Changes In Internal Friction Research Articles

Исследование рассеяния энергии и жесткости сварных соединений стыковой сварки давлением

Introduction. When studying the energy dissipation associated with internal friction in a weld, it is extremely important to choose a measurement technique, since the reliability and integrity of the data obtained depends on it. At the same time, it is necessary to investigate the change in internal friction depending on the presence of defects in the weld. Of the variety of methods for non-destructive testing of joints obtained by pressure welding, only ultrasonic is currently used. However, lightly oxidized lacks of welding penetration are not detected, which can be detected only in the presence of other defects accompanying it. Compounds of dissimilar materials are not controlled by ultrasound at all. Therefore, the development of non-destructive testing methods for such compounds is very relevant. The purpose of the work: to find a procedure for testing the quality of a welded joint in metals and alloys that will be a quick and simple alternative to the known methods of non-destructive testing, by measuring the energy dissipation in the weld of the sample by the static hysteresis loop method. The method of investigation is non-destructive quality control of the welded joint in metals and alloys by measuring the energy dissipation in the weld of the sample by the static hysteresis loop method. Results and discussion. It is established that with an increase in the lacks of welding penetration, the energy dissipation increases at the same values of the torque amplitude under static loading conditions. The rigidity of the qualitative welded joints remains constant, and the joints with lacks of welding penetration decrease with increasing torque amplitude. The relationship of strength with stiffness and damping ability obtained by the static hysteresis loop method is preserved for various structural states of the sample material.

Thermal stability of SPD-processed aluminum alloys - Internal friction as an indication for recovery, recrystallization and abnormal grain growth

In this study, we investigate the effect of different microstructures generated by severe plastic deformation on the thermal stability of an age-hardenable Al–Mg–Si alloy (AA6082). To analyze recovery and recrystallization we investigate the internal friction at various excitation frequencies and the microstructural evolution of the material in a wide range of temperatures. Severely deformed conditions of the alloy show a distinct increase of internal friction and a pronounced reduction of the materials hardness at elevated temperatures. Microstructural investigations reveal that different stages of recovery and recrystallization take place during the heating process. In a certain case, a remarkable correlation between frequency-dependent internal friction and abnormal grain growth in the microstructure is found. It is derived that internal friction measurements help to characterize the thermal stability of SPD processed materials. Since thermally-induced microstructural changes are directly related to changes of internal friction, these measurements help to identify characteristic temperatures of recovery, recrystallization and abnormal grain growth.

Microscopic hardness and dynamic mechanical analysis of rapidly solidified Fe-based amorphous alloys

A systematic work was conducted to investigate the nanoindentation, dynamic relaxation, high-temperature rheological behavior, and structural relaxation after high-temperature deformation of Fe52-xCo20NixB19Si5Nb4 (x = 7,12,17, labeled as S1, S2 and S3) metallic glass. The results of nanoindentation indicate that the hardness of amorphous alloy reduces first and then enhances with the increase of Ni content. S1 alloy exhibits the highest hardness of 13–16 GPa, while relatively excellent compression plasticity is reached in S2 alloy. Besides, the glass transition temperature (Tg), initial crystallization temperature (Tx), α relaxation temperature (Tα) and internal friction change at different temperatures were determined and compared. The critical temperature, strain rate during non-Newton to Newtonian rheology and Newtonian viscosity at Tg temperature were discussed. Moreover, it was found that the activation volume improved and then decreased due to structural relaxation. At last, combined with the width of the supercooled liquid region, relaxation behavior and rheological viscosity at high temperature, the microstructure evolution of the three kinds of metallic glass under Tg temperature deformation was explained.

Investigation of warm mix epoxy asphalt compaction with gyratory compactor and charge coupled photoelectric imaging

The object of this paper is to investigate the compaction characteristics of warm mix epoxy asphalt concrete with the aid of the viscosity test, gyratory compaction test, and two-dimensional image analysis. The compactability energy required from initial densification to 97% Gmm for epoxy asphalt concrete (CDIE) was proposed from the gyration compaction curve to evaluate the effect of curing temperature, curing time, and compaction effort on material workability. Microstructural indices in the sectional images of warm mix epoxy asphalt concrete specimen were obtained considering the same conditions with compactability energy. Results show that the viscosity of epoxy asphalt binder and mastic both increase over the curing time. The higher temperature is, the faster viscosity will increase. On the basis of compactability energy, a specific range of curing time exists in which warm mix epoxy asphalt concrete can be easily compacted. Two-dimensional images obtained from charge-coupled device photoelectric scanner indicate that aggregate orientation, aggregate distribution, aggregate contact, and proximity asphalt mortar film thickness are all affected by compaction effort and curing time. The overall test results show that Stribeck tribology theory could describe the internal friction change of warm mix epoxy asphalt concrete during the gyration compaction test. Based on the internal friction results, the epoxy asphalt mastic viscosity ranging from 100 to 200 Pa·s is recommended as the optimal for the compaction of warm mix epoxy asphalt concrete.

Low temperature peak of internal friction in high entropy Al0.5CoCrCuFeNi alloy

The dynamic elasticity and internal friction of the highly entropic Al0.5CoCrCuFeNi alloy were studied in a wide low temperature range of 4.2–300 K. In the experiments, the bending vibrations of thin plates at a frequency of 530 Hz were studied in two structural states: samples prepared after crystallizing a cast alloy (I); the same samples after prolonged high-temperature annealing (II). The temperature dependences of internal friction Q−1(T) and dynamic Young’s modulus E(T) were obtained and analyzed for these structural states. In state I, both dependences are monotonic functions without any specific features: the internal friction decreases with a decrease in temperature from QI−1(T=300K)≃10−3 to QI−1(T=4.2K)≃10−4, while Young’s modulus increases from EI(T = 300 K); 180 GPa to EI(T = 4.2 K); 190 GPa. Upon the transition to state II, the QII−1(T) plot acquires a peak with a height of about 10−4 and a center at Tp; 228 K, without significant changes in internal friction at other temperatures. Young modulus EII(Т) significantly increases (by 20% on average) at all temperatures, and near Tp; 228 K a blurred step with a height of ΔEII ≈ 0.3 GPa ≈ 10−4 EII(T = 4.2 K) appears on the EII(T) plot. Statistical and thermoactivation analysis of the anomaly of the alloy’s viscoelastic properties near Tp; 228 K by the previously developed algorithm [V. D. Natsik, Yu. A. Semerenko, FNT 42, 185 (2016)] led to the conclusion that it is caused by the resonance interaction of the plate’s elastic vibrations with the dynamic processes in the system of dislocation relaxators, i.e., the thermally activated unpinning of the dislocation segments from the local defects [M. Koiwa and R. R. Hasiguti, Acta Met. 13, 1219 (1965)]. High temperature annealing of the cast alloy is accompanied by significant changes in the morphology and dislocation structure of the samples, which results in a significant increase in their elasticity (Young’s modulus), and the appearance of an internal friction peak at moderately low temperatures. The properties of this peak are similar to those of Hasiguti peaks or β-peaks in simple metals with FCC and BCC lattices.

On the Hardness and Strain Rate Sensitivity of Electrodeposited Nanocrystalline Ni–18 wt% Co Alloy Studied by Nanoindentation

Ni–18wt% Co foils made by electrodeposition possesses an average grain size, computed using diffraction contrast in TEM, of about 30 nm. Vickers microindentation and depth-sensing nanoindentation have been adapted to assess the deformation parameters such as hardness, strain rate sensitivity (SRS) and activation volume. These foils with single-phase fcc-structured solid solution exhibit the hardness values of 4.5 ± 0.1 GPa and 6.2 ± 0.2 GPa measured by microindentation and nanoindentation, respectively. The dependence between hardness and applied load in the present solid solution cannot be attributed to the indentation size effect, but to the changes in internal friction and/or reduction in stacking fault energy that may have resulted from the Co additions. An elastic modulus of 193 ± 3 has been realized in these foils. Performing nanoindentation at various loading rates and subsequent analysis has resulted in a SRS of 0.017 and an activation volume of 7.6 b3. These values suggest that in these nanocrystalline Ni–18Co foils made by electrodeposition, interfaces such as grain boundaries, triple junctions and quadruple junctions play a governing role in dictating the deformation kinetics. A model reported in the literature has been successfully modified to reasonably explain the dependence of SRS on grain size for various Ni-based alloys including the one reported in the present study. However, the model fails to follow the established dependence for the materials with grain size below 10 nm as the deformation mechanisms at these extremely finer length scales (below 10 nm) are expected to be totally different from considerations applicable for the present alloy with a grain size of 30 nm.

DISPERSE SOILS DILATANCY STUDIES AND THE METHODS OF ITS QUANTITATIVE ASSESSMENT

The phenomenon of dilatancy is a unique property of dispersed media, and in the case of soils can have a significant impact on the shear resistance and the stress-strain state change during loading. In the conditions of free boundaries dilatancy leads to volume increase, and in the presence of volume expansion restrictions to the growth of average stresses. Thus, dilatancy leads to an increase in shear resistance, which makes it possible to increase the degree of use of the bearing capacity of the base. Many modern mechanical models of soil allow dilatancy calculation, most often on the basis of the Rowe’s theory, according to which the angle of internal friction changes during loading, and to calculate the base taking into account its hardening. In addition, the introduction of the plastic potential into the strength conditions allows the calculation of the final plastic strains. This is very important in case of complex loading trajectories, often implemented in soil foundations. The article provides an overview of dilatancy phenomenon studies in our country and abroad with main analytical dependencies given. Four main methods for determining the dilatancy angle are considered: the method of direct simple shear (DSS) and multiplane direct shear (MDS), triaxial compression and torsion shear, their main advantages and disadvantages are highlighted in a form of a table. It is shown that determination of the dilatancy angle does not present significant difficulties and does not require specialized equipment, at the same time, the effective use of this parameter in the design leads to economic effect, primarily in the case of sandy and coarse soils.

Changes in terrestrial near-surface wind speed and their possible causes: an overview

Changes in terrestrial near-surface wind speed (SWS) are induced by a combination of anthropogenic activities and natural climate changes. Thus, the study of the long-term changes of SWS and their causes is very important for recognizing the effects of these processes. Although the slowdown in SWS has been analyzed in previous studies, to the best of knowledge, no overall comparison or detailed examination of this research has been performed. Similarly, the causes of the decreases in SWS and the best directions of future research have not been discussed in depth. Therefore, we analyzed a series of studies reporting SWS trends spanning the last 30 years from around the world. The changes in SWS differ among different regions. The most significant decreases have occurred in Central Asia and North America, with mean linear trends of − 0.11 m s−1 decade−1; the second most significant decreases have occurred in Europe, East Asia, and South Asia, with mean linear trends of − 0.08 m s−1 decade−1; and the weakest decrease has occurred in Australia. Although the SWS in Africa has decreased, this region lacks long-term observational data. Therefore, the uncertainties in the long-term SWS trend are higher in this region than in other regions. The changes in SWS, caused by a mixture of global-, regional-, and local-scale factors, are mainly due to changes in driving forces and drag forces. The changes in the driving forces are caused by changes in atmospheric circulation, and the changes in the drag forces are caused by changes in the external and internal friction in the atmosphere. Changes in surface friction are mainly caused by changes in the surface roughness due to land use and cover change (LUCC), including urbanization, and changes in internal friction are mainly induced by changes in the boundary layer characteristics. Future studies should compare the spatio-temporal differences in SWS between high and low altitudes and quantify the effects of different factors on the SWS. Additionally, in-depth analysis of extreme SWS events and prediction of future mean and extreme SWS values at global and regional scales are also necessary.

Change of Internal Friction on Magnesium Alloy with 5.48% Al and 0.813% Zn

The article is focused on the analysis changes dependence on the temperature on the magnesium alloy with 5,48% Al, 0,813% Zn and 0,398% Mn by internal friction. Internal friction is a property of the material is measured on the ultrasonic resonant aparature at a frequency about f = 20470 Hz. The measured temperature range was from 30°C up to 420°C. Precisely measurement of the internal friction can be monitored ongoing structural changes and various mechanisms that prevent these changes.

Change of Internal Friction on Magnesium Alloy Depending on the Temperature and the Use of Mathematical Methods in the Evaluation of This Property

The article is aimed on present research of internal friction mechanisms that are responsible for the temperature behaviour of AZ91 magnesium alloys. These mechanisms have been studied by ultrasonic resonant apparatus at a frequency close to 20470 Hz and in a temperature range from 50 °C up to 400 °C. The specimen on internal friction measurement has an hour glass shape. The specimens were in the as cast state and after measurement showed dendritic structure. Structure of magnesium alloys AZ91 was carried out after the homogenization annealing at temperature 390 °C. It was also used application of mathematical calculations for a more accurately experimental measurement of internal friction depending on the temperature.

Change of Internal Friction on Aluminium Alloy with 10.1 % Mg Dependence on the Temperature

The article is focused on the analysis changes dependence on the temperature on the aluminium alloy with 10.1% Mg, 1.32% Si and 0.43% Mn by internal friction. Internal friction is a property of the material is measured on the ultrasonic resonant aparature at a frequency about f = 20470 Hz. The measured temperature range was from 50 °C up to 420 °C. Precisely measurement of the internal friction can be monitored ongoing structural changes and various mechanisms that prevent these changes.

Temperature Dependence of the Internal Friction Measured at Different Excitation Voltages

Internal friction reflects the ability of the material irreversibly dissipating mechanical energy oscillations. That means, the material of high internal friction ability is able to significantly reduce the vibration amplitude. Dispersion of mechanical energy in the material is just the one of the ways of energy transformation for example conversion of mechanical energy to heat energy. This article is focused on the analysis of the internal friction changes depending on the temperature. For experimental measurements was used AZ91 magnesium alloy. Measurements were performed at different excitation voltages. In experimental measurements was used only ultrasonic resonance method. This method is based on continuous excitation of oscillations of the test bar, and the entire apparatus vibrates at a frequency which is close to the resonance.

Temperature dependent damping studies of Ni-Mn-Ga polymer composites

Mechanical properties of ferromagnetic shape memory alloy (FSMA) polyurethane (PU) polymer composites are studied using dynamic mechanical analysis (DMA) at different temperatures. The sample used in the study is Ni-Mn-Ga/PU polymer composite. DMA studies reveal that the mechanical modulus decreases, when the temperature increases. The peak in internal friction (tanδ) appears twice due to martensite transformation of the reinforced particles and glass transition of the polymer matrix. The strain is due to the motion of twin boundaries rather than the phase transformations. Twin boundary motion is found to be the root cause for the martensite-austenite transformation and vice versa, and leads to enhanced damping mechanism. Speculations on twin boundaries of this sample to show concrete evidence on change in internal friction (tanδ) are still underway. This paper proposes that Ni-Mn-Ga/PU polymer composites can be used as efficient dampers.

Effect of microstructure on internal friction and Young's modulus of aged Cu–Be alloy

This study is intended to determine the effect of microstructure on internal friction and Young's modulus as a function of stress in the elastic region of an aged Cu–Be alloy and to investigate the influence of transformed phases caused by precipitation hardening on both properties. Results show that internal friction and Young's modulus were influenced by different precipitates. Transformed phases and micromechanical mechanisms could be responsible for the changes in internal friction and Young's modulus. The microstructure of the alloy having Guinier–Preston zones appears to have low internal friction and dependence on stress after aging at 315 °C for 2 h. The Young's moduli of the long-term aged samples increased by approximately 2 GPa compared to that for the short-term aged samples and elastic instability up to a stress of 20% of the yield strength was observed.

The effect of crossed electric and magnetic fields in loaded rock specimens

The idea of the work is to demonstrate that impacts of crossed electric and magnetic fields (Cr.EMF) are applicable to study the rate of internal fracturing processes in loaded rock specimens. Our previous experiments with rock specimens loaded by a press have revealed the effect of acoustic emission (AE) activity increment caused by electric pulses. The experiments have been held on a noiseless rheological machine available at Bishkek Geodynamic Research Center—RS RAS. We analyzed the temporal dependence of AE activity during exposure to crossed electric and magnetic field; the compressive load being constant. The effect of AE stimulation by power pulses (triggering) has been verified. AE measurements have confirmed the existence of explicit response to both kinds of Cr.EMF pulses: solitary pulses with major amplitudes of E and B and periodic long-term pulses of minor E and H amplitudes. The comparison of recent and previous results on AE triggering by external electromagnetic (EM) fields has demonstrated that two modes of activation can be distinguished. Both kinds of AE variations (responses) are manifestations of change in internal friction (microcracking and kinetics of other defects).

Laboratory investigation of the frictional behavior of granular volcanic material

We report on detailed laboratory experiments designed to illustrate the frictional behavior of granular volcanic debris. The materials include pyroclastic flow debris from Soufrière Hills Volcano, Montserrat, and from Stromboli Volcano, Italy, and lahar deposits from Mount St. Helens. Experiments were conducted in a servo-controlled, double-direct shear apparatus under conditions of displacement-control and with monitored temperature and humidity. The effects of loading velocity, normal stress, grain-size range, and saturation state were examined for normal stresses from 0.75 to 8 MPa. The Soufrière Hills debris was sampled in the field using a 2 mm sieve. Samples from Stromboli and MSH represent the original bulk material. The influence of grain-size and size distribution were examined in detail for the Soufrière Hills material for 1) two narrow size ranges (3–4 ϕ, 0.063–0.125 mm; and 0–1 ϕ, 0.5–1 mm), 2) a wide size range (3–0 ϕ, 0.125–1 mm), and 3) the natural size distribution in the range 0–1 mm. These four data sets show remarkably uniform properties: coefficients of residual internal friction varied from 0.62 to 0.64 and coefficients of peak internal friction varied from 0.66 to 0.69, with zero cohesion in each case. For the natural grain-size distribution, we find a small but clear increase in residual sliding friction with increasing slip velocity in the range 10 to 900 μm/s, i.e. velocity strengthening frictional behavior. For Soufrière Hills pyroclastic material the coefficient of internal friction changes very little when water saturated. The frictional characteristics were remarkably similar for the three volcanoes. For the natural grain-size distributions, the coefficient of residual internal friction ranged from 0.61 to 0.63 and peak internal friction values ranged from 0.65 to 0.66. Pre-loaded and over-compacted materials sheared at reduced normal stress gave peak coefficients as high as 0.80. Our results imply that granular volcanic debris should often fail via stable creep, but may exhibit stick-slip instability under some conditions.

Effect of ageing on internal friction and elastic modulus of Ti–Nb alloys

This study aims to investigate the changes in internal friction and Young's modulus during ageing phase transformations in titanium–niobium binary alloys. Four types of alloys, which had niobium concentrations of 25, 30, 35, and 40 mass%, were used. These alloys were solution-treated at 1223 K, and aged at 423, 573, and 723 K. Although the highest Young's modulus of the quenched specimens was observed in the α″ + β duplex structure of T30N and not the α″ martensite structure of T25N, it decreased with the amount of α″ martensite in other alloys. The internal friction of the quenched specimen decreased as the amount of the β phase increased. The internal friction increased, but Young's modulus decreased during the processes of α″ → β reverse transformation and α precipitation during the ageing treatments. On the other hand, the internal friction decreased, but Young's modulus increased during the process of aged ω precipitation. In particular, the decreased internal friction of the α″ martensite structure of Ti–25Nb alloys aged at 723 K and the changes in both the internal friction and Young's modulus during the process of aged ω precipitation of the α″ + β duplex structure were remarkable.

Internal friction characteristics of Ti 51.5Ni 26.0Pd 22.5 thin films formed by sputter deposition

The internal friction and the modulus have been measured on Ti 51.5Ni 26.0Pd 22.5 films under tension load, at three frequencies 0.5, 1.0, 5.0 Hz. in a wide range of temperatures covering the orthorhombic martensite and the reverse transformations. The effect of heat treatment and frequency on the internal friction has also been investigated. Only a transition around the orthorhombic transformation took place and a very sharp step-type internal friction was observed for all films with three kinds of heat treatments. The elastic modulus evolution reversed to internal friction change and a remarkable depression of the modulus corresponded to the internal friction peak. The internal friction of the films was enhanced by crystallization at 750 °C and the highest internal friction obtained at frequency 0.5 Hz. Ageing treatment at 450 °C after crystallizing at 750 °C promoted the peak of internal friction appearing and accelerated the microstructure variation. A high damping capacity of Q − 1 = 0.05 or 0.06 was reached in the films crystallizing at 750 °C with or without ageing at 450 °C respectively and sustained from room temperature to 100 °C.

Effect of TiX(X=C, N, O) additives on microstructure and properties of silicon nitride based ceramics

The additives of TiC, TiN, and TiO2 do not lead to a large amount of intergranular glass pockets in the resultant Si3N4 based ceramics, and have different effects on the internal friction change with temperature. The TiO2 and TiN additives advance the transformation of a -t ob-silicon nitride. � 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A low-temperature internal friction study of Y124 superconductors

A ceramic sample of Y Ba2Cu4O8 (Y124) was synthesized at atmospheric pressure with the addition ofNaNO3 as an enhancer. The internal friction was measured from liquid nitrogentemperature to room temperature at kilohertz frequency using the vibrating reedmethod. Instead of a broad internal friction peak around 220 K observed inY Ba2Cu3O7−δ (Y123) a small step in the internal friction spectrum was observed around 200 K with increaseof temperature in Y124. This internal friction behaviour is similar to that of Sr-substitutedY Ba0.8Sr1.2Cu3O7−δ. We expect that the internal friction step in Y124 originates from charge carriercrossover. The small size of the change in internal friction around 200 K in Y124 isdue to suppression of the lattice response compared with that in undoped Y123.