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This study primarily focuses on analyzing anelastic processes due to interstitial oxygen in the Ti–25Ta–40Zr alloy. From the structural and microstructural characterization (DRX and optical microscopy), it was detected that the Ti–25Ta–40Zr alloy is a α + β type. Peaks of anelastic relaxation were visualized in the Ti–25Ta–40Zr alloy, where the peaks are thermally activated, with the shift of Qp−1 to higher temperatures in tests performed at high frequencies. The activation energy (E), relaxation time (τ0), and diffusivity (Do) of oxygen in the alloy were obtained E = (0.49 ± 0.02) eV, τ0 = (6.3 ± 0.2) x10−19 s and D0 = (5.0 ± 0.1) x10−3 m2/s.

In this article, we studied the anelastic properties at low-load nanoindentations of different metallic glasses, including Zr-, Pd-, La-, Mg-, and Au-bases. It is verified that the "two-parameter Kelvin model" is suitable for analyzing the anelastic mechanical behavior. Despite the difference in the chemical composition of these alloys, the energy barrier against the local relaxation is almost equal. The energy barrier is much smaller than that of slow b relaxation, which denotes a faster relaxation mechanism. These findings give insights into the heterogeneous nature of mechanical behavior and relaxation characteristics of metallic glasses. [ABSTRACT FROM AUTHOR]

We focus on the relaxation dynamics of multilayer polymer structures having, as underlying topology, the Husimi cactus. The relaxation dynamics of the multilayer structures is investigated in the framework of generalized Gaussian structures model using both Rouse and Zimm approaches. In the Rouse type-approach, we determine analytically the complete eigenvalues spectrum and based on it we calculate the mechanical relaxation moduli (storage and loss modulus) and the average monomer displacement. First, we monitor these physical quantities for structures with a fixed generation number and we increase the number of layers, such that the linear topology will smoothly come into play. Second, we keep constant the size of the structures, varying simultaneously two parameters: the generation number of the main layer, G, and the number of layers, c. This fact allows us to study in detail the crossover from a pure Husimi cactus behavior to a predominately linear chain behavior. The most interesting situation is found when the two limiting topologies cancel each other. For this case, we encounter in the intermediate frequency/time domain regions of constant slope for different values of the parameter set (G, c) and we show that the number of layers follows an exponential-law of G. In the Zimm-type approach, which includes the hydrodynamic interactions, the quantities that describe the mechanical relaxation dynamics do not show scaling behavior as in the Rouse model, except the limiting case, namely, a very high number of layers and low generation number. [ABSTRACT FROM AUTHOR]

Long‐period zonal tidal Love numbers are more sensitive to lower‐mantle anelasticity (which is difficult to determine even from laboratory); however, the Love numbers of the zonal tides have not been adequately determined. In this study, we use the optimal sequence estimation method with the Global Positioning System (GPS) displacements to estimate the complex Love numbers of the long‐period zonal tides. For the first time, we retrieve the complex Love numbers h20 and l20 for the Msm, Msf, SN, Mstm, Mtm, Msqm, and Mqm tides from the Up‐ and North‐components of the global GPS displacements; we also re‐estimate the same complex Love numbers for the Mm (monthly) and Mf (fortnightly) tides with a higher precision. Based on the robust estimated h20 and l20 values for the nine zonal tides, we inverse their corresponding mantle anelastic parameters fr and fi, respectively. We finally obtain that the material‐dependent parameter α for the lower mantle is 0.189 ± 0.07, and find that the 18.6‐year nodal tide and the Chandler wobble, as well as the long‐period zonal tides, can be represented by a single absorption band. Our estimates for fr, fi, and α can be further used to construct attenuation and velocity models of the Earth's interior. Plain Language Summary: As the Earth is an anelastic body, the observed Earth tides will have different amplitudes from the theoretical tides for a perfectly elastic Earth model. The differences can be scaled by the Love numbers, k, h, and l. The Global Positioning System (GPS) displacements are affected by the Sun and Moon, and hence can record the tides. If we can separate different tidal signals, we can compare the observed signals with the theoretical signals from an elastic Earth model, and hence obtain the corresponding Love numbers. The long‐period zonal tides are only related to the spherical harmonic Y20, so here we use a special method, the optimal sequence estimation method, to isolate nine Y20‐related zonal tides from the global GPS displacement observations, and finally obtain their corresponding Love numbers h20 and l20. Among them, the results for the Msm, Msf, SN, Mstm, Mtm, Msqm, and Mqm tides are obtained for the first time, and the results for the Mm and Mf tides are estimated with higher precision. Based on those new estimated Love numbers, we further estimate the mantle anelastic parameters fr and fi. Finally, we confirm that those nine zonal tides can be represented by a single absorption with α = 0.189 ± 0.07. Key Points: The optimal sequence estimation method is used to retrieve the Love numbers of nine zonal tides from global Global Positioning System displacementsWe estimate the Love numbers h20 and l20 of seven zonal tides and re‐estimate those of the fortnightly and monthly tides with higher precisionMantle anelasticity is estimated from nine zonal tides for the first time; the final estimated material‐dependent value α = 0.189 ± 0.07 [ABSTRACT FROM AUTHOR]

Surface displacement and self‐attraction and loading (SAL) elevation induced by ocean tides are known to be affected by material properties of the solid Earth. Recent studies have shown that, in addition to elasticity, anelasticity considerably impacts surface displacements due to ocean tide loading (OTL). We employ consistent 3D seismic elastic and attenuation tomography models to construct 3D elastic and anelastic earth models, and derive corresponding averaged 1D elastic/anelastic models. We apply these models to systematically study the impact of anelasticity and lateral heterogeneity on M2 OTL displacements and SAL elevation. We find that neglecting lateral heterogeneities highly underestimates displacements and SAL elevation in mid‐ocean‐ridge regions and in some coastal areas of North and Central America. In comparison to PREM, 3D anelastic models can increase the predicted amplitudes of the vertical displacement and SAL elevation by up to 1.5 mm. The increased amplitudes reduce the discrepancy between GPS‐observed OTL displacements and their predictions based on PREM in places like Cornwall (England), Brittany (France), and the Ryukyu Islands (Japan). Applying our results to ocean tides, we discover that the impact on ocean tide dynamics exceeds the predicted SAL elevation correction with an RMS of about 1 mm, reaching an RMS of more than 5 mm in areas like North Atlantic or East Pacific. Due to the fact that such a value reaches the accuracy of modern data‐constrained tidal models, we regard the impact of anelastic shear relaxation as significant in tidal modeling. Plain Language Summary: How are the vertical displacement, sea level fluctuation with respect to the vertical displacement (hereafter SAL elevation) and ocean tide on Earth's surface affected by material properties of the Earth's interior? We study this problem using the ocean tide model TiME and two sets of 3‐Dimensional (3D) seismic elastic and attenuation models, one from the University of California, Berkeley and another from the École Normale Supérieure (ENS) de Lyon. Both the Berkeley and Lyon models confirm that strong lateral variations in elastic parameters and attenuation exist in places such as mid‐ocean‐ridge regions and some coastal areas of North and Central America. They cannot be neglected in modeling displacements and SAL elevation in these places. In addition, 1D attenuation has a strong impact on ocean tides in regions like North Atlantic or East Pacific. This impact is at the same level as the accuracy of modern data‐constrained tidal models. Key Points: Lateral heterogeneity in mantle elasticity derived from three‐dimensional seismic tomography models including attenuationModeling of deformations and self‐attraction and loading using a gravitationally consistent formulationFeedback of lateral heterogeneity and mantle anelasticity to ocean dynamics due to deviations in self‐attraction and loading [ABSTRACT FROM AUTHOR]

Scale-free networks are structures, whose nodes have degree distributions that follow a power law. Here we focus on the dynamics of semiflexible scale-free polymer networks. The semiflexibility is modeled in the framework of [M. Dolgushev and A. Blumen, J. Chem. Phys. 131, 044905 (2009)], which allows for tree-like networks with arbitrary architectures to include local constrains on bond orientations. From the wealth of dynamical quantities we choose the mechanical relaxation moduli (the loss modulus) and the static behavior is studied by looking at the radius of gyration. First we study the influence of the network size and of the stiffness parameter on the dynamical quantities, keeping constant ?, a parameter that measures the connectivity of the scale-free network. Then we vary the parameter ? and we keep constant the size of the structures. This fact allows us to study in detail the crossover behavior from a simple linear semiflexible chain to a star-like structure. We show that the semiflexibility of the scale-free networks clearly manifests itself by displaying macroscopically distinguishable behaviors. [ABSTRACT FROM AUTHOR]

We numerically analyze the influence of hydrodynamic interactions (HI) on scale-free polymer networks under external forces. We envisage that these polymer networks move under external applied fields: mechanical or electrical type. We work in the framework of the bead-spring model and include the HI in a preaveraged Oseen manner. We focus on physical quantities which depend on the eigenvalue spectrum: averaged monomer displacement and the mechanical relaxation modulus with its two components: the storage and the loss modulus. We analyze how these quantities depend on the underlying topology, such as the number of monomers and γ, which is the parameter that measures the connectivity of a network. The influence of topology appears in the intermediate region of time or frequency. For intermediate time/frequency region we do not encounter regions of constant slope by considering the hydrodynamic interactions, differently from the Rouse model, which neglects these HI. As expected we observe a more linear-like topology for high values of γ and a more star-like shape for low γs. [ABSTRACT FROM AUTHOR]

The mechanical spectra of Mn-substituted yttrium orthoferrite YFe1-xMnxO3 (x=0, 0.2, 0.3, 0.4) ceramics were performed at kilohertz from 100 to 360K. Two internal friction (IF) peaks are observed around 150K and 230K, respectively, and both the IF peaks exhibit frequency dispersion behavior. The IF peak around 150K is associated with a step increase in the modulus and its11 mechanical relaxation rate follows the Vogel-Fulcher relation with τ04.45x10-11s, Eα =0.03 eV, and TVF =155K. This IF peak can be explained in terms of a freezing of oxygen vacancies after excluding the possible magnetic spin glass transition. Another IF peak around 230K presents a relaxation behavior and it follows Arrhenius law. Furthermore, the relaxation behavior was verified by the dielectric spectrum and it can be ascribed to the charge carrier hopping between Fe2+ and Fe3+ . [ABSTRACT FROM AUTHOR]

The microscopic mechanisms of the negative electrocaloric effect (ECE) of the single-phase (1-x)(0.94Bi1/2Na1/2TiO3-0.06BaTiO3)-xBa1/2Sr1/2TiO3 (BNT-BT-BST) perovskite solid solutions fabricated via the sol-gel technique are explored in this study. Dielectric and mechanical relaxation analyses are employed to investigate the ferroelectric and structural transitions of the samples. The electrocaloric properties of the samples were measured by thermodynamics Maxwell relations. The difference between the depolarization temperature (Td) and the maximum dielectric constant temperature (Tm) was found to decrease with increasing BST content. Doping with BST stabilized the ferroelectric phase along with unifying the EC temperature changes (ΔT) to only negative values. The origin of the uniform negative ECE of BNT-BT-BST is discussed. [ABSTRACT FROM AUTHOR]

Here we consider the dynamics of semiflexible polymers subject both to angular and to dihedral constraints. We succeed in obtaining analytically the dynamical matrix of such systems by extending the formalism developed by Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)]. This leads to a set of Langevin equations whose eigenvalues determine many dynamical properties. Exemplarily, we display the mechanical relaxation loss moduli [G″(ω)] as a function of several, distinct sets of microscopic stiffness parameters; it turns out that such differences lead to macroscopically distinct patterns. [ABSTRACT FROM AUTHOR]

The influence of ion irradiation on structural rejuvenation and relaxation in a Zr-based metallic glass (MG) is investiagted. The MG can be structurally rejuvenated with increasing irradiation dosage from 0 to 3 dpa, which reflects in increased activation volumes of shear-transformation zones. However, structural relaxation dominates at a high irradiation dosage (4 dpa) resulting in higher hardness. The anelastic-relaxation processes in the irradiated MG can be understood in terms of the coordination mechanism of the deformation modes associated with free volume. Ion irradiation appears to be a promising and effective way to modify MGs and to, thus, manipulate plastic flow. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract We report a successful attempt to derive a closed-form expression for the relaxation function of a complex system by solving a set of coupled kinetic equations connecting the excitation/de-excitation rates to the number of particles (such as electrical charges, dipoles, etc.) in excited states. Our approach, originating from developments in dielectric and mechanical relaxation studies, allows the use of a unified treatment for a wide array of natural processes which often pose challenges to theoretical modeling. We use the notions that (i) a dipole represents any pair formed by a particle in an excited state (such as an energy level in optically excited molecules, or an electrode in dielectric spectroscopy) and its image in the ground state (or reference electrode), that (ii) coupling between such dipoles may be described as particle transfer from one excited state to another with lower energy, and that (iii) the relaxation function for such a system of dipoles is mathematically equivalent to the cumulative distribution function of particles, i.e., the total number of particles that are still in an excited state at a time t following excitation. Taken together, these ideas naturally lead to the identification of two types of relaxation – parallel and serial relaxation – and allow one to tackle systems with either geometrical or physical self-similarity within a unified mathematical scheme. Highlights • A kinetic model for relaxation in systems with self-similar architecture is proposed. • Analytical closed forms of the relaxation and impulse response function are derived from the model. • These allows determination of the corresponding dispersion function (in the frequency domain). • Serial and parallel relaxation are predicted, which apply to a large class of complex systems. [ABSTRACT FROM AUTHOR]

Abstract The mechanical relaxation technique is applied to investigate the fundamental dynamic behavior of BiVO 4 material. A prominent internal friction peak is observed around 430 K at 1 Hz, which is actually composed of three sub-peaks (P 1 , P 2 and P 3 from low to high temperature). And the associated modulus anomalies can also be found in any of the samples. The peak P 1 with activation energy E 1 ∼ 3.20 eV is probably related to the stress-induced unequal positions of Bi3+ ions; while the main P 2 peak with E 2 = 0.91 eV is associated with a complex mechanism, which originates from the viscous motion of domain walls and the interaction of domain walls with oxygen vacancies; and the responsive P 3 peak is resulted from the ferroelastic–paraelastic phase transition, accompanied by a minimum modulus value. Based on the relaxation process and crystalline structure of BiVO 4 , the motion model of ferroelastic domain walls and transport mechanism of diffusion are suggested. Our results pave the way for better understanding the intrinsic dynamic and multifunctional properties of BiVO 4. Highlights • Pave a novel method for understanding the intrinsic dynamic properties of BiVO 4. • The kinetic behavior has been systematically analyzed under mechanical measurement. • The motion evolution of ferroelastic domains of BiVO 4 is first reported. • The mixed electric/oxide conduction mechanism of BiVO 4 has been well established. [ABSTRACT FROM AUTHOR]

Abstract Plasticity improvement in metallic glasses resulting from cycling treatment between room and liquid nitrogen temperature has been reported and attributed to rejuvenation due to a non-uniform thermal expansion coefficient. However, the detailed microscopic effect is still unclear. The present study focuses on the microscopic effect of room-temperature ageing and cryogenic cycling. La 70 Cu 15 Al 15 and La 70 Ni 15 Al 15 metallic glasses were subjected to varying ageing times, after which some were also cryogenically cycled. Quasi-static anelastic relaxation measurements were then employed to characterize the time-constant spectra over seven orders of magnitude. The overall anelastic strain decreases with increasing ageing time, but is not noticeably affected by cryogenic cycling. On the other hand, while ageing also causes an increase in characteristic time constants, cycling reverses this effect. The new details shed light on the effect of structural relaxation and rejuvenation on the properties of shear transformation zones. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Acoustic emission was investigated in process of potassium hydrogen carbonate (PHC) thermal decomposition. Different literature sources indicate very wide range of temperatures for its thermal destruction start (from 100 to 400°C). Study of AE generated at this process has found to be helpful for more exact determination the temperature of its beginning. Heated transparent PHC crystals without losing their shape turn into opaque potassium carbonate (PC), while carbon dioxide (CO2) and water evaporate. Temperature of the thermal degradation onset ~ 130-150°С was determined in result of various samples tests: single PHC crystals, monolayer of dozen loosed crystals and tablets pressed from thousands of crystals. Data of PHC powder thermal decomposition obtained by thermogravimetric and differential thermal analyses found out a good compliance with AE data concerning the temperature range of the process. An X-ray diffraction analysis used to identify the initial substance and products of PHC thermal decomposition. Tests with tablets of PHC revealed two separate temperature regions of AE activity that do not intersect. 1st region of 60-90°C determined as an “elastic unloading range”. AE caused by mechanical relaxation of crystals releasing the elastic energy stored in the process of tablet pressing. 2nd region of 130-200°C related directly to the thermal decomposition of PHC. Kaiser effect was detected at the process of mechanical relaxation during the cyclic heating/cooling of PHC tablets in the temperature range of 60-90°C. In result of the study, the AE technique can be recommended to control the regeneration process of CO2 absorbers based on a composite from PC precipitated on an aluminum oxide γ- Al2O3 porous matrix, which is converted to PHC during the sorption of CO2. The temperature limits of the regeneration process, which results in the reverse transformation of PHC into PC, can be monitored by the AE activity accompanying this process. [ABSTRACT FROM AUTHOR]

Abstract The dynamic mechanical relaxation behavior of Zr 64.13 Cu 15.75 Ni 10.12 Al 10 bulk metallic glass was investigated by mechanical spectroscopy. The activation energy of the main α relaxation was determined to be 4.24 eV. In order to well understand the α relaxation process, several physical and phenomenological models such as Debye model, Kohlrausch-Williams-Watt (KWW) model and quasi-point defect (QPD) model were employed to analyze the dynamic mechanical performance. It was found that Debye model was not so persuasive due to the asymmetry of the main relaxation of Zr 64.13 Cu 15.75 Ni 10.12 Al 10 bulk metallic glass. By contrast, KWW model agreed well with the experimental data if taking Kohlrausch parameter β kww as 0.571. The QPD model, which had a definite physical meaning, could not only match the experimental data perfectly but also correlated the relaxation behavior with the microstructure evolution versus temperature in this bulk metallic glass. [ABSTRACT FROM AUTHOR]

• The increase in temperature decreased the elastic modulus value. • Anelastic relaxation peaks are detected around 400 and 650 K. • Ti-O, Ti-O-O, and Zr-O oxygen stress-induced ordering relaxation processes were identified. • Molybdenum decreased the diffusion coefficient of the Ti-20Zr-Mo alloys. This work investigated oxygen diffusion in Ti-20Zr-7.5Mo and Ti-20Zr-10Mo alloys by mechanical spectroscopy measurements. The relaxation parameters of the alloys with the body-centered cubic crystal structure were guided by Arrhenius law and mathematical analyses under the peak ratios. The results showed that the peaks are thermally activated, with the shift of Q p -1 to higher temperatures in tests performed at high frequencies. The activation energy (E) and diffusivity (D) of oxygen in the alloys were obtained using a mathematical treatment of the structures derived from the relaxation time, where was obtained E = 1.06 ± 0.01 eV and D = (5.75 ± 0.63) ×10−10 m2/s for Ti-20Zr-7.5Mo alloy, and E = (0.77 ± 0.04) eV and D = (2.64 ± 0.45) ×10−13 m2/s for Ti-20Zr-10Mo alloy. [ABSTRACT FROM AUTHOR]

The present article deals with the numerical integration of a six-equation single-velocity two-phase flow model with stiff mechanical relaxation. This model can be employed to approximate efficiently the well known single-velocity single-pressure five-equation model of Kapila et al. (2001). Work in the literature has shown the efficiency of the six-equation model in simulating complex two-phase flows involving cavitation and evaporation processes. The aim of this work is to present and discuss various numerical schemes for this two-phase model focusing on the integration of the nonconservative terms appearing in the phasic energy equations. In fact, previous work has suggested that the choice of the discretization method for the nonconservative terms often does not play a significant role. Two new methods are proposed: a path-conservative HLLC-type scheme that is based on the Dal Maso–LeFloch–Murat theory, and a generalized HLLC-type scheme that is based on a Suliciu’s Riemann solver. The latter scheme has the important property of preserving the positivity of the intermediate states of the conserved quantities. Moreover, we also approximate solutions of the six-equation model by applying two path-conservative schemes recently proposed in the literature, which have been derived from the Osher and HLLEM Riemann solvers. We show comparisons of the different numerical schemes for several test cases, including cavitation problems and shock tubes. An efficiency study for first and second order schemes is also presented. Numerical results show that different methods corresponding to different numerical treatments of the nonconservative terms give analogous results and they are all able to produce accurate approximations of solutions of the Kapila’s five-equation model, except, as expected, for shocks in two-phase mixtures with very high pressure ratios. [ABSTRACT FROM AUTHOR]

The ultrasound attenuation in langasite crystals increases rapidly at about 800 K with increasing temperature for reasons that are not well understood. In this paper, the attenuation quantified as $Q^{-1}$ of the langasite-type materials La3Ga5SiO14 (LGS) and La3Ta0.5Ga5.5O14 (LGT) was studied from room temperature to 1653 and 1608 K, respectively, using resonant ultrasound spectroscopy. Two to three attenuation peaks can be seen. A change of the magnitudes of the largest two attenuation peaks in LGT was correlated with the changing color of an LGT sample, which is related to its oxygen vacancy concentration. Thus, the attenuation likely involves oxygen vacancies. The observed $Q^{-1}$ can be explained well by a model based on the anelastic relaxation of two to three noninteracting point defects causing Debye peak-like attenuation maxima. The activation energies of the largest two relaxation peaks match the activation energies for different conductivity mechanisms in LGS and LGT. Thus, the oxygen movement-based conductivity and the relaxation processes seem to involve the exchange of ions and vacancies on the same positions. The largest two attenuation peaks are probably caused by the movement of ions induced by two different phenomena, the deformation of the lattice (point-defect relaxation) on the one hand and the electric field via the piezoelectric effect (piezoelectric/carrier relaxation) on the other hand. [ABSTRACT FROM AUTHOR]

Dynamic mechanical relaxation behavior of (Zr 55 Cu 30 Ni 5 Al 10 ) 100- x Fe x ( x  = 0, 1 and 2) bulk metallic glasses was investigated by mechanical spectroscopy. It is found that the main α relaxation of the Zr-based metallic glasses can be well described by the Kohlrausch-Williams-Watts (KWW) function. With the increasing of micro-alloying element content, i.e. iron, the value of Kohlrausch exponent β K W W diminishes for the (Zr 55 Cu 30 Ni 5 Al 10 ) 100- x Fe x ( x  = 0, 1 and 2) metallic glass, whereas the characteristic relaxation time increases. In the framework of the quasi-point defects theory, the physical correlation factor χ increases with higher iron content below the glass transition temperature T g . In addition, the parameter a of the quasi-point defect theory can describe the degree of deviations from the Arrhenius law. Based on the theoretical and experimental analysis, it is implied that structural heterogeneity of the Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass could be tailored through minor addition of the iron element. [ABSTRACT FROM AUTHOR]

Seismic tomography models have revealed two broad regions in the lowermost mantle marked by ∼3% slower shear velocity than normal beneath the south central Pacific and southern Africa. These two regions are known as large-low-shear-velocity provinces (LLSVP). There is debate over whether the LLSVPs can be explained by purely thermal variations or whether they must be chemically distinct from normal mantle. Elastic properties alone, have been unable to distinguish the thermal from chemical interpretations. Anelastic structure, however, can help discriminate among models of the LLSVPs since intrinsic attenuation is more sensitive to temperature than to chemical variations. Here we estimate Q μ (the shear wave quality factor) in the African LLSVP using PcS waves generated from a Scotia Arc earthquake, recorded by broadband seismometers deployed in Southern Africa during the Kaapvaal experiment. The upward leg of the PcS waves sweeps from normal mantle into the African LLSVP across the array. We use the spectral ratio (SR) and instantaneous frequency matching (IFM) techniques to measure the differential attenuation ( Δ t ⁎ ) between waves sampling the African LLSVP and the waves that sample normal lower mantle. Using both methods for estimating Δ t ⁎ we find that PcS waves sampling the LLSVP are more attenuated than the waves that miss the LLSVP yielding a Δ t ⁎ difference of more than 1 s. Using the Δ t ⁎ measurements we estimate the average Q μ in the LLSVP to be about 110. Using a range of activation enthalpy ( H ⁎ ) estimates, we find an average temperature anomaly within the LLSVP ranging from +250 to +800 K. Our estimated temperature anomaly range overlaps previous isochemical geodynamic studies that explain the LLSVP as a purely thermal structure although the large uncertainties cannot rule out chemical variations as well. [ABSTRACT FROM AUTHOR]

Using high energy X-ray diffraction we studied the temperature, stress, and time effect on structural changes in a Zr-based bulk metallic glass induced by thermo-mechanical creep. Pair distribution functions obtained from two-dimensional diffraction patterns show that thermo-mechanical creep induces structural disordering, but only when the stress beyond a threshold is applied. A similar threshold behavior was observed for anelastic strain. We conclude that anelastic creep strain induces rejuvenation, whereas plastic strain does not. [ABSTRACT FROM AUTHOR]

Most of the adhesives used in the marine industry are polymers with a mechanical behaviour which is strongly influenced by the strain rate. Therefore, it is important to predict with accuracy their viscous behaviour. To describe their mechanical behaviour in a bonded joint, a viscoelastic-viscoplastic constitutive law is proposed here. The viscous effects on the elastic behaviour are described using a spectral distribution, which divides the viscous strain as the sum of the strains of several viscous mechanisms, each of them with a different characteristic time and weight. The viscoplastic component of the model permits a better description of the strong non-linear behaviour of the adhesives. The parameters of the constitutive law are obtained using an inverse identification procedure coupled with a finite element model. Two creep tests, in two loading directions, are needed in order to identify the viscoelastic part. The viscoplastic part is identified using monotonic tests. In order to validate the behaviour law and the identification procedure, the adhesive Huntsman TM Araldite 420 A/B has been investigated and modelled. All the experimental tests have been conducted using the modified Arcan device. [ABSTRACT FROM AUTHOR]

Structurally ordered piezoelectric Ca 3 TaGa 3 Si 2 O 14 (CTGS) single crystals are studied. The elastic and piezoelectric constants are determined in the temperature range from 20 °C to 900 °C by two independent approaches: resonant and pulse-echo acoustic methods. Further, the temperature dependent acoustic losses are examined. These investigations reveal two loss peaks with maxima near 68 °C and 416 °C at 4.5 MHz that are attributed to anelastic point defect relaxations. Further, the transport of oxygen is investigated using the isotope 18 O as a tracer at temperatures from 1000 °C to 1200 °C. It is shown that the oxygen self-diffusion coefficients are at least three orders of magnitude lower than those of langasite, which is one reason for relatively low losses in CTGS at temperatures on the order of 1000 °C. Finally, the long-term stability of fundamental materials properties including electrical conductivity and resonance frequency is examined at 1000 °C. After one year of thermal treatment, the resonance frequency of resonators made from crystals of different sources is found to decrease only between 0.1% and 0.4%. [ABSTRACT FROM AUTHOR]

Sn has been proposed for use as a high capacity anode material. Because of its ductile metallic nature, Sn may exhibit unique stress evolution during lithiation. Here, 2D radiography and 3D tomography are employed to visualize the evolution of geometry, internal structure, alloying, and damage during lithiation, delithiation, and rest of Sn wires with micron scale diameters. Lithiation proceeds isotropically, resulting in geometric and dimensional changes after 25% of total lithiation when the tensile stresses are sufficiently high to exceed the flow stress of the unlithiated Sn core and cause elongation and diameter increase. Damage occurs at later stages in the form of cracks terminating at the wire surface and voids forming in the unlithiated core. Notably, significant fragmentation occurs during delithiation which, due to void formation that accommodates the resulting stresses, does not measurably alter the wire cross-section and length. The distinguishing feature of the chemo-mechanics of Sn compared to Si or Ge is the pronounced creep rate at applied strain rates as high as 10 −6 s −1 , which promotes large strains in the core, eventually leading to void nucleation in the unlithiated core during lithiation, and more importantly, continues driving the deformation of the anode while at rest. [ABSTRACT FROM AUTHOR]

The dynamic mechanical relaxation of metallic glasses is closely associated with the physical and mechanical properties. In the current work, the dynamic mechanical relaxation behaviors of Cu 46 Zr 45 Al 7 Y 2 and La 65 Al 14 (Cu 5/6 Ag 1/6 ) 11 (Ni 1/2 Co 1/2 ) 10 bulk metallic glasses are investigated by mechanical spectroscopy. In general, metallic glasses display two relaxation modes: main ( α ) relaxation and the slow secondary ( β ) relaxation. The α relaxation is linked to the dynamic glass transition phenomenon and viscous flow while the slow β relaxation is associated with many fundamental issues, such as diffusion and glass transition phenomenon. The experimental study shows La 65 Al 14 (Cu 5/6 Ag 1/6 ) 11 (Ni 1/2 Co 1/2 ) 10 bulk metallic glass displays a noticeable slow β relaxation. Contrarily, the Cu 46 Zr 45 Al 7 Y 2 bulk metallic glass relaxation process takes the form of an “excess wing”. In the framework of quasi-point defects (QPD) theory, the dynamic mechanical response of the metallic glasses is discussed. [ABSTRACT FROM AUTHOR]

The relaxation behavior of a styrene-acrylic latex polymer with a glass-transition temperature of ≤5°C and polymer composites on its basis modified by an indanthrene-type water-soluble dye was analyzed using the method of dynamic mechanical relaxation spectroscopy. The change in the intensity of maximum of dissipative losses of α-relaxation and also of the μ-process is found in polymer films in the negative-temperature range as dependent on the duration and number of their preliminary freezing-thawing cycles at‒30°C taking into account the modifier concentration, which is related to the change in Young’s modulus (modulus defect). Theoretical analysis is performed involving phenomenological model concepts as to the relationship between the vibration-process frequency and Young’s modulus of the polymer material. [ABSTRACT FROM AUTHOR]

An environmental friendly method for enhancing mechanical properties of recycled aggregate concrete (RAC) is proposed by using sodium silicate and silica fume. The proposed method, applied to 100% coarse recycled concrete aggregate compared to untreated RAC, can improve compressive strength up to 33–50%, splitting tensile strength 33–41%, and elastic modulus 15.5–42.5%. Tests revealed that the direct tensile strength of RAC and natural aggregate concrete (NAC) were notably lower than the splitting tensile strength, but at 7 days, these values of treated RAC were higher than the splitting tensile strength. From the experimental data, the compressive strength of the treated RAC can be estimated at any age. Besides, the relationships between mechanical properties of treated RAC which were established were significantly different from those of NAC and untreated RAC in previous studies. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the mechanical relaxation of a multilayer polymer network built by connecting identical layers that have, as underlying topologies, the dual Sierpinski gasket and the regular dendrimer. Additionally, we analyze the dynamics of dipolar energy transfer over a system of chromophores arranged in the form of a multilayer network. Both dynamical processes are studied in the framework of the generalized Gaussian structure (GSS) model. We develop a method whereby the whole eigenvalue spectrum of the connectivity matrix of the multilayer network can be determined iteratively, thereby rendering possible the analysis of the dynamics of networks consisting of a large number of layers. This fact allows us to study in detail the crossover from layer-like behavior to chain-like behavior. Remarkably, we highlight the existence of two bulk-like behaviors. The theoretical findings with respect to the decomposition of the intermediate domain of the relaxation quantities, as well as the chain-like behavior, are well supported by experimental results. [ABSTRACT FROM AUTHOR]

In this work, we report about the mechanical relaxation characteristics of an intrinsically self-healable imidazole modified commercial rubber. This kind of self-healing rubber was prepared by melt mixing of 1-butyl imidazole with bromo-butyl rubber (bromine modified isoprene-isobutylene copolymer, BIIR). By this melt mixing process, the reactive allylic bromine of bromo-butyl rubber was converted into imidazole bromide salt. The resulting development of an ionic character to the polymer backbone leads to an ionic association of the groups which ultimately results to the formation of a network structure of the rubber chains. The modified BIIR thus behaves like a robust crosslinked rubber and shows unusual self-healing properties. The non-covalent reversible network has been studied in detail with respect to stress relaxation experiments, scanning electron microscopic and X-ray scattering. [ABSTRACT FROM AUTHOR]

Mechanical relaxation of glassy materials is strongly influenced by their mechanical and physical properties. In the current study, dynamic mechanical relaxation of Cu 46 Zr 46 Al 8 metallic glass has been investigated by mechanical spectroscopy and molecular dynamics simulations. Our results show that mechanical properties of metallic glasses are highly dependent on their thermal history. α relaxation in the frequency region of the Cu 46 Zr 46 Al 8 metallic glass was described by Havriliak-Negami (HN) model. In the framework of the quasi-point defects theory, the correlated factor χ could be used to characterize the concentration of “defects” of glassy materials. By molecular dynamics simulations of dynamic mechanical tests at different temperatures and frequencies, it is noted that adjusting of defects is inversely correlated to storage modulus at the atomic level. On the other hand, physical aging below the glass transition temperature T g reduces the concentration of defects and narrows down the width of shear bands, which corresponds to decreasing of the atomic mobility. [ABSTRACT FROM AUTHOR]

Titanium alloys with high refractory metals content are required to obtain advanced biomaterials with a low elastic modulus and good mechanical properties. This work studies the influence of Fe content on the microstructure and mechanical properties of powder metallurgy Ti35Nb10Ta(Fe) alloys, with Fe content additions of 1.5, 3.0 and 4.5 wt%. Samples are obtained by uniaxial compaction and sintering at 1250 °C and 1300 °C. Microstructural characterization is performed by scanning and transmission electron microscopy and mechanical characterization by bending, compression and a hardness test. The elastic modulus is measured by the ultrasounds technique. The results show a 10% increase in the maximum bending strength with an increase in the sintering temperature. The obtained microstructure is composed of β-Ti phase (bcc) and some regions where laths of the α-Ti (hcp) phase occur along the grain boundaries. Fe addition slightly improves the stability of the β-Ti phase and conversely decreases the maximum strength and final deformability due to increased porosity. The Ti35Nb10Ta alloy composition displays better properties, with an elastic modulus of 75 GPa, a bending strength of 853 MPa and compression strength of 1000 MPa.

We have analyzed the recently developed pan-European strong motion database, RESORCE-2012: spectral parameters, such as stress drop (stress parameter, Δ σ), anelastic attenuation ( Q), near surface attenuation ( κ ) and site amplification have been estimated from observed strong motion recordings. The selected dataset exhibits a bilinear distance-dependent Q model with average κ value 0.0308 s. Strong regional variations in inelastic attenuation were also observed: frequency-independent Q of 1462 and 601 were estimated for Turkish and Italian data respectively. Due to the strong coupling between Q and κ , the regional variations in Q have strong impact on the estimation of near surface attenuation κ . κ was estimated as 0.0457 and 0.0261 s for Turkey and Italy respectively. Furthermore, a detailed analysis of the variability in estimated κ revealed significant within-station variability. The linear site amplification factors were constrained from residual analysis at each station and site-class type. Using the regional Q model and a site-class specific κ , seismic moments ( M ) and source corner frequencies f were estimated from the site corrected empirical Fourier spectra. Δ σ did not exhibit magnitude dependence. The median Δ σ value was obtained as 5.75 and 5.65 MPa from inverted and database magnitudes respectively. A comparison of response spectra from the stochastic model (derived herein) with that from (regional) ground motion prediction equations (GMPEs) suggests that the presented seismological parameters can be used to represent the corresponding seismological attributes of the regional GMPEs in a host-to-target adjustment framework. The analysis presented herein can be considered as an update of that undertaken for the previous Euro-Mediterranean strong motion database presented by Edwards and Fäh (Geophys J Int 194(2):1190-1202, 2013a). [ABSTRACT FROM AUTHOR]

Abstract.: The properties of amorphous polymers and of organic compounds under pressure are interpreted in the framework of the modified Van der Walls Equation of State (mVW-EOS) the Vogel-Fulcher-Tamann (VFT) law and of the compensation law. We have shown recently that polymers and organic compounds in amorphous liquid and crystalline states verify the mVW-EOS which depends on three parameters, $P^{\ast}$ $V^{\ast}$ and $T^{\ast}$ . In this paper we compare the characteristic pressure $P^{\ast}$ of the mVW-EOS to the various pressures $P_{X}= \Delta H_{X}/\Delta V_{X}$ deduced from thermodynamic and kinetic properties of polymers in the liquid and solid states. $\Delta H_{X}$ and $\Delta V_{X}$ are: a) the enthalpy and volume change at the melting and glass transitions (the glass being isotropic or oriented and annealed below $T_{g}$ at various aging conditions); b) the activation parameters of individual $\beta$ and cooperative $\alpha$ motions in crystalline liquid and amorphous polymers studied by dielectric or mechanical spectroscopy; and c) the activation parameters of amorphous (solid and liquid) polymers submitted to a deformation depending on the time frequency temperature and strain rate. For a same material, whatever its state and whatever the experimental properties analyzed (dielectric and mechanical relaxation, viscosity, auto-diffusion, yielding under hydrostatic pressure), we demonstrate that $P_{X}=P^{\ast}=1/\gamma\kappa$ , ( $\gamma$ Grüneisen parameter, $\kappa$ compressibility). In all polymers and organic compounds (and water), these pressures, weakly dependent on T and P near $T_{g}$ and $ T_{m}$ at low pressure are characteristic of the H-H inter-molecular interactions. It is shown that the two empirical Lawson and Keyes relations of the compensation law can be deduced from the mVW-EOS. Graphical abstract: [ABSTRACT FROM AUTHOR]

Micro-Raman spectroscopy and X-ray diffraction were used to study time-dependent structural changes in sputtered Ce 1-x Gd x O 2-x/2 films. The F 2 g peak position was measured at five well-defined film locations; X-ray diffraction assessed in-plane compressive strain and unit cell volume. For x = 0.05, at all locations monitored post-annealing, the F 2 g frequency continued to increase during two weeks and for x = 0.10, at 4 of 5 locations during six weeks. This time-dependent behavior is attributed to relaxation of local elastic dipolar strain fields. Raman spectroscopy can properly evaluate strain in thin films of these materials only when mechanical properties, defect structure, temporal and thermal history are considered. [ABSTRACT FROM AUTHOR]

We give an exact formulation for the transport coefficients of incommensurate two-dimensional atomic multilayer systems in the tight-binding approximation. This formulation is based upon the C* algebra framework introduced by Bellissard and collaborators [Coherent and Dissipative Transport in Aperiodic Solids, Lecture Notes in Physics (Springer, 2003), Vol. 597, pp. 413-486 and J. Math. Phys. 35(10), 5373-5451 (1994)] to study aperiodic solids (disordered crystals, quasicrystals, and amorphous materials), notably in the presence of magnetic fields (quantum Hall effect). We also present numerical approximations and test our methods on a one-dimensional incommensurate bilayer system. [ABSTRACT FROM AUTHOR]

Mechanical stability of Ag and Cu printed and evaporated metallization lines on polymer substrates is investigated by means of monotonic tensile and cyclic bending tests. It is shown that lines which demonstrate good performance during monotonic tests fail at lower strains during a cyclic bending tests. Evaporated lines with the grain size of several hundreds of nanometers have good ductility and consequently good stability during monotonic loading but at the same time they fail at low strains during cyclic bending. Printed lines with nanocrystalline microstructure, in contrast, demonstrate more intensive cracking during monotonic loading but higher failure strains during cyclic bending. Apart from the grain size effect, the effect of film thickness on the saturation crack density after cyclic bending is also demonstrated. Thinner films have higher crack density in accordance with the shear lag model. [ABSTRACT FROM PUBLISHER]

The results of research into the viscoelastic properties and processes of mechanical relaxation of polyvinylchloride (PVC) containing Cu nanoparticles obtained by means of electroerosion crushing and electrohydraulic destruction of agglomerates of disperse Cu in the presence of an ultrasonic field are presented. It is shown that, in the case of longitudinal shear deformation at a frequency of 0.4 × 10 s over a wide range of temperatures and content of ingredients, viscoelastic phenomena depending on structural changes in the PVC system occur. An analysis of quantitative results of the elastic and viscoelastic deformation of a body is carried out taking into account the energy and entropy components of interaction of the polymer and filler at their interface. [ABSTRACT FROM AUTHOR]

A coupling between diffusional and mechanical relaxation raised from composition-dependent elastic constants, and its effects on the evolution of precipitates with finite misfit strain are investigated. Inverse ripening has been observed where smaller precipitate grows at the expense of a larger one. This occurs due to fluxes generated under elastically-strained solute gradients around precipitates that scales with R r 6 where R and r are the precipitate radius and the radial coordinate, respectively. Both isotropic and anisotropic dependency of elastic constants on the composition were considered. The latter leads to the emergence of new patterns of elastic anisotropy and rearrangement of precipitates in the matrix. [ABSTRACT FROM AUTHOR]

Low-frequency internal friction study has been conducted for a copper-manganese-rich alloy (Cu-60 at%, γ Mn). The study used a forced torsion pendulum working in low-frequency scans at constant temperatures, damping experiments ranging between 40 Hz and 10 −4 Hz. The dependence on temperature was extended from room temperature to the spinodal curve frontier at 923 K. Phenomenological stages in anelastic relaxations of (Cu, γ Mn) were evidenced. Three thermally activated relaxation peaks were assigned respectively to point defects (Zener relaxation), dislocation segments and dislocation walls. [ABSTRACT FROM AUTHOR]

The development of thermal stresses in solid oxide fuel cells (SOFCs), and thus their structural stability and reliability, depends directly on the thermal expansion and elastic moduli of the constituent materials. Therefore, it is important to study these properties of SOFC materials. In this study, the thermal expansion and elastic properties of common electrolyte materials, namely yttria stabilized zirconia (YSZ), scandia and ceria stabilized zirconia (SCSZ) and gadolinia doped ceria (GDC), are reported. High temperature X-ray diffraction (HT-XRD) was used to show that the cubic structure of YSZ and GDC samples is stable throughout the temperature range of 30–800 °C. However, SCSZ undergoes partial cubic to rhombohedral phase transition at around 300 °C but transferred completely back to cubic phase at around 500 °C upon heating. The coefficient of thermal expansion (CTE) of electrolyte materials was measured using thermo-mechanical analyzer (TMA). It was found that the CTE of SCSZ is almost identical to that of YSZ, but lower than that of GDC. Elastic properties (Young's and shear moduli) were determined in the 25–900 °C temperature range using resonant ultrasound spectroscopy (RUS). Young's and shear moduli of GDC decrease almost linearly with temperature, with an exception of the small anomaly between 100 °C and 300 °C. However, the variation of elastic moduli with temperature was found to be highly non-linear for YSZ and SCSZ with minimum values measured at around 600 °C. The deviation from the linear decrease of elastic moduli with increasing temperature is related to the relaxation of oxygen vacancy complexes and phase transformations. [ABSTRACT FROM AUTHOR]

Elastic and anelastic properties of ceramic samples of multiferroic perovskites with nominal compositions across the binary join PbZrTiO-PbFeTaO (PZT-PFT) have been assembled to create a binary phase diagram and to address the role of strain relaxation associated with their phase transitions. Structural relationships are similar to those observed previously for PbZrTiO-PbFeNbO (PZT-PFN), but the magnitude of the tetragonal shear strain associated with the ferroelectric order parameter appears to be much smaller. This leads to relaxor character for the development of ferroelectric properties in the end member PbFeTaO. As for PZT-PFN, there appear to be two discrete instabilities rather than simply a reorientation of the electric dipole in the transition sequence cubic-tetragonal-monoclinic, and the second transition has characteristics typical of an improper ferroelastic. At intermediate compositions, the ferroelastic microstructure has strain heterogeneities on a mesoscopic length scale and, probably, also on a microscopic scale. This results in a wide anelastic freezing interval for strain-related defects rather than the freezing of discrete twin walls that would occur in a conventional ferroelastic material. In PFT, however, the acoustic loss behaviour more nearly resembles that due to freezing of conventional ferroelastic twin walls. Precursor softening of the shear modulus in both PFT and PFN does not fit with a Vogel-Fulcher description, but in PFT there is a temperature interval where the softening conforms to a power law suggestive of the role of fluctuations of the order parameter with dispersion along one branch of the Brillouin zone. Magnetic ordering appears to be coupled only weakly with a volume strain and not with shear strain but, as with multiferroic PZT-PFN perovskites, takes place within crystals which have significant strain heterogeneities on different length scales. [ABSTRACT FROM AUTHOR]

Perovskite oxides find applications or are studied in many fields related to energy production, accumulation and saving. The most obvious application is oxygen or proton conductors in fuel cells (SOFCs), but the (anti)ferroelectric compositions may find application in high energy capacitors for energy storage, efficient electrocaloric cooling, and electromechanical energy harvesting. In SOFCs, the diffusion of O vacancies and other mobile ionic species, such as H+, are at the base of the functioning of the device, while in the other cases they constitute unwanted defects that reduce the performance and life-time of the device. Similarly, the (anti)ferroelectric phase transitions are a requisite for the use of some types of devices, but the accompanying domain walls can generate extended defects detrimental to the life of the material, and structural phase transformations should be avoided in SOFCs. All these phenomena can be studied by mechanical spectroscopy, the measurement of the complex elastic compliance as a function of temperature and frequency, which is the mechanical analogue of the dielectric susceptibility, but probes the elastic response and elastic dipoles instead of the dielectric response and electric dipoles. The two techniques can be combined to provide a comprehensive picture of the material properties. Examples are shown of the study of structural transitions and hopping and tunneling processes of O vacancies and H in the ion conductor BaCe1-xYxO3-x and in SrTiO3-x, and of the aging and fatigue effects found in PZT at compositions where the ferro- and antiferroelectric states coexist. [ABSTRACT FROM AUTHOR]

High precision stress relaxation tests (SRT) at four temperatures were conducted on T91 (9%Cr) steel after extended boiler service, and also after re-heat treatment. Relative differences in creep strength, measured over five decades in strain rate were dependent on test temperature. Using an established correlation between strain rate sensitivity and elongation at failure, intrinsic ductility values as a function of stress and test temperature were determined. The general trend of a minimum in ductility in terms of stress or strain rate was consistent with long term creep rupture data on T91, and with literature data on alloy steels. However, the precision and repeatability of the SRT analysis contrasted with the appreciable scatter and heat to heat variation in traditional testing. It is argued that the current creep strength evaluation based on the nearly constant state measurement from the SRT test is superior to the measurement of stress dependence of minimum creep rate in traditional creep rupture testing. The complexity of primary creep in laboratory testing, which may not be significant at operating stresses where loading strains may be fully recoverable (anelastic), does not apply to the SRT. Since very low strain rates are achieved in a one day test, the procedures for setting of design allowables and design analysis based on the SRT data should not be significantly different from current practice. This technique offers accelerated alloy development and optimisation for creep strength and also ductility, and hence resistance to notch sensitivity. [ABSTRACT FROM AUTHOR]

Perovskites in the ternary system PbTiO (PT)-PbZrO (PZ)-Pb(FeNb)O (PFN) have attracted close interest because they can display simultaneous ferroelectric, magnetic and ferroelastic properties. Those with the most sensitive response to external fields are likely to have compositions near the morphotropic phase boundary (MPB) which lies close to the binary join Pb(ZrTi)O (PZT)-PFN. In the present study, the strength and dynamics of strain coupling behaviour which accompanies the development of ferroelectricity and (anti)ferromagnetism in ceramic PZT-PFN samples have been investigated by resonant ultrasound spectroscopy. Elastic softening ahead of the cubic-tetragonal transition does not fit with models based on dispersion of the soft mode or relaxor characteristics but is attributed, instead, to coupling between acoustic modes and a central peak mode from correlated relaxations and/or microstructure dynamics. Softening of the shear modulus through the transition by up to ~50 % fits with the expected pattern for linear/quadratic strain/order parameter coupling at an improper ferroelastic transition and close to tricritical evolution for the order parameter. Superattenuation of acoustic resonances in a temperature interval of ~100 K below the transition point is indicative of mobile ferroelastic twin walls. By way of contrast, the first-order tetragonal-monoclinic transition involves only a small change in the shear modulus and is not accompanied by significant changes in acoustic dissipation. The dominant feature of the elastic and anelastic properties at low temperatures is a concave-up variation of the shear modulus and relatively high loss down to the lowest temperature, which appears to be the signature of materials with substantial local strain heterogeneity and a spectrum of strain relaxation times. No evidence of magnetoelastic coupling has been found, in spite of the samples displaying ferromagnetism below ~550 K and possible spin glass ordering below ~50 K. For the important multiferroic perovskite ceramics with compositions close to the MPB of ternary PT-PZ-PFN, there must be some focus in future on the role of strain heterogeneity. [ABSTRACT FROM AUTHOR]

The effect of glycerol on the solvent transportation behavior of mechanically constrained agarose gels was studied. The sample hydrogels were prepared using a water/glycerol mixed solvent containing various concentrations of glycerol. The compression load relaxed under the compression, and the volume of the agarose gels decreased synchronously with mechanical relaxation. This implied that the solvent is squeezed out due to mechanical constraints; the time constants for both the mechanical relaxation and the volume change are directly related to the friction between the solvent and the gel network structure. Both time constants increased with an increase in glycerol concentration. These results indicate that glycerol changes the gel network structure, and this is confirmed by other experimental evidence. The compression fracture stress and strain improved with an increase in glycerol content. Moreover, scanning electron microscope images showed that the mesh size of the gel network decreased with an increase in glycerol content. [ABSTRACT FROM AUTHOR]

A mechanical spectroscopy study of Cu-Zr-Al bulk metallic glasses, was performed with two types of equipment: a Kê-type inverted torsion pendulum and an acoustic elastometer, working in the frequency ranges of Hz and kHz, respectively, with a heating rate of 1 K/min. The analysis of the anelastic relaxation shows similar spectra for both types of equipment resulting in internal friction patterns that vary with temperature and are not reproducible at each thermal cycle. The normalized of the square of the frequency changes from the first to later measurement cycles. These results indicate that the specimens of Cu-Zr-Al alloys were changing by mechanical relaxation, owing to the motion of atoms or clusters in the glassy state and possible "defects" produced during the processing of alloys.

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy were obtained using the mechanical spectroscopy technique. The sample with heat treatment at 1170K for 30 minutes and water quenched with subsequent aging treatment at 670 K for 3 hours (TNZ + WQ + 670 K/3 h), was characterized through decay of free oscillations of the sample in the flexural vibration mode. The spectra of anelastic relaxation (internal friction and frequency) in the temperature range from 300 K to 625 K not revealed the presence of relaxation process. As shown in the literature, the hcp structure usually does not exhibit any relaxation due to the symmetry of the sites in the crystalline lattice, but if there is some relaxation, this only occurs in special cases such as low concentration of zirconium or saturation of the stoichiometric ratio of oxygen for zirconium. Dynamical elastic modulus obtained for TNZ + WQ + 670 K/3 h alloy was 87 GPa at room temperature, which is higher than the value for Ti-13Nb-13Zr alloy (64 GPa) of the literature. This increment may be related to the change of the proportion of α and β phases. Besides that, the presence of precipitates in the alloy after aging treatment hardens the material and reduces its ductility.

Hyperbranched polymers are typically treelike macromolecules with a very disordered structure. Here we construct hyperbranched polymers based on the degree distribution of the small-world networks. This algorithm allows us to study a transition from monodisperse linear chains to structurally-disordered dendritic polymers by varying the parameter p ( 0 ≤ p ≤ 1 ), which measures the randomness and the degree of branching of the network. Employing the framework of generalized Gaussian structures, we determine for the obtained structures the relaxation spectra, which are exemplified on the mechanical relaxation moduli (storage and loss moduli). We monitor these physical quantities for networks of different sizes and for various values of the parameter p . In the intermediate frequency domain, we encounter macroscopically distinguishable behaviours. [ABSTRACT FROM AUTHOR]

In the present work, specimens prepared from coarse grained low carbon steel with different prestrains were baked and then, their bake hardening (BH) property and internal friction were determined. TEM was used to characterize the dislocation structure in BH treated samples. The measurements of internal friction in prestrained samples and baked samples were carried out using a multifunctional internal friction apparatus. The results indicate that, in coarse grained low carbon steel, the bake hardening properties (BH values) were negative, which were increased by increasing the prestrain from 2 to 5%, and then were decreased by increasing the prestrain from 5 to 10%. In the specimen with prestrain 5%, the BH value reached the maximum value and the height of Snoek-Köster peak was observed to be the maximum alike. With increasing the prestrain, both of the BH value and Snoek-Köster peak heights are similarly varied. It is concluded that Snoek-Köster and dislocation-enhanced Snoek peaks, caused by the interactions between interstitial solute carbon atoms and dislocations, can be used in further development of the bake hardening steels. [ABSTRACT FROM AUTHOR]