inhomogeneities in rare-earth orthoferrites are determined experimentally in real time. The results obtained agree satisfactorily with the parameters calculated for the physical model of parametric resonant deceleration of the domain boundary on wall (Winter) magnons. The lower threshold frequency of bending vibrations of the domain wall is of the order of 108 Hz.

Summary A dimensional analysis is reported for the dynamic plastic response and failure of structural members, which includes material strain hardening, strain rate and temperature effects. Critical shear failure conditions are also discussed based on the dimensional analysis results. It is shown that the response number Rn proposed in [3], is an important independent dimensionless number for the dynamic plastic bending and membrane response of structural members. However, additional dimensionless numbers are necessary when transverse shear, strain hardening, strain rate, and temperature effects are important.

This paper gives the results of experimental studies of the influence of thermomechanical treatment and post-annealing on the level of damping capacity of titanium alloys VT3-1 and VT8. We subjected VT3-1 alloy to both treatment modes, and VT8 alloy to only one. We evaluated the efficiency of the thermomechanical treatment modes by the vibration strength criterion (σaδ).

An SU(2) algebraic model is proposed forvibrational spectra of bent triatomic molecules, whereFermi resonances between the stretching and the bendingmodes are considered. As an example, the model is applied to the 142 vibrational energy levelsbelow 9000 cm-1 in the electronic groundstate of nitrogen dioxide.

We study the problem of bending vibrations of a prestressed flexible annular plate made of a cylindrically anisotropic material. The problem is solved using the method of initial functions and the theory of multiplicative integration. Using the resulting computational formulas we analyze the critical values of the loading parameters of the plate by the dynamic criterion.

The molecular geometry of silicon tetraiodide was determined by gas-phase electron diffraction at 378 K. The molecule has a regular tetrahedral shape with an Si—I bond length (r g) of 2.432(5) A and an I⋅⋅⋅I nonbonded distance (r g) of 3.971(8) A. There is an apparent anharmonicity in both the stretching and the bending vibrations, with the latter especially pronounced.

We describe a method for the design and numerical analysis of compact mechanical vibrating systems with generators of vibrations on their inertial weights and establish the conditions of damping of unwanted vibrations in these systems aimed at guaranteeing the absence of favorable conditions for the introduction of systematic errors to experimental results. The designed and manufactured vibrating systems are dynamically balanced, and predicted values of the frequencies of their natural vibrations satisfactorily agree with the experimental data.

Aq-deformed boson-realization model is presented to study both stretching and bending vibrations of sulfur dioxide, where Fermi resonances are taken into account. Our results are compared with those of other models.

Equations are derived for bending vibrations of bimorph piezoceramic plates allowing for the type of polarization of the layers and the conditions of application of electric power to electrode surfaces. Boundaryvalue conditions with open electrodes are considered.

This paper studies the problem of free bending vibration of annular cylindrical tank partially filled with liquid in the consideration of surface wave. The exact formulae of the mode shape functions and frequencies are deduced. Results can be obtained by means of computer. The analysis shows that the effect of liquid on vibration of annular cylindrical tank is equivalent to different generalized distributive masses attached to inner and outer cylinders respectively.

This paper describes a new method for inserting parts with very close clearance in the assembly process. The inserting motion becomes smooth and easy by the application of ultrasonic vibration to either the peg or the hole to be mated. In the experiments, longitudinal vibration and/or bending vibration were applied to the peg by using an ultrasonic exciter. Smooth mating with a clearance of less than several micrometers was realised by a robot under rough control to about several hundred micrometers. This effect is due to the result of the reduction of the apparent friction and the generation of surface force on the parts' surfaces.

A review of works dealing with the IR spectra and structure of hydroxylated surfaces of oxides is presented. Influence of crystal structure and other factors on OH stretching modes, as well as data about bending vibrations of hydroxy groups are discussed. Experimental results are compared with data of computer simulations.

An asympototic method developed by V.V. Kucherenko and the author is applied to the problem of free vibrations of a thin plate strip in a state of a plane strain. The first few terms of an asymptotic expansion of the natural frequencies are calculated. The results are compared with those obtained by using the “classical” and refined theories.

An experimental-computational method of accounting for energy dissipation under complex (bending-twisting) mechanical oscillations is proposed. Decrements of the bending, twisting, and bending-twisting oscillations of a steel St. 3 specimen are obtained. The possibility of converting from actual simple-vibration decrements to decrements of complex interrelated oscillations is demonstrated on the basis of the hypothesis of the decisive role of octahedic tangential stresses in a material subject to energy dissipation.