Variable Shear Research Articles

Dynamic analysis and structural optimization study of porous FG-MEE microplate with impact and hygrothermal loads

Functionally graded magnetic-electro-elastic (FG-MEE) materials with their remarkable multifunctional energy conversion capabilities are widely used in several components such as biosensors, micro imaging devices, micro robotics and micro actuators. This paper presents vibration analysis and optimization studies of FG-MEE microplate resting on nonlinear visco-elastic foundation under hygrothermal loads. The equations of motion for a two-dimensional (2D) functionally graded MEE porous microplate are first obtained using four variable higher order shear deformation plate theory in conjunction with the modified couple stress model. By considering the material grading and porosity distribution functions, the dynamic formulation of the microplate is derived using variational approach. The general analytical procedure is employed to obtain the stiffness and mass matrices for different boundary conditions. Initially, the model is validated using free vibration analysis results. Further, dynamic analysis of FG-MEE microplate subjected to different impulse excitations is conducted to obtain the response amplitudes. Parametric studies are performed to investigate the effects of grading indices, porosity factor, length-scale parameter, foundation parameters, multi-physical loads on the fundamental frequency and dynamic response. Using design of experiments, it is noticed that five factors only have vital influence on the dynamic response of the microplate. Accordingly, a multilayer perceptron neural network model is trained with parametric data acting as a surrogate model. Finally, the optimal parameters are predicted to improve the stability by solving a constrained optimization problem using firefly optimization scheme with the trained neural network model. From optimization results it is noticed that the fundamental frequency has improved by 63.66% with enormous saving of computational time using the neural network surrogate model.

A two-step dynamic FEM-FELA approach for seismic slope stability assessment

The determination of the factor of safety (FoS) of slopes during seismic excitation can be complex if the relevant effects of pore water pressure accumulation, nonlinear material response and variable shear strength are duly accounted for. A rational two-step approach to tackle this task based on a hydro-mechanically coupled dynamic simulation and finite element limit analyses is henceforth introduced. To ensure accurate transfer of the hydro-mechanical soil state, a mapping concept is presented, accounting for spatial distributions of stresses, excess pore water pressures, inertial forces and shear strength. The proposed approach is compared to limit equilibrium method (LEM) for the case of a large-scale water-saturated open cast mine slope subjected to seismic loading. In comparison with LEM, the new approach to assess seismic slope stability proves to be simpler in its implementation and straightforward, which could be an important asset for practitioners.

Pulse-Echo Ultrasound for Quantitative Measurements of Two Uncorrelated Elastic Parameters

ObjectiveThis paper describes the relationship between elastic tissue properties and strain and presents an initial investigation of pulse-echo ultrasound to measure two uncorrelated elastic parameters in tissue-mimicking phantoms. The two elastic parameters are the shear modulus, related to deformation of shape, and what we in the paper define as the nonlinear compressibility, related to deformation of volume. MethodsWe prepared tissue-mimicking phantoms containing lesions of variable shear modulus and variable nonlinear compressibility. An in-house framework for shear wave imaging was developed using ultrasound radiation force at 4.5 MHz to induce shear waves and plane wave imaging with pulses in a frequency band centered around 12.5 MHz to track the shear waves. For measurements of nonlinear compressibility, co-propagating dual-frequency pulse complexes at 0.7 MHz and 14 MHz were applied. Algorithms were implemented on a Verasonics Vantage ultrasound scanner and a custom-made multi-frequency ultrasound transducer was used. Mechanical indentation measurements were performed to validate ultrasound measurements of the shear modulus. For the nonlinear compressibility, ultrasound measurements were compared to results derived from the literature. ResultsWe found good agreement in elasticity results from ultrasound measurements and mechanical indentation as well as when comparing with results derived from the literature. ConclusionResults of the current investigation were promising. We plan patient studies involving thyroid lesions and liver steatosis to explore whether measurements of elastic parameters related both to shape deformation and volume deformation are useful in clinical practice.

Improved Bayesian model updating of geomaterial parameters for slope reliability assessment considering spatial variability

In engineering practice, Bayesian model updating using field data is often conducted to reduce the substantial inherent epistemic uncertainties in geomaterial properties resulting from complex geological processes. The Bayesian Updating with Subset simulation (BUS) method is commonly employed for this purpose. However, the wealth of field data available for engineers to interpret can lead to challenges associated with the “curse of dimensionality”. Specifically, the value of the likelihood function in the BUS method can become extremely small as the volume of field data increases, potentially falling below the accuracy threshold of computer floating-point operations. This undermines both the computational efficiency and accuracy of Bayesian model updating. To effectively address this technical challenge, this paper proposes an improved BUS method developed based on parallel system reliability analysis. Leveraging the Cholesky decomposition-based midpoint method, the total failure domain in the original BUS method, which involves a low acceptance rate, is subdivided into several sub-failure domains with a high acceptance rate. Facilitated with an improved Metropolis-Hastings algorithm, the improved BUS method enables the consideration of a large volume of field data and spatial variability of geomaterial properties in the probabilistic back analysis. The results of an illustrative soil slope, involving spatially variable undrained shear strength, demonstrate that the improved BUS method is effective in simultaneously incorporating a substantial volume of field measurements and observations in the model updating process. Through a comparison with the original BUS method, the improved BUS method is shown to be useful for Bayesian model updating of high-dimensional spatially variable geomaterial properties and slope reliability assessment.

Variability in interseismic strain accumulation rate and style along the Altyn Tagh Fault

Major strike-slip faults that develop between strong and weaker regions are thought to focus along narrow shear zones at the rheological boundary. Here we present the InSAR-derived velocity field spanning almost the entire length of one such fault, the 1600 km-long Altyn Tagh Fault (ATF), and analyse the strain distribution. We find that localisation of strain is actually variable, in contrast to other major strike-slip faults that show little variation, with strain concentrated at the fault for some sections and distributed over broad (>100 km) shear zones for others. Slip rate along the ATF is also variable, decreasing along the fault from 11.6 ± 1.6 mm/yr in the west to 7.2 ± 1.4 mm/yr in the central portion, before increasing again to 11.7 ± 0.9 mm/yr over the eastern portion. We show that the variable shear zone width may be linked to geological variability and the influence of heat flow, and the results imply that sub-parallel faults play an important role in the overall deformation field. This demonstrates the significance of accurately characterising strain rates over a broad region when assessing seismic hazard.

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Using glass powder and rice husk ash as supplementary cementitious materials (SCM) can effectively reduce cement usage, protect the environment, and promote waste recycling. In this study, ordinary concrete, glass powder concrete, and glass powder rice husk ash concrete were studied through a series of experiments, including tests for slump and water absorption, uniaxial compression, variable angle shear, cyclic compression, and numerical simulation. The following results were identified. Glass powder increases the slump of concrete and reduces its water absorption, whereas the opposite is the case with the addition of rice husk ash. The uniaxial compressive strength of glass powder concrete is higher than that of ordinary concrete at 28 days of curing. Glass powder concrete has the maximum bearing capacity, in terms of the shear test. The minimum damage index is shown under cyclic compression. When the rice husk ash content is 15 %, the combination with glass powder has the strongest pozzolanic effect, while the replacement rates of 30 % and 45 % are not suitable for pozzolanic materials. The dissipation energy conversion rate of the sample containing rice husk ash is always greater than the elastic strain energy conversion rate. In addition, the samples containing rice husk ash showed ductile failure and reduced cracks during compression. This study can provide new insights into the combination of glass powder and rice husk ash as SCM.

Insight into the Evolution of the Eastern Margin of the Wyoming Craton from Complex, Laterally Variable Shear Wave Splitting

Abstract Dense seismic arrays such as EarthScope’s Transportable Array (TA) have enabled high-resolution seismic observations that show the structure of cratonic lithosphere is more heterogeneous and complex than previously assumed. In this study, we pair TA data with data from the Bighorn Arch Seismic Experiment and the Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny (CIELO) to provide unprecedented detail on the seismic anisotropic structure of the eastern margin of the Wyoming Craton, where several orogens emerged from nominally strong cratonic lithosphere during the Laramide Orogeny. In this study, we use the splitting of teleseismic shear waves to characterize fabrics associated with deformation in the Earth’s crust and mantle. We constrain distinct anisotropic domains in the study area, and forward modeling shows that each of these domains can be explained by a single layer of anisotropy. Most significantly, we find a fast direction in the southern part of the Powder River Basin, which we refer to as the Thunder Basin Block (TBB), that deviates from absolute plate motion (APM). This change in splitting behavior coincides with changes in other modeled geophysical observations, such as active source P-wave velocity models, potential field modeling, and seismic attenuation analysis, which all show a significant change moving from the Bighorn Mountains to the TBB. We argue that these results correspond to structure predating the Laramide Orogeny, and most likely indicate a Neoarchean boundary preserved within the lithosphere.

A comparative study of the water based drilling fluid viscoelasticity versus shear viscosity effects on the filtration loss control

Drilling fluid shear viscosity and the elasticity are two of the most influential factors controlling the volume of fluid invasion into reservoir and the resultant formation damage. Previous studies were inconclusive regarding individual effects of the fluid shear viscosity vs elasticity, mainly because of the difficulty to separate and measure their impacts independently. In this study, two groups of fluids were formulated: one group with the same shear viscosity and variable elasticity and the other group with the same elasticity and variable shear viscosity. Detailed rheological characterizations were carried out by conducting amplitude sweep and controlled shear rate tests. Viscoelastic properties were quantified in terms of the energy dissipation. Static filtration tests and core flooding experiments were conducted to determine the static fluid loss, pressure drop across the core at different fluid flow rates, and the resultant formation damage induced by each fluid. The observations from this study provided several key insights: i-) The static filtration rate can be more effectively controlled by altering fluid viscoelasticity than the fluid shear viscosity; ii-) Both the shear viscosity and the elasticity strongly influence the pressure drop across the core, however, the effect of the fluid elasticity on the pressure drop is more pronounced; iii-) Increasing the fluid elasticity inhibits fluid invasion into the formation more effectively than increasing the fluid shear viscosity; iv-) The fluid elasticity can be effectively used for developing non-invasive fluids, which would reduce static filtration rate, increase pressure drop, and minimize formation damage by effectively reducing fluid invasion.

High-Temperature Rheometric and Melting Experiments of Refining-Type Ladle Slag Systems

Refining ladle slags play an irreplaceable role in the production technology of appropriate quality steel of a given assumed grade. Without good slag, there is no high-quality steel. In this work, we have analyzed the behavior of the slag-forming powder used in industrial conditions, forming a typical refining slag system. The slag-forming powder, Al2O3-SiO2-CaO-MgO-Fe2O3, was examined using a microscope and a high-temperature rheometer. Rheometrical tests were carried out in variable shear conditions, at shear rates of 3–30 s−1 and temperatures in the range of 1451–1500°C. In addition, thermodynamic calculations were performed using FactSage 7.3 databases. Based on the tests performed and the results obtained, it can be concluded that it is impossible to perform rheometric tests of basic slag-forming powder in the analyzed conditions of chemical composition and temperature. In order to obtain rheological characteristics, a slag-forming powder, CaO, was added, modeling the refining slag system. Such a modification of the chemical composition gave the opportunity to perform experiments in the liquid and semi-liquid state.

Quantifying uncertainty in free vibration characteristics of nanobeam with one variable first-order shear deformation theory: an analytical investigation

Quantifying uncertainty in free vibration characteristics of nanobeam with one variable first-order shear deformation theory: an analytical investigation

Ispitivanje poprečne unutarnje sile sandučastog nosača primjenom principa varijacije energije

This study investigated the transverse internal force of a box girder with a trapezoidal cross-section under eccentric loading. The effects of the box girder distortion and frame shear difference on the transverse internal force were considered. An energy variation method based on the minimum potential energy principle was adopted for transverse internal force analysis of the frames. The variable shear difference of the top slab was considered an unknown quantity, and a fourth-order governing differential equation was established. The transverse bending moment of the frame was obtained by solving for the shear difference. Two examples were used to verify the proposed method and analyse the differences between the transverse internal force results calculated using different methods. The effect of the distribution of the box-girder distorted transverse bending moment on each slab was investigated for various stiffness ratios. The results showed that the transverse internal force of the box girder calculated using the proposed method agreed well with the finite element results, with a maximum error of less than 9.68 %. When the stiffness ratio of the box girder increased, the distribution of the distorted transverse bending moment on the top slab increased, whereas that on the bottom slab decreased.

A Comparative Study of Newtonian and Non-Newtonian Nanofluids with Variable Thermal Conductivity Over a 3-D Stretching Surface

This study presents a comprehensive numerical and statistical analysis of the flow, heat/mass transfer management of Newtonian and non-Newtonian nanofluid over a bidirectional Darcy-Forchheimer stretching sheet. The external effects of MHD, Joule heating, thermal radiation, heat generation/absorption, Brownian motion, thermal diffusion and chemical reaction are taken into account. It is presumed that the thermal conductivity of fluid varies linearly with temperature. The non-linear coupled P.D.Es are converted into nonlinear coupled O.D.Es using similarity transformation. These equations are solved using MATLAB by implementing four-stage Lobatto IIIa formula and the outcomes of numerous flow parameters are presented graphically. In addition to numerical investigations, a comprehensive statistical analysis is performed using R-software to evaluate the sensitivity of key input parameters towards variable thermal conductivity. The values of local wall friction, local wall heat flux, and wall mass flux for various parameters are tabulated. The study reveals that the heat transmission is significant for dilatant fluids (156.8%) when compared to the pseudoplastic fluids (113.8%). Enriching the values of the Brownian motion parameter suppresses the molecular diffusion while a contrary nature is observed for the thermal diffusion parameter. Further, the mass transfer coefficient shows a very strong negative correlation with variable thermal conductivity parameter for Shear thinning fluids, whereas for Newtonian and Shear thickening fluids it shows a very strong positive correlation.

Deconstructable variable stiffness shear connectors in FRP deck resting on multigirder bridge system: Analytical model

Deconstructable structures offer great flexibility and reduce material waste. Fiber Reinforced-Polymer (FRP) decks resting on steel girders combine high durability, lightweight, fast construction, and deconstructablility. Composite action between the decks and girders is achieved using shear connectors. Until now, most shear connectors use adhesives or grouts, limiting their maintenance, reuse, or recycling. This paper presents a closed-form solution to analyze the behavior of an FRP deck connected to multi-girders using variable sequential stiffness shear connectors considering partial Degree of Composite Action (DCA). The analytical model, which is verified using Finite Element model and prior experimental studies, is further used to study stress and deflection for various multigirder configurations. Finally, the DCA considering variable stiffness shear connectors is presented and linked to effective width ratios, paving the way for adopting variable stiffness in bridge standards.

Thick-shell finite element analysis of reinforced concrete flat plates with non-uniform connection stresses

This paper presents the application of a thick-shell nonlinear finite element analysis procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. In the analyses performed, varied connection shear stress conditions stem from slabs being supported by columns with different cross-section aspect ratios, being subjected to different distributions of gravity loading, being constructed with different planar reinforcement ratios in orthogonal directions, as well as the application of unbalanced bending moments. Forty-eight isolated slab-column connection specimens presented in the literature were modelled and analyzed using a thick-shell finite analysis procedure. All numerical results were developed using a predefined set of material models and analysis parameters, a consistent meshing procedure, and are shown to provide meaningful agreement with experimental data without the need for case-specific model calibration or the adoption of specialised failure criteria. The results show that thick-shell modelling methods can be suitable for estimating the punching shear response of slabs subjected to non-uniform shear stress development in connection regions, and can provide similar levels of precision to that obtained for the analysis of idealised slab-column connections typically used for design procedure and model development.

Nanopore Direct RNA Sequencing Reveals the Short-Term Salt Stress Response in Maize Roots

Transcriptome analysis, relying on the cutting-edge sequencing of cDNA libraries, has become increasingly prevalent within functional genome studies. However, the dependence on cDNA in most RNA sequencing technologies restricts their ability to detect RNA base modifications. To address this limitation, the latest Oxford Nanopore Direct RNA Sequencing (ONT DRS) technology was employed to investigate the transcriptome of maize seedling roots under salt stress. This approach aimed to unveil both the RNA transcriptional profiles and alterations in base modifications. The analysis of the differential expression revealed a total of 1398 genes and 2223 transcripts that exhibited significant variation within the maize root system following brief exposure to salt stress. Enrichment analyses, such as the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway assessments, highlighted the predominant involvement of these differentially expressed genes (DEGs) in regulating ion homeostasis, nitrogen metabolism, amino acid metabolism, and the phytohormone signaling pathways. The protein–protein interaction (PPI) analysis showed the participation of various proteins related to glycolytic metabolism, nitrogen metabolism, amino acid metabolism, abscisic acid signaling, and the jasmonate signaling pathways. It was through this intricate molecular network that these proteins collaborated to safeguard root cells against salt-induced damage. Moreover, under salt stress conditions, the occurrence of variable shear events (AS) in RNA modifications diminished, the average length of poly(A) tails underwent a slight decrease, and the number of genes at the majority of the variable polyadenylation (APA) sites decreased. Additionally, the levels of N5-methylcytosine (m5C) and N6-methyladenosine (m6A) showed a reduction. These results provide insights into the mechanisms of early salt tolerance in maize.

Effect of intensity of sedimentary cover deformation on hydrocarbon accumulation in Dongying Sag, Bohai Bay Basin, China

The developmental phase of the fault deformation zone denotes the zone of weak deformation (with strong concealment) that evolves within the sedimentary cover of the basin. Recent studies have unveiled the objectively existing tectonic phenomenon of weakly deformed tectonic belts within the sedimentary basin cover, closely intertwined with oil and gas accumulation. To elucidate the deformation intensity and hydrocarbon accumulation scale within the cap cover deformation zone, a pivotal concern in oil and gas geology, this study focuses on the Dongying Sag. The structural physical simulation experiment method, incorporating variable caprock thickness and variable shear strength, is employed to scrutinize the impact of basement fault strike-slip activity on the development of faults in the sedimentary caprock of the basin and dyed oil is charged. In conjunction with sag examples, Early R shear single-channel migration-isolated aggregation, Early and mid-term R shear main channel migration-geese and beaded aggregation, P shear main channel migration-intermittent zonal aggregation, Full channel migration-continuous belt aggregation accumulation models of basement faults are established. It is emphasized that the R shear pressurized deformation section and the R and P shear intersection section in the deformation zone are favorable target areas for oil and gas exploration.

The importance of nodal plane orientation diversity for earthquake focal mechanism stress inversions

Abstract Inversions of earthquake focal mechanisms are among the most accessible and reliable methods for determining crustal stress. However, the use of this method varies widely, and the assumptions that underpin it are often violated, potentially compromising stress estimates. We investigate the consequences of violating the little-studied assumption that the focal mechanisms have diverse orientations. Our approach is to employ data-informed synthetic mechanisms, with nodal plane orientations defined by recent earthquake lineaments in the Midland Basin, western Texas, and rakes consistent with slip in the mapped stress field. Using both the traditional stress inversion method that assumes constant shear stress magnitudes on the causative faults as well as a recently published variable shear stress method, we show that low fault plane diversity can cause maximum horizontal stress ( S Hmax ) orientation and relative principal stress magnitude (faulting regime) estimates to differ markedly from the true values. This problem is compounded for catalogues with even modest amounts of noise (≤15°) or few (e.g. 20) mechanisms. Significantly, traditional approaches for quantifying uncertainty such as the bootstrap can severely underestimate the true uncertainty under these circumstances. To remedy this, we provide simple tools to quantify nodal plane orientation diversity and stress inversion reliability.

Variable angle of insulated shotcrete under different loading rates and temperature and humidity cycles- shear test and analysis.

The new thermal insulating shotcrete is of great significance for the management of thermal damage in deep mines, and its own strength has a greater impact on the roadway insulation and safe production, so it is very necessary to study the shear strength of the new thermal insulating shotcrete under the influence of the deep hot and humid environment and the stress of mining. For the heat-insulating shotcrete, firstly, we carried out the concrete variable angle shear test under different loading rates, which concluded that the shear rate and peak shear stress showed a trend of increasing and then decreasing; as the angle increases, the different rates have a greater impact on the peak shear stress of the specimen. Secondly, the concrete variable angle shear test was carried out under the temperature and humidity cycle, which revealed that the shear strength of thermal insulated shotcrete increased firstly and then decreased with the increase of temperature at the same number of cycles. Finally, the empirical equations between the cohesive force c, the angle of internal friction ϕ and the number of warm and wet cycles n and the temperature of warm and wet cycles T are fitted with the MATLAB software respectively, and the research results provide technical references for the management of geothermal temperature in deep well projects.

A Hybrid ANN Multiaxial Fatigue Model for the Assessment of Fretting Fatigue under Variable Amplitude Shear Loading.

To foresee the life of fretting fatigue with variable shear amplitude loading, a hybrid model incorporating non-local multiaxial fatigue parameters and artificial neural networks (ANN) in conjunction with cumulative damage models has been proposed. The model has been developed based on equivalent stress parameters associated with crack nucleation and Miner's cumulative damage rule-inspired models, enabling the assessment of the impact of variable amplitude loading. To validate the models, fretting fatigue tests conducted under variable shear loading amplitude are employed to compare the predictions of four different models. The results demonstrate that while all models provide satisfactory estimates falling within the two-band limit, the hybrid model combining two ANN models outperforms the others and emerges as the most effective in predicting fretting fatigue life under these conditions. The proposed methodology effectively addresses the inherent complexities of fretting fatigue under variable amplitude stress, while also examining the influence of load block order on material behavior. Additionally, these types of fatigue ANN models have been demonstrating a strong capacity for generalization, making them highly promising for future industrial applications.

Bearing capacity of strip footings seated on unreinforced and reinforced granular layers over random homogeneous and isotropic spatially variable undrained soft clay

The bearing capacity of a footing seated directly on a soft clay foundation with constant undrained shear strength is the classical Prandtl geotechnical problem. However, a footing seated directly on an undrained clay soil is an unlikely arrangement in practice. Rather, a granular layer is used as a working platform for the construction of the footing and to dissipate the footing loads over a wider area of the clay foundation surface. This paper revisits the footing problem for the case of a footing seated directly on the clay foundation, and seated on an unreinforced and geosynthetic reinforced granular layer overlying the clay foundation. Both deterministic and stochastic numerical modelling of the bearing capacity problem using the program FLAC 2D were carried out. The relationship between the design factor of safety and probabilistic margins of safety is explored for clay foundations with random homogenous and isotropic spatially variable undrained shear strength with mean strengths from 5 to 25 kPa (very soft to soft clay). For practical target probabilistic margins of safety against exceeding a design bearing capacity, the random homogenous soil condition is shown to be the most critical case for design.