Internal Friction Peak Research Articles

Mechanical Spectra in Various Weld Area of an Extruded Al-12.7Si-0.7Mg Alloy with MIG Welding

Mechanical spectra of ascending and descending temperature in the various areas of weld for an Al-12.7Si-0.7Mg alloy with an extruded states were measured under different frequencies. It is found that there is an obvious internal friction peak near∼200°C in the ascending temperature spectrum and the value of internal friction goes up started at∼300°C resulting in the ∼200°C peak lowered and appeared an peak nearly ∼270°C in the descending temperature spectrum for the matrix and heat affected zone; while there is not any peak in the weld zone, Discussion to the results was made.

The Shear Strength of the Nature Loess Joint: A Case Study in Shaanxi Province

Abstract Shear strength of the loess joint has significant influence on the stability of loess engineering with joints. “Joint” is the weak structural plane of loess, and its shear strength determines the stability of loess. In this study, a series of loess joint samples was collected from Binxian County, Liquan County, and Zichang County in Shaanxi Province. The shear strength of the loess joint was determined by means of the direct shear test. The influence of the water content on the shear strength parameters of the loess joint was investigated by means of tests. The results showed that initially the internal friction angle varied slightly with the water content but decreased very quickly as the water content surpassed the threshold value of 14 %. The relationship between shear strength and water content can be expressed as an exponential function. This study devised a new empirical formula that determines the peak internal friction angle by observing the effects of dry density, water content, shear strength, and joint surface morphology.

Effect of deformation and aging on internal friction of AZ31 magnesium alloy

The effect of aging and deformation on the microstructure and internal friction of rolled AZ31 magnesium alloy was investigated via optical micrograph (OM), transmission electron microscopy (TEM), and internal friction tests. The results revealed that the rolled sample underwent recrystallization after an aging treatment at 623 K, the average grain diameter of the sample aged for 0.5 h was 8.5 μm and the average grain size increased gradually with increasing aging time, this samples were used for tensile deformation tests. The results revealed that the density of dislocations and twin crystals increased with increasing deformation. In addition, an intragranular cellular substructure formed at a deformation level of 5%, and the deformation cells were further refined when the deformation was increased to 15%. Two internal friction peaks were observed for each of the rolled samples, aged at 623 K samples, and deformed samples, denoted P1 and P2. P1 peaks was around 450 K, corresponding to an activation energy of 116–120 kJ mol−1, which was attributed to grain boundary sliding. P2 peaks was around 525 K, corresponding to an activation energy of 132–139 kJ mol−1, which was attributed to internal friction correlated with precipitation of a secondary phase.

Snoek-type relaxation caused by interstitial atoms in sintered <i>β</i>-type Ti-Nb alloy

<sec> The <i>β</i>-type Ti-Nb alloys are potential shape memory and superelasticity materials. The interstitial atoms in the alloys have important effect on their physical and mechanical properties. For the interstitial atoms, the internal friction technique can be used to detect their distributions and status in the alloys. The influences of chemical compositions and heat treatments on the microstructures of the containing-oxygen Ti-Nb alloys are given, and a clear understanding and the relaxational mechanism of the internal friction peak correlated with oxygen are also clearly discussed by investigating the internal friction behavior of the alloys and the detecting their microstructures. </sec><sec> The Ti-Nb alloys with different Nb content values are prepared by powder metallurgy. The internal friction behaviors of Ti-Nb alloys with different Nb content values and heat treatments are investigated by using dynamic mechanical analysis (dynamic mechanical analyzer, DMA) Q800 from TA Instruments in single cantilever mode under different testing parameters and conditions from room temperature to 350 ℃. The X-ray diffraction experiments are also carried out in order to detect the differences among the microstructures of the specimens with different heat treatments for the Ti-35.4Nb alloy. It is shown that relaxational internal friction peaks are found on the internal friction temperature dependent curves of the sintered and water-quenched alloys. The internal friction peak is correlated with Nb content. The peak does not appear in the sintered Ti-Nb alloys with low Nb content. The maximum of the internal friction peak appears in the quenched alloy with about 35% Nb. The internal friction peak height increases monotonically with Nb content increasing in the present testing composition range for the sintered alloys. The relaxation parameters are the activation energy <i>H<sub>wq</sub></i> = (1.67 ± 0.1) eV and the preexponential factor <i>τ</i><sub>o<i>wq</i></sub> = 1.1 × 10<sup>－17 ± 1</sup> s for the quenched Ti-35.4Nb alloy . In addition, the peak height also depends on heat treatment. The water-quenched Ti-35.4Nb alloy has much higher internal friction peak than the as-sintered alloy with identical compositions. The internal friction peak height is also correlated with the quenching temperature. It is found that the peak is linked to the <i>β</i> phase of Ti-Nb alloys and that the peak height is determined by the stability and amount of the <i>β</i> phase from their microstructures. When the stability of the <i>β</i> phase decreases, the peak height increases, and the increase in the amount of <i>β</i> phase results in the increase of the peak height. The <i>β</i> phase in the quenched Ti-35.4Nb specimen is metastable <i>β</i> phase (<i>β</i><sub>M</sub>), which can be transformed into the stable <i>α</i> and <i>β</i><sub>S</sub> by ageing. The <i>β</i> phase in as-sintered specimen is the stable <i>β</i> phase (<i>β</i><sub>S</sub>). The modifications of microstructures of the specimens with different heat treatments result in the difference in peak height between the water-quenched and as-sintered Ti-35.4Nb specimens. That the peak height presents a maximum in the vicinity of 35 wt.% Nb for the quenched alloys results from the variation of the stability and amount of <i>β</i><sub>M</sub> with Nb content. That the height of the peak increases monotonically with Nb content increasing in as-sintered alloys is attributed to the increase of the amount of <i>β</i><sub>S</sub>. It is suggested that the internal friction peak is related to oxygen jump in lattice or the interaction between the oxygen-substitute atoms in <i>β</i><sub>M</sub> phase for the water-quenched alloys and those in <i>β</i><sub>S</sub> phase for the as-sintered alloys.</sec>

Internal friction characteristics of compacted billet of metal powder in sintering process

Sintering plays a decisive role to determine final product quality in the powder metallurgy process. Understanding the law of structure and defects as well as determining the initial sintering temperature and crystallization temperature will prove clear information to determine favorable sintering technology for the powder compacted billet. In this paper, the internal friction characteristics in the sintering process for powder compact billet, pure Al, Mg, Cu, Fe are systematically studied in terms of internal friction technology. Two internal friction peaks, named heating peak and cooling peak are respectively found in the first run. The cooling peak is a stable relaxational internal friction peak. It is concluded that the peak is associated with the viscous sliding of grain boundary based on the activation energy and peak temperature location. The heating peak is an unstable internal friction peak corresponding to the decline of resistance and relative dynamic modulus, the peak temperature being considered as an initial sintering temperature due to the great change of material performance. Furthermore, the heating peak is dependent on powder particle size and compressing pressure, which increases with the decrease of particle size or compressing pressure. The dependence can be understood according to the increase of weak bonding interface and activated slipping distance between powder particles. The internal friction of the powder compacted billet in the heating process gradually increases with the temperature increasing, which is mainly due to the micro sliding of the weak bonding interface, but the enhancing trend stops and internal friction rapidly declines when the temperature approaches to the peak location due to the transition of weak bonding interface to grain boundary, as a result, leading to the formation of the heating peak. The occurrence of therising temperature peak indicates the formation of grain boundary between powder particles in the sintering process of powder compacted billet. Correspondingly, the peak temperature can be used as a crystallization temperature.

The Contribution of Mechanical Spectroscopy to Understanding Grain Boundary Sliding

This review paper shows that grain boundary sliding (GBS) is a general phenomenon occurring in all classes of inorganic materials: ceramics, metals and composite materials. The occurrence of relaxations attributed to GBS is also quite general and therefore the mechanical spectroscopy constitutes a sensitive and universal technique to study such phenomenon. GBS is widely observed in ceramics. It can be due to the presence of an amorphous layer between the grains as in zirconia or to dislocations, as in alumina. In each case, a high temperature GBS peak has been identified. In metals, GBS is observed in some deformed materials but the correlation of such phenomenon with internal friction peaks has been controversial. In 1941, C. Zener describes a geometrical model of GBS that could give rise to a relaxation mechanism. In 1947, Ke observed a large relaxation peak in polycrystalline aluminum. This peak being absent in single crystals, the relaxation was attributed to GBS. Today, the Zener model can still be used in most cases for relaxations occurring in the grain boundaries. Instead, according to the grain boundary type, the material or the temperature, either dislocations or the gliding of a disordered layer produce the grain boundary relaxations.

Dynamic behavior of BiVO4 material under mechanical studies

The mechanical relaxation technique is applied to investigate the fundamental dynamic behavior of BiVO4 material. A prominent internal friction peak is observed around 430 K at 1 Hz, which is actually composed of three sub-peaks (P1, P2 and P3 from low to high temperature). And the associated modulus anomalies can also be found in any of the samples. The peak P1 with activation energy E1 ∼ 3.20 eV is probably related to the stress-induced unequal positions of Bi3+ ions; while the main P2 peak with E2 = 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 P3 peak is resulted from the ferroelastic–paraelastic phase transition, accompanied by a minimum modulus value. Based on the relaxation process and crystalline structure of BiVO4, 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 BiVO4.

Damping Capacity of Ni–Mn–Ga–Gd High-Temperature Shape Memory Thin Film

The damping capacity of Ni–Mn–Ga–Gd films annealed for different durations has been investigated by dynamic mechanical analysis (DMA) measurement. The DMA results show that the internal friction peaks are absent in the IF curves, due to very low transformation rate and low transformation strain in the films. With the increase of annealing time, the value of tan delta in martensite first increases then decreases due to the combined effect of grain size and martensite structure change. Owing to the occurrence of high-temperature creep behavior, an abrupt increase of tan delta takes place over 400 °C in the film annealed for 10 h. The film annealed for 5 h shows good thermal stability of phase transformation and keeps a high damping capacity in martensite after ten times of repeated DMA measurement. In terms of the high damping capacity (tan δ = 0.046) in martensite, high transformation temperature (As = 292 °C), and good thermal stability, the film annealed for 5 h can be used as a damping material for MEMS devices in elevated temperature.

High Temperature Internal Friction Relaxations in Cold-Rolled Titanium

The high temperature relaxation in cold-rolled Ti (CR-Ti) and commercial pure Ti (CP-Ti) has been investigated using internal friction apparatus operating in forced oscillations from room temperature to 650°C. It is shown that there is an internal friction peak at around 510°C for the CR-Ti and there is no 510°C internal friction peak in the CP-Ti. The internal friction peak shows typical features of phase transformation in the CR-Ti. It is tentatively suggested that this peak is due to the ordering of disordered lattices resulted from cold-rolling. The high temperature background damping (HTBD) in the CP-Ti is much lower than that in the CR-Ti. It is concluded that the HTBD is related to the microstructure observed inside the grains and does not dependent on grain size.

Effect of freeze-thaw cycles on shear strength of saline soil

Freeze-thaw (F-T) cycle is an important external factor affecting the mechanical properties of saline soils in cold regions. In this study, the effects of F-T cycles (0, 1, 5, 10, 30, 60 and 120) and salt contents (0, 0.5, 1.0, 2.0 and 3.0%) on the shear properties of saline soil in western Jilin Province of northeastern China, including stress-strain behavior, peak undrained shear strength (τu), resilient modulus (ER), cohesion (cu) and internal friction angle (φu), were investigated by conducting unconsolidated-undrained (UU) triaxial compression tests. The results demonstrated that, when the salt content was the same, the τu, ER and cu basically showed a decreasing-steady-decreasing trend with increasing F-T cycles, and the dynamic evolutions of soil microstructure were mainly responsible for such variations. The Gouy-Chapman diffuse double layer together with matrix suction theories were employed to analyze the mechanism of the effects of salt content on the cu and φu at different freeze-thaw cycles; the thicker diffuse double layer induced by higher sodium ion contents and the decreasing matrix suction were deemed as the main reasons that led the cu to continuous reduction; the φu was believed to be successively affected by the enhanced lubrication effect and the salt crystallization process, and there was a threshold salt content (2.0%) which was influenced by the number of F-T cycles. Finally, by categorizing the different experimental combinations into relative undamaged, single-factor damaged and two-factor damaged states concerning the τu, an empirical mathematical equation of high reliability (R2 > 0.985) was established to describe the combining effects of F-T and salinity on the changes in τu.

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

We evaluate two methods to improve the background internal friction of the Double Paddle Oscillator (DPO), which has a nominal low temperature value of Q-1 ≈ 2×10-8. We find that annealing the DPO in vacuum at 300°C for 3 hours systematically reduced Q-1 at all temperatures and revealed a 100K internal friction peak by permanently removing it. We also find a striking decrease of low temperature Q-1 as the DPO geometry is altered through extended etching. This decrease is evaluated via Finite Element Method modeling in terms of mode mixing and attachment loss.

High-temperature internal friction and dynamic moduli in copper

New measurements of dynamic shear and Young's moduli and their associated internal frictions were made with torsional and flexural forced-oscillation methods, respectively, on three polycrystalline specimens of pure copper. The tests spanned the 1–1000 s range of oscillation periods, at temperatures ranging from those of annealing close to the melting point (1050 °C) down to room temperature. A broad internal friction peak, found at temperatures around 700 °C (at 1 Hz) for samples annealed at 1050 °C, is superimposed on a monotonic relaxation background. Non-linear viscoelastic behaviour is observed above strains around 5×10−6. The period- and temperature-dependence of both shear modulus and internal friction is adequately captured by an extended “background plus peak” Burgers model for viscoelastic rheology. Activation energies are found to be around 200 kJ mol−1 for both the high-temperature peak and monotonic damping background, consistent with common diffusional control of both the dissipation background and superimposed peak, plausibly involving stress-induced migration of dislocations. Complementary torsional microcreep tests at selected temperatures reveal that most of the inelastic strain is anelastic (viscous) for loading durations less (greater) than 1000 s. Such linear viscous deformation, observed at low stress in coarse-grained polycrystalline copper, involves much higher strain rates than expected from published rheology, plausibly attributable to the Harper-Dorn mechanism.

Study on the performance and strain aging behavior of solid-solution state low-carbon steel

Herein, the strain aging behavior of low-carbon steel subjected to heating at 850 °C followed by a 5-min holding time and water cooling cycle was studied. Various aging periods were tested using a 2% pre-deformation and baking step at 170 °C. The aging performance was characterized by tensile testing. Furthermore, the organizational structure variation was analyzed with transmission electron microscopy (TEM) and by measuring the internal friction of the low-carbon steel. Finally, age hardening mechanisms were discussed. The test results indicated that when the aging period ranged between 5 and 100 min, both the yield strength and tensile strength declined rapidly and the bake-hardening (BH) value decreased from 104.6 MPa to −13.2 MPa. In addition, morphological differences were observed: fine carbides gradually formed in the microstructure and continued to coarsen over time. Furthermore, the height of the Snoek peak decreased rapidly and was accompanied by the appearance of 3 internal friction peaks, denoted P1, P2 and P3. When the aging period exceeded 100 min, the yield strength, tensile strength and BH value varied only slightly. Moreover, the number of carbides in the microstructure decreased, and their morphology coarsened. Furthermore, the height of the Snoek peak decreased slowly and was accompanied by the gradual disappearance of 2 of the internal friction peaks, P1 and P2.

Static shear fracture influenced by historic stresses path and crack geometries in brittle solids

Historic stress path strongly influences the variations of shear fracture, and crack geometry has a great significance for the mechanical properties of brittle solids (e.g., rock, ceramic, glass, and concrete, rock is the major object in this study) in static compression. In this study, a new analytic method is proposed to predict the effect of historic stress path on static shear properties under different crack angles. An improved stress intensity factor containing crack angle effect is derived by use of the wing crack model. Drawing a relation between crack growth and strain obtained from the correlation of micro and macro damages into this improved stress intensity factor, a crack growth- based stress- strain relation considering crack angle effect is given. Coupling the crack growth-based stress–strain relation, the Mohr-Coulomb failure criterion and the Mohr-Coulomb strain-softening model, an analytic solution describing the variation of shear properties along with the increasing strain at the post- peak area of stress- strain curve is proposed. And then drawing the time-dependent strain caused by subcritical crack growth considering the effect of stress path into this analytic solution, the effects of stress path on variations of shear properties over time caused by subcritical crack growth under different crack angles are studied in static compression. Furthermore, the effects of crack angle and crack size on compressive strength, static failure time, peak internal friction angle, and peak shear strength are analyzed. The stress-stepping evolutions of cohesion, internal friction angle and shear strength under different crack angles are also discussed. Rationality of the analytic method is verified by comparing with the published experimental results. The study results provide a possible analytic method to explain the effects of external loadings and internal crack geometries on unmeasured shear properties of brittle rocks in static compression.

The in-situ mechanical spectroscopy and electric resistance study of WE43 magnesium alloy during aging

The WE43 magnesium alloy was studied by mechanical spectroscopy and electric resistance measurements in-situ during aging at 210 and 250 °C. Isothermal aging up to 196 h at these temperatures promotes only minor increase in the Young's modulus (0.4–2.5%). The mechanical spectroscopy results correlate with the resistance measurements and are discussed with respect to the precipitation sequence in this material. Furthermore, during heating up to 450 °C, the mechanical spectroscopy measurements identified an internal friction peak at ∼350 °C which is brought about by the relaxation at interfaces between the semicoherent and incoherent precipitates and the matrix. Height of the peak is dependent on the material thermal history.

Effect of roughness on interface shear behavior of sand with steel and concrete surface

The present study evaluates the interface shear strength between sand and different construction materials, namely steel and concrete, using direct shear test apparatus. The influence of surface roughness, mean size of sand particles, relative density of sand and size of the direct shear box on the interface shear behavior of sand with steel and concrete has been investigated. Test results show that the surface roughness of the construction materials significantly influences the interface shear strength. The peak and residual interface friction angles increase rapidly up to a particular value of surface roughness (critical surface roughness), beyond which the effect becomes negligible. At critical surface roughness, the peak and residual friction angles of the interfaces are 85-92% of the peak and residual internal friction angles of the sand. The particle size of sand (for morphologically identical sands) significantly influences the value of critical surface roughness. For the different roughness considered in the present study, both the peak and residual interaction coefficients lie in the range of 0.3-1. Moreover, the peak and residual interaction coefficients for all the interfaces considered are nearly identical, irrespective of the size of the direct shear box. The constitutive modeling of different interfaces followed the experimental investigation and it successfully predicted the pre-peak, peak and post peak interface shear response with reasonable accuracy. Moreover, the predicted stress-displacement relationship of different interfaces is in good agreement with the experimental results. The findings of the present study may also be applicable to other non-yielding interfaces having a similar range of roughness and sand properties.

On the Effect of Hydrogen on the Low-Temperature Elastic and Anelastic Properties of Ni-Ti-Based Alloys.

Linear and non-linear internal friction and the effective Young’s modulus of a Ni50.8Ti49.2 alloy have been studied after different heat treatments, affecting hydrogen content, over wide ranges of temperatures (13–300 K) and strain amplitudes (10−7–10−4) at frequencies near 90 kHz. It has been shown that the contamination of the alloy by hydrogen strongly affects the internal friction and Young’s modulus of the martensitic phase. Presence of hydrogen gives rise to a non-relaxation internal friction maximum due to a competition of two different temperature-dependent processes. The temperature position and height of the maximum depend strongly on the hydrogen content. We conclude that many of the internal friction peaks, reported earlier for differently treated Ni-Ti-based alloys, had the same origin as the present maximum.

Internal Friction Peaks in Mg-0.6% Zr and Mg-Ni High Damping Magnesium Alloys

Abstract A broad relaxation peak, which contributes to the high damping capacity around room temperature, has been obtained in all high damping magnesium alloys. This peak is a dislocation-related relaxation peak, which is probably caused by the interaction between dislocation and point defects (vacancy and solid atoms) during the dislocation movement on the basal plane activated by heat. The grain boundary relaxation peak also has been observed in both Mg-Ni and Mg-0.6%Zr high damping alloys. However, it is necessary to point out that microstructure can affect the gain boundary relaxation. With Ni content increasing, the grain is refined and the grain boundary internal friction peak shifts to lower temperature. Compared with Mg-0.6%Zr alloy, the grain boundary internal friction peak shifts to higher temperature after adding a little yttrium (Y).

Damping Characteristics of Inherent and Intrinsic Internal Friction of Cu-Zn-Al Shape Memory Alloys

Damping properties of the inherent and intrinsic internal friction peaks (IFPT + IFI) of Cu-xZn-11Al (x = 7.0, 7.5, 8.0, 8.5, and 9.0 wt. %) shape memory alloys (SMAs) were investigated by using dynamic mechanical analysis. The Cu-7.5Zn-11Al, Cu-8.0Zn-11Al, and Cu-8.5Zn-11Al SMAs with ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peaks exhibit higher damping capacity than the Cu-7.0Zn-11Al SMA with a ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peak, because the γ 3 ′ martensite phase possesses a 2H type structure with abundant movable twin boundaries, while the β 3 ′ phase possesses an 18R structure with stacking faults. The Cu-9.0Zn-11Al SMA also possesses a ( IF PT + IF I ) β 3 ( L 2 1 ) → γ 3 ′ ( 2 H ) peak but exhibits low damping capacity because the formation of γ phase precipitates inhibits martensitic transformation. The Cu-8.0Zn-11Al SMA was found to be a promising candidate for practical high-damping applications because of its high (IFPT + IFI) peak with tan δ > 0.05 around room temperature.

Mechanical and impedance spectroscopy studies on the fast oxide ion conductor Na0.54Bi0.5Ti0.94Mg0.06O2.94

The perovskite structure Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample was prepared by the conventional solid state reaction. The electrical properties and the mechanism of oxide ion diffusion in the Na0.5Bi0.5Ti0.94Mg0.06O2.94 compounds were investigated with the method of AC impedance spectroscopy and internal friction spectroscopy. The bulk oxide ionic conductivity of the Na0.5Bi0.5Ti0.94Mg0.06O2.94 compound at 673 K is about 3.3 × 10−4 S/cm, 1.2 times higher than that of the Na0.5Bi0.5TiO3 sample at the same temperature. A prominent relaxation internal friction peak was observed and the relaxation parameters is E = 0.92 eV, \({\tau _0}=\) 1.6 × 10−13 s. Compared with the Na0.5Bi0.5TiO3 compound, the factors of the higher oxygen vacancy content and better oxygen vacancy mobility are responsible for the oxide ionic conductivity improvement of the Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample. By the investigation of dielectric frequency spectroscopy in the temperature range from 473 to about 720 K, the Arrhenius plot of the Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample was divided into two parts by an inflection point (540 K), which corresponds to the transition between the rhombohedral anti-ferroelectric phases to the tetragonal para-electric phase in the Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample. The activation energies of oxide ionic diffusion in the rhombohedral and tetragonal structure Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample are about 0.94 and 0.62 eV, respectively. The oxygen vacancy mobility of the tetragonal structure Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample is superior to that of the rhombohedral structure Na0.5Bi0.5Ti0.94Mg0.06O2.94 sample, which is meaningful to improve the oxide ionic conductivity of the Na0.5Bi0.5TiO3-based materials.