Variation Of Internal Friction Research Articles

Heat Treatment and Dynamic Mechanical Analysis Strain Sweep Effects on the Phase Structure and Morphology of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has been mainly used in vibration mitigation or self-adjustable axial displacement applications. Dynamic mechanical analysis (DMA), performed by strain sweeps (SS), enables the monitoring of the evolution of storage modulus and internal friction variations with increasing strain amplitudes at different constant frequencies and temperatures. Thus, applying dynamic bending with various frequencies and amplitudes that actually represents an isothermal mechanical treatment. In the present paper, an Fe-28Mn-6 Si-5Cr (mass. %) SMA was cast by ingot metallurgy, hot-rolled, and water quenched in order to obtain thermally induced martensite and avoid the occurrence of cooling cracks. The influence of the holding time, between 2 and 10 h, at 1050 °C and the effects of DMA-SS performed at three different frequencies were analyzed by a differential scanning calorimetry, an X-ray diffraction, and a scanning electron and atomic force microscopy. The effects of the holding time and mechanical treatment on the structure and morphology of martensite plates were corroborated with the results of the thermal analysis.

Unusual internal friction and its size dependence in nanoscale metallic glasses

The internal friction of Cu50Zr50 metallic glass nano-pillars was investigated by using molecular dynamics simulations. An unusual non-monotonic variation of internal friction is revealed against the size of the specimen, which differs significantly from that of the bulk metallic glass. Meanwhile, by analyzing the rearranged atoms with high mobility, which play a vital role in affecting the internal friction, it is found that the rearrangement of surface atoms is more significant than that of the bulk ones, and their fraction depends on the sample size as well. With reducing the sample size, the fraction of rearranged atoms in the surface region increases, which could be described by an exponential equation. This finding suggests that the size dependence of internal friction originates directly from the different fractions of the rearranged atoms in the surface region of nano-pillars. Furthermore, a phenomenological model was established to describe the internal friction of the nano-pillars against their diameters. The presented results provide a quantitative insight into the size effect on internal friction in nanoscale metallic glasses, also shedding light on the atomistic mechanism of surface relaxation of amorphous solids.

A modified piezoelectric ultrasonic composite oscillator technique for simultaneous measurement of elastic moduli and internal frictions at varied temperature.

In this work, a modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT) is developed for measuring a material's elastic moduli and internal frictions, as a function of temperature. Different from the traditional PUCOT that employs two quartz bars as the drive and gauge, here, a single small piezoelectric transducer (PZT) ring is used to drive and sense longitudinal or torsional vibration in a cylinder specimen. Because of the strong piezoelectric effect and relatively large bandwidth of the PZTs compared to their quartz counterpart, the frequency match condition between the transducer and the specimen is not required in this M-PUCOT. For high temperature measurement, a fused quartz spacer, whose resonance frequency matches the specimen's, is bonded between the transducer and the specimen to provide thermal insulation. First, the united equivalent circuit of the transducer- (spacer) -specimen composite system was derived. Then, Young's modulus, longitudinal friction, shear modulus, and torsional friction were explicitly obtained by measuring the resonance frequency and antiresonance frequency of the 2- or 3-component system's electrical susceptance curve using an impedance analyzer. The accuracy of this method was validated both by measuring the system's amplitude-frequency curves using a laser vibrometer and through finite element simulations. The repeatability error of the M-PUCOT is only ∼0.2% for moduli measurement and ∼2.5% for internal friction measurement, which is very promising for studying the moduli and internal friction variations during damage, fatigue, and phase transitions. Finally, the M-PUCOT was employed to measure the variations in moduli and internal frictions of an Fe64Ni36 Invar alloy from room temperature to 500 °C. Results show that above the ferromagnetic phase transition temperature Tc, both moduli reach their maxima, and both internal frictions reach their minima. The proposed M-PUCOT is expected to be widely used in the near future for its quick measurement, high repeatability, and low cost.

Storage modulus and internal friction variations in a Fe-28 Mn-6Si-5Cr (mass. %) shape memory alloy analyzed by three-point-bending DMA

An Fe-28Mn-6Si-5Cr (mass. %) shape memory alloy (SMA) was investigated, observing the behavior of the material when subjected to dynamic mechanical analysis (DMA) cycling performed as a function of temperature and as a function of amplitude. Strain sweeps were performed at three temperatures: T1 = RT, T2 = A50ε and T3 = TN, where A50 and TN are the critical temperatures for the middle of reverse transformation of martensite to austenite and for antiferromagnetic-paramagnetic transition. During temperature scans, a modulus increase, with several GPa, and two internal friction maxima were observed on heating. The temperature scans revealed that internal friction increased with increasing the frequency as compared to similar data presented by other authors where a decreasing tendency was noticed.

Studies on Internal Friction and Curie Temperature of NiMgCuZn Spinel Ferrites for Micro-Inductor Applications

Three series of NiMgCuZn ferrites were prepared by conventional double sintering ceramic process. The formation of single phase in these ferrites was confirmed by X-ray diffraction. A brief review of the important investigations carried out on the internal friction behaviour of NiMgCuZnFe2O4, in the temperature range 40oC to 360oC, has been reported. In the present investigation, the composite piezoelectric resonator method has been used. The effect of compositional changes of ferrites on Curie temperature and internal friction are reported. Results and discussions on the temperature variation of internal friction of the three series of NiMgCuZnFe2O4samples are discussed. In all the series studied, only single stress induced relaxation peaks are observed. These studies were carried out to develop a ferrite composition for their use as core materials for microinductor applications. The results are explained in the light of structural phase transitions.

Thermal Variation of Elastic Modulus on Nanocrystalline NiCuZn Ferrites

The nanopowders of Ni0.38Cu0.12Zn0.5Fe2O4 with particle size, 20 nm have been synthesised using Microwave-Hydrothermal method and characterized. Then the ferrite samples were microwave sintered at different temperatures in an air atmosphere and characterized. The magnetic properties were measured at room temperature. The dielectric constant (ɛ), initial permeability (μi) and quality factor (Q) has been measured on sintered samples at 1 MHz. Thermal variation of initial permeability has been measured over temperature range of 300 K–600 K. A detailed study of elastic behaviour of NiCuZn ferrites has been under taken using a composite piezoelectric oscillator method over a temperature of 300 K–600 K. The room temperature elastic moduli is found to be slightly sample dependent and decreases with increasing the temperature, except near the Curie temperature, TC, where a small anomaly is observed. The internal friction at room temperature is also found to be more particle size dependent. The temperature variation of internal friction exhibits a broad maximum around 500 K, just below Curie temperature TC 530 K. The above observations were carried on in the demagnetized state; on the application of a 400 mT magnetic field allowed us to reach the saturated state of the sample at any of the measuring temperature. The anomaly observed in the thermal variation of elastic moduli and internal friction is explained with the help of temperature variation of magneto-crystalline anisotropy constant.

Universal behavior of internal friction in glasses belowTg: Anharmonicity versus relaxation

Comparison of the internal friction at hypersonic frequencies between a few K and the glass transition temperature Tg for various glasses brings out general features. At low temperature, internal friction is only weakly dependent on the material. At high temperature but still below Tg the internal friction for strong glasses shows a T-independent plateau in a very wide domain of temperature; in contrast, for fragile glass, a nearly linear variation of internal friction with T is observed. Anharmonicity appears dominant over thermally activated relaxational processes at high temperature.

Phase transformation in BST ceramics investigated by internal friction measurements

Ferroelectric (BaSr)TiO 3 materials are widely used for numerous applications in microelectronic ranges. This paper concerns investigation of variation of internal friction and shear modulus versus temperature in a low frequency range for Ba x Sr 1− x TiO 3 systems ( x = 0.4, 0.55, 0.7 and 0.8). This makes it possible to report energy dissipation phenomena such as phase transitions and relaxation processes due to interactions between domain walls and oxygen vacancies. Temperature of loss peak for each phase transition decreases and peaks become more diffuse with increasing Sr content in BST materials. An experimental phase diagram has been established for Ba x Sr 1− x TiO 3 systems. Effects of MgO doping have been investigated for the composition x = 0.8. Both level of mechanical loss and temperatures of phase transitions are sensitive to the Mg dopant.

Anelastic Properties of Polycrystalline Copper

An attempt has been made to measure the temperature dependence of dynamic Young's modulus together with the related variation of internal friction in polycrystalline copper. A mechanical spectroscopy study was used a standard servo hydraulic fatigue testing machine equipped with a scanning laser extensometer. Dynamic Young’s modulus and internal friction are measured over a temperature range of 298 to 873K at very low frequencies of 0.1, 0.05 and 0.01Hz. One internal friction peak was observed over the ranges 450K to 700K, together with marked decreases in the dynamic Young.s modulus in the same temperature ranges. From a quantitative analysis of the experimental data with the relaxation strength, relaxation time and activation energy, it is concluded that the peak phenomenon is due to grain-boundary sliding relaxation.

Temperature dependence of the force sensitivity of silicon cantilevers

The resonance frequency $\ensuremath{\omega}$ and internal friction ${Q}^{\ensuremath{-}1}$ of the first eigenmode of microfabricated silicon cantilevers are measured in the temperature range of 15--300 K. The analysis shows that variation of Young's modulus is responsible for the temperature dependence of the resonance frequency, whereas the dependence of the geometrical dimensions can be neglected. Accordingly, the data can be fitted by the Wachtman equation, yielding a Debye temperature ${\ensuremath{\Theta}}_{D}=634\mathrm{K}.$ The temperature variation of internal friction ${Q}^{\ensuremath{-}1}$ is analyzed in terms of Zener's theory of thermoelastic damping. Due to the temperature dependence of the thermal expansion coefficient $\ensuremath{\alpha},$ thermoelastic damping is expected to vanish at 20 K and 125 K. A minimum of internal friction is observed at 20 K, whereas the minimum at 125 K appears to be hidden by other dissipation effects. A maximum of internal friction at 160 K is observed, which is an activation peak due to phonon scattering by atomic-scale defects. The best force sensitivity is achieved at 20 K, where a factor of 10 is gained compared to room temperature.

Dynamic Young’s modulus and internal friction in polycrystalline copper

An attempt has been made to measure the temperature dependence of dynamic Young’s modulus together with the related variation of internal friction in polycrystalline copper. A mechanical spectroscopy study was employed using a standard servo hydraulic fatigue testing machine equipped with a scanning laser extensometer. Dynamic Young’s modulus and internal friction were measured over a temperature range of 298 to 873 K at very low frequencies of 0.1, 0.05, and 0.01 Hz. One internal friction peak was observed over the ranges 450 to 700 K, together with marked decreases in the dynamic Young’s modulus in the same temperature range. From a quantitative analysis of the experimental data with the relaxation strength, relaxation time, and activation energy, it is concluded that the peak phenomenon is due to grain-boundary sliding relaxation.

NUMERICAL ANALYSIS OF THE NONLINEAR ANELASTIC INTERNAL FRICTION PEAK (P′1 PEAK) UNDERLOW STRESS AMPLITUDE

The longitudinal diffusion equation of the solute atom along dislocation core for P′1 peak is numerically solved and the P′1 peak is derived on the base of dislocation kink atmosphere model. The variation of internal friction and modulus defects with temperature and strain amplitude is calculated. The theoretical and experimental results are compared and found to be in consistence with each other. Therefore, the P′1 peak can be quantitatively explained.

Viscous behavior of interfaces in fluorine-doped si 3n 4/sic composites

The influence of fluorine addition on the grain/phase boundary structures and their viscous behavior at high temperature were systematically investigated in Si 3N 4/SiC composites. As a reference, a simple system densified by hot isostatic pressing (HIP) and containing only SiO 2at the boundaries was selected for this basic investigation. In addition, increasing amounts of F dopant were incorporated into the composite bodies by adding Teflon during the mixing procedure of the raw powders and then pre-firing the mixture under high vacuum at 1200°C. Analytical transmission electron microscopy showed that fluorine remained localized at the grain boundary films and triple points, constituting an amount up to a few percent by weight of the intergranular glassy-SiO 2phase. Detailed structural characterizations of both grain and phase boundaries were performed by using high-resolution electron microscopy (HREM) and atomic force microscopy (AFM). The high-temperature mechanical behavior of the undoped and F-doped SiO 2phases was characterized by both measurements of torsional creep rate and variation of internal friction at temperatures up to 1600°C. F-doped materials showed creep rates several orders of magnitude higher compared to the undoped sample and damping temperature curves markedly shifted to lower temperature values. According to the above set of microstructural and mechanical data, the inherent viscosity of the SiO 2intergranular phase could be quantitatively evaluated and the viscous-sliding mechanism under stress modeled.

Mechanical dissipation in the high- Tc superconductor HgBa 2CuO 4+ x

With the vibrating reed technique, we investigated the internal friction and resonant frequency of the high- T c superconductor compound HgBa 2CuO 4+ x as a function of temperature. An internal friction peak, accompanied by a change of the resonant frequency, was observed below T c in an applied magnetic field, and as the magnetic field increased, the internal friction peak shifted towards lower temperature and its height increased. The depinning line determined from the peak temperature of internal friction was found to be higher than that of Bi-based samples but lower than that of Y-based ones. In addition, the probable position of oxygen atoms in the lattice was discussed and compared with Bi/Y-based superconductors according to the variation of internal friction with temperature at zero field below T c.

Internal friction of metallic glass Ni74P16B6Al4 near Tx

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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.

Revised calculation of point defect equilibria and non-stoichiometry in gallium arsenide

From an analysis of relevant published literature, it is deduced that the dominant disorder in GaAs is Frenkel defect formation on the arsenic sub-lattice with the arsenic vacancy exhibiting donor-like behaviour at high temperatures. Standard methods of chemical thermodynamics are used to derive expressions for the concentrations of the neutral and charged point defects. Mass action constants are obtained from a combination of a priori estimates and fitting to experimental data. The phase extent of GaAs is mapped and the model shown to account adequately for the density, lattice parameter and internal friction variations in as-grown and heat treated material as well as for the high temperature Hall coefficient behaviour.

Critical test of radiation-damage models by means of dislocation pinning experiments on copper

Abstract The hypotheses of one-dimensional migration and of thermal convertibility of the low-temperature interstitials in irradiated copper are critically tested by measuring the variation of internal friction and elastic modulus due to dislocation pinning as a function of the electron energy E in electron irradiation experiments (0.26 MeV ≤ E ≤ 0.7 MeV). The predictions of the crowdion model that one should observe a low threshold energy (ΔE 1 = threshold for production of on-line crowdions) at sufficiently high irradiation temperatures (T irr = 220 K), and a high threshold energy (Δ E 2 = threshold for production of off-line crowdions) at sufficiently low irradiation temperatures (Tirr = 75 K) or in annealing experiments following low-temperature irradiations, have been fully confirmed. Alternative interpretations in terms of the one-interstitial model are also discussed but are not very satisfactory. Furthermore, it is shown that, in addition to the two mentioned processes characterized by 10 eV ≤ Δ E...

Effects of neutron irradiation on strain-amplitude dependent internal friction in sodium chloride single crystals

A method has been developed which allows the dependence of internal friction on strain amplitude for a crystal to be measured in a period of 30 s. This method was used to study the variation of internal friction with strain amplitude in sodium chloride single crystals as a function of neutron irradiation. The results were found to agree with the Granato- Lucke theory of strain-amplitude dependent internal friction and this theory was used to examine the variation of pinned dislocation loop length with irradiation time. It was found that the loop-length variation from amplitude-dependent results was different to that from amplitude- independent results. An explanation is offered for this difference.

Etude du frottement interieur dû aux joints de grains dans le magnesium

We have studied the variation of internal friction in magnesium as a function of temperature in the range 20–350 °C by means of a low-frequency pendulum as developed by Ké. We used doubly sublimed magnesium containing less than 500 ppm of impurities, and also performed some experiments with zone-refined magnesium and with commercial (99.8%) magnesium. With the annealed doubly sublimed magnesium we observed around 185 °C at one c/s an internal friction peak which presents all the characteristics of a relaxation peak, and which we interpret as a grain-boundary peak. The activation energy for this peak, measured by changing the frequency, is 31.7 kcal/mole, whereas the activation energy for volume self-diffusion is 32 kcal/mole. The width of the peak exceeds the theoretical width by a factor of 2. We have studied the influence of irradiation and of deformation on the grain-boundary peak. After neutron-irradiation at low temperature (9 × 10 18 fast neutrons/ cm 2) the peak is slightly displaced towards higher temperatures and its profile is appreciably altered. When a specimen was plastically deformed in compression at low temperature, a very large increase in the internal friction was observed at the normal peak temperature, and this completely masked the grain-boundary peak itself; the appearance of this appears to be linked to recrystallisation.