Internal Friction Results Research Articles

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.

Characterization of dislocation evolution during creep of 9Cr[sbnd]1Mo steel using internal friction measurement

Using the internal friction measurement, this work dealt with the change of dislocation configuration during the creep of 9Cr1Mo steel at 873 K. At different creep times, specimens of this steel were firstly prepared by the interrupted test to simulate various creep states. Then, the internal friction of these specimens was measured by a dynamic mechanical analyzer (DMA) to characterize the dislocation configuration. Based on the analysis of internal friction results, it showed that both the density and distribution of diffusion-controlled dislocations vary continuously with creep time, and there has a density peak at the end of primary creep. Meanwhile, the kinetics of dislocation motions was introduced to study the evolution of dislocations during present creep in detail. In comparison with the calculated results, the movement mechanism of above diffusion-controlled dislocations was clarified successfully by the modeled dislocations. In addition, the present work offered a powerful tool to evaluate the configuration of dislocations rather than mobile dislocations.

Effects of prestrain and grain boundary segregation of impurity atoms on bake hardening behaviors of Ti+V-bearing ultra-low carbon bake hardening steel

The distribution pattern of solute atoms, interaction between C atoms and dislocations, and bake hardening behaviors of the P-added and P-free ultra-low carbon bake hardening (ULC-BH) steels were investigated, which were annealed at 810 °C for 2 min and subsequently treated with prestrains and baking. The three-dimensional atomic probe (3DAP) and internal friction results revealed that C atoms were homogeneously distributed in the matrix of the P-added ULC-BH steel, but they were strongly segregated in the P-free ULC-BH steel after annealing at 810 °C for 2 min. The solute C concentration of the P-added ULC-BH steel was higher than that of the P-free ULC-BH steel. The addition of P greatly strengthened the BH behavior of the ULC-BH steel. The variation in the BH behavior with the prestrain was apparently different between the P-added and P-free ULC-BH steels. The BH value of the P-added ULC-BH steel gradually increased with an increase in the prestrain ranging from 1% to 10%. However, the value of the P-free ULC-BH steel increased by increasing the prestrain up to 8% and decreased subsequently. The BH behavior showed higher sensitivity to the solute C concentration for the ULC-BH steel than for the low carbon (LC) steel. The BH value either increased or decreased with an increase in the prestrain, which mainly depended on the solute C concentration, i.e., whether the solute C concentration was sufficient or not to saturate the dislocation generated by the prestrain during the baking process.

Phase transitions and phase diagram of Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 Pb-free system by anelastic measurement

The internal friction and storage modulus of Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) Pb-free ceramics have been measured by dynamic mechanical analysis. The anelastic properties show clear anomalies with regard to the transformations between cubic (C), tetragonal (T), orthorhombic (O), and rhombohedral (R) phases, which are all of ferroelastic in nature. The previous reported T-R transition region in the BZT-xBCT system can be divided into the T-O and O-R transitions, consistent with recent studies on the appearance of an intermediate O phase. Based on the internal friction and storage modulus results, a revisited version of BZT-xBCT phase diagram is proposed.

A method for determining the crystallization temperature in studying internal friction behaviors of bulk metallic glasses

As well known, internal friction (Q−1) is one of useful resorts for investigating the mechanical relaxation behaviors of bulk metallic glasses (BMGs). However, so far it has been controversial on ascertaining the authentic position of crystallization temperature (Tx) when the peak arises on Q−1-T heating curve of BMGs. Based on the isochronous measurement results of internal friction and resistivity (ρ) on a series of BMGs, a novel method for determining Tx of BMGs was proposed. By differentiating the curve of Q−1-T with respect to temperature to obtain dQ−1/dT-T curve, the inflexion temperature at the left side of the Q−1-T peak can easily be determined. It is interesting to find that, for all the investigated BMGs in this paper, this inflexion temperature (the peak position of the dQ−1/dT-T curve) is in correspondence with the Tx obtained from ρ-T curve (ρ is very sensitive to crystallization), with the temperature error of ±1.5K. These results suggest that in studying the internal friction behaviors of BMGs, the crystallization temperature can be determined with the inflexion temperature of the Q−1-T curve, and the position of Tx for BMGs locates at the left side of the Q−1-T peak, rather than at the Q−1-T peak temperature or others as pointed in some references.

The Influence of Cold-Rolling on the Internal Friction Behavior of TiNi Shape Memory Alloy

This work is focused on the influence of cold-rolling on the transformation and internal friction behavior of TiNi shape memory alloy. The DSC results show the endothermic peaks disappeared with the increasing of cold-rolling reduction and there was an exothermic peak around 330 � C on the curve during the first heating process. The exothermic peak is associated with recrystallization of amorphous phase induced by cold-rolled work. During the second heating process, the endothermic peak showed up but the exothermic peak didn’t. These phenomena are confirmed by the internal friction results. During the first heating process, the transformation internal friction decreased with the increasing of the cold-rolling reduction and the internal friction augmentation appeared around 330 � C which is related to recrystallization. [doi:10.2320/matertrans.M2011036]

EFFECT OF PRE-DEFORMATION ON DAMPING CAPACITY OF TINI/NBTI COMPOSITE

The present work aims to investigate the internal friction and effect of pre-deformation on damping capacity of Nb 60 Ti 25 Ni 15 alloy, which could be considered as TiNi / NbTi metal matrix composite. The internal friction results showed that this composite possesses excellent damping behavior, which is associated with the movement of a set of abundant interfaces, such as those between the TiNi and NbTi phases, those between martensitic variants and those between martensite and parent phase. Meanwhile, the peak temperature and the width of the internal peak increased with increasing of prestrain level. It appears to be due to the release of the stored elastic strain energy, or the pinning effect by the deformed structures. Furthermore, the height of internal friction peak decreased as the prestrain level increased.

Superplasticity by internal frictional heat under biased cyclic loading

A new damping method was developed not only as a testing tool to investigate in situ deformation under stress, but also as a processing method to superplastically deform ceramics. The specific damping capacity (SDC) at low frequencies (<0.2 Hz) decreased with increasing frequencies, which matched previous internal friction results. However, at higher frequencies (0.2–5 Hz) SDC increased with frequencies, which was explained by a new internal frictional heat mechanism. Three different ceramics: a non-superplastic one and two superplastic ones with different activation energies, showed the same behavior at the high frequency damping tests (1–5 Hz). From these results, it was deduced that a cyclic load at high frequencies, superimposed on a static one, has a great potential to enhance superplasticity by specifically heating up grain boundaries from internal frictional heat.

Inelastic Relaxation in Tin Dioxide Thin Films

Internal friction results obtained in thin SnO2 films produced by reactive magnetron sputtering (thickness of the film ~ 1 μm) and by the dehydration of water solution of tin salts (thickness of the film ~ 10 μm) are reported. It is suggested that internal friction peak observed in SnO2 films at around 170 oC is caused by relaxation processes on grain boundaries (average grain size is 20 nm). The investigation of internal friction in SnO2 films can yield new information about the structure of thin films.

Anelastic and dielectric studies of La 2Mo 2O 9-based oxide-ion conductors

This paper reports the results of internal friction and dielectric relaxation studies on novel oxide-ion conductors (La 1− x A x ) 2Mo 2O 9− δ (A = Ca, Bi, K; x = 0–0.075). Two relaxation peaks associated with short-distance diffusion of oxygen vacancies were observed. Doping at La site with different elements shifts both relaxation peaks towards higher temperature and increases the activation energy of oxygen ion diffusion. In the case of internal friction, the height of the higher temperature peak (dominant component) decreases with increasing dopant content, while the lower temperature peak increases slightly. In the case of dielectric relaxation, on the other hand, the variation of the peak heights as a function of doping content exhibits a maximum around 2.5% K and 4% Bi. Furthermore, in undoped and slightly doped La 2Mo 2O 9 samples, there is an internal friction peak around 570 °C associated with the order–disorder phase transition. In heavily doped samples, this peak disappears, indicating that this phase transition is suppressed and the high temperature phase is stabilized.

Transformation and Damping Characteristics of NiTi/NiTi Alloys Synthesized by Explosive Welding

The present work aims to investigate transformation and damping characteristics of a Ni51Ti/Ni50.2Ti alloy synthesized by explosive welding. The DSC results showed that the two endothermic peaks of the unprestrained specimen corresponded to the reverse transformation of each NiTi component. The reverse transformation temperature of Ni50.2Ti increased with increasing prestrain level, whereas the reverse transformation peak of Ni51Ti was split up into two independent endothermic peaks. Meanwhile, the internal friction results showed that the temperatures of the internal friction peaks of the Ni51Ti/Ni50.2Ti alloy and the range of reverse transformation temperature increased with increasing of prestrain level, which is consistent with the DSC results. Explosive welding is confirmed an effective method to fabricate chemical heterogeneous shape memory materials.

AC calorimetric study of the thermoelastic martensitic transformation in Cu–Al–Ni alloys

We present an accurate study by AC calorimetry on the thermoelastic martensitic transformation in Cu–Al–Ni shape memory alloys , both under quasi-isothermal conditions and by using a dynamic method. The AC calorimetry results suggest that the martensitic transformation exhibits some kinetic effects strongly dependent on the temperature rate, in agreement with internal friction results. Calorimetric results obtained by DSC do not exhibit this behaviour, but dynamic measurements obtained under oscillating fields show a net dependence on the temperature rate.

Relaxations in polystyrene below the glass transition studied by internal friction measurement

The results of internal friction (IF) measurement for polystyrene made over a wide frequency range of 0.001–10 Hz and in a temperature range of 11–74 °C were analyzed. At lower frequencies and higher temperatures, IF increases when the frequency is decreased, and the increase is larger for higher temperatures; IF increases when the temperature is increased, and the increase is larger for lower frequencies. These behaviors were explained by the viscosity relaxation based on the Maxwell model causing IF inversely proportional to frequency and viscosity. The relaxation time was experimentally determined as functions of temperature and frequency. The observed relaxation time could be represented as τ = τ 0exp( E/ k B T) (thermal activation); a combination of two relaxations was seen (double relaxation); τ 0 and E were dependent on the frequency; log τ 0 linearly decreased with increasing E (compensation effect). The relaxing elements were considered to jump cooperatively, and the element could be a part of molecular chains in the material. The results of the present study were compared with those obtained from our previous viscosity experiment.

A STUDY ON THE EFFECT OF ANNEALING PROCESS ON SOUND VELOCITY AND INTERNAL FRICTION USING THE VIBRATING REED TECHNIQUE

Al has unique intrinsic characteristics, which are of interest to scientists as well as engineers. Al and its alloys are slightly paramagnetic materials. Al has very low cross section for thermal neutrons of 0.23 barn, hence Al can be used in nuclear fields as a structural material which is virtually transparent to neutrons. We report VRT as a new technique to study material problems. We also discuss, the results of sound velocity and internal friction, and resonance frequency as a function of temperature range for a pure aluminum sample under investigation. By using VRT, we found that the annealing temperature (450°C) is sufficient to remove the type of defects introduced in the materials under study. The activation energy to remove point defect for Al samples was calculated and found to be about 0.0624 eV. Also, we could easily observe that Q-1 is a function of annealing time. From these measurements of sound velocity and internal friction we can conclude that VRT is a powerful tool for detecting and probing the physical properties of the material under study. Internal friction is a microscopic property for the indication of the purity of the sample. Sound velocity depends on the state of the materials (which depends on the process of treatment).

Temperature dependence of liquid structures in In–Sn20: diffraction experimental evidence

In our prior studies, it was suggested, by the internal friction and thermal analysis experimental results, that a temperature-induced discontinuous liquid–liquid structure change might occur in some alloys such as Pb–Sn, Pb–Bi and In–Sn. By means of X-ray diffraction, in the present study, we observed directly the occurrence of such a structure change in the melt In–Sn20. During the change, a sudden drop happened for both the nearest neighbor distance and the coordination number, and the size of short-range orders decreased abruptly. The calculated results of the pair correlation entropy showed that the ordering degree of the melt altered obviously and revealed the discontinuous feature of the change. Thus it presents a challenge to our conventional picture of liquids as entities with continuously varying averaged structure.

Intrinsic kinetic effects during martensitic transformations

In this paper, we present a study by AC calorimetry on the thermoelastic martensitic transformation in a Cu-Al-Ni shape memory alloy, both under quasi-isothermal conditions and by using a dynamical method. Whereas internal friction measurements have shown that the martensitic transformation behaviour exhibits a strong dependence on the rate of change of temperature in both cooling and heating, calorimetric measurements using DSC do not usually show this dependence, Therefore, it is usually argued that the internal friction results are linked to the measurement technique and not to the martensitic transformation itself. However, our AC calorimetry measurements also suggest that the martensitic transformation exhibits some intrinsic kinetic effects dependent on the rate of change of temperature.

Comparative internal friction study of bulk and ribbon glassy Zr 52.5Ti 5Cu 17.9Ni 14.6Al 10

The results of comparative internal friction (IF) investigation of a Zr-based metallic glass prepared in the bulk and ribbon forms are presented. It is shown that absolute values and temperature alterations of the IF and normalized modulus during heating of bulk and ribbon samples are fairly similar. This fact indicates that change of the quenching rate by three to four orders of magnitude either does not affect the amount of the free volume frozen in or the relaxation centres responsible for the relaxation behavior are not connected with the free volume. The possible consequences of this observation are discussed.

Internal friction study of Pb(Zr,Ti)O3 ceramics with various Zr/Ti ratios and dopants

The Pb(Zr,Ti)O3 (PZT) ceramics with Zr/Ti ratios of 30/70, 52/48 and 70/30 and the PZT(52/48) ceramics doped with La, Ta and Co at various percent were prepared by a standard solid-state reaction method, respectively. Internal friction and modulus were measured as a function of temperature at low frequencies by using a inverted torsion pendulum. Two internal friction peaks (P1 and P2), related to oxygen vacancies and domain walls, respectively, were observed in all the undoped PZT ceramics with different Zr/Ti ratios. In addition, a minimum in modulus associated with a phase transition internal friction peak appearing at Curie temperature was observed in all samples. The effects of the Zr/Ti ratios and some dopants (such as La, Ta and Co) on the internal frictions were investigated. The internal friction results indicate the changes of the concentration of oxygen vacancies and the domain structure with the variations of Zr/Ti ratios and dopants, which will be helpful in the utilities of the PZT ceramics.

Amplitude dependent viscoelastic internal friction of metallic glass

The results of low frequency internal friction (IF) measurements of Co 70Fe 5Si 15B 10 metallic glass at various strain amplitudes will be presented. It will be shown that the glass displays amplitude dependent viscoelastic IF at temperatures T>300 K. An analysis of the IF data allows to calculate the strain rate sensitivity which was found to decrease with temperature approaching one at high T.

Phonon scattering and internal friction in dielectric and metallic films at low temperatures

We have measured the heat conduction between 0.05 K and 1.0 K of high purity silicon wafers carrying on their polished faces a variety of thin dielectric films and polycrystalline thin metallic films. Using a Monte Carlo simulation to analyze the conduction measurements, we have determined the phonon mean free path within the films, and found all of them to be much shorter even than in typical bulk amorphous solids, with no exceptions. We have also measured the internal friction of these films below 10 K and found, however, their internal friction at low temperatures strikingly close to that of amorphous solids, both in magnitude and in their temperature independence, with the exception of the MBE Si and alloy Al 5056, whose internal friction is even much smaller than that of amorphous solids. The internal friction results indicate the phonon scattering in these thin films is the same as, or even much less stronger than, in other amorphous solids, according to the Tunneling Model. Thus, we conclude that the heat conduction measurements do not support the picture that the lattice vibrations of these films are glasslike, as had been surmised earlier for thin metallic films, on the basis of low temperature internal friction measurements alone [Phys. Rev. B 59, 11767 (1999)]. At the least, the films must contain additional scattering centers which lead to the very small phonon mean free path. Most remarkably, the MBE Si shows the same strong scattering of thermal phonons as do the other films, while having the negligible internal friction expected for a perfect film. The disorder causing the strong scattering of the thermal phonons in this film is completely unknown. The non-glasslike phonon scattering phenomena observed here in thin dielectric and metallic films deserve further investigations.