Shear Yield Stress Research Articles

EFFECTIVE PARAMETERS OF TAIL PROCESSING GOLD-BEARING ORE HYDROTRANSPORT FOR VERNINSKAYA PROCESSING FACTORY

The paper shows that in order to increase the efficiency of hydraulic transport systems in mining the transportation of slurries with a high concentration of solids in the slurry flow. Experimental studies have shown that slurry tailings of gold-containing ore with mass concentration of more than 55% are viscoplastic fluids. Experiments on a rotational viscometer allowed us to establish the main rheological characteristics of the studied slurries. Experimental studies of hydraulic transport performed on a laboratory setup, confirmed the results obtained on a rotational viscometer. Curved mixture streams are inclined straight lines that cut off on the axis of the head the sections, which determine the initial hydraulic slope corresponding to the shear stress yield on the rheological curves. According to the results of the experiments, a method has been developed for calculating the hydraulic transport of highly concentrated slurries of tailings of gold-bearing ore. Head loss values increase with increasing concentration. A sharp increase in head loss occurs in the concentration range from 60 to 65% and above

Boron nitride‐reinforced polysilazane‐derived ceramic composites via direct‐ink writing

AbstractIn this study we investigate the use of hexagonal boron nitride (hBN) as a rheology modifier in polysilazane resin to enable direct‐ink writing (DIW) of polysilazane‐derived boron nitride‐reinforced ceramic composites. hBN is shown to effectively modify the flow properties of the resin by imparting strong shear thinning and yield stress behavior, and to reduce the mass loss and shrinkage associated with the polymer‐to‐ceramic conversion process, when compared with unfilled polysilazane resin. DIW inks are formulated with 40 vol.% hBN and used print flexural specimens and complex structures with high resolution. Mechanical properties of the resulting polymer‐derived ceramic composites were evaluated by 3‐pt. flexure and Vickers microhardness. The printed composites exhibit flexural strength of 56.4 MPa and microhardness of 111.4 HV2.

Experimental study of the impact of filter cakes on the evaluation of LCMs for improved lost circulation preventive treatments

Methods to prevent the losses of drilling fluids involve approaches to prevent the initiation of fractures and to inhibit the growth of any pre-existing or drilling-induced microfractures. The inclusion of lost circulation materials (LCMs) in drilling fluids is a common method for managing these microfractures. Recent studies have indicated the critical role of filter cakes in continually strengthening the wellbore; however, most of the current LCM design and evaluation methods neglect the effects of filter cakes. In this study, experimental investigations were conducted to understand the effects of LCMs on the creation of filter cakes and the facilitation of fracture sealing. The processes of filter cake rupture and fracture sealing were investigated by changing and monitoring the differential pressure across the filter cakes. The performance of the filter cakes and LCMs in preventing and reducing fluid losses was evaluated based on the maximum sealing pressure, sealing structure stability, and total fluid loss upon the formation of an effective fracture seal. The effects of the filter-cake thickness, shear yield stress, as well as the type, concentration, and particle size distribution of LCM on the filter cake rupture and fracture-sealing processes were investigated.The test results show that filter cakes accelerate the sealing of microfractures, thus facilitating preventive treatments for lost circulation. The properties and effectiveness of filter cakes for these processes are affected by the particle size distribution of the LCMs in the drilling fluids. Therefore, it is recommended to evaluate the performance of LCMs considering the effects of the filter cakes. The results of this study can be used as a reference to develop more realistic evaluations and improved design of LCMs in lost circulation preventive treatments.

Novel ring-type measurement system of shear yield stress for magnetorheological fluid under high temperature

In order to investigate the shear yield stress of magnetorheological (MR) fluid at different temperatures, shear gaps, and shear rates, a ring measurement system is designed based on the MR characteristics. The magnetic field and temperature field of the system are simulated and analyzed, which proves that the design of the measurement system is reasonable. On this basis, the measurement system is manufactured and experiments are carried out to verify its performance. The results show that the system can provide a uniform and strong enough magnetic field to make MR effects occur. Meanwhile, the temperature of the shear gap can reach 100 °C in 610 s, and it can increase up to 240 °C when heating continues, which can provide stable measurement conditions at different temperatures, especially at high temperatures. All the results of the experiments show that the measurement system meets the requirements of measuring the shear yield stress of MR fluid. To test the accuracy of the measurement system, repeated experiments are carried out as well. The shear yield stress by the system is almost the same as that provided by the manufacturer, showing excellent measuring precision. The repeatability error of the measurement system is less than 4.02%, indicating that the measurement system is of high accuracy.

Effective Parameters of Tail Processing of Gold-Bearing Ore Hydrotransport for Verninskaya Processing Factory

The article is devoted to the analysis of the composition and properties of the materials and liquids during transportation using pipeline and shows that in order to increase the efficiency of hydraulic transport systems in mining a transition to the transportation of slurries with a high concentration of solids in the slurry flow is necessary. Experimental studies have shown that slurry tailings of gold-containing ore with mass concentrations of more than 55 % are viscoplastic fluids. Experiments on a rotational viscometer allowed us to establish the main rheological characteristics of the studied slurries – shear stress and the dynamic effective viscosity. It has been established that over the entire range of concentrations from 55 to 65 %, the flow of slurries is described by the Bingham rheological equation. Experimental studies of hydraulic transport performed on a laboratory setup with a pipeline diameter of 50 mm confirmed the results obtained on a rotational viscometer. The curved of mixture stream is inclined straight lines that are cut off on the axis of the head in the sections, which determine the initial hydraulic slope corresponding to the yield shear stress on the rheological curves. According to the results of the experiments, a method has been developed for calculating the hydraulic transport of high concentrated slurries of tailings of gold-bearing ore. Calculations showed that in a given range the performance of the hydrotransport system and the mass concentration of the solid phase pressure losses vary from 11 to 84 m of water column/m. Head loss values increase with the increasing concentration. A sharp increase in the head loss occurs in the concentration range from 60 to 65 % and higher.

Particle-chain evolution and constitutive model of magnetorheological polishing fluids based on hexagonal close-packed structure

This paper proposes a novel constitutive model of magnetorheological polishing fluids (MRPFs) to predict field-dependent properties such as yield shear stress. First, the invasion of polishing particles to carbonyl iron particle (CIP) chains is analyzed in terms of the destructive effect on the distance of particles and the enhancement of chain structures. Subsequently, the hexagonal close-packed structure of magnetorheological fluids (MRFs) is utilized to formulate a constitutive model of MRPFs after examining the reconstructed distance and the proportional property of carbonyl iron particle chains affected by the polishing particles. According to the constitutive model, several factors that may affect the performance of MRPFs are considered, and experiments are carried out to prove these conjectures. A series of experiments explore the influencing mechanism of the radius and volume fraction of the polishing particles on the field-dependent properties of MRPFs such as the yield shear stress. The results, which are highly consistent with the simulation data based on constitutive model, show that the radius and volume fraction of polishing particles significantly affect the field-dependent properties of MRPFs. In addition, at a given magnetic field intensity the optimum radius and volume fraction of the polishing particles can be obtained to enhance the field-dependent yield shear stress of MRPFs.

The shear and compressive yield stress of fibrillated acacia pulp fiber suspensions

Abstract The degree of interactions between fibers and the tendency of fibers to form flocs play an important role in effective unit operation in pulp and paper industry. Mechanical treatments may damage the structure of the fiber cell wall and geometrical properties, and ultimately change the fiber-fiber interactions. In this study, the gel crowding number, compressive and shear yield stress of fibrillated acacia pulps were investigated, and the results showed that the gel crowding number of the refined pulp samples ranged from 8.7 to 10.7, which were much lower than that of un-refined pulps. As the concentration increased, both the compressive yield stress P y {P_{y}} and shear yield stress τ y {\tau _{y}} of all suspensions increased accordingly, and the yield stress was found to depend on a power law of the crowding number. Moreover, the values of τ y / P y {\tau _{y}}/{P_{y}} were also examined and the variation of τ y / P y {\tau _{y}}/{P_{y}} became largely dependent on the fiber morphology and mass concentration.

Revisiting the estimation of cutting power with different energetic methods while sawing soft and hard woods on the circular sawing machine: a Central European case

In the classical approaches, used in Central Europe in practice, cutting forces and cutting power in sawing processes of timber are commonly computed by means of the specific cutting resistance kc. It needs to be highlighted that accessible sources in handbooks and the scientific literature do not provide any data about wood provenance, nor about cutting conditions, in which cutting resistance has been empirically determined. In the analyses of sawing processes, the use of a model with elements of fracture mechanics involved is an alternative way. In this work, predictions of the newly developed model (FRAC_MOD) for the circular sawing machine are presented. Thanks to this modern approach, it was possible to reveal the usefulness of the FRAC_MOD, using experimental results data on fracture toughness and shear yield stresses of both Polish pine (Pinus sylvestris L.) and Czech beech wood (Fagus sylvatica L.). The achieved results were compared to the forecasted values obtained with classical models (CLAS_PL and CLAS_CZ), which are commonly applied in Central European sawmills. The carried out analyses allowed us to discover undesired effects in the form of underestimation of cutting power when applying the CLAS_PL and CLAS_CZ models. For that reason, the FRAC_MOD cutting model could be suggested for the prediction of energetic effects in cases of dynamical analyses and even unsteady cases.

Preliminary experimental evaluation of a novel loudspeaker featuring magnetorheological fluid surround absorber

<span>A novel design of magnetorheological fluids (MRF) based surround device in a loudspeaker system was studied in this article. The main objective of this research is to design a new surround device of the loudspeaker that can be easily controlled its damping. Therefore, it was predicted that the audio pressure level on the loudspeaker could be easily manipulated at a different sound source by applying a certain magnetic field. This function could not be reached using one conventional speaker system. Firstly, a set of an electromagnetic device containing MRF was designed to replace the conventional rubber surround. The magnetic circuit was then evaluated using the finite element method magnetics to study the flux distribution in the MRF area. The current was varied from 0.25 to 0.75 A by an interval of 0.25 A. The magnetic flux resulted from the simulation was then logged and used as the based value for predicting the change of shear yield stress. The base properties of the shear yield stress of the MRF against the magnetic flux was obtained from previous experimental result. Therefore, it was hopefully the prediction could be closed to the real system. Based on the simulation result, the shear yield stress varied from 43 to 49 Mpa or about 15 % increment. </span><span lang="IN">A simple experimental work was carried out. By applying particular direct current into the coil, the sound quality generated by the loudspeaker shows different values</span><span>.</span><span lang="IN"> Based on the preliminary experiment, the level of decibel decreased about 3 dB as the application of magnetic fields. The idea has been proven in this preliminary experimental evaluation.</span>

Study on Morphology and Rheological Property of Organoclay Dispersions in Soybean Oil Fatty Acid Ethyl Ester over a Wide Temperature Range.

This work attempted to establish the relationship between the dispersion morphology and the viscous flow behavior of clay dispersions in soybean oil fatty acid ethyl ester (FAEE) at 2 and 65 °C. The clays used in this study include raw montmorillonite (Mt) and three kinds of organoclays prepared by ion exchange modification of Mt by cetyltrimethylammonium chloride (OC16), dihexadecyldimethylammonium chloride (ODC16), and trihexadecylmethylammonium chloride (OTC16), respectively. The X-ray diffraction and water contact angle results demonstrated that greater alkyl chain number of surfactants led to greater interlayer space and stronger hydrophobicity of organoclays. Due to the good affinity of the surfactant and FAEE, OC16 exhibited the most stable dispersion in FAEE between 2–65 °C, which resulted in the best flat rheological property. The molecular structures of multiple chain surfactants were quite different from that of FAEE, resulting in weak affinity between organoclays (ODC16 and OTC16) and FAEE. The sheets of ODC16 and OTC16 tended to aggregate at 2 °C, forming a gel structure, thus significantly increasing the low shear rate viscosity (LSRV) and yield stress. At 65 °C, with the expansion of FAEE and the stronger thermal motion of sheets, the dispersions of ODC16 and OTC16 were improved, destroying the original gel structure and resulting in significant decreases in LSRV and yield stress. This study confirmed that stable clay/FAEE dispersions tended to exhibit flat rheology, which could serve as a basis for the application of clay/biodiesel dispersion in deep-water drilling.

Micro-mechanical theory of shear yield stress for strongly flocculated colloidal gel.

Shear yield stress is an important parameter in the processing of colloidal suspensions as it characterizes the solid-to-fluid transition. Although shear rheology of colloidal gel is of widespread academic and industrial interest, first principles theory that connects the microscopic properties to the macroscopic mechanical response in a self-consistent manner is lacking. In this work, we derive a constitutive relation to predict the yield stress for a strongly attractive gel undergoing quasi-static shear deformation as a function of volume fraction, inter-particle potential, contact scale properties and the micro-structure of a strongly-aggregated colloidal gel. The model also predicts the strain at which the colloidal gel network will yield under shear load. To test the model, discrete element simulation is performed using a non-central potential with friction while accounting for the rolling resistance, which is important in real colloidal gel systems. The theoretical predictions are not only in good agreement with the simulation results, but also with previous experiments.

A Novel Preparation Process for Magnetorheological Fluid with High Working Temperature

We report the preparation of a magnetorheological fluid with a high working temperature by using fluorocarbon surfactant and titanate coupling agent as additives at appropriate contents determined by a series of experiments. The sedimentation ratio, apparent viscosity, and yield stress are measured to evaluate the performance of the prepared magnetorheological fluid. Results indicate that AES dispersants, titanate coupling agents, and fluorocarbon surfactants all have improved dispersion properties, and that the compounding fluorocarbon surfactants and titanate coupling agent can further improve the settlement stability of magnetorheological fluid, with 7 % one-week settlement rate. Diatomite has a good thixotropic effect, and the antisettling effect enhanced with increased content. The types of carrier fluid have no significant effect on the performance of MR fluids. The prepared MR fluid can also work at 180 °C, which is higher than most commercial fluids, and the shear yield stress can reach 50 kPa.

Yield Stress Dependent Foaming of Edible Crystal-Melt Suspensions

Crystal-melt suspensions (CMSs) are yield stress shear thinning fluids in which crystal network formation is responsible for the appearance of a yield stress. This study investigates the influence ...

GO CaBER: Capillary breakup and steady-shear experiments on aqueous graphene oxide (GO) suspensions

Aqueous solutions of graphene oxide (GO) with a very large average flake aspect ratio, AR = O ( 10 4 ), are probed using capillary breakup experiments and shear rheological measurements for concentrations up to ϕ = 0.4 vol . %. GO, a chemically oxidized sheet of graphene that we obtained from graphite exfoliation, is suspended in distilled water to produce solutions with volume concentrations spanning 0.02 ≤ ϕ ≤ 0.4 vol . %. For concentrations between 0.1 ≤ ϕ ≤ 0.4 vol . %, the apparent shear yield stress, τ y (determined from creep tests), scales with concentration following a power-law relationship with exponent ∼ 2.2. Using capillary breakup extensional rheometry (CaBER), we demonstrate that for concentrations ϕ ≳ 0.1 vol . %, aqueous GO solutions exhibit power-law fluid behavior in uniaxial elongation. The deformation-rate-dependent transient Trouton ratio over the range where the deformation rates match in shear and capillary breakup experiments is independent of the deformation rate, but inversely proportional to the volume concentration with all values exceeding 3. An attempt is made to estimate the apparent elongational yield stress (for ϕ ≥ 0.3 vol . %) by using the Laplace pressure within the fluid filament as its surrogate, and we find that in the strain rate regime that we can observe, the apparent elongational yield stress, τ y , e, is not 3 times the shear yield stress, i.e., for our aqueous GO solutions, we are not able to observe agreement with the von Mises plasticity criterion. GO samples at a given concentration probed in capillary breakup extensional rheology experiments under different protocols, i.e., slow-retraction opposed to step-stretch, exhibited different responses confirming that GO is highly sensitive to the deformation history; however, they still exhibit power-law fluid behavior even given the different initial conditions. Although slightly limited in our ability to quantify the extension-thinning yield-stress-like behavior of aqueous GO in uniaxial elongational flow by the fact that we cannot prescribe the strain rates in CaBER experiments, we demonstrated that even a very small amount of GO flakes can significantly alter the shear rheology and the pinch-off dynamics of a liquid bridge in comparison to Newtonian fluids of equivalent shear viscosity.Aqueous solutions of graphene oxide (GO) with a very large average flake aspect ratio, AR = O ( 10 4 ), are probed using capillary breakup experiments and shear rheological measurements for concentrations up to ϕ = 0.4 vol . %. GO, a chemically oxidized sheet of graphene that we obtained from graphite exfoliation, is suspended in distilled water to produce solutions with volume concentrations spanning 0.02 ≤ ϕ ≤ 0.4 vol . %. For concentrations between 0.1 ≤ ϕ ≤ 0.4 vol . %, the apparent shear yield stress, τ y (determined from creep tests), scales with concentration following a power-law relationship with exponent ∼ 2.2. Using capillary breakup extensional rheometry (CaBER), we demonstrate that for concentrations ϕ ≳ 0.1 vol . %, aqueous GO solutions exhibit power-law fluid behavior in uniaxial elongation. The deformation-rate-dependent transient Trouton ratio over the range where the deformation rates match in shear and capillary breakup experiments is independent of the d...

Microstructure and Mechanical Properties of Nanostructured CoCrFeMoTi High-Entropy Alloy Fabricated by Mechanical Alloying and Spark Plasma Sintering

CoCrFeMoTi high-entropy alloy (HEA) was synthesized using mechanical alloying and spark plasma sintering. The corresponding microstructural features and phase composition were compared with those of CoCrFeNi, CoCrFeNiTix (x = 0, 0.3 and 0.5) and CoCrFeNiMox (x = 0, 0.3, 0.5 and 0.85) HEAs. Co, Cr, Fe, Mo and Ti elemental powders were mixed in equiatomic ratio and mechanically alloyed in a planetary ball mill at 300 rpm for up to 80 h. The influence of the milling duration on the evolution of microstructure, constituent phases and morphology was studied. After 40 h of ball milling, two supersaturated BCC solid solution phases were obtained. Milling time increasing resulted in grain refinement and higher solid solution homogenization characterized by a high internal strain. A partial phase transformation from BCC to intermetallic phases when the temperature exceeds 660 °C was revealed. After SPS consolidation, the Vickers hardness was 778 ± 10 HV, in combination with an ultimate shear stress of 216 ± 20 MPa and a yield shear stress of 81 ± 15 MPa for the material sintered at 950 °C and 65 MPa. Further increasing in the sintering temperature resulted in enhanced hardness value of 1600 ± 5 but reduced yield shear stress. The failure analysis revealed a brittle fracture of the synthesized materials.

Mitigation of nonlinear rub-impact of a rotor system with magnetorheological damper

In this work, a new method of using a magnetorheological damper to improve the self-adaptive ability of a rotor system to rub-impact is developed. To validate the feasibility of this method, a finite element model of the rub-impact rotor system with magnetorheological damper is investigated. A revised formula describing the relationship between the yielding shear stress and magnetic field intensity is proposed. Focusing on the mitigation effect of magnetorheological damper on the nonlinear dynamic response of the rotor system, numerical simulation is conducted. The results show that magnetorheological damper has a considerable effect on the vibration and stability of a rub-impact rotor system. When a suitable current is applied, magnetorheological damper can effectively mitigate the vibration of the rotor system to prevent rub-impact. If contact of the rotor/stator is inevitable, magnetorheological damper can further stabilize heavy rub-impact to slight rub-impact by adjusting the current to an appropriate value. This research reveals the influence mechanisms of magnetorheological damper on normal and rub-impact rotor systems and is helpful for vibration control and fault self-healing of rotating machinery.

Extrafibrillar matrix yield stress and failure envelopes for mineralised collagen fibril arrays

Bone metabolic diseases such as osteoporosis constitute a major socio-economic challenge. A detailed understanding of the structure-property relationships of bone's underlying hierarchical levels has the potential to improve diagnosis and the ability to treat those diseases, especially with regards to the onset of failure. Therefore, elastic and yield properties of mineralised turkey leg tendon (MTLT), a mineralised tissue that is similar to bone but has a simpler multiscale structure, were investigated. Elastic properties were identified using a multiscale micromechanical model. The input parameters include constituent mechanical properties, volume fractions and inclusion aspect ratios and these were obtained from a wide variety of literature sources. The determined elastic properties were used to formulate micromechanically informed yield surfaces and to identify yield properties of MTLT at the nanometre length scale where failure is first reported to occur. This was done in conjunction with experimental results from the compression of micropillars extracted from individual mineralised collagen fibres. This data was then used to identify micromechanically informed failure envelopes. The shear yield stress of the extrafibrillar matrix, associated with interfibrillar sliding, was identified as 137.65 MPa. The ratio between tensile and compressive yield stress in the Drucker-Prager yield criterion was 0.65. For both criteria apparent yield stress of the mineralised collagen fibril decreased to 25.3–31.4% when varying fibril orientation from 0° to 90°. This study identified yield properties of extrafibrillar matrix using an aligned mineralised tissue. The ability to obtain yield stress data and unloading stiffness from micropillar compression tests of MTLT at the level of the mineralised collagen fibril array and downscaling these into the EM mitigates against possible errors associated with macroscopic stiffness predictions and proved to be an invaluable advantage compared to similar modelling approaches. Results may help to improve computational models that may then be used in pre-clinical testing or development of personalised treatment strategies.

Study of a magnetorheological brake under compression-shear mode

A magnetorheological (MR) brake under compression-shear mode is designed, simulated and experimentally investigated in this paper. A MR brake under compression-shear mode was first designed considering compression enhanced shear yield stress of MR fluid. Then, the operating principle of the MR brake was illustrated and mathematical torque expressions, operating under compression-shear mode assuming Herschel–Bulkley model, was further established. Moreover, simulation analysis of the designed magnetic circuit was performed as well. An experimental prototype was fabricated and tested to evaluate the transmission performance of MR brake. The results showed that the large torque could be produced at high applied currents, high compressive stress, large compressive strain and small initial gap distances. The rotational speed and compressive speed had little effect on the torque. The characteristic rising time of the torque was greatly affected by the rotational speed, the compressive strain, and compressive speed. However, the current had little effect on the rising time. The time constant would became shorter when both the rotational speed and the compressive speed were faster. Through analyzing the compression of particle chains in MR fluids directly, it was found that the diameter and the length of the particles chains brought a strong influence on the essential property of MR fluids under compression. Thus, the compressive stress or compressive strain and the initial gap distance also played an important role in enhancing the torque. The results also showed that the proposed MR brake could generate a maximum torque of 241 Nm, about 17.9 times the magnitude of braking torque without compression, and achieve a high torque density of 125.6 kN m–2 and a time constant of 58 ms. This study provides a better understanding of MR brake under compression-shear mode and the implications for many high-power applications.

Dynamic burst pressure analysis of cylindrical shells based on average shear stress yield criterion

The cylindrical shell is a basic structure in transportation of dangerous goods, hydrogen storage, public safety, aerospace industries, nuclear and power engineering. The dynamic burst pressure of cylindrical shells is crucial to personal safety, environmental pollution and property damage. Based on average shear stress yield (ASSY) criterion, a novel equation is developed to predict the dynamic burst pressure of cylindrical shells. The ASSY criterion is a weighted average of the maximum shear stress and octahedral shear stress. Firstly, the non-uniform impact load is reduced to a parabolic load acting on the inner wall of cylindrical shells. The width of load is the same as the outer diameter of the cylindrical shell. And then, ASSY criterion is adopted to predict the dynamic burst pressure of cylindrical shells for the first time. In the end, the accuracy of our method is validated by comparing with the finite element method (FEM) under different pulse duration. The results indicate that our method can accurately predict the dynamic burst pressure of cylindrical shells under a non-uniform impact load. In addition, the ASSY criterion can be extended to solving dynamic problems with a high precision. Finally, our method can be used as a benchmark for approximate or numerical solutions. It is beneficial to assess the safety and integrity of cylindrical shells under a non-uniform impact load.

One-step solvothermal synthesis of porous MnFe2O4 nanoflakes and their magnetorheological properties

In this study, porous MnFe2O4 nanoflakes were synthesized by a facile one-step solvothermal method, and the obtained products were employed as new magnetorheological (MR) materials to prepare a well dispersed MR suspension. The synthesized MnFe2O4 nanoflakes were systematically examined using XRD, FE-SEM, TEM, XPS, BET and VSM. The shear stress, yield stress, storage modulus and loss modulus of MR fluid strongly depended on the applied magnetic field strengths, indicating typical MR performances. More importantly, the obtained MR fluid demonstrated enhanced sedimentation stability in the recording time. This phenomenon was mainly attributed to the unique porous lamellar structure and the decreased particle-fluid density mismatch. In conclusion, the prepared MnFe2O4 nanoflakes as novel MR materials will serve as a bright candidate in various technological applications.