Internal Friction In Solids Research Articles

On the Vacancy Nature of the High-Temperature Background of Internal Friction in Solids

On the Vacancy Nature of the High-Temperature Background of Internal Friction in Solids

On the vacancy nature of the high-temperature background of internal friction in solids

High-temperature internal friction in an amorphous CuTi alloy is investigated. Exponential regions with different activation energies are observed on the dependence of internal friction on temperature on both sides of the glass transition temperature. An exponential increase in the background of internal friction with temperature in both sites is associated with the migration of vacancy-like defects in the amorphous structure under the influence of mechanical stresses, while frozen defects of constant concentration migrate to the glass transition temperature. After the transition to a state of thermodynamic equilibrium, the concentration the number of migrating defects increases exponentially. Based on the experimental results of measuring the high-temperature background, estimates of the activation energy of migration and the formation of vacancies of similar defects in the amorphous structure of the alloy under study are made. Keywords: Internal friction, relaxation time, high temperature background, amorphous alloy.

A New Inverted Torsion Pendulum-Based Mechanical Spectrometer to Study Soft Matter

A new multifunctional mechanical spectrometer is developed based on an inverted torsion pendulum showing high precision in a wide frequency range to study soft matter. Apart from measuring the internal friction of solids it can also be used to study viscoelasticity. In this report we describe basic principles of the novel instrument.

Measuring of Low Frequency Internal Friction in Solids

The principles and apparatus of measuring low frequency internal friction are described in this paper. The low frequency internal friction apparatus have been evidently improved in automation and functions since the Ke,s pendulum was invented in 1947. The degree of automation of the internal friction apparatus is elevated and the functions of the apparatus are increased/ strengthened. The resolution of internal friction is increased. The accuracy of strain and frequency is also enhanced. The scope of measuring parameters such as temperature, strain, frequency and so on is enlarged.

High-temperature background of internal friction in alloys

Experimental results for the high-temperature background of internal friction in solids are analyzed. Common features are noted for the high-temperature background of internal friction in solids independent of structure. The exponential increase observed in internal friction is associated with point defect migration.

Discontinuous deformation in an elastic material. Part 1. Energy dissipative and storage applications

AbstractThe concept of energy or work dissipation from a perfectly elastic material, due to a discontinuous deformation mechanism, is developed in this study. Dissipation occurs even from a perfectly elastic material, preferably an elastomer, when subjected to a discontinuous “jump” stretch or “jump” contraction. Stretching an elastomeric member through free extension requires a large amount of work. Such a sudden jump stretch of an elastic material is difficult to accomplish and is equivalent to thermodynamic free compression of a gas. The amount of work required can greatly exceed the strain energy stored in the material if the extension were applied without the jump or “shock” process. Interestingly, only part of the stored energy is recovered on unloading the elastomer the same way (through contraction). Excess work lost in contraction dissipates as heat but is not due to the common viscoelastic/plastic losses associated with internal friction in solids. Dissipation is possible even from a perfectly elastic material. Energy values associated in this jump deformation process are independent of the stress–strain curve path, and depend only on initial and final states for the material. Heat dissipation from an elastic rubber belt is examined and some applications extended from the developed principle are enunciated. POLYM. ENG. SCI., 47:1511–1520, 2007. © 2007 Society of Plastics Engineers

Internal friction studies by resonant ultrasound spectroscopy

Abstract A description is given of the use of resonant ultrasound spectroscopy (RUS) to study internal friction in solids. The technique is applicable to a wide range of sample sizes and shapes. A method to extract the internal friction from the RUS spectrum in the presence of a coherent background signal is discussed. RUS has been used to study the internal friction due to hydrogen motion in hydrogen–metal materials. A comparison is made of internal friction due to hydrogen motion in a C15 Laves-phase intermetallic compound with that in a quasicrystalline material. The internal friction peak in the quasicrystalline material is much broader, probably reflecting a distribution of local environments for the hydrogen in this material. A low-temperature, internal friction peak due to deuterium motion in TaV 2 D 0.17 is discussed. This peak was shown previously to result from a rapid local motion of D on a hexagon of interstitial g sites. A novel explanation is proposed for the temperature dependence of this peak.

A fully automated precise measurement system for sound velocity and internal friction in solids down to liquid helium temperatures using the vibrating reed technique

The design and fabrication of a fully automated, computer controlled, precise measurement system for sound velocity and internal friction using the vibrating reed technique is described in detail. Relative variation of sound velocity and internal friction has been measured using automatic frequency locking. A detailed description of the apparatus is given. The associated electronics that took care of quite a few problems in getting a good lock-in condition have been highlighted. With a bath cryostat and sample insert, measurements were made down to liquid helium temperatures with a temperature control accuracy better than 10 mK. The resonance frequency and the peak amplitude were recorded as a function of temperature which in turn provided temperature variation of sound velocity and internal friction with a relative accuracy better than 1 part in 104 and 1.5%, respectively. Precise nature of the results obtained using this setup is highlighted for a specimen of an amorphous alloy near it’s Curie temperature.

Analysis of cathodoluminescence from indented MgO crystals subjected to thermal environments

Abstract Using colour cathodoluminescence, spectral analysis and cathodoluminescence mapping in scanning electron microscopy, some peculiarities of cathodoluminescence from the indentation centre and the rosette on MgO (100) crystals were investigated over a wide temperature range 80–1000 K. The sensitivity of indentation-induced defects to thermal environments has been revealed. An attempt has been made to explain the spatial distribution of cathodoluminescence from around indentations in terms of dislocation internal friction in solids.

Internal friction in Cu-Ti glass

Internal friction in solids is highly structure-sensitive and can be an effective means of studying the kinetics of atomic rearrangements associated with structural relaxation and crystallization in metallic glasses. Though a very large number of studies have been carried out on the crystallization behavior of metallic glasses, studies on structural relaxation, particularly the atomic rearrangement mechanism during structural relaxation, are few in comparison. Internal friction technique is a very useful method of studying thermally activated relaxation in an amorphous structure. Earlier studies have shown that metallic glasses exhibit a considerable amount of internal friction, particularly above 473 K, which besides being markedly reducible by structural relaxation, increases exponentially with increasing temperature, reaching a maximum during crystallization and then falls rapidly to a very low value at the completion of crystallization. In the present investigation, internal friction behavior of Cu[sub 49.5]Ti[sub 50.5] glass is studied in the temperature range covering both structural relaxation and crystallization. The glass transition temperature T[sub g] as well as crystallization temperature T[sub p] are determined and the distribution spectrum of activation energies for structural relaxation is discussed. Some comparisons are made with the DSC results and also with the results obtained in the case of Zr[submore » 76]Ni[sub 24] glass.« less

Internal friction in solids

Study of the damping of vibrations in solids has developed into an acoustical spectroscopy which can elucidate many geometrical, thermodynamic, and kinetic characteristics of solids. In a relatively brief 15 years, between 1935 and 1950, Clarence Zener contributed physical insight, analytical procedures, and suggestions for important topics which persist even today. This review traces development of ideas and techniques from that period to the present. It uses chiefly as examples the flow of heat across vibrating reeds (and the corollary Gorsky effect), the Snoek effect in interstitial alloys, and the Zener effect in substitutional alloys. Internal friction of molecular reorientation in polymeric solids is described. Finally, the joint use of internal friction and dielectric loss is demonstrated to provide additional insight into molecular configurations in solids which are both mechanical and electric dipoles.

Intrinsic internal friction in solids measured by torsion pendulums

A mechanical theory is developed for composite torsion pendulums emphasising the interaction between components. The interaction is eliminated to obtain the intrinsic internal friction in solids. A definition of internal friction is given in a general form as a function of frequency and the moment of inertia. Two equivalent formulations of internal friction, which are related to each other through a simple relation, are obtained by the use of the definition. A torsion pendulum in forced oscillation is considered to clarify the significance of the formulation.

Direct measurement of internal friction with continuous variation of frequency

A method for the measurement of the internal friction in solids by measuring the instantaneous values of applied sinusoidal stress, the resulting strain and the phase difference between them is presented in this paper. The experimental setup utilizes the instruments normally used in the vibration analysis and the variation of internal friction with frequency can be recorded automatically on a level recorder. The values obtained by this method are compared with those by the amplitude repsonse method for two epoxy resin systems. The agreement is found to be satifactory. The method is very suitable for locating the relaxation peaks up to 2000 Hz.

Microdynamics of the Internal Friction in Solids

Microdynamics of the Internal Friction in Solids

Devices for acoustics

During the last decade there has been considerable activity in the field of physical acoustics, much of which has been reviewed in the ten books edited by Mason (1964–70). Acoustic techniques at frequencies in the range 106–1010 Hz have been used to study gases, liquids and especially quantum effects and the internal friction in solids.

Measurement of the Mechanical Properties of Solids at High Pressure

Apparatus for making precision measurements of the stress-strain curves of solids under high pressure has been developed. Constant deformation rate is obtained by use of an electric motor drive system operating within the pressure vessel. Forces are measured with a resistance strain gauge load cell also within the vessel. The equipment may be adapted for making compression or tension tests, stress relaxation and creep experiments, microhardness measurements, and observations of internal friction in solids under true hydrostatic pressure.

The Mechanical Impulse Method for Determining Dynamic Elastic Moduli and Internal Friction of Solids

The theory governing the excitation of a linear mechanical system by delta function impulse is summarized. In the case of a finite elastic rod excited by an impulse, the Fourier transform of the output function enables the frequency spectrum of the rod to be obtained. A spectrometer for accomplishing this operation is described and a comparative study is made between the impulse and resonance responses of a cylindrical rod

Some Aspects of Internal Friction in Solids

Some Aspects of Internal Friction in Solids

Frottement interne et anélasticité des solides

Having recalled a few essential definitions in the theory of internal friction in solids, the authors, in a first chapter, study the propagation of longitudinal waves in a rod; they start from a simple law relating locally stress, strain and their first derivatives with respect to time. This law which is more general thanHooke's law has been proposed first byZener to explain the anelastic behaviour of a standard linear solid. The authors calculate the internal friction resulting from energy dissipation when the vibration is forced then free. The second chapter deals with problems arising when one tries to measure the internal friction in flexure of metallic specimens having the shape of rods or circular plates. The authors develop the basic flexure equations applied to the two types of specimen; then they determine the fundamental characteristics, which appear in internal friction measurement purposes.

Apparatus for Measuring the Elastic Moduli and Internal Friction of Solids from 1.7 to above 77°K and Some Values for α-Quartz

Apparatus for measuring the moduli and internal friction of solids at temperatures from 1.7 to above 77°K is described. The resonant piezoelectric method with quartz transducers is used. The frequency range is 30 to 450 kc/sec. For calibration variously oriented quartz crystals were measured over this temperature range and the values are given.