Deformation Rheology Research Articles

ДЕГРАДАЦИОННЫЕ ПОВРЕЖДЕНИЯ ЖЕЛЕЗОБЕТОННОЙ РАМЫ В УСЛОВИЯХ ДЛИТЕЛЬНОЙ ЭКСПЛУАТАЦИИ

A method for calculating a reinforced concrete frame under rheological deformation conditions is proposed, taking into account degradation damage as a result of corrosion during long-term operation, reflecting their real work under the combined action of a load and an aggressive environment based on the modern phenomenological theory of deformation of an elastic-creeping body. The possibility of considering the processes of long-term deformation of reinforced concrete in conditions of long-term exploitation is shown. Analytical dependencies and a calculated example are given for the considered service life.

The Stability of Roadway Groups under Rheology Coupling Mining Disturbance

The deep roadway groups play an important role in transportation and ventilation in coal mine production. Therefore, it is very important to comprehensively analyze the coupling effect of rheological deformation and coal mining on the stability of the roadway groups. In this paper, the disturbance effects of different stop-mining lines on roadway groups under long-term rheology were investigated by numerical simulation, and the failure mechanism of roadway groups with large sections and multiple disturbances in a deep well was revealed. The results show that the long working face will lead to the collapse of key strata, and the influence range will spread to the adjacent roadway groups. When the distance between the working face and the stop-mining line is 100 m, the roadway groups cannot be affected by the working face mining, and the reserved width of the coal pillar can be determined to be 100 m, which increases the stability of the roadway’s surrounding rock and maintains the mine safety production. This paper aims to provide a reference for groups design and control under similar conditions.

Rheological Properties of Argillaceous Intercalation under the Combination of Static and Intermittent Dynamic Shear Loads

The construction and long-term operation stage of the rock slope with argillaceous interlayer will be subjected to intermittent dynamic loads, such as blasting and earthquake. For the argillaceous interlayer in the rock slope, its rheological properties are not only related to the initial stress state caused by the gravity of the overlying rock mass but also affected by intermittent dynamic loads. In order to investigate the rheological properties of argillaceous intercalation under the combination of static and intermittent dynamic shear loads, the rheological tests of argillic intercalated soil samples under static shear, static and cyclic dynamic shear, and static and intermittent dynamic shear were carried out, and the rheological deformation characteristics of soil samples under different shear conditions were analyzed. The results show that when the soil specimens in the static shear rheological process are disturbed by intermittent dynamic shearing load, the intermittent dynamic disturbances might have no remarkable influence on the rheological deformation of the specimens if the initial static shearing stress and intermittent dynamic shearing stress were comparatively low. However, low-intensity intermittent dynamic disturbances might accelerate the rheological deformation process of the specimens remarkably if the initial static shearing stress state was close to their shearing strength. There was a stress threshold when the soil specimens failed under the static and cycling dynamic shear and static and intermittent dynamic shear, which is determined by the sum of static shear stress and dynamic shear stress peak. For rock slopes controlled by rheological weak structural planes and influenced by long-term blasting vibrations, the transient and long-term dynamic stability should be comprehensively analyzed.

Simulation of jet printing of solder paste for surface mounted technology

Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%. Research limitations/implications The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension. Practical implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration. Social implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print. Originality/value While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.

Dilute dispersion of compound particles: deformation dynamics and rheology

Compound particles are a class of composite systems in which solid particles encapsulated in a fluid droplet are suspended in another fluid. They are encountered in various natural and biological processes, for e.g. nucleated cells, hydrogels, microcapsules etc. Generation and transportation of such multiphase structures in microfluidic devices is associated with several challenges because of the poor understanding of their structural stability in a background flow and the rheological characteristics of their dispersions. Hence, in this work, we analyse the flow in and around a concentric compound particle and investigate the deformation dynamics of the confining drop and its stability against breakup in imposed linear flows. In the inertia-less limit (Reynolds number, $Re \ll 1$ ) and assuming that the surface tension force dominates the viscous forces (low capillary number, $Ca$ , limit), we obtain analytical expressions for the velocity and pressure fields up to ${O}(Ca)$ for a compound particle subjected to a linear flow using a domain perturbation technique. Simultaneously, we determine the deformed shape of the confining drop correct up to ${O}(Ca^2)$ , facilitating the following. (i) Since ${O}(Ca^2)$ calculations account for the rotation of the anisotropically deformed interface, the reorientation dynamics of the deformed compound particles is determined. (ii) Calculations involving the ${O}(Ca^2)$ shape of the confining interface are found to be important for compound particles as ${O}(Ca)$ calculations make qualitatively different predictions in generalised extensional flows. (iii) An ${O}(Ca)$ constitutive equation for the volume-averaged stress for a dilute dispersion of compound particles was developed to study both shear and extensional rheology in a unified framework. Our analysis shows that the presence of an encapsulated particle always enhances all the measured rheological quantities such as the effective shear viscosity, extensional viscosity and normal stress differences. (iv) Moreover, linear viscoelastic behaviour of a dilute dispersion of compound particles is characterised in terms of complex modulus by subjecting the dilute dispersion to a small-amplitude oscillatory shear (SAOS) flow. (v) Various expressions pertaining to a suspension of particles, drops, and particles coated with a fluid film are also derived as limiting cases of compound particles.

Numerical Investigation on Time-Dependent Deformation in Roadway

The roadway deformation normally relates to time especially for underground coal roadway. The strength of soft coal is low, and therefore the deformation increases gradually under constant stress with time, which is called rheology deformation. In this study, based on a field case, the rock mass properties and deformation data of the roadway were obtained according to the field test. A 3D numerical model was then established, and the rheological deformation including horizontal and vertical deformation of the coal roadway was systematically analyzed. The results showed that the rheological deformation of horizontal sidewall accounts for almost 30% of the whole deformation, and the stable time for such roadway is around 60 days after excavation. The tendency of the roof deformation is similar to the sidewalls, and however, the floor deformation is different. Then the related suggestions for maintaining the stability of such roadway were proposed, which is useful in-field application.

Experimental Research on the Rheology Slip Damage Mechanical Properties of Sandstone under the Dynamic Loading

The soft sandstone is taken as samples, and the RLW-2000M triaxial rheological testing machine is used as the main equipment to test the axial stress-strain, the axial rheological deformation in this paper. The axial strain is selected as damage variables, the damage degree expression is derived, and the effect of each factor on damage degree is studied. Research results show that axial deformation increases with the passage of time, and the hysteresis curve change from sparse to dense under the action of the dynamic loading. The axial deformation increase with the increase of the dynamic loading amplitude, and it increases with the decrease of frequency. The damage degree of specimen tends to be stable after mutation and increases with the increase of the dynamic loading amplitude. The research results will provide the scientific basis for us to disclose the rule of rheology-damage evolution of sandstone under the action of dynamic loading.

A Solution to the Time-Dependent Stress Distribution in Suborbicular Backfilled Stope Interaction with Creeping Rock

The creep behavior of deep weak rock masses is important due to an underground opening. Appreciating the nature and source of these deformations requires the knowledge of rock mass and ground support interaction. The theoretical solution of the backfill’s internal stresses needs to consider the time-dependent effect. In the present study, the coupling interaction between the creep behavior of the nearby rock material and the internal stresses in the backfilled stope is considered and the interaction characteristics are given analytically. A solution is then proposed regarding the time-dependent stress distribution in suborbicular backfilled stope interaction with creeping rock. Besides, the correctness of the theoretical solution is verified by numerical simulation, while influential parameters such as stope buried depth, lateral pressure coefficient, horizontal stress ratio, creep time of surrounding rock mass, delay time of the backfill, and Young’s modulus are thoroughly discussed. Research shows that when the stope buried depth becomes large as well as the rheological effect of the nearby rock materials becomes significant, the stress distribution in the backfill material exceeds its self-weight stress and presents significant time-dependent characteristics. The delayed backfilling weakens the backfill’s ground support effect on the nearby rock material. Hence, timely and multipoint simultaneous backfilling is needed for a stope with significant rheological deformation of surrounding rock mass. Lastly, this work will offer useful knowledge while designing the backfill materials for underground mines.

Experimental Investigations on Rheological Properties of Mudstone in Kilometer-Deep Mine

The soft rock roadway in deep high-stress environment has the problems of strong rheology and large deformation. Based on the analysis of the stress distribution of the surrounding rock of the roadway in a kilometer-deep mine, rheological tests under different stress paths are carried out for mudstone in a kilometer-deep mine. The rheological deformation curve, damage characteristics, and change rule of the main mechanical parameters of mudstone under different stress conditions are studied. The results show the following: (1) the peak strength of the triaxial compression of mudstone is closely related to confining pressure, and, with increasing confining pressure, the confining pressure effect decreases gradually; (2) the strain increases slowly under uniaxial loading, and, with increasing axial pressure, the velocity of rheological deformation increases nonlinearly, and the amount of mudstone deformation increases with time; (3) under the condition of unloading confining pressure with constant axial pressure, with decreasing confining pressure, the instantaneous axial and radial strains of mudstone specimen increase nonlinearly, the rheological strain and velocity of mudstone increase gradually, and the lateral rheological strain is close to the axial rheological strain; and, (4) in the unloading confining pressure with axial compression triaxial test, with increasing deviating stress, the axial and radial instantaneous strain increments of mudstone decrease gradually, the lateral strain and rheological velocity of mudstone increase gradually, and the lateral strain is approximately 2.05 times the axial strain. These conclusions reveal the rheological characteristics of the mudstone under different surrounding rock conditions and provide a theoretical basis for the excavation deformation and support control of roadways.

Modeling Elastic and Dissipative Properties of Feed Grain Subjected to Vibration

Appropriate parameters of feed grain crushers are to be selected relying on the in-depth knowledge of fragmentation regularities in single grains and clear understanding of their deformation rheology. Mathematically, the vibration deformation is a considerably complex process related with originating and propagating cracks in a grain body. Therefore, mechanical analogues and adequate models are needed. The paper demonstrates a suggested rheological model – a combination of Ishinsky, Hook, and Newton bodies correctly demonstrates mechanical processes taking part in a being deformed grain when crushing. Analytically, the loading and unloading curve of a grain is reduced to an appropriate form of the Davidenkov mathematical model.

Extensional Rheological Measurements of Surfactant-Polymer Mixtures.

Polymer solutions flowing in the porous media during enhanced oil recovery (EOR) processes are subjected to both shear and extensional rheological deformation. However, the previous rheological studies conducted on a surfactant–polymer (SP) system or polymer systems were only shear-based. In this paper, the extensional rheological performance of hydrolyzed polyacrylamide (HPAM) in the presence of an anionic surfactant at various concentrations (0, 0.01, 0.05, 0.1, 0.2, and 0.3%) is studied with deionized water and 1% NaCl. Further, the extensional rheological behavior of HPAM in the presence of NaCl and CaCl2 is studied at varying ionic strengths (1–10%). A capillary break-up extensional rheometer is used for performing extensional rheological characterization. Results revealed that the extensional resistance of HPAM is enhanced in the presence of a surfactant. Particularly, around the critical micelle concentration value of the surfactant (0.1%), HPAM showed higher extensional resistance. Higher extensional resistance for the SP system is observed with deionized water when compared to 1% NaCl. HPAM showed improved performance at 1% NaCl salinity when compared to the higher concentration of NaCl salinity. However, the presence of even 1% of calcium ions is detrimental to the extensional properties of HPAM.

Rheological deformation and failure laws of boreholes in granite under thermo-mechanical coupling and its application in deep hole drilling of hot dry rock for geothermal energy exploitation

The key technology issue in deep hole drilling of hot dry rock (HDR) for geothermal energy exploitation is the stability of the surrounding rock. The temperature and in situ stress of the borehole play a significant role in its deformation and instability under high-pressure and high-temperature conditions. Based on the occurrence conditions of the granite reservoir of the Yangbajing geothermal field in Tibet, a research was conducted by means of experimental study, numerical simulation, and theoretical analysis, from which the following conclusions were drawn. (1) The deformation and failure laws of borehole are based on the physical experiment on granite specimen under high-temperature and high-pressure conditions. (2) The Weibull distribution of the thermal expansion coefficient is used for establishing rock heterogeneity, and the COMSOL software is used to reproduce the temperature and stress distribution of the borehole during physical experiment, thus demonstrating the distribution of the temperature field, stress field, and displacement field under thermo-mechanical coupling (TMC) condition. (3) Based on the complete analysis of the temperature field and stress field, combined with the conclusions of the deformation and failure of granite specimen under high-temperature and high-pressure conditions, the failure laws of borehole under the TMC condition were analyzed, as well as the critical conditions of borehole instability during deep hole drilling of HDR. (4) With the critical conditions of borehole instability during deep hole drilling of HDR, which the relation between the in situ stress σ and temperature T is σ = 241.9–0.3998 T. These conclusions have practical guiding significance to the stability control of the surrounding rocks of borehole in relation to projects such as geothermal energy exploitation from HDR, deep oil and gas resource extraction, and deep hole drilling in mainland China.

Pendant drop tensiometry: A machine learning approach.

Modern pendant drop tensiometry relies on the numerical solution of the Young-Laplace equation and allows us to determine the surface tension from a single picture of a pendant drop with high precision. Most of these techniques solve the Young-Laplace equation many times over to find the material parameters that provide a fit to a supplied image of a real droplet. Here, we introduce a machine learning approach to solve this problem in a computationally more efficient way. We train a deep neural network to determine the surface tension of a given droplet shape using a large training set of numerically generated droplet shapes. We show that the deep learning approach is superior to the current state of the art shape fitting approach in speed and precision, in particular if shapes in the training set reflect the sensitivity of the droplet shape with respect to surface tension. In order to derive such an optimized training set, we clarify the role of the Worthington number as a quality indicator in conventional shape fitting and in the machine learning approach. Our approach demonstrates the capabilities of deep neural networks in the material parameter determination from rheological deformation experiments, in general.

Uniaxial stress relaxation behavior of marble after cyclic disturbance loads

It is known that time-dependent rheological deformation of rocks is influenced by cyclic disturbance loads. However, the stress relaxation behavior after cyclic disturbance is still poorly understood. To study such effects, a dynamic disturbance electrohydraulic servo triaxial test system was developed. A series of disturbance relaxation tests with different disturbance numbers and amplitudes were carried out on marble at several strain levels. The influence of cyclic disturbance parameters on the relaxation magnitude, relaxation rate, and peak stress was analyzed. Relaxation magnitude and relaxation rate after cyclic disturbance loads are larger than those of conventional relaxation. In addition, sensitivity analysis reveals that the relaxation magnitude is more sensitive to the disturbance amplitude. Damage variables defined by the plastic strain method can well reflect the evolution law of relaxation damage under different disturbance conditions. It is believed that the damage model constructed by Harris function can better describe the relaxation damage evolution law at various strain levels.

Influence of differential structural deformation on shale reservoirs: a case study of the lower Silurian Longmaxi Shale in north Guizhou, Southern China

AbstractSouthern China is affected by multi-stage tectonic activities, with strong fold deformation, complex fault systems and poor shale gas preservation conditions. Here, we used shale samples from the lower Silurian Longmaxi shale in the complex tectonic area of Southern China, to study the relationship between differential structural deformation, and pore structure and adsorption capacity. According to the deformation mechanism of the shale, it is further divided into brittle-slip rheological deformation (BD) and ductile-slip rheological deformation (DD). The results show that all micro-fractures can be observed under scanning electron microscopy in deformed shale samples, but in shale samples with different types of rheological deformation, the micro-fractures have large differences in scale, fracture length and lateral connectivity. The micro-fractures developed in DD shales are small in scale and short in fracture length, but have strong local connectivity. In contrast, brittle minerals are more developed in BD shales, and interlayer shearing has formed micro-fractures with large fracture length and good lateral connectivity, which is beneficial for later fracturing. In these two types of deformed shales, pores in organic matter are rare, and sporadic organic pores have small pore size and poor connectivity. The total pore volume (1.8–2.4 × 10−2 cm3 g–1) of BD shale samples is higher than that of DD shale samples (0.8–1.6 × 10−2 cm3 g–1). There is a positive correlation between total pore volume and quartz content. In addition, the specific surface area (12–18 m2 g–1) of DD shale samples is larger than that of BD shale samples (6–12 m2 g–1).

Using a coupled FEM-DEM method to study the nonlinear phenomena of third-body behavior

Third-body lubrication is widely applied in the design of mechanical frictional pair, but the relation between the lubrication performance and third-body rheology is hardly focused on. In this paper, the behavior of two plates shearing granular third-body is modeled by a coupled FEM-DEM method to study the nonlinear phenomena during this process. The upper plate is modeled by FEM, while the third-body and lower plate are modeled by DEM. During the simulation, the upper plate compresses the granular third-body at a certain pressure. Then, the lower plate shears at a constant speed. The fluctuations of friction force and dilatancy phenomenon of clearance between two plates, which show strong nonlinearity over time, are studied over different external loads, shearing speeds, and elastic moduli. The nonlinear distributions of averaged stress and velocity across the height of third-body are also studied to further reveal the relation between the nonlinear phenomena and the discreteness of third-body. The perspective of the paper is that the coupled FEM-DEM method can elucidate the nonlinear nature of third-body by efficiently processing both the third-body rheology and first-body deformation.

Process to assess rheological characteristics of rocks by underground geodesic data in terms of a viscoelastic model

Under consideration is the process for evaluation of rheological properties of construction components in the underground chamber-and-pillar system to mine solid mineral reserves. The process is based on solving the inverse mixed-type problems in terms of a 2D viscoelastic geomedium model. Feasibility is demonstrated to evaluate in-situ state parameters characterizing rheological deformation of rocks. Numerical experiments with the use of synthetic input data (viz. relative displacements of the worked-out space contour points recorded by underground geodesic monitoring) for the prescribed absolute precision of the instruments made it possible to establish a required population of measurement data to provide an inverse problem-solving procedure.

Study on the horizontal continuous casting of Cu-based bulk metallic glass slab

To improve the fabrication efficiency of bulk metallic glasses (BMGs) with high mechanical properties and low costs, Cu47Zr45Al8 and (Cu47Zr45Al8)98.5Y1.5slabs with the cross-section of 50 ×6 mm were produced by horizontal continuous casting method (HCC). It is proved that by adding Y to Cu47Zr45Al8, the crystallization behavior could be significantly decreased, and an amorphous structure was obtained when it was casted at DT=80 K. The obtained amorphous structure was proved by XRD, TEM, DSC analysis. The glass transition behavior and crystallization were identified with Tgof 671 K, Txof 771 K, ΔTxof 80 K, andΔH0of 46.2 J/g, respectively. In terms of mechanical properties, the compressive strength and Vickers hardness reached 1803 MPa and 493 HV, respectively. Fracture morphology revealed that the fracture is characterized by limited rheological deformation and high localization of shear band expansion, which results in a mixed fracture mode of ductile and brittle.

Understanding the role of gluten subunits (LMW, HMW glutenins and gliadin) in the networking behavior of a weak soft wheat dough and a strong semolina wheat flour dough and the relationship with linear and non-linear rheology

The differences in viscoelastic properties of gluten from two very different wheat flours, a weak soft flour dough and a strong semolina dough, primarily caused by their gliadin and glutenin content including gliadin to glutenin ratio were studied. The doughs were subjected to oscillatory time sweep tests at small and large amplitudes as well as small and large frequencies. The gluten subunits (LMW, HMW glutenins and gliadins) tagged with specific fluorescent quantum dots with a distint excitation wavelength were imaged with confocal laser scanning microscopy and their distribution and interactions were measured. The quantitative imaging data was converted into networking data that included lacunarity, network area, and number of network junctions. This networking data was correlated with rheology. The two different dough systems showed different oscillatory behavior during time sweeps. The critical role of LMW glutenins in keeping the structural integrity of semolina doughs was demonstrated by a direct correlation between the non-linear elastic component ‘e3/e1’ of the dough and protein network parameters of LMW glutenins. It was also shown that gliadins and HMW glutenins co-localize and associate throughout rheological deformations of the dough. The disruption of the three gluten subunits are responsible for rheological breakdown of soft wheat flour dough, with gliadins influencing the breakdown of the network at higher amplitude deformations. This research presents a new method to analyze the microstructure of wheat doughs and new understanding of how the network structure of the dough subunits contribute and are correlated with fundamental rheological tests.

Rheological Deformation Behavior of Soft Rocks under Combination of Compressive Pressure and Water-Softening Effects

Abstract The purpose of this article is to investigate the rheological deformation behavior of soft rocks subject to the combination of externally applied compressive pressure and water-softening effects. To achieve this goal, a series of mechanical tests on soft rocks were performed by using a customized meso-mechanical triaxial test system consisting of a bidirectional servo confining pressure loading subsystem and a water pressure chamber. The system has the capability of simulating the actual compressive stress and water environment of soft rocks in engineering practice. The experimental results show that, under compressive stresses, water-softening effects could significantly increase the deformation rate of the soft rocks, ultimately lead to a larger deformation of the rocks. To further understand the combination of compressive pressure and water-softening effects on the deformation behavior of the soft rocks, an elastoplastic damage model was developed. It shows that the model can reproduce the experimentally observed deformation behavior of soft rocks. In addition, it reveals that, with the rock–water interaction, the deformation process of the compressed soft rocks can be described as the change from the attenuation state to the steady state of rheological deformation.