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Detecting mechanical fatigue of metallic components is always a challenge in industries. In this work, we proposed to monitor the low-cycle fatigue of a 6061 aluminum alloy based on internal friction (IF) measurement, which is realized by a quantitative electromechanical impedance (Q-EMI) method using a small piezoelectric wafer bonded on the specimen. Large stress amplitude (230 MPa) was employed in the testing; thus, the fatigue life can always be below 105 cycles. It was found that except for the initial testing stage, the IF always increases steadily with the increasing fatigue cycles. Before the fatigue failure, the IF can reach 2.5–3.4 times the initial value, which is thought to be caused by the micro-cracks forming and growing. In comparison, the resonance frequency of the specimen just drops by about 2% compared with the initial value. Finally, a fatigue criterion based on IF measurement is suggested for aluminum alloys and it can also be extended to other metals. [ABSTRACT FROM AUTHOR]

The mechanical behaviour of materials can be described by a phenomenological relationship that binds strain to stress, by the complex modulus function: M (ω) , which represents the frequency response of the medium in which a transverse mechanical wave is propagated. From the experimental measurements of the internal friction obtained when varying the frequency of a transverse mechanical wave, the parameters that characterize the complex module are determined. The internal friction or loss tangent is bound to the dissipation of the specific mechanical energy. The non-equilibrium thermodynamics theory leads to a general description of irreversible phenomena such as relaxation and viscosity that can coexist in a material. Through the state variables introduced by Ciancio and Kluitenberg, and applying the fractional calculation due to a particular memory mechanism, a model of a viscoanelastic medium is obtained in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

• An automated system is developed for ultrasonic fatigue and internal friction testing. • Fatigue damage can be effective monitored using system damping. • Internal frictions of damaged copper specimens are over 3 times of fresh specimens. • Yield stresses of damaged specimens are obviously lower than the fresh specimens. • A practical damage variable based on internal friction is proposed. Fatigue damage in metals and alloys would reduce their strength and should be identified as early as possible. However, fatigue damage is usually difficult to detect even using advanced nondestructive testing method. Here we developed an automated damping monitoring system for ultrasonic fatigue testing based on a quantitative electromechanical impedance method. During fatigue testing, the damping and resonance frequency of the Piezo actuator/horn/specimen system is measured regularly using an impedance analyzer. When the system damping suddenly increases, it implies that fatigue damage may be generated in the specimen. Separate impedance measurements on the copper specimen in a vacuum chamber show that the internal frictions of damaged specimens are much larger than the fresh specimens. Subsequent X-Ray micro-CT scanning shows that microcracks up to 0.8 mm in length were generated in those fatigued specimens with increased internal frictions. Further tensile testing shows that compared to the fresh specimen, specimens with fatigue damage exhibits reduced tensile strength and elongation at break. Furthermore, the larger the internal friction, the smaller the remaining yield strength and a nearly linear relationship between them holds. Finally, a damage variable D Q is defined based on internal friction which can act as a measure of fatigue damage in metals. [ABSTRACT FROM AUTHOR]

Geophysical flows, characterized by diverse particle-size mixtures, pose challenges for hazard risk assessment due to their anomalous fluidity and rheological behavior. This study investigates the rheological behavior of dry granular mixture flow in a flume setup using particle image velocimetry and triaxial force measurement. Key findings include a power-law relationship between the inertia value and the internal friction coefficient, affirming the applicability of the monodisperse friction model in mixed particle-size scenarios. A strong positive correlation is identified between the effective basal friction coefficient and internal friction coefficient, suggesting an influence of internal frictional properties on basal friction for granular flows on a flat surface. Additionally, positive correlations are observed between normalized stress fluctuation and both internal friction coefficient and inertia number, linking basal stress fluctuations to variations in internal frictional characteristics. These insights enhance our understanding of granular material dynamics, holding potential implications for geological disaster risk assessment. [Display omitted] • Experimental verification the μ (I) rheological law of dry granular mixtures. • The relationship between the effective basal friction coefficient and internal friction coefficient is analyzed. • The internal friction between particles is emphasized as a controlling factor for basal stress fluctuation. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the microstructural anisotropy of Ti-6Al-4V samples fabricated by selective laser melting. Design/methodology/approach: Specimens are fabricated through a Renishaw AM400 selective laser melting machine. Three microstructures (as-built, 850°C annealed and 1,050°C annealed) and two building orientations, parallel (PA) and perpendicular (PE) to the building platform, are considered. Starting from in-depth microscopic observations and comprehensive electron backscattered diffraction imaging, the study addresses non-conventional techniques such as internal friction and electrical resistivity measurements to assess the anisotropy of the fabricated parts. Findings: Microscope observations highlight a fine texture with columnar grains parallel to the building direction in the as-built and 850°C annealed samples. Besides, coarse grains characterized the 1,050°C annealed specimens. Internal friction measurements pointed out the presence of internal stress while storage modulus analyses appear sensitive to texture. Electrical resistivity is resulted to be dependent on grain orientation. Originality/value: The work uses some novel characterization techniques to study the anisotropy and internal stresses of Ti-6Al-4V samples processed by selective laser melting. Mechanical spectroscopy results suitable in this kind of study, as it mimics the operating conditions of the material. [ABSTRACT FROM AUTHOR]

We performed high-frequency (0.4–1.7 MHz) measurements of the internal friction (IF) on 14 bulk metallic glasses (MGs). It is found that 12 of these MGs display relaxation IF peaks at temperatures ≈ 400–500 K, which are weakly affected by heat treatment within the amorphous state. The corresponding relaxation time is about 0.3 μ s. This fast relaxation is reported for the first time in the literature. The apparent activation enthalpy for 4 MGs is determined. It is shown that if measured at a low frequency of 1 Hz, these IF peaks would appear near room temperature or by 30–50 K below it. Thus, the IF peaks found in the present investigation are direct analogues of low-temperature/low-frequency β ′ - and/or γ -relaxations described in the literature. It is argued that the origin of these IF peaks is related to the relaxation of structural defects similar to dumbbell interstitials, which are frozen in solid glass from the liquid state upon melt quenching. These defects can be considered as elastic dipoles and their re-orientation in the applied stress provides anelastic deformation and corresponding IF peak. After correction for temperature dependence of the shear modulus, the true activation enthalpy (0.62–1.08 eV) and activation entropy (4 ≤Δ S ∕ k B ≤15) for defect re-orientation are determined. • High-frequency (0.4–1.7 MHz) internal friction (IF) measurements are performed. • IF peak located at 400–500 K is found in 12 metallic glasses. • The relaxation time corresponding to this peak is about 0.3 μ s. • Corresponding activation enthalpy and activation entropy are determined. • The origin of the IF peak is supposed to be due to defect re-orientation. [ABSTRACT FROM AUTHOR]

An approximate analytical solution to Johanson's rolling theory is derived. It is shown that the solution yields a single dimensionless parameter invariant in process scale-up or equipment transfer, which relates the densification factor with process parameters (roll force and gap), geometric parameters (roll diameter and width) and material properties. It is shown that, to a first approximation, the model prediction does not depend on the nip angle evading the need to powder rheometry measurements such as wall friction and internal shear angle. The model is benchmarked against data obtained from pilot-scale roller compactors from different manufacturers as well as literature data from Nesarikar. The model yields good ribbon density predictions even when calibrating material properties from uniaxial die compression. [ABSTRACT FROM AUTHOR]

Mechanical spectroscopy techniques and internal friction measurements have historically offered a key contribution to the understanding of fundamental mechanisms of defects mobility and phase transformations in many kinds of materials. Nowadays, at the beginning of the millennium, the apparition of the new paradigm of nanotechnology reveals new unforeseen properties of the materials at the nano-scale. Nevertheless, instrumented nanoindentation appears as a new mechanical spectroscopy technique to approach the measure of internal friction at the nano-scale through the direct evaluation of the loss factor η. Indeed, nano compression tests on micro and nano pillars recently measured ultra-high mechanical damping in several Cu-based shape memory alloys (SMA). A step forward is given in the present work, approaching the design of potential micro dampers of SMA working in bending and torsion modes. Several micro devices were milled by focused ion beam (FIB) technique, on [001] oriented single crystals of a Cu-Al-Ni SMA. Ultra-high mechanical damping is demonstrated during superelastic bending of square section micro pillars by in-situ testing inside the scanning electron microscope, using a flat apex 60º-conical indenter in off-axis mode. Then, a series of micro beams and micro cantilevers were designed and milled by FIB, and tested using instrumented nanoindentation equipment by applying the load in bending mode as well as in a mixed bending-torsion mode during off-axis tests. In all cases, the internal friction, or mechanical damping per cycle and per unit of volume, was calculated from the measured load-displacement curve. Superelastic cycling during bending of micro pillars, micro beams and micro cantilevers, exhibits stable and reproducible ultra-high mechanical damping with a loss factor η > 0.1. These results paved the road for designing micro-dampers of Cu-based SMA, able to work in different mechanical modes of compression, bending and torsion, opening the way for many applications of mechanical damping at the nano-scale. • Ultra-high mechanical damping at nano-scale by bending micro beams and micro cantilevers. • Ultra-high damping during superelastic bending of micro beams of shape memory alloys. • In-situ nano-testing inside the electron microscope to measure damping at the nano-scale. • Nanoindentation reveals to be a new technique of mechanical spectroscopy. • Internal friction measured by nanoindentation in micro devices of shape memory alloys. [ABSTRACT FROM AUTHOR]

Hydrogen interactions with different microstructural defects were analysed in ultra-low carbon steel, with specific focus on the influence of carbon distribution. For this purpose, the steel was cold rolled and subjected to various annealing treatments, obtaining microstructures ranging from as cold rolled, over recovered up to fully recrystallized. Optical microscopy, transmission electron microscopy and hardness measurements were used to obtain information on the grain boundary structure and dislocation density. Positron annihilation spectroscopy measurements revealed metastable open volume defects related to both dislocations and vacancy clusters. The carbon distribution was characterized by internal friction experiments. Hydrogen interactions were studied by thermal desorption spectroscopy and internal friction measurements of samples electrochemically pre-charged with hydrogen. The most dominant contribution in hydrogen trapping in the cold rolled material is provided by dislocations. However, their contribution is strongly reduced after annealing at temperatures in the range between 300 K and 600 K due to dissolution of metastable kink-pairs and small carbon-vacancy clusters. Dissolution of such clusters provides fresh supply of carbon to dislocations, which reduces the dislocation trapping capacity for hydrogen due to carbon-hydrogen repulsion. The presence of carbon also reduces the vacancy mobility, allowing clustering and growth during cold rolling resulting in strong hydrogen trapping sites. Binding energies at dislocations were obtained from thermal desorption spectroscopy and internal friction measurements and compared to various models. The small discrepancy in the activation energy is argued to originate from the quantum effect. Hydrogen release from vacancy clusters is determined by the energy required for complete cluster dissolution. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymer 3D printing has been utilised in aerospace to produce complex lightweight structures, in medical fields to print tissues and organs, and in a number of other industries to combat the rising demand for weight-saving engineering solutions. Pure polymer goods created through 3D printing, on the other hand, lack strength and functionality. Therefore, by combining matrix and reinforcing materials, 3D printing of polymer composites can overcome these problems. Also various researchers have used matrix system either epoxy resin or vinyl ester resin. Despite its wide usage, resins have few drawbacks like microleakage and high curing time which could be eliminated by 3D printing. In this work, we have focused on using 3D printed polymer matrix system. To enhance the property, shape memory alloys (SMAs) are introduced in the structure as a reinforcement. Shape memory alloys are a class of smart material that, when heated over a certain temperature, can recover deformation. SMAs exhibit two main characteristics i.e., shape memory effect (SME) and superelasticity (SE). SMAs are available in a variety of shapes, including wires, springs, sheets, and tubes. The SMA wires can be embedded in the composites for a variety of reasons, such as enhancing mechanical properties, shape morphing of structures and for use as actuators. Damping is one such mechanical property which can enhanced by reinforcing SMA wires. In this research work, the samples were fabricated using 3D printing of PLA and PETG with SMA wires embedded in two different forms i.e., continuous and discontinuous. The samples were then examined under a dynamic mechanical analyzer to study the damping (internal friction) behaviour of the smart composites. It has been found that the incorporation of SMA wires into the matrix had a significant influence on the dynamic mechanical properties. Also, the samples with SMA reinforced in continuous manner had the higher value of tan δ i.e., it had good damping properties in comparison to short fibre reinforced composites. [Display omitted] • Ni-Ti reinforced smart composites was fabricated through additive manufacturing with 2 different matrix materials (PLA and PETG). • DSC and XRD were performed for characterising the Ni-Ti wire. • DMA was performed on the smart composite and the effect of different orientation and length of the SMA with 2 different matrix material on the internal friction was analysed. • PLA smart composite had higher internal friction value compared to PETG smart composite. [ABSTRACT FROM AUTHOR]

This paper proposes a new way to detect recrystallization in beta-metastable alloys Ti5553 and Ti4733. Samples of these alloys were cold rolled and thermally treated. Internal friction was measured during heat cycles using a torsion pendulum. A correlation between recrystallization and sharp peak in internal friction specra was shown. The mechanism of dissolution of alpha phase triggering the recrystallization is proposed. In subsequent temperature cycles, the internal friction high temperature background decreases and stabilizes after three cycles. This is attributed with secondary recrystallization leading to grain growth. The size of the grains for different recrystallization time and temperature was measured and is coherent with the mechanical spectroscopy results. This result tends to prove that internal friction measurement can be used to optimize recrystallization treatment in beta metastable titanium alloys. • Mechanical spectroscopy was used to detect recrystallization in Ti5553 and Ti4733 • Ti4733 shows a lower recrystallization temperature than Ti5553due to α " metastable phase dissolving at lower temperature • The dissolution of α and α " is important to achieve recrystallization • Heat treatment at the recrystallization temperature of deformed samples results in grain refinement [ABSTRACT FROM AUTHOR]

Snoek relaxation in bcc crystals is the delayed strain response to an applied stress resulting from the interaction of the interstitial atoms with the stress field. It is responsible for the Snoek peak observed in internal friction measurements of ferrite. However, although martensite is carbon supersaturated, several authors denied the possibility of Snoek relaxation in bct-martensite. We investigated this matter by means of Monte Carlo simulations and mean-field thermo-kinetic modeling. Our results show that Snoek relaxation does occur in bct-martensite. The computed Snoek profiles of temperature-dependent and frequency-dependent internal friction exhibit unexpected features: both peak height and peak temperature decrease when the carbon content is increased. We explain this behavior in the frame of the linear-response approximation. Our theoretical predictions are in qualitative agreement with experiments. • The existence of Snoek relaxation in bct-martensite is demonstrated theoretically. • The Snoek peak height decreases when the solute carbon content is increased. • The peak temperature is carbon-content dependent. [ABSTRACT FROM AUTHOR]

In this study, the recrystallization process in deformed high-purity aluminum was investigated by using the internal friction (IF) and hardness measurement. In the heating process, two IF peaks were detected when the heating rate is 2 °C/min: a sharp peak (P 1 peak) at ~139 °C and a wide peak (P 2 peak) at ~278 °C (0.5 Hz). In the subsequent cooling process, the P 1 peak disappears while the P 2 peak remains. The P 2 peak shifted towards higher temperatures with increasing frequency and can be ascribed to grain boundary relaxation. For the P 1 peak, however, its position did not change with increasing frequency but shifted towards higher temperatures with increasing heating rate in the range of 1–5 °C/min, and the corresponding modulus varied abnormally in the temperature range of 115–160 °C. These facts indicated that the P 1 peak is a non-relaxational peak and can be ascribed to the recrystallization process. The recrystallization activation energy deduced via the shift of peak position with heating rate by using the Kissinger equation is 57± 3 kJ/mol, which is as same as that deduced from the classical isothermal recrystallization process as assessed by microhardness measurement. The classical isothermal recrystallization temperature can be deduced from the peak temperature of P 1 peak by simply adjusting the heating rate. This provided a method to determine the recrystallization temperature via internal friction measurement in a continuously heating process, which needs only two or three samples. • The P 1 peak associated with the recrystallization process of Al was detected. • Recrystallization activation energy of Al during continuously heating was estimated. • Classical recrystallization process was simulated via continuously heating process. • Feasibility of determining recrystallization temperature by IF was investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] The low-temperature plasticity of body-centered cubic (bcc) metals is governed by 1 2 〈 111 〉 screw dislocations due to their compact, non-planar core. It has been proposed that 70.5 ° mixed (M111) dislocations may also exhibit special core structures and comparably large Peierls stresses, but the theoretical and experimental evidence is still incomplete. In this work, we present a detailed comparative study of the M111 dislocation in five bcc transition metals on the basis of atomistic simulations. We employ density functional theory and semi-empirical interatomic potentials to investigate both the core structure and the Peierls barrier of the M111 dislocation. Our calculations demonstrate that reliable prediction of M111 properties presents not only a very stringent test for the reliability of interatomic potentials but is also challenging for first-principles calculations for which careful convergence studies are required. Our study reveals that the Peierls barrier and stress vary significantly for different bcc transition metals. Sizable barriers are found for W and Mo while for Nb, Ta and Fe the barrier is comparably small. Our predictions are consistent with internal friction measurements and provide new insights into the plasticity of bcc metals. [ABSTRACT FROM AUTHOR]

• Influence of Nb on Ti diffusion observed in TiAl intermetallics for aeronautic applications. • γ-TiAl based alloys exhibit a common atomic relaxation associated with Ti diffusion. • Atomic mechanism of Ti diffusion impeded by Nb in γ-TiAl based alloys. • Mechanical Spectroscopy allows measuring diffusion at high temperature. The development of intermetallic titanium aluminides has been driven by the aeronautic and aerospace industries because of the excellent mechanical properties and low density of γ-TiAl based alloys. Up to now, several generations of γ-TiAl based alloys were developed with increasing complexity of the alloy systems. Nb is one of the most important alloying elements in γ-TiAl alloys and although it is considered as a slow diffuser, its influence has not been fully quantified yet. In this work we demonstrate, through mechanical spectroscopy measurements conducted on several γ-TiAl based alloys with different Nb content, that Nb impedes the diffusion of Ti atoms in the α 2 -Ti 3 Al phase. Internal friction measurements show a relaxation peak P(α 2), which is associated with short distance diffusion of Ti atoms in the α 2 phase, involving stress-induced rotation of dipoles Al-V Ti -Al, whose activation energy is dependent on the Nb content. The increase of the activation energy is quantified as ΔE a (Ti)= 0.037 eV × at% Nb, being attributed to the next-neighbor interaction of Nb atoms with the local configuration of Ti-V Ti. This mechanism also produces a further broadening of the relaxation peak, which is attributed to the near-next-neighbor interactions for high Nb contents. Finally, an atomic model for the mechanism responsible for this relaxation is proposed allowing to explain the observed experimental behavior. [ABSTRACT FROM AUTHOR]

The martensitic transformation of Ni 49.5 Ti 35.5 Hf 15 high temperature shape memory alloy is characterized by internal friction measurements. The temperatures for the reversible B2 ↔ B19' transformation appear in the range 410–479 K on cooling and 447–526 K on heating. In addition, a strong anomalous pre-martensitic softening of the dynamic modulus is reported in the high-temperature phase, between 850 K and 550 K, evidencing the thermoelastic character of this family of alloys. Based on the analysis of the internal friction spectra, a theoretical and experimental methodology is proposed to measure the Clausius-Clapeyron coefficient through mechanical spectroscopy. This new non-destructive method could be extremely useful for the development of advanced prototypes of shape memory alloys. • Internal friction on a Ni–Ti-Hf High-Temperature Shape Memory Alloys. • Martensitic transformation on a Ni–Ti-Hf High-Temperature Shape Memory Alloys. • Anomalous pre-martensitic softening measured on a Ni–Ti-Hf Shape Memory Alloy. • Mechanical Spectroscopy allows measuring the Clausius-Clapeyron coefficient. [ABSTRACT FROM AUTHOR]

Motivated to create a germanium analog to nearly two-level-tunneling-system (TLS)-free amorphous silicon, six germanium films, all about 350 nm thick, were deposited by molecular beam epitaxy onto substrates held at temperatures between room temperature and 280∘C. The internal friction and speed of sound of the films was measured between 375 mK and 300 K. Although the intent was to study amorphous thin films, those grown at 200∘C and higher were shown to be at least partially crystalline. The tunneling strength C , a measure of the interaction between phonons and two-level tunneling systems, decreased monotonically with increasing substrate growth temperature, and for films grown on substrates at temperatures above room temperature, C was below the glassy range. The lowest value for an amorphous film, for the 160∘C-grown film, was C = 1.9 × 10 − 5 . • Two-level Tunneling Systems measured in amorphous germanium via internal friction. • Fewer two-level systems as substrate temperature increases during film deposition. • Crystallization confounds higher temperature preparations of amorphous germanium. • Conflicting interpretations of amorphous germanium two-level systems are resolved. [ABSTRACT FROM AUTHOR]

• FeCrAl alloys with 1.0 wt% Nb addition exhibit the highest mechanical properties. • Strengthening mechanism is assessed by internal friction measurement. • High density nanoscale Fe 2 Nb Laves particles precipitate on the grain boundaries. • High density nanoscale Fe 2 Nb Laves particles can also precipitate within the matrix. • Dislocation/grain boundary cannot move below 800 °C because of pinning of Fe 2 Nb phase. The Fe–13Cr–4.5Al–2Mo (FeCrAlMo) alloys, one of the most promising candidates for the accident tolerant fuel cladding in the light-water reactors, were strengthened with Nb addition and the strengthening mechanism were assessed by an internal friction (IF) measurement method combined with microstructure characterization. The FeCrAlMo alloy with 1.0 wt% Nb addition exhibited the highest ultimate tensile strength (UTS) and an acceptable ductility at each tested temperature (room temperature, 300 °C or 700 °C). For example at 700 °C, the UTS of FeCrAlMo −1 wt%Nb was about 215 MPa, which was 53.5% higher than that of Nb-free FeCrAlMo alloy. For Nb-free FeCrAlMo alloy, a high IF peak P 2 appeared at about 680 °C was related to the recovery and recrystallization process during the first heating cycle, which was characterized by an internal friction measurement method. Another small IF peak P 1 corresponding to Zener relaxation process and a predominant IF peak P 3 corresponding to the grain boundary relaxation process were observed at 560 °C and 720 °C, respectively, during the second heating cycle. However none of IF peaks was detected for the Nb containing FeCrAlMo alloys up to 800 °C. Based on the IF theory, the disappearance of P 1 (Zener peak), P 2 (recrystallization peak) and P 3 (grain boundary peak) in the first and second heating cycles was owing to the pinning of dislocations and grain boundaries by high density Fe 2 Nb nanoscale particles dispersed in the FeCrAlMo matrix, which enhanced the tensile strength of the Nb containing FeCrAlMo alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The β relaxation in bulk metallic glasses (BMGs) is reversible and dynamic and is directly related to local atomic cooperative motions. In this study, the effects of thermal cycle and crystallization friction on the reversibility of β relaxation of a LaCe-based BMG are studied by measuring internal friction and by using thermal cycle to certain characteristic temperatures single or repeatedly. Experimental results show that unstable structural units are released after heating to the end temperature of the β relaxation, and partial crystallization does not impede the reversibility but postpones the appearance of the β relaxation. By investigating the atomic mobility and the β relaxation, compression testing at the temperature range that corresponds to the activation of the β relaxation shows a large plastic deformation behavior. • Effects of thermal cycle and crystallization friction on reversibility of the β relaxation of a LaCe-based BMG are studied. • Unstable structural units exist in the as cast BMG and will be released after heating to the end of the β relaxation. • Partial crystallization does not impede the reversibility but postpones the appearance of the β relaxation. [ABSTRACT FROM AUTHOR]