Shear Yield Research Articles

Self-Compacting Mixtures of Fair-Faced Concrete Based on GGBFS and a Multicomponent Chemical Admixture—Technological and Rheological Properties

The use of superplasticizers in a self-compacting concrete mix without the addition of a foaming agent in practice leads to a well-known problem associated with increased air entrainment and promotes the formation of harmful large bubbles, high-void content, and ununiform appearance. This paper presents research on the properties of cement paste consisting of Ordinary Portland Cement (OPC), powder based on ground granulated blast furnace slag (GBBS), and superplasticizer. The methodology of this study was the estimation of flow diameter and flow time, as well as the evaluation of the rheological characteristics. The influence of ground granulated blast furnace slag and polycarboxylate plasticizer on the flowability and viscosity of cement paste was studied. The effect of superplasticizer (SP) based on polycarboxylate esters (PCE) anti-foaming agent (AFA) based on a glycol ester and air-entraining admixture (AEA) based on an amphoteric surfactant on flowability, viscosity, rheological properties and the strength of the cement paste was evaluated. It was found that the increase of slag content in cement paste (25%) with the presence of superplasticizer (0.64%) significantly changes the flowability and viscosity. It was stated that the addition of 0.04% anti-foaming agents increases flowability (20%) and reduces viscosity (44%) of cement paste. It was stated that the addition of small dosages of glycol ester-based anti-foaming agent (0.02 and 0.04%) significantly changes the rheological properties, decreases the shear yield stress by 2.1–2.8 times, the plastic viscosity by 2.4–2.6 times and apparent viscosity 1.6–2.5 times, improves the compressive strength at the age of 1 and 7 days by 2.5 and 1.4 times, respectively. The addition of air-entraining admixture led to a decrease in the plastic viscosity by 1.2–1.4 times. It was stated that the presence of air-entraining admixture assists in increasing the apparent viscosity by 1.7–2.4 times. It was shown that the presence of complex admixtures of various origins, purposes, and mechanisms of action would assist in predicting the behavior of concrete mixtures under the conditions of the building site and reduce the consumption of polycarboxylate esters due to the enhancing plasticizing effect of anti-foaming agent and air-entraining admixture.

Effect of soft magnetic particles content on multi-physics field of magnetorheological composite gel clutch with complex flow channel excited by Halbach array arrangement

In this paper we investigate the influence of soft magnetic particle mass fraction on the multi-physics field of proposed magnetorheological (MR) gel clutch. A novel MR gel clutch with complex cup-shaped gap is described, whose performance is based on the relative placement between Halbach array arrangement and MR gel. Smart MR gel with 40 wt%, 50 wt%, 60 wt%, 70 wt% and 80 wt% of soft magnetic particles used as the transfer medium and Halbach array is adopted as magnetic excitation system. Its magnetic/mechanical analysis is carried out based on Bingham-plastics model using COMSOL Multiphysics software, which takes into account the variation of dynamic viscosity with magnetic flux density. The distribution of the magnetic flux density, shear yield stress, post-yield viscosity, shear stress and torque in the four flow channels during the transition from engagement state to disengagement state are obtained and analyzed in detail. Multi-physics field characteristics of proposed MR gel clutch with five kinds of MR gels are studied and compared in order to give some useful suggestions in the design phase. Finally, the dynamic torque of the MR clutch with different MR gel is experimentally evaluated.

Environmental disposal of sulphide-rich and desulfurized tailings: Thickening, rheological, mechanical, and leaching performance

The surface disposal of sulphide-rich tailings (compared to ordinary tailings, it contains many sulphides) will cause environmental and groundwater pollution, and it is an eco-friendly method to prepare cemented paste backfill (CPB) from sulphide-rich tailings and backfill it into underground goafs. However, the thickening performance of sulphide-rich and desulfurized tailings is unclear, the sulphide-rich CPB strength cannot meet the standard. Therefore, a comprehensive study was conducted on its thickening performance through settling columns and dynamic thickening experiments, mechanics, and leaching tests were also conducted. The optimal flocculant conditions with different sulphide contents were obtained through settling column experiments. Meanwhile, it was found that turbidity and initial settling rate (ISR) were linearly related to tailings feeding concentration. Due to the higher specific gravity of sulphide-rich tailings, under different flocculation conditions, the higher the sulphide content, the higher the concentration, and there is a linear correlation between sulphide content and concentration. The results of dynamic thickening show that rake-shearing can improve the concentration and the shear yield stress, both of which increase rapidly at first and then slowly with the extension of shearing time. A logarithmic model of concentration based on shear yield stress was established. The unconfined compressive stress of the CPB prepared from tailings desulfurized to 20.7 wt%-S (S20.7) is much higher than that of 30.7 wt%-S sulphide content tailings (S30.7), which can meet the backfilling requirements. The concentration of metal ions in the soaking solution of S20.7 CPB is higher, and the environmental impact is small. Finally, it is recommended to choose S20.7 for backfilling. The study is significant for revealing the thickening and mechanical performance evolution of sulphide-rich tailings and environmental protection disposal.

Influence of mixed particle sizes on shear yield stress of magnetorheological fluid

AbstractThis study investigated the effect of magnetic particle size and volume fraction on the shear yield stress and dynamic viscosity of magnetorheological fluids. Magnetorheological fluids with varying volume fractions of micro‐ and nanoscale magnetic particles were prepared. A plate‐on‐plate shear test bench was constructed to evaluate the fluids under a constant shear rate, with the applied current ranging from 0 A to 1.2 A. Results indicated that the shear yield stress initially increased and then decreased as the volume fraction of magnetic nanoparticles increased, reaching a maximum of 47 kPa at a volume fraction of 7 %. However, the excessive addition of magnetic particles or large‐diameter particles led to settling and reduced stability of the fluids. The findings suggest that optimizing the size and volume fraction of magnetic particles is crucial for maximizing the shear yield stress of magnetorheological fluids.

Rapid Urban-Scale Building Collapse Assessment Based on Nonlinear Dynamic Analysis and Earthquake Observations

Rapid damage assessment after an earthquake is crucial for allocating and prioritizing emergency actions. Building damage due to an earthquake depends on the seismic hazard and the building’s strength. While it is now possible to promptly access acceleration data as seismic input through online strong motion networks in urban areas, good models are necessary to evaluate the damage in different zones of the affected area. This study aims to present a rapid method for such an urban-scale building collapse evaluation by conducting a nonlinear dynamic analysis of modeled buildings. Based on the Nagato and Kawase model, this study estimates the yield shear strength of 3-story steel buildings, 3-story reinforced concrete buildings, and 1-story masonry buildings in Sarpol-e-Zahab City after the 2017 Mw7.3 earthquake. The damage ratio is calculated through nonlinear dynamic analyses using estimated records from the main earthquake shock in different city zones. The research found that the seismic yield shear strength of steel and reinforced concrete buildings might be weaker than that of the Iranian seismic code’s standard value. Conversely, masonry-building resistance is stronger than the guidelines assumed. The constructed numerical models can be used for the rapid building damage assessment immediately after a damaging earthquake.

A novel prediction method for rolling contact fatigue damage of the pearlite rail materials based on shakedown limits and rough set theory with cloud model

Evaluation and prediction of wheel-rail rolling contact fatigue (RCF) damage can provide important theoretical guarantees for the service safety of wheels and rails and help make maintenance easier to plan. This study aims to develop a novel method for evaluating and predicting RCF damage of the pearlite rail materials with various initial shear yield strengths (ke). Based on the rough set mathematical theory incorporated within the cloud model of the comprehensive evaluation index (P0/ke*μt), a novel evaluation and prediction method for RCF damage states of various pearlite rail materials was constructed using the shakedown limits for pearlite rail materials with various initial shear yield strengths. To develop this novel prediction method, different evaluation indices for RCF damage states were designed. A comprehensive certainty approach was introduced to quantitatively analyze the actual measured values of distinct evaluation indices that corresponds to different RCF damage states, wherein the maximum value rule was applied. Moreover, the prediction results were confirmed after further verifying using the actual measured value of the P0/ke*μt. The results indicated that the predicted results were consistent with the test outcomes. The key feature of this prediction method was that it involved both the intrinsic shear yield strength of evaluated pearlite rail materials and wheel-rail rolling contact variables. On the basis of the two-dimensional classical shakedown map, a three-dimensional shakedown limit diagram for rail materials with varying initial shear yield strengths was further constructed using this novel prediction method. The three-dimensional shakedown limit diagram featured an inclined curved surface. As the initial shear yield strength of the pearlite rail materials increased, the curved surface tilted downward, indicating that an increase in the initial ke value of the pearlite rail materials could result in a lower shakedown limit.

Microstructure, thermal, and mechanical properties of hierarchical porous silicon carbide made by direct ink writing

AbstractHierarchical porous silicon carbide (SiC) ceramics were fabricated by combining particle‐stabilized emulsions and three‐dimensional (3D) printing. Direct ink writing (DIW) was used as the 3D printing technique. The formulation for successful printing is discussed in relation to the rheology of the emulsions. The SiC emulsions were able to be printed with a lower storage modulus (G′) and apparent yield shear stress (τy) than previously reported SiC ink pastes. The printed and sintered porous SiC ceramics possess a total porosity of 73.7% with an average pore size within the filaments of 2.2 µm in diameter. A hierarchical pore structure that contains pore sizes of about 250 µm, around 1–10 µm and smaller than 0.5 µm can be observed in the microstructure and pore size distribution. The mechanical properties showed a good strength‐to‐density ratio, and the thermal conductivity was reduced to 4.9 W/m·K. This study provides a new reliable approach for fabricating hierarchical porous SiC ceramics with low thermal conductivity.

Significant Improvement in Magnetorheological Performance by Controlling Micron Interspaces with High Permeability Submicron Particles.

The shear yield strength, sedimentation stability and zero-field viscosity of magnetorheological fluids (MRFs) are crucial for practical vibration damping applications, yet achieving a balanced combination of these performances remains challenging. Developing MRFs with excellent comprehensive performance is key to advancing smart vibration damping technologies further. Theoretically, incorporating a multiscale particle system and leveraging synergistic effects between their can somewhat enhance MRFs' performance. However, this approach often faces issues such as insignificant increases in shear yield strength and excessive rise in zero-field viscosity. In response, this study employs a DC arc plasma method to synthesize a high magnetic permeability, low coercivity submicron FeNi particles, and further develops a novel CIPs-FeNi bidisperse MRFs. The introduction of submicron FeNi particles not only significantly enhances the shear2019 yield strength of MRFs under low magnetic fields but also promotes improvements in sedimentation stability and redispersibility without excessively increasing viscosity. Comprehensive performance analysis is conducted to explore the optimal content ratio, and detailed mechanisms for the enhancement of performance are elucidated through analysis of parameters such as chain-like structure, magnetic flux density and friction coefficient. Most importantly, the superior comprehensive performance combined with straightforward fabrication methods significantly enhances the engineering applicability of the CIPs-FeNi bidisperse MRFs.

Biobased hydrogel bioinks of pectin, nanocellulose and lysozyme nanofibrils for the bioprinting of A375 melanoma cell-laden 3D in vitro platforms

Melanoma is one of the most aggressive types of skin cancer, and the need for advanced platforms to study this disease and to develop new treatments is rising. 3D bioprinted tumor models are emerging as advanced tools to tackle these needs, with the design of adequate bioinks being a fundamental step to address this challenging process. Thus, this work explores the synergy between two biobased nanofibers, nanofibrillated cellulose (NFC) and lysozyme nanofibrils (LNFs), to create pectin nanocomposite hydrogel bioinks for the 3D bioprinting of A375 melanoma cell-laden living constructs. The incorporation of LNFs (5, 10 or 15 wt%) on a Pectin-NFC suspension originates inks with enhanced rheological properties (shear viscosity and yield point) and proper shear-thinning behavior. The crosslinked hydrogels mimic the stiffness of melanoma, being stable under physiological and cell-culture conditions, and non-cytotoxic towards A375 melanoma cells. P-NFC-LNFs (10 %) reveals good printability (Pr = 0.89) and printing accuracy (51 ± 2 %), and when loaded with A375 cells (3 × 106 cells mL−1) the bioink originates 3D-constructs with high cell viability (92 ± 1 %) after 14 days. The potential of the constructs as in vitro models is corroborated by a drug-screening test with doxorubicin, where cells within the model displayed high sensitivity to the drug.

Machine learning based multi-objective optimization on shear behavior of the inter-module connection

Prefabricated prefinished volumetric construction (PPVC) has become a research hotspot in recent years. Inter-module connections have a crucial influence on the mechanical behavior of PPVC. However, current studies on shear behavior and optimization design method of the inter-module connection are insufficient. This paper investigated shear behavior and machine learning based optimization method of an innovative fully bolted liftable connection (FBLC) for PPVC. The failure mode, force transferring mechanism, and ultimate load bearing capacity of the FBLC under shear force were revealed by the shear behavior tests. Four specimens were tested and the design parameters included the strength and number of the long stay bolts. Subsequently, a refined finite element model (FEM) of the FBLC was established and validated with the ratios of the shear bearing capacity between the FEA and test results ranging from 0.99 to 1.10. Then, six mainstream machine learning algorithms were utilized to predict shear behavior of the FBLC. The Genetic Algorithm Optimized Neural Network (GANN) provided better prediction accuracy on the shear bearing capacity, with an improvement on R2 by 0.1% to 3% compared with other algorithms. Similarly, the Support Vector Regression (SVR) showed higher prediction accuracy on the ultimate displacement, improving R2 by 0.4% to 12.9% compared with other algorithms. A stacking algorithm combing the GANN and SVR was developed as the proxy model between the input variables and optimization metrics. In addition, the NSGA-II algorithm was linked to establish a multi-objective optimization method on shear behavior of the FBLC. The yield load, ultimate load and steel consumption were selected as the optimization objectives and the stacking algorithm was used as the proxy model. The Pareto optimal solution sets on the optimization objectives were explored by the NSGA-II algorithm and the optimization design method of the FBLC was established. Compared with the unoptimized specimen, the yield and ultimate shear bearing capacity of the optimized specimen were increased by 113.5% and 123.6%, respectively, with the steel consumption reduced by 26.3%. Finally, a four-story PPVC was established, and the static analysis was carried out under vertical load and wind load. The shear behavior of the FBLC and inter-story drift ratio of the PPVC before and after optimization were compared to verify the reliability of the optimization method.

Shear-driven stability of a rigid particle in yield stress fluids

The stability of a rigid particle in yield stress fluids, comprised of soft particle glasses (SPGs), is investigated in shear flow under an applied external force, such as weight, using particle dynamics simulations. Results provide the critical force threshold, in terms of the dynamic yield stress and the flow strength, required to initiate sedimentation of the rigid particle over a wide range of shear rates and volume fractions. The streamlines of the SPGs show local disturbances when the rigid particle settles. The form of these disturbances is consistent with the microdynamics and microstructure response of the neighboring soft particles of the sedimenting rigid particle. Sedimenting particle induces non-affine displacement to the suspensions at low shear rates and high applied forces, while these dynamical events are localized and suppressed at high shear rates. Stability diagrams, which provide the conditions of the sedimentation of the rigid particle, are presented in terms of the applied force and the shear rate. These individual stability diagrams at each volume fraction map onto a universal stability diagram when the external force is scaled by the dynamic yield stress and shear rate with a ratio of the solvent viscosity to the low-frequency modulus of the SPGs.

A generalized, computationally versatile plasticity model framework - Part II: Theory and verification focusing on shear anisotropy

Shear-dominated deformation (SHDD) is pivotal in sheet metal forming; however, comprehensive modeling of plastic anisotropy in SHDD, specifically shear anisotropy considering both yield stress and plastic flow, has been inadequately addressed in existing literature. In this work, a generalized constitutive framework is introduced on the basis of stress triaxiality-dependent state variable to accurately emulate plastic anisotropy and the physics-based shear constraint in SHDD. The framework is capable to seamlessly integrate with existing yield criteria, preserving computational efficiency and versatility. Notably, the yield function, anisotropic parameters, and their optimization or analytical determination for the non-shear deformation state remain unaltered. When integrated with the Hill48 yield function, featuring either one or two anisotropic parameters within the generalized constitutive framework, precise characterization of yield strength and plastic flow in SHDD is achieved. The applicability of the framework extends to various anisotropic yield functions such as the widely employed Yld2k-2d and the sixth-order polynomial (Poly6) function as a class of associated flow rule-based yield functions, and one non-quadratic yield function for non-associated flow rule scenarios. Experimental validation with two engineering sheet metals, high-strength dual-phase steel DP980 and high-strength aluminum alloy AA7075-T6, was conducted. Comparative analyses with several recently proposed yield criteria, especially Poly6-18p, highlighted the efficiency of the proposed constitutive framework. Furthermore, this study explores intrinsic shear constraints, particularly the absence of through-thickness strains under in-plane shear stress. Additionally, it offers an enhanced description of plastic anisotropy in shear yield stress within the general framework, providing valuable insights into the complexities of SHDD.

Analysis of electrothermal shape memory alloy and disc-type magnetorheological fluid combined transmission

In this article, a disc-type magnetorheological fluid and electrothermal shape memory alloy spring-loaded slider friction combined transmission device is proposed. A heating model of the electrothermal shape memory alloy spring is used to calculate the relationship between current and spring temperature. Experiments are used to investigate the link between spring temperature and restoring force, as well as magnetorheological fluid temperature, magnetic flux density, and shear yield stress. The torque characteristics of the combined device were evaluated utilizing the coupled magnetic field and thermal field finite element method for the characteristics of the two materials. The results showed that the magnetorheological fluid showed an approximately linear decrease in shear yield stress at high temperatures, up to 37.94 %. The heating rate of the electrothermal shape memory alloy spring was influenced by the surrounding temperature, and the heating rate was too fast to easily cause the time lag of the martensite phase transformation, resulting in the spring restoring force becoming smaller, and its restoring force shows a non-linear increase when the temperature rises from 22 °C to 100 °C. By applying the two materials together, the torque of the combined transmission has been significantly increased, by 91.58 % compared to the same size magnetorheological transmission.

Shear strength of steel-concrete composite I-beams with corrugated steel webs

Corrugated steel webs have been widely applied to steel-concrete composite beams due to their excellent shear performance. However, there needs to be adequate research on the shear behavior of steel-concrete composite I-beams with corrugated steel webs, and the proportional distribution of shear forces between concrete flanges and corrugated steel webs in composite I-beams has yet to be clarified. This paper experimentally investigates steel-concrete composite I-beams with corrugated steel webs with different shear span ratios. With the increase of the shear span ratio, the shear failure mode of the beam gradually evolves from shear-dominated to flexural-dominated, the shear capacity and structural stiffness of the beam are negatively affected, and the improvement of the shear resistance of the beam after webs buckling is gradually limited. As the primary shear component, corrugated steel webs contribute about 71 % to 92 % of the total sectional shear force. Notably, accounting for 15 % to 35 % of the shear capacity of the beam, the shear contribution of the concrete flange must also be typically considered. For the generalizability of research results, parametric studies are conducted using validated numerical models to comprehensively investigate the effects of steel yield strength, concrete strength, web thickness, web height, and shear span ratio. Afterward, an efficient analytical model considering the shear capacity of the concrete flange is proposed to estimate the shear strength of composite I-beams with corrugated steel webs. The proposed analytical model agrees satisfactorily with experimental and numerical analysis results. The research results can provide valuable support for designing and optimizing steel-concrete composite I-beams with corrugated steel webs.

Evaluation of basalt fibers and nanoclays to enhance extrudability and buildability of 3D-printing mortars

A study of the rheological and fresh mechanical properties of fly ash-cement 3D printing (3DP) mortars with six types of nanoclays (NC) as rheology modifiers, two sepiolites, three attapulgites and one bentonite, and reinforced with short basalt fibers (BF) was carried out. Fresh mortar properties were evaluated with a flow table test (FTT), cylindrical slump test (CST) and cone-penetration test (CPT) on samples left at rest and stirred before testing. Squeeze test (SQT) was carried out on samples cast-in-the-mold and 3D printed to compare the effects of 3DP on the fresh mechanical behavior. Extrudability was assessed with an electrical barrel extrusion device. NC and BF enhanced mortar cohesion by preventing water drainage and improving material extrudability. NC increased shear yield stress (τ0) over time on samples left at rest, enhancing reversible thixotropy. Besides, NC required larger amounts of superplasticizer, increasing open time windows. Among NC, Sepiolite in powder form showed the best fresh mechanical performance on 3DP samples. BF enhanced extrudability due to the bridging effect but also shows mechanical synergies with some NC. 3DP samples showed lower compressive yield stress and Young modulus evolution over time (σ˙ and Ė) than cast-in-the-mold samples, due to their layered structure.

Hydrodynamic coupling of a cilia–mucus system in Herschel–Bulkley flows

The yield stress and shear thinning properties of mucus are identified as critical for ciliary coordination and mucus transport in human airways. We use here numerical simulations to explore the hydrodynamic coupling of cilia and mucus with these two properties using the Herschel–Bulkley model, in a lattice Boltzmann solver for the fluid flow. Three mucus flow regimes, i.e. a poorly organized regime, a swirly regime, and a fully unidirectional regime, are observed and analysed by parametric studies. We systematically investigate the effects of ciliary density, interaction length, Bingham number and flow index on the mucus flow regime formation. The underlying mechanism of the regime formation is analysed in detail by examining the variation of two physical quantities (polarization and integral length) and the evolution of the flow velocity, viscosity and shear-rate fields. Mucus viscosity is found to be the dominant parameter influencing the regime formation when enhancing the yield stress and shear thinning properties. The present model is able to reproduce the solid body rotation observed in experiments (Loiseau et al., Nat. Phys., vol. 16, 2020, pp. 1158–1164). A more precise prediction can be achieved by incorporating non-Newtonian properties into the modelling of mucus as proposed by Gsell et al. (Sci. Rep., vol. 10, 2020, 8405).

Exploring the strain rate influence on shear yield behavior of acrylonitrile-butadiene-styrene: Experimental and numerical study

Most experimental and numerical studies are limited to examining the effect of strain rate on the compressive and tensile yield behavior of Acrylonitrile-Butadiene-Styrene (ABS), an amorphous material of significant industrial relevance, rather than its shear yield behavior; therefore, this study is dedicated to addressing this notable gap in the literature by exploring the effect of strain rate on the shear yield behavior of ABS. To this end, shear tests were carried out using the Wyoming version of the Iosipescu (V-notched) shear test fixture at five distinct loading rates, ranging from 5 × 10−3 to 1 × 101 mm/s, which correspond to strain rates between 5.5 × 10−4 s−1 and 7 × 10−1 s−1. Shear strain distributions in the specimens were measured using the Digital Image Correlation (DIC) technique. The shear test results not only revealed a substantial increase in the shear yield strength of ABS with increasing strain rate, but also demonstrated that the shear yield strength of ABS is more sensitive to strain rate than its compressive and tensile yield strengths. The findings of the study also suggested that using shear-tension test data pairs at the same strain rates is more effective for determining the hydrostatic pressure sensitivity parameter than using tension-compression and shear-compression test data pairs. The experimental results were validated against numerical predictions obtained through finite element analyses employing an elastic-viscoplastic constitutive model, which comprehensively accounted for non-linear material properties, geometric complexities, and non-linearities arising from boundary contacts.

Ballast stiffness estimation based on measurements during dynamic track stabilization

Ballast compaction with the Dynamic Track Stabilizer (DTS) is known to improve the lateral track resistance by increasing the stiffness of the ballast. This paper presents two approaches for estimating the strain dependent ballast shear modulus G based on measurements during dynamic track stabilization. One approach uses the Hardin equation with its enhancement for coarse-grained soils to estimate the small strain shear modulus for a given grain size distribution curve. Since different shear strains are induced on an observed sleeper (with fixed location) by a bypassing DTS, the measurement of ballast shear strains with accelerometers on the top and the bottom edge of the ballast layer yield shear modulus degradation curves G/Gmax. It is shown for data from a regular maintenance operation, that these shear modulus degradation curves are in accordance with previous research. For the second approach, a SDOF model for the track-ballast interaction under harmonic loading (caused by the dynamic track stabilizer) is developed. Influence lines are used to estimate the mass, the mass moment of inertia and the geometry of an equivalent machine foundation (with spring and dashpot coefficients according to the Hall analog). An optimization algorithm is used to fit the model response to the measured data from field tests with the DTS. The resulting shear moduli show plausible values for loose and compacted ballast conditions, which proves the potential of the presented method as a basis for a future system for Intelligent Compaction (IC) with the DTS.

Orientation-dependent yield and Bauschinger effects in two-dimensional Yukawa solids

Langevin dynamics simulations of two-dimensional (2D) Yukawa solids are performed to investigate the orientation-dependent yield and Bauschinger effects in solid 2D dusty plasmas. The yield stress of 2D Yukawa solids under different conditions is determined from the corresponding stress-strain response curve, defect fraction, and deviation from the affine displacement. It is discovered that both the shear modulus and yield stress are orientation dependent, exhibiting the significant anisotropic behaviors. It is found that the dependence of the calculated atomic elastic constant on the lattice orientation completely agrees with those of the shear modulus and yield stress. It is also found that, for different initial lattice orientations, the Yukawa solid exhibits the significant regular or reverse Bauschinger effects, or even non-Bauschinger effect. Published by the American Physical Society 2024

Experimental study of mechanical properties of deep-sea hydrate-bearing sediments under multi-field coupling conditions

To ensure the long-term safety of hydrate-bearing sediments (HBSs) in the deep sea, it is necessary to conduct a comprehensive study of the mechanical properties of HBSs, which is closely related to the safe extraction of natural gas hydrates (NGH). In this study, a HBSs preparation method was proposed preparing HBSs artificially to meet the test requirement. A series of triaxial shear tests were carried out by the self-developed HBSs multi-field coupling intelligent triaxial test device to analyze the effects of different hydrate saturation and NaCl concentration on the mechanical properties of HBSs. The results show that HBSs have elastic-plastic properties under multi-field coupling conditions, and the stress-strain curves show a strain-hardening trend. Hydrate saturation affects the shear strength of hydrate-bearing sediment critically. When the hydrate saturation is Sh>35 %, the cohesion and internal friction angle is directly proportional to the hydrate saturation. When the NaCl concentration is low, the cohesion of HBSs is more affected by the NaCl concentration, and the shear strength and yield strength are proportional to NaCl concentration. When NaCl concentration is high, the internal friction angle of HBSs is more affected by NaCl concentration and the shear strength is inversely proportional to NaCl concentration. Under the condition of multi-field coupling, the influence of each factor on the mechanical properties of HBSs has an upper limit, which is not a purely linear relationship.