Shear Internal Friction Research Articles

Direct Shear Strength on the São Francisco River Bank, Northeastern Brazil, With or Without Roots of Different Native Species

Several plant species have been studied as reinforcement elements against landslides at slopes, either to protect against the splash effect offered by shoots or anchoring the soil by the root system. The objective of this work was to investigate the influence of roots from shrub species over the soil mechanical attributes such as cohesion and angle of internal friction at the São Francisco riverbank, northeastern Brazil. A trench was excavated under the treetop of every shrubby individual, sampling blocks at 0-0.25, 0.25-0.50, 0.50-0.75, and 0.75-1.00 m depths. The moisture contents, particle size, liquidity limits, plasticity and actual specific mass of the samples were determined. The soil physical and mechanical attributes such as initial and final specific weight, initial and final void content, initial and final degree of saturation, shear resistance peaks, cohesion, and internal friction angle were identified through direct, elementary, consolidated, and undrained tests. In the samples with Solanum paniculatum, Mimosa pigra species, the highest values for cohesion were registered for the samples with roots. Sesbania virgata presented the greatest variation in cohesion and internal friction angle among samples with and without roots. The position and root status influenced the results of the direct shear tests.

Shear Mechanical Properties of Artificial Rock Specimen with Symmetrical and Asymmetric Toothed Structural Joints

Direct shear tests on cement mortar samples with symmetrical and asymmetric toothed structural joints were conducted in this study. The main objective is to study the effect of the left undulation angle (i1), the right undulation angle (i2), and the length (l) of the undulation body on the shear properties of artificial jointed rock samples. The test results show that for artificial rock samples with through-symmetrical toothed structural joints (i1 = i2), there is a significant increase in the shear strength and cohesion c of the test specimens when i1 remains constant and l gradually increases. An increase occurs in the shear strength and internal friction angle φ when there is a gradual increase in i1 and l remains constant. For those samples with through-asymmetrical toothed structural joints (i1 ≠ i2), there is a significant increase in the shear strength and cohesion c of the test specimens when i1 remains constant and l gradually increases, and the shear strength of the specimen first increases and then decreases when i1 increases from 15° to 75° and l remains constant.

Characterization of Shear Strength and Interface Friction of Organic Soil

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

Water Softening Mechanism and Strength Model for Saturated Carbonaceous Mudstone in Panzhihua Airport, China

To identify the water softening mechanisms that caused landslides in Panzhihua Airport, China, property and saturation tests of the mudstones extracted from a representative landslide were proposed. In this paper, water saturation tests were carried out on samples of carbonaceous mudstone collected from the east side of the No. 12 landslide at the airport. A number of different analytical techniques and mechanical tests were used to determine changes in chemical composition, mineral assemblages, and mudstone structural characteristics, including shear strength, after the mudstone had been softened. Three kinds of changes caused by water and three mudstone softening stages are proposed. The results show that the water has a significant influence on the properties of the mudstone, so the stability of the mudstone in the watery period is a big threat to the upper structure. A model for water immersion mudstone strength softening is developed. The model incorporates a permeability coefficient, the hydraulic gradient, and time; the model can be used to determine the mudstone’s shear strength and internal friction angle. This study provides a reference for the study of rock softened by water immersion.

Study on the Shear Band of Sand with Various Particle Characteristics Using PIV Analysis

The phenomenon of ground undergoing large plastic deformation, leading to collapse, occurs due to the localization of unstable deformation. The investigation of shear band is important in order to understand the destructive phenomenon. Therefore, a series of experiments were conducted on sands with different particle characteristics so that behaviour of the shear band of sand under plane strain compression could be investigated. Specifically, Toyoura sand and two kinds of coral sand, hereafter referred to as coral sand A (with smaller average particle size) and coral sand B (with larger average particle size) were used. The shear band was evaluated using PIV (Partial Image Velocimetry) analysis. As a result, it became clear that the relationship between shear inclination angle and internal friction angle does not hold for the two kinds of coral sand because the shear inclination angle is low. The ratio of the average value of the shear band width to the average grain size at the peak was 10 to 20 times, 7 to 10 times, and 5 to 8 times in the order of Toyoura sand, coral sand A, and coral sand B. The sample standard deviation was 0.1 to 0.9 mm, 0.9 to 1.6 mm, and 1.4 to 1.9 mm.

Method of predicting soil mechanical parameters in shallow formation while jetting process in deep-water drilling

ABSTRACTThe mechanical properties of shallow soils in deep water play an important role in drilling design and construction as well as later oil and gas development. Since it is difficult to collect soil samples from layers deeper than 10 m below the sea floor, the acquisition of shallow soil mechanics, based on the variation of drilling parameters in the deep-water drilling process, is not only economical but also reliable. In this article, we analyze the variation of subsea soil properties based on the variation of deep-water jet-drilling construction parameters, calculate the lateral friction resistance of conductor by use of weight-on-bit (WOB) and displacement parameters in the jetting process, and determine the drilled formation’s shear strength and internal friction angle in consideration of restored friction resistance. To verify the accuracy of the prediction-while-drilling model on seabed shallow soil mechanics, indoor unit and field simulation experiments were separately conducted. Moreover, the calculations from field application examples indicate that the prediction-while-drilling of deep-water seabed shallow soil mechanics achieves high conformity with the local practice results, which also indicates that this method could effectively guide field construction operations.

Temperature Dependent Thermal Conductivity and Elastic Properties of a-InGaZnO4 and a-In2Ga2ZnO7 Thin Films

Amorphous In-Ga-Zn-O is an important oxide semiconductor in advanced display technologies. Despite its importance, little has been reported on the thermal and elastic properties of this material. Here, the temperature dependence of the thermal conductivity, shear modulus, and internal friction of a-InGaZnO4 and a-In2Ga2ZnO7 films are presented. The thermal conductivity of a-In2Ga2ZnO7, measured from 100 K to room temperature, was found to be larger than that of a-InGaZnO4 over the entire temperature range. At room temperature the thermal conductivities were 1.9 W/m K and 1.4 W/m K for the a-In2Ga2ZnO7 and a-InGaZnO4 films, respectively. The shear modulus and internal friction of these films were measured in the temperature range of 340 mK to 65 K. At 4.2 K the shear modulus of the a-InGaZnO4 and a-In2 Ga2ZnO7 films was 44 GPa and 42 GPa, respectively. The internal friction of thin films at each composition exhibited a temperature dependence and magnitude that is in agreement with that observed in all amorphous solids. As the self-heating effect is of concern in the development of amorphous In-Ga-Zn-O based thin film transistors on low thermal conductivity substrates, a thermal model of such a device utilizing a-In2Ga2ZnO7 or a-InGaZnO4 as the active layer was explored. It was found that the temperature increase of the thin film transistor channel is essentially independent of the thermal conductivity of the active layer.

Shear modulus and internal friction hystereses during structural relaxation of metallic glasses based on Pd and Zr in the vicinity of the glass transition range

Cooling of metallic glasses based on Pd and Zr from the supercooled liquid state with a low rate causes significant shear modulus and internal friction hystereses, which indicates a long relaxation time in the vicinity of the glass transition range. The nature of the observed phenomenon has been discussed within the interstitialcy theory.

Anisotropic elastic moduli and internal friction of graphene nanoplatelets/silicon nitride composites

Abstract Elasticity and internal friction of graphene nanoplatelets (3 wt.%)/Si 3 N 4 composite is analyzed by ultrasonic methods. It is shown that the composite exhibits a degenerate (elliptic) form of transversal isotropy with the graphene nanoplatelets acting effectively as spheroidal voids and inducing significant softening in all directions. The shear internal friction is strongly anisotropic with the maximal value corresponding to the volume-preserving, ‘breathing’ vibrations of the nanoplatelets. Possible relations between the observed behaviors and the micromorphology of the composite are discussed.

Influences of Abnormal Climates on Engineering Characteristics of Expansive Soil

Expansive soil is a kind of high plastic clay which is more sensitive to changes of climatic and hydrogeologic conditions, and it has the character of swelling when watering and shrinking when drying out. Such repeated fluctuations from dry to wet induce irreversible deformation ,which will make the shear strength and internal friction of soil drop sharply and cause slope fracture. In recent years, abnormal climatic changes worldwide make foundation stability of expansive soil face severe test . Atmospheric influence depth can supply design basis for slope fracture of expansive soil. But in the situation of abnormal climates , the depth will exceed original design criterion and hazard engineering accidents will happen. Therefore, It has great importance in engineering application of studying influences of abnormal climates to engineering characteristics of expansive soil.

Robustness towards application of multi-objective optimisation for autonomous off-road vehicle on rough terrain

Force distribution emerged as a major concern in the case of autonomous vehicle because of its importance of control in unknown environment. Tipover and deadlocks are vital problems arising in remote operations of the vehicle. An evolutionary approach was used to attain multiple trade-off solutions, which minimised force variations along with the maximisation of draw bar pull and torque within optimisation of available power. Robustness towards Pareto optimal solutions was analysed as a major concern. Furthermore, different Pareto fronts was obtained with different noise induced into the terrain characteristics mainly soil cohesion (c), shear deformation modulus (k) and internal friction angle (phi). Result presented shows that the noise intensity > 2% impacts greater in the solution quality should be taken as less robust solution and can be implemented to the control algorithm.

Effects of Interfacial Friction on the Microstructures of Magnesium-Tin Alloy during Continuous Rheo-Forming Process

The influence of the interfacial friction on the continuous rheo-forming microstructures of magnesium alloy. The effects of interfacial friction on the microstructure evolution in magnesium alloy were investigated. It was shown that strong shear stress and internal friction occur inside the melt under the interfacial friction. In roller-shoe chamber, the growth direction of dendrites growing along the normal direction of the roller near the roller-shoe is changed under shear stress and melt resistance force. when the degree between dendrite and normal direction of roller is about 45 degree, the dendrites can be stablized and grow easily along this direction. Under an appropriate pouring temperature, with the increase of pouring temperature, there is enough room for the grains near the roller-shoe to grow, the grains are not easy to collide mutually, so the dendrites form. In roller-shoe chamber, coarse dendrites near the roller become gradually refined when they grow into the mushy region. Moreover, because dynamic friction force and shear stress of roller are stronger at the exit of the chamber, dendrites fracture and fracture layer or cracks appears. The microstructures consist of mainly rosette and spherical grains on the central position.

Low-temperature dependence of elastic moduli and internal friction for glassy Pd42.5Ni7.5Cu30P20

Longitudinal and transverse wave velocities, eight kinds of elastic parameters, and the dilational and shear internal friction of Pd42.5Cu30Ni7.5P20 glassy alloy have been simultaneously measured as a function of temperature in the range from 77 to 373 K, using an ultrasonic pulse method. Monotonic decreases in the Young and shear moduli and in the Debye temperature in the range above 77 K are interpreted in terms of thermal relaxation of squeezed free volumes, accompanied by an increase in the interatomic distances, the appearance of entropy elasticity, and a uniaxial volume-preserving deformation. A 272-K valley of dilational friction seems to correspond to a topological change associated with electron–phonon coupling caused by the release of strains.

Temperature dependence of elastic parameters and internal frictions for MnCu20Ni5Fe2 alloy

Using ultrasonics, MnCu20Ni5Fe2 (M2052) alloy's acoustic characteristics were observed in order to understand its high damping properties. Longitudinal and shear wave velocities, eight kinds of elastic parameters, and dilational and shear internal frictions were simultaneously measured as functions of temperature in cooling and heating runs between 218 and 373 K in M2052 alloy. A valley in Young and shear moduli, Debye temperature and internal friction peaks at around 345 K showed a M2052 fcc/fct trans-formation, accompanied by volume-nonpreserving lattice softening. The increment of dilational friction in the low temperature can be interpreted as boundary effect of the misfit domain, associated with nonharmonity of potential between pairs of atoms. The M2052 alloy shows highest elasticity below 300 K, indicating large resistance for volume-preserving distortion. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Temperature dependency of elastic moduli and internal dilational and shear frictions of polyetherimide

AbstractTo investigate the thermally activated structural change of polyetherimide, longitudinal and transverse wave velocity, six kinds of elastic parameters (Young's, shear, and bulk moduli, Lamé parameter, Poisson's ratio, and Debye temperature), and dilational and shear internal frictions were simultaneously measured over a temperature range 69–474 K, using the ultrasonic pulse method. All elastic moduli decreased with increasing temperature, suggesting a lowering of molecular bonding strength. From shear internal friction, the 190, 314, 371, 395, and 430 K peaks are interpreted as the γ‐ [derived from –C(O)– motion], β‐ (interplane slippage between benzene rings), β‐ (softening‐glass transition) peaks, and rotational vibration of main benzene rings and a local relaxation of the main chain, respectively. The abrupt increase peak from 449 K in dilational friction would be a low‐temperature side shoulder of the α–glass‐transition peak. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 759–764, 2003

Variation of Formwork Pressure with Thixotropy of Self-Consolidating Concrete

An experimental investigation was carried out to determine the influence of thixotropy on the development of formwork lateral pressure. Five self-consolidating concrete (SCC) mixtures prepared with different combinations of cementitious materials and set-modifying admixtures were evaluated. An experimental column measuring 2100 mm in height and 200 mm in diameter was used to determine lateral pressure distribution using five pressure sensors mounted at 50, 250, 450, 850, and 1250 mm from the base. This paper offers a comprehensive review of key factors affecting formwork pressure developed by fresh concrete and presents the results pertaining to the influence of thixotropy on variations in lateral pressure of SCC. The results show that the lateral pressure exerted by the plastic SCC is directly related to thixotropy. With the increase in thixotropy, the initial lateral pressure registered following casting decreases, and the rate of drop in lateral pressure is accelerated. This is attributed to the reversible effect of the thixotropy which enables the material to regain its shear strength, internal friction, and cohesion when left at rest without any shearing action. Immediately after casting, any decrease in lateral pressure was attributed to the increased internal friction resulting from the use of ternary cement and greater concentration of coarse aggregate. The use of a set-retarding agent resulted in a delay in cement hydration that led to a slower rate of drop in lateral pressure. Conversely, the incorporation of a set-accelerating agent resulted in an increase in the rate of pressure drop.

Low-temperature damping anomaly in an yttria-stabilized tetragonal zirconia polycrystal

Dilational and shear internal friction and four elastic parameters (Young's modulus, the shear modulus, the bulk modulus and the Lame parameter) have been cyclically measured between 68 and 400K in an yttria-stabilized tetragonal zirconia polycrystal ((Y)TZP), using an ultrasonic pulse wave of frequency 3.8MHz. A 200K peak in the shear friction, which was observed in repeated cooling runs, decreases with increasing repetition number, suggesting a martensitic-like transition due to short-range cooperative movement of oxygen ions in the (Y)TZP lattice.

Thermal Stability of Bulk Metallic Glasses. Influence on Mechanical Properties

AbstractTwo Zr-base bulk metallic glasses were investigated in the present work. DSC experiments were performed at different heating rates (dT/dt). Evolution of the characteristic temperatures, glass transition and onset of crystallisation, were determined as a function of dT/dt. Evolution of shear elastic modulus and internal friction are measured as a function of temperature and resulting microstructural evolution; these evolutions are related to variation of the atomic mobility.

Low-Temperature Elastic Moduli and Dilational and Shear Internal Friction of Polycarbonate

Longitudinal and transverse wave velocity, and five kinds of elastic parameters (Young's, shear and bulk moduli, Lamè parameter, Poisson's ratio) for polycarbonate were simultaneously measured over a temperature range of 68 to 434 K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting the lowering of molecular bonding strength, accompanied by fluctuation of density due to loosely packed chains. From dilational and shear internal frictions, the 201, 313, 359 K peaks, an abrupt increase from 421 K and a decrease to 148 K are interpreted as free motion of carbonate group in the main chain (γ dispersion), motion of molecular chains between weak intermolecular bonds (β dispersion), dipole-dipole association between ester side chains (β' dispersion), glass transition (α dispersion) and a δ peak, respectively.

Low‐temperature elastic moduli and internal dilational and shear friction of polymethyl methacrylate

AbstractLongitudinal and transverse wave velocity, five kinds of elastic parameters (young, shear and bulk moduli, Lamér; parameter. Poisson's ratio) and dilational and shear internal friction of polymethyl methacrylate were simultaneously measured over a temperature range 68–400K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting lowering of molecular bonding strength. From dilational and shear internal frictions, the 139, 382, and 385K peaks are interpreted as rotation of x‐methyl estel groups, micro Brownian motion of main chains and stress relaxation, and abrupt increases from 242 and 395K are regarded as free motion of side chains and glass transition, respectively. ©1995 John Wiley & Sons, Inc.