Vibration Limits Research Articles

Dynamics and Control of Machines

Dynamics and Control of Machines

Nuclear Vibron Model with 2 and 3 Clusters for Heavy Nuclear Molecules

An algebraic vibron model for two- and three-cluster nuclear molecules is presented, where all clusters are deformed. It is shown that if the clusters are deformed a minimum can be obtained for r ≠ 0, even in the relative vibrational limit UR(4) ⊃ UR(3) for the case of two clusters, and UR(7) ⊃ UR(3) ⊗ UR(3) for three clusters. By using coherent states, the geometrical mapping is discussed.

The vibration resistance of young and early-age concrete

During early age, concrete is vulnerable to disturbance from vibrations of large magnitudes. Today, conservative vibration limits are used as standards, and guidelines provide little information. The literature cited in this study contains experiences and results from the construction and civil engineering field, in-situ testing, laboratory testing and computer modelling. On the basis of the reviewed literature, recommended maximum vibration levels for young and early-age concrete are given.

The vibration resistance of young and early-age concrete

During early age, concrete is vulnerable to disturbance from vibrations of large magnitudes. Today, conservative vibration limits are used as standards, and guidelines provide little information. The literature cited in this study contains experiences and results from the construction and civil engineering field, in-situ testing, laboratory testing and computer modelling. On the basis of the reviewed literature, recommended maximum vibration levels for young and early-age concrete are given.

Vocal dose measures: quantifying accumulated vibration exposure in vocal fold tissues.

To measure the exposure to self-induced tissue vibration in speech, three vocal doses were defined and described: distance dose, which accumulates the distance that tissue particles of the vocal folds travel in an oscillatory trajectory; energy dissipation dose, which accumulates the total amount of heat dissipated over a unit volume of vocal fold tissues; and time dose, which accumulates the total phonation time. These doses were compared to a previously used vocal dose measure, the vocal loading index, which accumulates the number of vibration cycles of the vocal folds. Empirical rules for viscosity and vocal fold deformation were used to calculate all the doses from the fundamental frequency (F0) and sound pressure level (SPL) values of speech. Six participants were asked to read in normal, monotone, and exaggerated speech and the doses associated with these vocalizations were calculated. The results showed that large F0 and SPL variations in speech affected the dose measures, suggesting that accumulation of phonation time alone is insufficient. The vibration exposure of the vocal folds in normal speech was related to the industrial limits for hand-transmitted vibration, in which the safe distance dose was derived to be about 500 m. This limit was found rather low for vocalization; it was related to a comparable time dose of about 17 min of continuous vocalization, or about 35 min of continuous reading with normal breathing and unvoiced segments. The voicing pauses in normal speech and dialogue effectively prolong the safe time dose. The derived safety limits for vocalization will likely require refinement based on a more detailed knowledge of the differences in hand and vocal fold tissue morphology and their response to vibrational stress, and on the effect of recovery of the vocal fold tissue during voicing pauses.

Thermodynamics of phonon-stabilized Fermi distributions with application to uranium

Since phonons are built on the free energy of electrons, their frequencies can be altered by thermal electronic excitations, implying that thermal electronic excitations can alter the phonon entropy. The effect of this extra phonon entropy on electronic distribution functions and thermodynamic properties is calculated in the limit of classical vibrations. The phonon entropy stabilizes electrons above the Fermi level by more than the usual k B T. The thermodynamic coupling of electron and phonon degrees of freedom allows far more heat capacity than in equivalent independent systems. The method developed is used to explain uranium data from the literature.

Vibration Simulation Method to Control Stability in the Northeast Corner of Escondida Mine

Vibrations due to production blasting can induce damage to the rock mass at large distances by altering larger geological structures, fault areas or other structures, where the orientation with respect to the mine geometry is unfavorable and can cause displacement of large rock volumes. Past occurrences of this nature in Escondida Mine placed geomechanical safety restrictions as to maximum allowable blast size in the northeast area of the mine. These restrictions limited the efficiency of drilling and blasting operations seriously limiting daily production. This is what prompted this study to attempt to increase shot size while reducing stability problems. This would permit keeping stable the slope over which the ore extraction belts are located, as well as the main access ramp to the mine. Using a rigorous and systematic instrumentation and monitoring effort of blasting vibrations at multiple locations with respect to an unstable location allowed the development of a database to establish acceptable vibrations limits. A parallel effort was the development and gauging of a mechanistic model for the prediction and simulation of blasting vibrations. Excellent results were obtained from a comparison between the measured and predicted results. This allowed the use of the gauged model to verify the practicality of increasing the shot size in the restricted blasting zones, without exceeding safe vibration limits. The practical success achieved using this research approach resulted in increased blasting size, with a consequent increase of blasted material per shot, and contributed to more flexible mining operations.

Supersymmetry model in73Asrevisited: Electromagnetic transition rates and U(6/12)

New experimental data on ${}^{73}\mathrm{As}$ were used to test the predictions of the U(6/12) supersymmetry scheme in its vibrational limit. A reasonable description of the energies and branching ratios of the low-lying states was obtained using the U(6/12) model. A comparison with former interacting boson-fermion model results is also discussed.

Relating Road Roughness and Vehicle Speeds to Human Whole Body Vibration and Exposure Limits

Every road authority targets good ride quality in their pavement management. Ride quality depends strongly on the experienced in-vehicle vibration, induced by road roughness. International Roughness Index (IRI) is the most common way to describe road roughness, while ISO 2631-1 defines how to quantify human whole-body vibration (WBV), experienced by the driver and the passengers during the ride, in relation to health and comfort. IRI is defined by means of a quarter car model. In this paper the same model is used to get a relationship between road roughness, speeds and vertical human WBV. The new EU Physical Agents Directive—Vibration (PAD—V) contains action and exposure limits for WBV, with respect to the exposure of professional drivers. The derived relationship, therefore, helps us to use ISO 2631 and PAD-V to justify management policies for roughness and speed limits, for usage in IRI-based pavement management systems.

Harmonic? Anharmonic? Inharmonic?

In molecular spectroscopy, an anharmonic oscillator has a nonparabolic potential which results in a nonharmonic absorption spectrum, but the same oscillator treated classically has a precisely harmonic vibrational spectrum. To avoid confusion, it is suggested that such an oscillator should simply be called nonlinear. The term “inharmonic” is suggested as an appropriate descriptor for classical oscillators, such as metal bars, that have nonharmonic vibrational spectra even in the linear limit of small vibrations.

Variable Energy Explosives for Soft Ground Blasting

A range of bulk explosives, the NOVALITE range hay been specifically developed for soft ground blasting. These explosives can be used in both wet and dry blasting conditions, range in density from 0.3-1.2 g/cc and range in VoD from 2-4.5 km/s. This range of explosives hay the potential to be tailored to ground type and is predicted to be suitable for a variety of applications which include: blasting in soft to medium overburden, coal blasting, wall control, and low vibration blasting. Trials have been conducted in several applications with encouraging results. Several cast/throw blasts have been conducted with these products partially replacing either ANFO or Heavy ANFO. The results from the blast have been equivalent in cast (per cent) and at reduced cost per unit volume. These products have also been used in presplit blasting and have again achieved equivalent or better results when compared to conventional presplit blasting at a lower cost per unit volume. This product has also been used in a vibration sensitive area replacing traditional explosive products, and generating excellent fragmentation and digging whilst maintaining vibration limits. This new range of products, NOVALITE, has shown great potential in many applications either reducing cost per unit volume, improving wall quality or improving productivity in environmentally sensitive areas.

초정밀 측정/가공 장비의 외부진동에 대한 상대변위의 추출과 진동성능 평가에 관한 연구

Generally, there are laser operating equipments( aligner, stepper) and electronic microscope( SEM, TEM) as a high precision manufacturing and inspection equipment in semiconductor production companies, precision examination and measuring laboratories. Mostly, these equipments are characterized by projection and target part. The relative displacements between projection and target part are dominant roles in vibrational problem in these precision equipments. These relative displacements are determined by the position of incoming vibration and the difference of vibration response in projection and target part. In this study, the allowable vibrational limits are suggested and the vibrational reduction plans are proposed by measurement and analysis of vibration phenomenon in the Clean Room in PDP(plasma display panel) production building. The vibration performance is evaluated by comparison relative displacements between projection and target part before/after the vibration isolation plan.

Simultaneous Optimization of Tooth Flank Form of Involute Helical Gears in Terms of Both Vibration and Load Carrying Capacity. 1st Report. Fundamentals for Optimization.

The transmission gear noise of passenger car becomes usually of problem during cruising condition, i. e. under light loading condition. Three dimensional tooth flank form must therefore be optimized in designing to satisfy not only strength reliability under the maximum loading, but also low vibrational characteristics under the light loading. For designing tooth flank forms to meet those requirements, it should also be taken into consideration that the amount of misalignment of gear shafts under the light loading is quite different from that under the maximum loading, because the stiffness of gear support of automotive transmission is considerably low. In this report, the influence of profile and lead form on vibrational excitation under the light loading and that on tooth root stress, Hertz stress and flash temperature under the maximum loading are clarified: There are local optimum conditions, where vibrational excitation is low, as function of combination of the amount of tooth profile modification, of lead crowning, and of lead inclination. In a definite local optimum condition, the tooth flank form that brings the minimum average rotational displacement between driving and driven gears makes vibrational excitation minimum. The range of the amount of lead inclination that satisfies the requirements for load carrying capacity and vibrational limit becomes smaller with increasing the amount of profile modification, if transverse geometrical contact ratio and overlap ratio are both over 1. The fundamentals for designing the optimum tooth flank form in terms of both vibration and load carrying capacity are shown.

Neutron-proton quadrupole interaction in the nucleon-pair shell model

The nucleon-pair shell model truncated to the S-D subspace is applied to nucleus Ba-134 for examining the effects on collectivity due to long-range n-p quadrupole forces. It is found that symmetric and mixed-symmetric states, consequently M1 transitions, are primarily controlled by the n-p quadrupole interaction. In comparison with surface-delta interaction, when the quadrupole n-p Coupling is weak, the model can produce approximately the vibrational limit. and when the quadrupole n-p coupling is strong, the O(6) limit can be realized.

High-Temperature Investigation of the Dynamics and Thermodynamics of ZrH-U System by Neutron Scattering

Inelastic neutron scattering (INS) measurements of the vibrational frequencies in δ-Zr hydride containing uranium, ZrH1.6U0.32, have been performed in the range of high temperatures (between 293 and 973 K) at the DIN-2PI time-of-flight spectrometer at the IBR-2 pulsed reactor of JINR, Dubna. From the temperature dependence of the generalized vibrational density of states (GVDS), information on the H potential has been obtained. Also the high frequency limit of lattice vibrations as well as the frequency of optical vibrations have been studied as functions of temperature. Starting from basic properties, the main thermodynamic functions, the characteristic Debye and Einstein temperatures and the total specific heat have been derived.

A Comparison of Vibration Magnitudes on the Tool with Different Subject According to the ISO 8662-7 Standard.

Recently, ISO has defined the guidelines for the evaluation of the measurement and exposure limits of hand-transmitted vibrations at the handle of hand-held portable power tools. In a measurement of vibrations at pneumatic impact wrenches that tighten and remove screws. ISO 8862-7 standard: 1997 and ISO 5349 standard: 1986 are set as international standards. In order to make an exact measurement of the quantities of vibrations exposed to the hand-arm system of a human body, ISO 8662-7 gives specifications to a measurement device and a loading device. As to a measurement device, for instance, the mass, installation method etc. of transducers and mechanical filters are defined. In addition, it specifies with each tolerance the working conditions of a pneumatic tool, the number of revolutions of socket in a loading device, the feed force, the number of subjects, and such an evaluation method as how to decide a declaration value of vibrations. These specifications give toolmakers a comparative measurement of vibration values of their tools before shipment. Meanwhile, although the measurement condition described in ISO8662-7: 1997 is that skilled operators conduct vibration measurement, no provisions as to operators are made in detail. Hence, this study focuses its concern on ambiguous work experience years in measuring vibrations of the tools in conformity with ISO 8662-7, and hereby the effect of years of work experience upon measurement values is considered and at the same time a knowledge of how to select operators is made clear.

The dynamics of noble gas--halogen molecules and clusters.

The vibrational relaxation of noble gas-halogen van der Waals clusters has been fertile territory for the development of experimental and theoretical tools for state-to-state dynamics studies. Proceeding through the various combinations of noble gas atoms and halogen molecules, one goes from "simple" direct vibrational predissociation, through sequential relaxation pathways, to the statistical intramolecular vibrational relaxation limit. In some cases the vibrational processes dominate, in others electronically nonadiabatic processes, including chemical reactions, interfere. Thus the noble gas-halogen species provide test cases for most of the dynamical processes available to more "normal" molecules. This review discusses the current state-of-the-art for such studies and points to important problems that remain to be solved.

Improved prediction of ground vibrations from blasting at quarries

An examination of data recorded for 23 blasts at a lime-stone quarry in North Yorkshire, England, led to the the formulation of a modified scaled-distance model. By taking account of the specific conditions at the blast monitoring locations the modified model gives increased confidence in vibration predictions, thus allowing the quarry operator to employ greater maximum instantaneous charge weights without increasing the risk that prescribed peak particle velocity vibration limits will be exceeded.

Interacting Boson Model of Collective States I. The Vibrational Limit

We propose a unified description of collective nuclear states in terms of a system of interacting bosons. We show that within this model both the vibrational and the rotational limit can be recovered. We study in detail the vibrational limit and bring attention to the possible existence of an unbroken SU(5)⊃0+(5) symmetry. We derive a large set of analytic relations for energies and electromagnetic transitions.

On the High-Frequency Limit of Lattice Vibrations in Zirconium Hydrides and Deuterides

The changes of the dynamic properties of the zirconium lattice at transition from pure metal to different hydride and deuteride phases have been studied by investigating the generalized vibrational density of states (GVDS) or Zr, ZrH1.6, ZrD1.6, ZrH2, ZrD2 and ZrH1.6U0.32 in the region of the host lattice modes. The spectra obtained from inelastic neutron scattering (INS) measurements have been analysed in terms of the classical Debye model. The dependence of the high-frequency limit of lattice vibrations to different regular structures of zirconium atoms and its correlation with the main thermodynamic quantities, lattice specific heat CV and Debye temperature θD have been reported.