Internal Friction Tests Research Articles

Severe elastic modulus shift of deformed CoNiCrMo alloy under relative low-temperature exposure

Elastic modulus (EM) is usually considered to be a relatively stable physical quantity; even phase transformation only results in a little change in EM, while this work demonstrates that it is not so straightforward. Internal friction tests reveal that the EM of a 60% cold-worked CoCrMoNi (MP35N) alloy increases by over 17% after exposed at $100\text{--}700{\phantom{\rule{0.28em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, with no change in phase or grains. Analysis of nanoscale structure of the alloy by high-resolution transmission electron microscope shows that high-density nanosized unstable stacking faults and incoherent nanotwins are formed in the cold-worked MP35N alloy, which severely weaken the bonding between the atom planes and decrease the EM. During the exposure process, the unstable fault interfaces and incoherent nanotwins transform into coherent nanotwins or annihilate to decrease the system energy, which repairs the crystal structure and increases the interatomic bonding force and the EM. The segregation of solute atoms at the twin boundaries and stacking faults also contribute a little to the increase in EM. These mechanisms should also suit for the faced centered cubic (FCC)-structured alloys with low-level stacking-fault energy.

Sensitivity to dynamic strain aging of carbon–manganese steels measured by ultrasonic fatigue testing

AbstractSome carbon–manganese (C–Mn) structural steels are known to be sensitive to aging under deformation between 100 and 350°C, phenomenon called dynamic strain aging (DSA). This paper is aimed at studying the DSA sensitivity through the thermal response of C–Mn steels during ultrasonic fatigue tests. For this purpose, self‐heating tests are conducted on two C–Mn steel grades, extensively used in the nuclear industry. Tests are monitored by infrared thermography. DSA effect clearly appears on self‐heating curves by a singular temperature rise. The DSA occurrence is correlated with results from internal friction tests, in particular with the presence of the cold work peak. The temperature of 100°C related to the start of the thermally activated DSA phenomenon is retrieved by self‐heating tests. Based on a further intrinsic dissipation computation, DSA distinctly differs from the classical dislocation glide mechanism. Furthermore, a stress threshold of irreversibility is shown to emerge.

Hydrogen Diffusion and Hydrogen Embrittlement Failure Behavior of AH36 Marine Steel Subjected to High Heat Input Welding

AH36 marine steel processed through high heat‐input welding is subjected to microstructural characterization, hydrogen permeation test, internal friction test, and slow strain rate tensile test to reveal its hydrogen diffusion and hydrogen embrittlement failure behaviors. Compared with the base metal, the coarse‐grained heat‐affected zone (CGHAZ) exhibits a significantly coarsened microstructure and decreased hydrogen trap density, resulting in a high hydrogen diffusion coefficient and short hydrogen permeation time. The presence of hydrogen yields a hydrogen‐induced Snoek internal friction peak and promotes the movement of the Snoek–Kê–Köster internal friction peak to the low‐temperature region. In addition, B and Kê peaks, which are not found in the base metal, appear in the CGHAZ. With increasing hydrogen content, the plastic loss and brittle fracture of the AH36 marine steel become increasingly significant, and the hydrogen embrittlement sensitivity of the heat‐affected zone increases compared with that of the base metal. The discontinuous yield phenomenon gradually disappears under slow strain rate tension owing to the weak pinning effect of the Cottrell atmosphere on mobile dislocations.

Soil Characteristics of Padma Multipurpose Bridge

Padma Multipurpose Bridge is situated on a section of the Padma river where the soil condition is highly heterogeneous and intermixed with different soil layers, for which pile design was the critical part. This paper describes the soil properties and ground profiling of the Padma Multipurpose Bridge. Different types of field and laboratory tests were carried out to obtain accurate soil parameters and ground profiles along the whole alignment of the bridge. Standard Penetration Tests, Cone Penetration Tests, and grain size analyses were conducted for the soil classifications and ground profiling. Flat Plate Dilatometer Tests, High Pressure Dilatometer Tests, and Self-Boring Internal Friction Tests were performed to obtain the stiffness of the different soil layers and shear strength parameters in field conditions. Cross-hole and Seismic Tomography Geophysical tests were executed to obtain seismic waves and dynamic shear modulus of each soil layer. Gel Push Soil Sampling technique was used to collect undisturbed samples of sandy soils to get accurate stress–strength-dilatancy characteristics of sandy soils through different laboratory tests. The soil was classified into three Units and some sub-units based on grain size and SPT-N value. Soil parameters were finalized based on both laboratory and field test results. The pile design was possible for accurate measurement of soil parameters and ground profiling along the alignment of the bridge.

Mechanical Properties and Corrosion Resistance of TiAl6V4 Alloy Produced with SLM Technique and Used for Customized Mesh in Bone Augmentations

Bone augmentation procedures represent a real clinical challenge. One option is the use of titanium meshes. Additive manufacturing techniques can provide custom-made devices in titanium alloy. The purpose of this study was to investigate the material used, which can influence the outcomes of the bone augmentation procedure. Specific test samples were obtained from two different manufacturers with two different shapes: surfaces without perforations and with calibrated perforations. Three-point bending tests were run as well as internal friction tests to verify the Young’s modulus. Test samples were placed in two different buffered solutions and analyzed with optical microscopy. A further SEM analysis was done to observe any microstructural modification. Three-point flexural tests were conducted on 12 specimens. Initial bending was observed at lower applied stresses for the perforated samples (503 MPa) compared to non-perforated ones (900 MPa); the ultimate flexural strength was registered at 513 MPa and 1145 MPa for perforated and non-perforated samples, respectively. Both microscopic analyses (optical and SEM) showed no significant alterations. Conclusions: A normal masticatory load cannot modify the device. Chemical action in the case of exposure does not create macroscopic and microscopic alterations of the surface.

Investigation of Ga doping for non-stoichiometric sodium bismuth titanate ceramics

The electrical properties of Ga3+ doping Na0.5Bi0.5TiO3-based oxygen ionic conductors were studied. The Na0.52Bi0.47Ti1−xGaxO3−δ (x = 0, 0.01, 0.015, 0.02) samples were fabricated by the means of traditional solid-state reaction. The results of AC impedance measurements showed that the bulk conductivity of Na0.52Bi0.47Ti1−xGaxO3−δ samples decreased monotonously with the increase of Ga3+ doping concentration. At 673 K, the bulk conductivity of the Na0.52Bi0.47Ti0.98Ga0.02O3−δ sample is 7.19 × 10–4 S/cm, which is lower than that of the Na0.52Bi0.47TiO3−δ sample under the identical test temperature. The highest total conductivity emerged in the Na0.52Bi0.47Ti0.99Ga0.01O3−δ (x = 0.01) sample with 1.387 × 10–4 S/cm at 623 K, which demonstrated that the slight Ga3+ doping supported the enhancement of the total conductivity. A relaxation peak was observed in Na0.52Bi0.47Ti1−x GaxO3−δ compounds. As the Ga3+ ions were introduced into the Na0.52Bi0.47TiO3−δ compound, there was an increasing trend of the relaxation activation energy educed by the internal friction test. In addition, the oxygen relaxation height decreased with Ga3+ doping, which suggested that the introduction of Ga3+ ions resulted in the decrease of mobile oxygen vacancy.

Repair of SiC coating on carbon/carbon composites by laser cladding technique

A slurry-based laser cladding technique was used to repair the SiC coated carbon/carbon composites. The oxidation resistance of repaired samples at 1773 K for 10 h was investigated. Samples were characterized by X-ray diffraction pattern, scanning electron microscopy and confocal microscope; its interface characteristics were studied with scratch, thermal shock and internal friction tests. The results show that there is no obvious interface between the newly-formed coating and the original coating, and the newly-formed coating has a much smoother surface. With optimizing parameters, the new coating of 180 μm thickness possesses refined grains, flat surface, dense microstructure and good thermal stability. The number of internal defects in the samples repaired by laser cladding drops, compared with the damaged/undamaged samples. The weight loss of repaired samples decreases by 64.8% in comparison with the damaged ones, and it is almost the same with the undamaged samples according to a test of anti-oxidation behaviors. This is attributed to the enhanced oxidation resistance of dense newly-formed coating, which makes carbon/carbon composites well protected.

In situ X-ray diffraction and the internal friction study of the binary yellow 18-carat gold alloy

Phase transitions in AuCu alloy are investigated using in situ temperature XRD and mechanical spectroscopy. The measurements are carried out from room temperature up to 973 K starting from the ordered phase AuCuI. Using a temperature ramp rate of 1 K/min, the following phase transition sequence was recorded on heating: AuCuI - > AuCuI + AuCuII- > AuCuI + AuCuII + A1 - > AuCuII + A1 - > A1. The mechanical (elastic and anelastic) properties are determined by this phase transition sequence. The mechanical spectroscopy, using a forced torsion pendulum, shows a peak due to antiphase boundary movement in the orthorhombic phase AuCuII according to the temperature dependent internal friction tests. The isothermal frequency measurements show several thermally activated peaks in the phase transitions intervals.

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.

Application of Impulse Excitation Technique to Investigation of Concrete Damping and Its Changes at Early Ages

This paper considers experimental results of internal friction test of concrete blocks using impulse excitation technique. Three concrete blocks (120X80X40mm) have been tested at the ages of 7, 14, 28, 56 and 91 days with the Resonant Frequency Damping Analyzer (RFDA) Basic. Mix proportions of the material were selected according to the ACI method. The material of specimens is assumed to be isotropic, and it was proved that this assumption could be applied in practice. It was shown that damping of concrete reduces with time. The most significant changes occur at very early ages, before 14 days. After that this process slows down, however, it continues with lower rate.

Effect of heat treatment on ordering and functional properties of the Fe–19Ga alloy

Special attention in this work is paid to the study of the influence of cooling rates on microstructure and functional properties, magnetostrictive behavior and internal friction of polycrystalline Fe – 19 at.% Ga samples. After annealing at 900 and 1000°C for 40min, samples were water quenched (wq) or furnace cooled (fc). High resolution X-ray diffraction (XRD) exhibits the peak shoulder around 2θ=81° for the sample furnace-cooled from 900°C (fc900°C), which is ascribed to the formation of D03 ordered precipitates. Only a solid solution phase with an A2 structure is recorded in the samples water-quenched from 900°C (wq900°C) and 1000°C (wq1000°C). Annealing during 2h at 350°C of the water quenched from 900°C specimen (wqann) also leads to the formation of a shoulder around 2θ=81° due to the appearance of the D03 phase. Magnetic domain structure studied by magnetic force microscopy (MFM) reveals that the wq900°C sample exhibits a regularly aligned stripe domain structure, while irregular maze-like domain structure is observed in both the fc900°C, and wqann samples. Magnetostriction of the samples is measured as a function of an externally applied magnetic field. It was found that the wq1000°C sample comprises the highest magnetostriction, while the fc900°C and wqann samples have the lowest magnetostriction against the applied magnetic field; consequently, the damping capacity in wq samples is also the highest. Amplitude-, frequency- and temperature dependent internal friction tests of wq, fc, and annealed samples were carried out. Thermal history dependence of anelastic effects is analyzed on the basis of the A2→D03 transformation. Physical mechanisms for observed anelastic effects are discussed. Dilatometry and calorimetry studies are in agreement with the A2 (bcc)→D03 (bcc-based) ordering phenomenon at 200–300°C in as quenched samples.

Role of the β-phase in grain boundary and dislocation anelasticity in binary Al–Mg alloys

Abstract Temperature- and amplitude dependent internal friction (IF) of cold-worked, annealed and quenched Al–Mg alloys with 0.3–12 wt.%Mg is studied in the range from room temperature to 600 °C. Two thermally activated relaxation peaks, named P1 and P2 in the order of increasing temperature, are recorded. The first one (P1), with activation parameters H ≈ 1.1 eV, τ 0 ≈ 10 −13 s, relaxation strength Δ ≈ 0.008, and broadening parameter β τ ≈ 2 (for 1 Hz), is recorded only in Al–Mg alloys with 8–12%Mg predominantly in the as-quenched state, and classified as a Zener relaxation mechanism. The second one (P2, above 200 °C) is found at lower Mg contents (up to 5%) mainly in single-phase states (α solution of Mg in Al), with apparent parameters H ≈ 2 eV, τ 0 from 10 −16 to 10 −21 s, Δ up to 0.3 and β τ from 3 to 6. It is partly suppressed from the low-temperature side in Al–4Mg and Al–5Mg, due to precipitation of the β (Al 3 Mg 2 ) phase at the grain boundaries, and vanishes in the two-phase states of alloys with 8–12%Mg. The relaxation mechanism of P2 is associated with grain boundary sliding. At first heating from the cold-worked state, a recrystallization ‘pseudo’ peak is dominating in all alloys, whose position and height depend on degree of deformation, heating rate, vibrating frequency and chemical composition. Amplitude dependent damping measured during recrystallization demonstrates decreases in dislocation density and in critical stress for dislocation motion. Interaction energy ‘dislocation–point defects’ in Al–Mg alloys is estimated using amplitude dependent internal friction tests at different temperatures.

Internal friction, dilatometric and calorimetric study of anelasticity in Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga alloys

This paper investigates the structural transitions associated with different cooling rates from a high temperature disordered state and the effect of substitution of Ga atoms by Al atoms in Fe–Ga binary alloys on the ordering processes. Two iron-based low carbon (about 0.04 at.% C) alloys Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga are studied. Internal friction, dilatometric and calorimetric tests are carried out to check ordering in these alloys and contribution of structural defects to relaxation spectrum. Several thermally activated internal friction peaks have been observed and their activation parameters evaluated by means of temperature and frequency dependent internal friction tests using forced vibration. For most of these peaks physical mechanisms are proposed. Apart from these thermally activated relaxation peaks, a structural, frequency independent relaxation takes place at 250–300 °C. Dilatometric and DSC curves show the appearance of a contraction effect in the same temperature range. This effect was studied in alloys cooled down with different cooling rates. We believe that the frequency independent internal friction peak (denoted as the P3 peak in this paper) and peaks at dilatometric and DSC curves are controlled by the same structural mechanism and therefore the activation energy for this anelastic mechanism is derived from DSC data.

Mechanisms of anelasticity in Fe–13Ga alloy

Thermally activated frequency and temperature dependent anelastic effects in Fe–Ga alloys are practically not studied as yet in spite of the capacity of these alloys to dissipate energy of mechanical vibrations due to magneto-mechanical damping. In this paper we have studied iron-based composition with 13 at.% Ga. Several thermally activated peaks have been discovered and their activation parameters are evaluated by means of temperature and frequency dependent internal friction tests using free-decay and forced vibrations. Physical mechanisms are proposed for most of these peaks. In addition to thermally activated relaxation peaks, an irreversible internal friction peak is recorded due to structural transformation around 200 °C. This peak is frequency independent and is accompanied by inverted modulus behaviour. High damping capacity of Fe–13Ga alloy is confirmed.

Atrito interno em aços inoxidáveis austeníticos contendo cobre

Nesse trabalho, estudaram-se a influência dos tipos e as quantidades de martensitas induzidas por deformação nas curvas de atrito interno de um aço inoxidável do tipo ABNT 304 contendo cobre. Corpos-de-prova foram deformados por tração de 3 a 12% de deformação verdadeira em temperaturas no intervalo de 50 a 20ºC, visando à obtenção de diferentes quantidades das fases martensíticas ε (HC) e α' (CCC). Medidas magnéticas e ensaios dilatométricos foram realizados para avaliar as quantidades induzidas. Verificou-se que a' aumenta com a deformação, para uma mesma temperatura, e diminui à medida que a temperatura aumenta com deformação constante. Os ensaios de atrito interno foram realizados em um pêndulo de torção invertido em temperaturas de 40 a 400ºC. A influência de e, no atrito interno do aço, ficou bem estabelecida pela ocorrência de um pico nas temperaturas de reversão dessa martensita em torno de 100°C. A presença de a' parece estar relacionada a dois outros picos observados em torno de 220 e 350°C.

Magnetic losses evolution of a semi-processed steel during forced aging treatments

An ultra-low carbon steel (30 ppm after decarburization) containing Al and Si was aged for distinct soaking times at 210 °C. The core loss increased continuously until around 24 h. After that, only slight changes were verified. It was found that only the hysteresis loss component changed during the aging treatment. By internal friction test and transmission electron microscopy it was seen that carbon precipitation caused the magnetic aging. By scanning electron microscopy it could be concluded that the increase of aging index was attributed to the high number of carbides larger than 0.1 μm.

Measurement of sensitivity to dynamic strain aging in C–Mn steels by internal friction experiments

The dynamic strain aging (DSA) phenomenon is present in C–Mn steels and associated welds commonly used in many industrial applications. This phenomenon, which appears in metals containing solute atoms interacting with dislocations, induces an increase in flow stress and ultimate tensile strength (UTS) as well as a decrease in ductility. The DSA phenomenon was studied by tensile, strain rate sensitivity and internal friction tests between 20°C and 350°C in two C–Mn steels with very different sensitivities to DSA (a fully killed A42 steel and a semikilled A48 steel). The internal friction technique, which allows one to evaluate the balance between carbon and nitrogen atoms free in the lattice and carbon and nitrogen atoms interacting with mobile dislocations, appears to give results well correlated with those obtained by tensile (and strain rate sensitivity) tests. The ductility loss or the UTS increase is shown to be proportional to Snoek peak height. It is concluded that, even in industrial materials, a single internal friction test can give a good evaluation of DSA sensitivity.

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF WELDED JOINT USING VIBRATORY CONDITIONING TECHNOLOGY

The vibratory welding conditioning process is investigated in the electroslag welding of blast furnace steel. The metallographs show that a refined joint is produced. The residual stress, side bend property, tension and impact tests are carried out in different vibratory conditions (0g, 0.3g and 0.6g). The results of the test have fully proved that vibratory conditioning technology can effectively reduce residual stress and improve the comprehensive properties of weld joints. Especially, in the 0.6g vibratory condition, the qualification rate of side bend performance is up to 100%. The impact values at two vibratory accelerations (0.3g and 0.6g) are compared and the changing mechanism is discussed. The internal friction test indicates that the internal friction SKK (Snoek-Ke-Koster) peak of the weld metal has good correlation with the impact value of the weld.

Dynamic strain ageing in C-Mn steels and associated welds. Effect of metallurgical parameters on the tensile behaviour

C-Mn steels and their welds are sensitive to the dynamic strain ageing (DSA) phenomenon. The DSA sensitivity of different weld zones is not well known. Therefore, the influence of microstructure in the heat affected zones, the effect of post weld heat treatment and the effect of the chemical composition (manganese content) of the deposited metal were studied by correlation between tensile tests and internal friction tests (mechanical spectroscopy).

Dynamic strain aging sensitivity of heat affected zones in C–Mn steels

In weakly killed C–Mn steels, the dynamic strain aging (DSA) phenomenon induces an increase in the ultimate tensile strength associated with a ductility loss, usually measured in the 100–200°C temperature range. This phenomenon, which induces large toughness reductions, is not well characterized in the heat affected zones (HAZ) of the welds, since the sensitivity to DSA cannot be directly determined due to the very abrupt microstructure gradients existing in these zones. In order to study the influence of microstructure on DSA, tensile tests were performed on simulated HAZ, resulting from various quenching conditions of C–Mn steels. These results are interpreted through correlations with internal friction results on the same microstructures. It is concluded that the materials which have been submitted to the more severe quenching conditions appear to be less sensitive to DSA. This trend is attributed to the larger density of dislocations which can trap most of the interstitial atoms in these microstructures. Whatever the microstructure, the intensity of DSA, characterized by the ductility loss, is proportional to the Snoek peak height measured by internal friction. This result allows the evaluation of the sensitivity of C–Mn steels to DSA from a unique internal friction test.