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Concentrated solid solution alloys (CSAs) have attracted attention for their promising properties; however, current manufacturing methods face challenges in complexity, high costs, and limited scalability, raising concerns about industrial viability. The prevalent technique, arc melting, yields high-purity samples with complex shapes. In this study, we explore nanoindentation tests at room temperature where arc-melted samples exhibit larger grain sizes, diminishing the effects of grain boundaries on the results. Motivated by these findings, our investigation focuses on the atomistic-level exploration of plasticity mechanisms, specifically dislocation nucleation and propagation during nanoindentation tests. The intricate chemistry of NiFeCrCo CSA influences pile-ups and slip traces, aiming to elucidate plastic deformation by considering both pristine and pre-existing stacking fault tetrahedra. Our analysis scrutinizes dynamic deformation processes, defect nucleation, and evolution, complemented by stress–strain and dislocation densities–strain curves illustrating the hardening mechanism of defective materials. Additionally, we examine surface morphology and plastic deformation through atomic shear strain and displacement mappings. This integrated approach provides insights into the complex interplay between the material structure and mechanical behavior, paving the way for an enhanced understanding and potential advancements in CSA applications. [ABSTRACT FROM AUTHOR]

With large-scale non-equilibrium molecular dynamics simulations and in situ x-ray diffraction analysis, we conducted a systematic investigation into the effects of pre-existing shear strain (γ x y ) on the shock response of single crystal iron. Our findings reveal significant effects of γ x y on the deformation of the crystal structure during shock loading, leading to noticeable alterations in the propagation of shock waves. Specifically, during the elastic stage, the presence of γ x y results in a reduction of shock strength, consequently diminishing the magnitude of elastic lattice strain (ε e ). In the plastic stage, γ x y stimulates the α – ε phase transformation, and structure deformation undergoes a transition from the sequential activity of dislocation-to-transformation to the synchronous activity of dislocation and transformation. This transition inhibits the propagation of plastic waves and consequently broadens the elastic regime. Additionally, the introduction of γ x y activates different slip systems, as it alters the corresponding resolved shear stress. Concurrently, the presence of γ x y triggers the activation of different high-pressure phase variants. Our investigation sheds light on the fundamental physics of iron under shock compression and the influence of pre-existing shear strain on its behavior. [ABSTRACT FROM AUTHOR]

The effects of tensile strain and contact transmissivity on the performance limits of monolayer molybdenum disulfide ( MoS 2) nanoscale n-channel MOSFETs are studied using a semi-classical Monte Carlo method. Density functional theory calculations were performed to parametrize the electronic band structure of MoS 2 subject to tensile and shear strain. Tensile strain decreases the bandgap, increases the inter-valley band-edge energy separation between the light-mass K-valleys and heavier-mass Q-valleys, and decreases the K-valley effective mass in a way that depends on the direction and the amount of the applied strain. Biaxial tensile strain and uniaxial tensile strain along the x- or y-directions are found to have the largest effect. In bulk materials, low-field phonon-limited electron mobility is enhanced, peak and saturation drift velocities are increased, and high-field negative differential resistance becomes more pronounced. Both 200 and 15 nm gate length MoS 2 MOSFETs with end-contacts with ideal (unity) and more realistic (significantly sub-unity) contact interface transmissivity were simulated. These MoS 2 devices exhibited substantial sensitivity to strain with ideal contact transmissivity, and more so for the 15 nm quasi-ballistic device scale than 200 nm long-channel devices. However, the results showed much less strain sensitivity for devices with more realistic contact transmissivities, which may be good or bad depending on whether strain-insensitive or strain-sensitive performance is desired for a particular application and may be possible to modify with improved contact geometries. [ABSTRACT FROM AUTHOR]

Evaluation of physical and mechanical heterogeneity in commercial paperboards is needed to promote their use in structural applications, especially within the field of packaging. Understanding the range of their behaviors is needed to compete with other materials in the current marketplace and expand in others. This work describes the physical and stiffness heterogeneities of twelve commercial materials using tensile tests in the cross-machine direction and several inverse analyses. The effects of grammage, thickness, and apparent density on tensile stiffness were evaluated in both the linear elastic and nonlinear regimes. Thickness and density provided the best explanation for elastic heterogeneous behavior in most of the materials; local grammage was not the best descriptor for any material. The analyses used here were not able to provide a good explanation of the nonlinear behavior, which was attributed to the development of large shear strains within the materials as they neared failure. This work provides a methodology for additional heterogeneous behavior examinations. [ABSTRACT FROM AUTHOR]

The utilization of ultrahigh-performance concrete (UHPC) as lateral or U-shaped thin layers to strengthen the shear-deficient normal-strength concrete (NSC) beams is an effective and promising way to increase their stiffness and shear capacity. However, the lack of an accurate analytical model to estimate the shear capacity of UHPC-strengthened beams could be a critical obstacle to its further application. This paper presents a new analytical model for calculating the shear capacity of UHPC-lateral-strengthened beams, which is the first to be based on the simplified modified compression field theory (SMCFT). The model is also distinguished by considering the full compressive and tensile stress–strain curves of UHPC instead of only using their ultimate strengths. By assuming a complete strain transfer at the NSC–UHPC interface and the coincidence of the principal stress and strain axes in the NSC substrate and UHPC layers, the strain compatibility between the two components are included in the shear calculation. The model predictions were validated in two steps, first by using principal strain measurements in the shear span of five beams from digital image correlation (DIC) data to confirm the strain evaluation of the model, and second by reproducing the shear capacities of 12 beams from five experimental campaigns. Results showed a clear agreement between the strains calculated by the analytical model and those measured in experiments. The shear capacities of UHPC-lateral-strengthened beams calculated by the analytical model obtained a very high accuracy and a low variance to replicate experimental results. The model allows evaluation of the contributions of each beam components (NSC substrate, stirrups, and UHPC layers). Results confirmed that the increase in the shear capacity of strengthened beams mainly comes from the high tensile strength of the UHPC and the thickness of the UHPC layer, as well as the improved contribution of the stirrups. [ABSTRACT FROM AUTHOR]

Background: Dysfunctional gliding of deep fascia and muscle layers forms the basis of myofascial pain and dysfunction, which can cause chronic shoulder pain. Ultrasound shear strain imaging may offer a non-invasive tool to quantitatively evaluate the extent of muscular dysfunctional gliding and its correlation with pain. This case study is the first to use ultrasound shear strain imaging to report the shear strain between the pectoralis major and minor muscles in shoulders with and without chronic pain. Case presentation: The shear strain between the pectoralis major and minor muscles during shoulder rotation in a volunteer with chronic shoulder pain was measured with ultrasound shear strain imaging. The results show that the mean ± standard deviation shear strain was 0.40 ± 0.09 on the affected side, compared to 1.09 ± 0.18 on the unaffected side (p<0.05). The results suggest that myofascial dysfunction may cause the muscles to adhere together thereby reducing shear strain on the affected side. Conclusion: Our findings elucidate a potential pathophysiology of myofascial dysfunction in chronic shoulder pain and reveal the potential utility of ultrasound imaging to provide a useful biomarker for shear strain evaluation between the pectoralis major and minor muscles. [ABSTRACT FROM AUTHOR]

In this study, we introduce a comprehensive investigation into the buckling behavior of carbon nanotubes (CNTs) using a combined approach of quantum mechanics and molecular mechanics methods. A novel aspect of our research lies in the exploration of the quantum effects of fine scaling on the buckling behavior of finite‐length nanotubes across various dimensions and chiralities. Specifically, we analyze the critical buckling strain variations in CNTs with distinct lengths, diameters, and chiralities, revealing pronounced differences influenced by atomic arrangement and the type of structure used in nanotube construction. Our findings elucidate that at smaller dimensions, nn2$$ \left(\ n,\frac{n}{2}\right) $$ nanotubes exhibit a higher critical buckling strain than other chiralities, while zigzag atomic arrangements demonstrate greater resistance to torsional loading at larger diameters. Additionally, we compare the buckling behavior of nanotubes obtained by wrapping armchair and zigzag nanosheets, highlighting differential resistance trends. This research not only underscores the critical role of quantum effects in determining nanotube buckling but also provides valuable insights into the nuanced influences of atomic arrangement and nanosheet type on the mechanical properties of CNTs. Thus, our work contributes a novel perspective to the field, bridging the gap between quantum mechanics and the mechanical behavior of nanostructures, which has significant implications for the design and application of nanoscale materials [ABSTRACT FROM AUTHOR]

Background: First metatarsophalangeal joint arthrodesis is a typical medical treatment performed in cases of arthritis or joint deformity. The gold standard for this procedure is arthrodesis stabilisation with the dorsally positioned plate. However, according to the authors' previous studies, medially positioned plate provides greater bending stiffness. It is worth to compare the mechanical conditions for bone formation in the fracture callus for both placements of the locking plate. Methods: Two finite element models of the first metatarsophalangeal joint with the dorsally and medially positioned plate were defined in the Abaqus software to simulate differentiation of the fracture callus. A simplified load application, i.e. one single step per each day and the diffusion of the mesenchymal stem cells into the fracture region were assumed in an iterative hardening process. The changes of the mesenchymal stem cells into different phenotypes during the callus stiffening were governed by the octahedral shear strain and interstitial fluid velocity according to Prendergast mechanoregulation theory. Basing on the obtained results the progress of the cartilage and bone tissues formation and their distribution within the callus were compared between two models. Findings: The obtained results suggest that after 6 weeks of simulation the healing progress is in general comparable for both plates. However, earlier closing of external callus was observed for the medially positioned plate which had greater vertical bending stiffness. This process enables faster internal callus hardening and promotes symmetrical bridging. [ABSTRACT FROM AUTHOR]

The majority of ice mass loss from Antarctica flows through narrow, fast sliding regions of ice. The lateral boundaries of these regions, termed shear margins, are characterized by lateral shear strains in excess of ∼10−3 yr−1. Shear heating within these margins could warm ice significantly–even to the melting point–but other processes such as lateral advection of cold ice and fabric development compete with this effect. Radar observations can help constrain where temperate ice exists because englacial temperature increases electric conductivity which increases radar attenuation. We utilize the temperature‐dependent attenuation of ice to develop a novel method for constraining englacial temperature in shear margins by combining existing thermal models with very high frequency radar depth‐sounding data. We find evidence supporting temperate shear margins in 18 locations and find evidence for non‐temperate margins in 37 locations, notably in the Amundsen Sea Embayment. Plain Language Summary: Most of the ice lost from Antarctica to the ocean goes through narrow areas of fast sliding ice. At the sides of these fast sliding areas the fast ice abuts slow ice and heavily deforms. Deformation warms the ice–potentially to its melting temperature. This warming should be noticeable in radar data because ice at or near the melting point reduces the power of radar waves. We develop a method for using airborne radar measurements to look for the presence of this warm ice, and apply our method across the Antarctic continent. We find evidence supportive of warm ice in many locations, but we notably find little evidence of warm ice in the Amundsen Sea Embayment where the inflow of cold ice may offset warming. Key Points: We develop a novel method for identifying evidence for temperate ice in Antarctic shear margins using existing airborne radar data setsWe find evidence for temperate ice in 18, and evidence contrary in 37, of 106 radar lines over shear margins we consider across AntarcticaNeglecting heats sinks like advective cooling overpredicts the size of temperate zones, particularly in the Amundsen Sea Embayment [ABSTRACT FROM AUTHOR]

Ensuring military and police personnel protection is vital for urban security. However, the impact response mechanism of the UHMWPE laminate used in ballistic helmets and vests remains unclear, making it hard to effectively protect the head, chest, and abdomen. This study utilized 3D-DIC technology to analyze UHMWPE laminate's response to 9 mm lead-core pistol bullets traveling at 334.93 m/s. Damage mode and response characteristics were revealed, and an effective numerical calculation method was established that could reveal the energy conversion process. The bullet penetrated by 1.03 mm, causing noticeable fiber traction, resulting in cross-shaped failure due to fiber compression and aggregation. Bulge transitioned from circular to square, initially increasing rapidly, then slowing. Maximum in-plane shear strain occurred at ±45°, with values of 0.0904 and −0.0928. Model accuracy was confirmed by comparing strain distributions. The investigation focused on bullet-laminate interaction and energy conversion. Bullet's kinetic energy is converted into laminate's kinetic and internal energy, with the majority of erosion energy occurring in the first four equivalent sublaminates and the primary energy change in the system occurring at 75 μs in the fourth equivalent sublayer. The results show the damage mode and energy conversion of the laminate, providing theoretical support for understanding the impact response mechanism and improving the efficiency of protective energy absorption. [ABSTRACT FROM AUTHOR]

In this paper, a novel methodology is presented to evaluate the true nonlinear shear response of continuous fiber-reinforced plastic (CFRP) unidirectional laminae. It requires simple off-axis tensile experiments to be conducted and a finite element (FE) representation of them with a material constitutive law capable of handling nonlinearity in shear. Upon successful evaluation of the normal stiffness properties, the shear stress-strain response is derived via numerical calibration of the underlying FE models. The presented approach is also demonstrated by processing the raw data of an extensive material characterization test campaign conducted on a thermoplastic matrix CFRP. The outcome is compared to the conventional methods for shear response derivation using relevant standards such as ASTM D3518 and ASTM D5379. It has been successfully demonstrated that the pseudo-hardening phenomenon obtained from standard shear experiments as a result of fibers aligning with load direction can be eliminated with off-axis specimen tension experiments, thus, the true shear stress versus deformation response can be extracted up to failure. The main purpose of current work is to demonstrate the inconsistency in the available standard methods related to mechanical testing-based derivation of nonlinear in-plane shear behavior of UD plies. In addition, a novel technique is presented to achieve a more accurate prediction of nonlinear shear stress and strain along the entire representative loading range that contributes to more accurate simulations of composite parts up to failure and thus, better strength predictions. [ABSTRACT FROM AUTHOR]

Although the cardioid-shaped traffic loading path can be implemented using hollow cylinder apparatus, the preparation of inherently anisotropic sand with different bedding plane angles could be difficult. Consequently, the macro-scale response of inherently anisotropic sand under traffic loading has not been adequately investigated to reveal the underlying microscopic mechanism. In this paper, elongated particles with various aspect ratios were used to approximate the natural sand particles, and uniform three-dimensional specimens with different bedding plane angles were generated using discrete element method based on a modified version of under-compaction method. The cardioid-shaped loading path was implemented using an advanced servomechanism that can apply arbitrary loading paths. The internal structure of specimen was quantified through a contact-normal-based fabric tensor, which could describe the load-bearing structure of granular specimens. The interplay between the macro-scale observations and the fabric evolutions was elucidated. The influences of both bedding plane angle and aspect ratio on the accumulations of volumetric strain and generalized shear strain are not monotonic, with the largest strains at the bedding plane angle of 45° and the aspect ratio of 1.4. Results provide useful insights into the underlying mechanism of the deformation behavior of inherently anisotropic granular materials under traffic loading. [ABSTRACT FROM AUTHOR]

Displacement mode has a significant influence on the distribution and magnitude of lateral earth pressures and the failure mechanisms of retaining walls. This study performed five model tests to evaluate the responses of coarse sand-backfilled retaining walls under five displacement modes including uniform translation (UT), rotation around the base (RB), rotation around the top (RT), counter-clockwise rotation around the midpoint (RM-CC), and clockwise rotation around the midpoint (RM-C). The measured lateral earth pressures behind each wall were compared with the calculated values using the analytical solutions from the literature. The failure mechanisms of the retaining walls under different displacement modes were evaluated in terms of their backfill deformation and shear strain contours. Test results show that the measured lateral earth pressures at rest and limit equilibrium (LE) had nonlinear distributions, and the RM-C mode resulted in the largest LE earth pressures as compared with the other four modes. The comparisons show that the measured at-rest and LE earth pressures were in good agreement with those calculated by Jaky's method and Harrop-Williams' method, respectively. For the retaining walls under the UT, RB, and RT modes, the required wall movement to reach the LE state was approximately 0.4%H where H is the height of the retaining wall. For the retaining walls under the RM-CC and RM-C modes, the required wall movements above the rotation point and below the rotation point to reach the limit equilibrium were 0.4%H and 0.2%H, respectively. The backfill behind the wall under the RB or RM-C mode showed progressive failure, while the backfill under the UT, RT, or RM-CC mode showed quick failure. [ABSTRACT FROM AUTHOR]

Identifying distributed strain sensing (DSS) patterns (or signatures), particularly those arising from different hydraulic fracture geometries, has gained significant attention and research effort. Recent works have generated a catalogue of signatures for planar hydraulic fractures in an elastic rock formation. Yet, in numerous cases (e.g., fault motion and some geothermal reservoir stimulation), the main mode of deformation is a shear on a fracture or a network of natural fractures (particularly during low pressure injection/circulation). However, the specific fiber signatures that result from such shear deformation have not been studied. In this study, we use a three-dimensional poroelastic hydraulic fracture simulator to capture the strain signatures resulting from the shear deformation of fractures in various orientations with respect to the monitoring well. Five key cases are examined: one where the fracture strike is perpendicular to the fiber, another with the strike running parallel to the fiber, a third case where the fracture strike is at 45 degrees to the fiber, a fourth case with a strike slip fault perpendicular to the fiber, and a fifth case where fiber is intersecting the fracture. Theoretically and physically meaningful results were obtained in all five cases, which completely differ from the heart-shaped signature of tensile fracture propagation. It was discovered that the strain pattern changes with the shear deformation direction with respect to the fiber. The model is then used to simulate the response of a fracture network at Utah FORGE to injection to assess whether a signature might be expected in response to the planned injection and circulation rates, and, if so, what strain pattern might be expected. The simulation confirms that a strain response can indeed be observed. More importantly, the fiber response that would be detected in the monitoring well would be a combination of strain signatures from dilation and shear deformation of differently oriented natural fractures. The results in this study provide useful insights on the application of fiber to other stimulation and/or circulation scenarios where shear deformation of a fracture or fracture network plays a major role. [ABSTRACT FROM AUTHOR]

In the present investigation, nonlinear forced vibration analyses of porous functionally graded material viscoelastic sandwich beams are studied. The analytical formulation takes into account normal and shear strains in the core layer by employing the higher-order Zig-Zag theories. The sandwich structure consists of FGM faces that exhibit porosities, while the core layer is composed of viscoelastic material. The proposed model is developed in the frequency domain, by incorporating the material properties of the viscoelastic material through complex numbers. The introducing of the geometric nonlinearity effect results in a sixth-order frequency-amplitude equation, affected by numerous intricate coefficients. This equation was resolved using the balanced harmonic method in conjunction with a one-mode Galerkin's method to predict damping and frequency response curves. These latters are presented and discussed for several geometrical and mechanical sandwich beams configuration. The parametric study is specifically aimed at delineating the influence of the FGM parameters of the face sheets, particularly, the power-law index and the porosity parameter on the response curves and the variation of the nonlinear loss factor with the amplitude of vibration. [ABSTRACT FROM AUTHOR]

To reveal the dynamic shear mechanical properties of laser cladding Inconel 625 (IN625) alloy, dynamic shear mechanical properties experiments are conducted on forged specimens and laser cladding specimens by split Hopkinson press bar experimental device. Optical microscopy, scanning electron microscopy, and electron backscattered diffraction (EBSD) are used to characterize the microscopic morphology, crystal orientation, and grain size of laser cladding specimens before and after dynamic shear deformation. In the results, it is shown that the yield strength and shear strength of both forged and laser clad specimens increase with the increase of shear strain rate, reflecting a remarkable strain‐rate‐strengthening effect, and the shear strength of the laser cladding specimen is higher than that of the forged specimen. After dynamic shear loading, the grains in the shear region of the laser cladding specimen are severely deformed, deformation bands appear, and some dendrites are transformed into equiaxed crystal. After shear deformation, the preferred orientation strength of the crystal increases, the small‐size grain and low‐angle grain boundary increase, and a large number of dislocations are formed in the shear region, which dominates the dynamic shear deformation behavior of the material. Dislocation is an important dominant mechanism of dynamic shear deformation. [ABSTRACT FROM AUTHOR]

The paper investigates the seismic performance of a novel passive vibration isolation and damping device termed Extended KDamper (EKD). The concept is applied to a representative two-span highway bridge, initially designed on conventional seismic isolation (CSI) bearings. An optimization process is developed and executed to design the EKDs, underscoring the importance of accounting for seismic motion variability. Compared to CSI, the incorporation of EKDs leads to a 40% to 70% reduction in deck drifts. In contrast to the CSI bridge, which may sustain excessive bearing shear strains when subjected to the most adverse seismic motions within the examined set, the bearings of the EKD bridge never exceed the 200% threshold. Through the use of nonlinear 3D time-history analyses, it is demonstrated that the nonlinearity of the EKD elements may result in residual deck drifts. The nonlinear EKDs exhibit a variation in maximum drifts and accelerations on the order of ±20% compared to the preliminary (linear elastic) design for the examined set of spectrum-compatible motions. The increased accelerations result from the stiffening of the negative stiffness elements (NSEs), being more pronounced for seismic motions that entail large displacement demands. With the aid of a fully nonlinear 3D model of the entire soil – foundation – structure system, the effects of soil-structure interaction (SSI) are explored and shown to significantly influence the seismic response of the system. Deck collision with the abutments restricts the movement of the deck and pier; however, it compromises the performance of the EKDs and leads to a substantial increase in deck accelerations. Overall, EKDs may facilitate a more economical design and enhanced seismic performance, particularly for displacement-sensitive structures like rail bridges. [ABSTRACT FROM AUTHOR]

Pore pressure oscillations induced by stress variations, including propagating seismic waves from remote earthquakes, have been widely observed in various groundwater systems. The monitored pressure change in wells shows significant water-level oscillations to volumetric strain as well as to S and Love waves. Recent observations demonstrated azimuthal dependence of the pore pressure oscillations with respect to stress indicators and fault zone orientation. Within the fault zone, damage-induced anisotropy is the result of the alignment and orientation of cracks and other internal flaws within the rock. In this work, we provide a complete quantitative description of the pore pressure changes induced by passing seismic waves associated with different orientations and values of principal stress and damage tensor components. The model quantifies the azimuthal dependence of the pore pressure response by a non-dimensional ratio defined as the amplitude of the pressure oscillations induced by a shear strain normalized to the volumetric strain. Three angles and two values are needed to calculate the azimuthal dependence of the pore pressure response: the angle between the directions of the maximum horizontal stress and the seismic event; fault zone orientation; microcrack orientation within the fault zone; and damage and stress values. The model predicts that maximum pore pressure response occurs when microcracks and maximum horizontal stress are in the same orientation, high damage and high stress anisotropy. By adjusting these quantities, we recalculate results of recent seismological studies in the Arbuckle disposal well, Osage County, Oklahoma. The presented model successfully predicts the observed azimuthal dependence in wave-induced fluid pressure response and relates the anisotropic response to tectonic indicators such as the orientations of the maximum horizontal stress, fault zone, and microfractures. [ABSTRACT FROM AUTHOR]

Mountain tunnels portal often have to pass through slope terrain unavoidably, thus forming a shallow buried bias tunnel. During the construction of shallow buried bias tunnel, disasters such as slope sliding and tunnel collapse frequently occur. The failure mode of surrounding rock obtained by current research is based on the limit equilibrium theory, which cannot reflect the progressive failure characteristics of the surrounding rock of shallow buried bias tunnel. In order to reveal the failure mechanism of the gradual instability of surrounding rock of shallow buried bias tunnel, the problem of gradual failure of the surrounding rock is reduced to an elastic–plastic analysis problem for surrounding rock considering the strain-softening characteristics. Based on the elastic–plastic analysis of the failure process of shallow buried bias tunnel, MATLAB was used to compile a program to read the finite-difference calculation result file, extract the effective information such as shear strain and tensile strain at the center point of each unit, and establish the analysis method of the progressive failure mode of shallow buried bias tunnel. The reliability of the method proposed was verified by comparing the failure process of the model test with the development process of shear strain increment. Under the condition of no support, the formation mechanism of failure plane of surrounding rock on both sides of shallow buried bias tunnel is different. The shallow buried side is the shear failure plane formed by the collapse of surrounding rock, while the deep buried side of the tunnel is the shear failure plane formed by the collapse of surrounding rock and slope sliding. Under the conditions of excavation and support, the failure plane of the shallow buried bias tunnel can be divided into three parts according to the formation sequence and reasons. The part I is the failure plane, which is formed by active shear under the influence of tunnel excavation. The part II is the failure plane formed by tensile crack of slope top. The part III is the failure plane formed by passive shear under the push of the soil in the upper part of the slope. [ABSTRACT FROM AUTHOR]

Mantis shrimps deliver one of the fastest strikes with their powerful dactyl clubs. The kinematic energy derived by a saddle storing and releasing mechanical energy with large deformation. As an exoskeleton, the toughness of saddles can achieve a remarkable value ≈15.28 ± 2.32 MJ m−3, which exceeds most bulk natural materials. The excellent toughness of saddles is mainly attributed to the synergy of the helical mineralized fiber architectures and interlaminar fibrils. The interlaminar fibrils connect adjacent mineralized fiber layers closely, enhancing the toughness through viscoelastic deformation during sliding and separating of adjacent layers. They further cooperate with rigid interlacing fiber structure induced by helical structure to transform little normal strain to large shear strain utilizing incompressibility of soft fibrils further to enhance strain energy for toughening. Inspired by unique laminated saddles, the laminate composites are designed with basalt fabrics achieving remarkable fracture toughness to solve the problem of delamination in traditional laminate composites with poor interlaminar toughness. The Mode I and Mode II interlaminar fracture toughness of bio‐inspired laminate composites respectively increase by 44% and 118% reaching 906.8 and 1394.6 J m−2, which provides an innovative bionic strategy for designing new generation structural engineering materials with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Understanding the shear mechanical properties of shale reservoirs is of great significance in the study of the formation stability around horizontal shale wells and the propagation and evolution of fractures for shale fracturing. However, the existing direct shear test results are limited due to small sample sizes and low shear rates. Based on previous experimental research results, the mechanical properties of anisotropic reservoir shale in direct shear tests with different experimental conditions were explored in this study. It was found that the shear mode, shear strain rate, and normal stress have a significant impact on the deformation and failure characteristics of shale. The peak shear displacement, peak shear strength, and shear stiffness of shale present an increasing trend of fluctuation, with an increase in the bedding angle. The peak shear strength of shale decreases with an increase in the shear strain rate, and this decrease trend descends with an increase in the shear strain rate. The shape of the shear fracture zone and the shear fracture mode of shale exhibit bedding effect characteristics. The fractal dimension of the shale shear fracture surface morphology shows a trend of fluctuation with the variation in the bedding angle. Further, the shear strain rate was found to play a dominant role in the fractal dimension of the shear fracture surface. The larger shear strain rate strengthens the bedding effect of the roughness for the shear fracture surface morphology. The results of this study provide a theoretical reference for determining the engineering geomechanics characteristics of shale reservoirs. [ABSTRACT FROM AUTHOR]

We investigated gated multilayer graphene with stacking order changes along the armchair direction. We consider that some layers cracked to release shear strain at the stacking domain wall. The energy cones of graphene overlap along the corresponding direction in the k-space, so the topological gapless states from different valleys also overlap. However, these states strongly interact and split due to atomic-scale defects caused by the broken layers, yielding an effective energy gap. We find that for some gate voltages, the gap states cross and the metallic behavior along the stacking domain wall can be restored. In particular cases, a flat band appears at the Fermi energy. We show that for small variations in the gate voltage, the charge occupying this band oscillates between the outer layers. [ABSTRACT FROM AUTHOR]

High-pressure torsion (HPT) can facilitate phase transformations in titanium dioxide (TiO2) and stabilize its high-pressure columbite phase, as an active photocatalyst, by shear straining under high pressure. This study aims to understand the mechanism underlying the acceleration of the anatase-to-columbite phase transformation by shear strain. A mechanism by considering sheared crystal structures as intermediate phases was proposed and examined using quantum mechanics in the framework of density functional theory (DFT) and HPT experiments. DFT energy and phonon calculations demonstrated the viability of the sheared structures as intermediate phases. Furthermore, the sheared structures were observed experimentally as new metastable phases using high-resolution transmission electron microscopy. These findings can explain the significant effect of shear strain on pressure-induced phase transitions, reported during severe plastic deformation of various metals and ceramics. [ABSTRACT FROM AUTHOR]

The current research addresses the kink band-assisted grain fragmentation of (CrFeNi)99Si1 medium-entropy alloy during high-pressure torsion (HPT) using combinatorial experimental and crystal plasticity simulations approach. The HPT experiments were carried out at room temperature with a pressure of 6 GPa for 0.2, 0.5, 1, 2, and 5 turns to achieve different levels of shear strain followed by detailed microstructural characterization using electron backscatter diffraction, transmission electron microscopy, and nanoindentation. Microstructural characterization at different length scales shows the fragmentation of grains aided by the formation of kink bands due to the activation of {111} < 10 1 ¯ > and {111} < 11 2 ¯ > slip system followed by gradual conversion of low-angle grain boundaries to high-angle grain boundaries by continuous dynamic recrystallization (cDRX) observed in medium and low stacking fault energy FCC metals and alloys. This aforementioned mechanism occurs over a range of length scales, scaling down the grain size over three orders of magnitude from 40 ± 5 μm to 35 ± 3 nm. Crystal plasticity simulations using the fast Fourier transform solver were employed for full-field simulations to capture the process of kink band-assisted grain fragmentation using the open-source Dusseldorf advanced material simulation kit (DAMASK) software. Finally, constitutive strength equations were developed to quantitatively predict the evolution of strength as a function of HPT deformation to establish the processing-microstructure-mechanical property in (CrFeNi)99Si1 medium-entropy alloy. [ABSTRACT FROM AUTHOR]

We implement a plastic damage parametrization, distinct from the elastic damage in the elasto-brittle framework, in the standard viscous–plastic (VP) sea ice model to disentangle its effect from resolved model physics (visco-plastic with and without damage) on its ability to reproduce observed scaling laws of deformation. To this end, we compare scaling properties and multifractality of simulated divergence and shear strain rate, as proposed in the Sea Ice Rheology Experiment (SIREx) studies, with those derived from the RADARSAT Geophysical Processor System (RGPS). Results show that including a plastic damage parametrization in the standard viscous–plastic model increases the spatial but decreases the temporal localization of simulated linear kinematic features (LKFs) and brings all spatial deformation rate statistics in line with observations from RGPS without the need to increase the mechanical shear strength of sea ice as recently proposed for lower-resolution viscous–plastic sea ice models. In fact, including damage with a healing timescale of th=30 d and an increased mechanical strength unveils multifractal behavior that does not fit the theory. Therefore, a plastic damage parametrization is a powerful tuning knob affecting the deformation statistics of viscous–plastic sea ice. [ABSTRACT FROM AUTHOR]

Constraining strain localization and the growth of shear fabrics within brittle fault zones at sub‐seismic slip rates is important for understanding fault strength and frictional stability. We conducted direct shear experiments on simulated sandstone‐derived fault gouges at an effective normal stress of 40 MPa, a pore pressure of 15 MPa, and a temperature of 100°C. Using a passive strain marker and X‐ray Computed Tomography, we analyzed the spatial distribution of deformation in gouges deformed in the strain‐hardening, subsequent strain‐softening, and then steady‐state regimes at displacement rates of 1, 30, and 1,000 µm/s. We developed a machine‐learning‐based automatic boundary detection method to recognize the shear fabrics and quantify displacement partitioning between each fabric element. Our results show fabrics oriented along R1 and Y (including boundary) shears are the two major fabric elements. At rates of 1 and 30 µm/s, the relative amount of displacement on R1 shears is displacement dependent, increasing to ∼20% of the total displacement up to the strain‐softening stage, then decreasing to ∼10%–18% at the steady state. This trend is absent at the high rate where ∼18% of the displacement occurs on R1 shears throughout all investigated stages. At all rates, the relative amount of displacement on Y shears increases linearly with displacement to a total of larger than 50% at the steady state. Our study provides constraints on the development of the active slip zone, which is an important factor controlling heating and weakening associated with small‐magnitude earthquakes with limited displacement (mm‐dm), such as induced seismicity. Plain Language Summary: In the past few decades, several studies have focused on the mechanical behavior of simulated fault zones to understand earthquake nucleation. However, minor attention has been paid to the microstructural characterization of fault‐zone gouges due to the difficulties in quantifying deformation. An understanding of brittle fault‐zone fabrics and their development provides crucial constraints on the mechanical strength and stability of faults. We conducted laboratory experiments on simulated sandstone‐derived fault gouges with a passive strain marker under the conditions relevant to earthquake nucleation to explore the development and evolution of shear zone fabrics and their relations to fault strength. We combined X‐ray Computed Tomography (XCT) and a custom‐designed machine‐learning‐based automatic boundary detection method to analyze the spatial distribution of gouge deformation and to quantify displacement partitioning between deformation features. The results show that our samples have similar evolution of the shear fabrics, partitioning of displacement, and mechanical response with increasing shear strain at all tested nucleation velocities. The evolution of the mechanical behavior from strain‐hardening, to softening, to steady‐state stages is related to the transformation of R1 to shear‐parallel shear bands. Up to 50% of the total displacement can be accommodated within shear‐parallel shear bands, facilitating strain weakening of the materials. Key Points: We performed 3‐D analyses on the evolution of shear zone fabrics within sandstone‐derived fault gouges utilizing the X‐ray CT techniqueOur samples show similar evolution of shear fabrics, slip partitioning, and mechanical response with shear strain at all tested velocitiesUp to 50% of the total imposed displacement can be accommodated within shear‐parallel shear bands during earthquake nucleation [ABSTRACT FROM AUTHOR]

Crack interactions leading to shear localization were quantified using microstructural analysis for brittle faults and high‐temperature ductile faults formed during experiments on quartz sandstone. In both faulting regimes, the nucleation of macroscopic faults results from the interactions of microfractures at two length scales in ensemble. Brittle faults nucleate when the longest mesoscale shear fractures and transgranular tensile cracks critically interact. In contrast, ductile faults nucleate when the longest mesoscale shear fractures and multi‐grain scale intergranular shear cracks critically interact. For both faulting regimes, we conclude the interaction and coalescence of the longest mesoscale shear fractures is the fundamental process responsible for fault nucleation. Hence, mesoscale shear fractures, which accommodate the majority of axial strain prior to shear localization in both faulting regimes, also serve as the nucleus of macroscopic faults. Locally, the growth of the mesoscale shear fractures is promoted by the interaction and coalescence of the multi‐grain scale cracks in both faulting regimes. We hypothesize that attainment of a critical microstructure for shear localization (i.e., local clustering of the longest microfractures) requires a characteristic amount of plastic axial strain, which depends on deformation conditions. In brittle faulting, distributed microfracturing is confined within limited regions of the rock volume, which expedites crack clustering and fault nucleation at low characteristic strains. In ductile faulting, distributed microfracturing occurs more uniformly throughout the rock volume, delaying shear localization to high characteristic strains. Accurate prediction of shear localization requires models that describe crack interactions of the largest flaws that account for crack clustering. Plain Language Summary: How do earthquakes begin? During the interseismic period, the crust deforms by distributed microfracturing (microseismicity) within the broad region that encompasses a seismogenic fault. As the tectonic stress approaches the fault strength, the distributed microfractures grow, interact, and coalesce to result in localized, dynamic fault rupture (earthquake). However, it remains poorly understood how microfracture interactions lead to the nucleation of dynamic rupture, particularly at seismogenic depths. We quantified crack interactions using microstructural analysis for brittle faults and high‐temperature ductile faults formed during experiments on quartz sandstone. For both faulting regimes, the nucleation of sample‐scale faults results from the interactions of microfractures at two length scales in ensemble. Most importantly, the interaction and coalescence of the longest mesoscale shear fractures (i.e., the largestflaws) is the fundamental process responsible for the nucleation of both brittle and ductile faults. In addition, the interaction of multi‐grain scale cracks locally promotes the growth of the mesoscale shear fractures—by tensile cracking in brittle faulting, and by shear cracking in ductile faulting. The observed fault nucleation processes resemble those inferred for many earthquakes, which involve the interaction of multiple precursory slow slip events and foreshocks. Laboratory studies of fault nucleation help geophysical interpretations of earthquake precursory signals. Key Points: Faults nucleate by crack interactions at two length scales in ensembleInteraction and coalescence of the longest mesoscale shear fractures is the fundamental process responsible for fault nucleationMulti‐grain scale crack interaction is also necessary for the growth of the mesoscale shear fractures (i.e., the fault nuclei) [ABSTRACT FROM AUTHOR]

The small strain shear modulus is an important characteristic of geomaterials that can be measured experimentally using piezoelectric sensors (bender elements). However, most conventional signal interpretation techniques are based on the visual observation of the output signal and therefore inherently subjective. Objective techniques also exist, like the cross-correlation of the input and output signals, but they lack physical insight, as they rely on the (incorrect) assumption that input and output signals are similar. This paper presents GeoHyTE, the first objective and physically consistent toolbox for the automatic processing of the output signal of bender element sensors. GeoHyTE updates a finite element model of the experiment, iteratively searching for the small strain shear modulus that maximises the correlation between the experimental and numerical output signals. The method is objective, as the results do not depend on the experience of the user, and physically consistent, as the wave propagation process is modelled in full and signals of the same nature (output) are correlated. Moreover, GeoHyTE is nearly insensitive to grossly erroneous input by the user, both in terms of the starting point of the iterative maximisation process and refinement of the finite element model. The results obtained with GeoHyTE are validated against benchmark measurements reported in the literature and experimental data obtained by the authors. A detailed statistical analysis of the results obtained with GeoHyTE and conventional interpretation techniques is also presented. [ABSTRACT FROM AUTHOR]

This paper presents a semi-analytical approach for nonlinear vibration and dynamic response of ceramic–metal functionally graded doubly curved shallow shells reinforced by carbon nanotubes under three different types of boundary conditions. This approach utilizes a new sinusoidal shear deformation theory combined with von Kármán's geometric nonlinearity. The proposed theory contains the sinusoidal distribution of transverse shear strains and satisfies the conditions of free transverse shear stress on both the top and bottom surfaces of the shell with only four unknown variables. The shells are made of a ceramic–metal matrix reinforced by carbon nanotubes with two types of distributions, both uniform distributions and functionally graded distributions. Equations of motion are derived from Hamilton's principle and then solved by the Galerkin method and Airy's stress function in which the closed-form solutions of the shells with fully simply supported edges, fully clamped edges, and two opposite simply supported and two opposite clamped edges are obtained. The study investigates the effects of boundary conditions, distribution types, volume fraction of carbon nanotubes, and geometrical parameters on the dynamic response, free and forced vibration of doubly curved shallow shells through numerical results. [ABSTRACT FROM AUTHOR]

Context: This study investigates the dynamic stability of monolayers MoS2, WS2, and MoS2/WS2 van der Waals heterostructures (vdWHs) and the influence of shear strain on their electronic properties. The computational results of the binding energy and phonon dispersion demonstrate the excellent dynamic stability of MoS2/WS2 vdWHs. The MoS2/WS2 vdWH, with a type-II band alignment and an indirect bandgap, reduces electron–hole recombination, enhancing the efficiency and performance of optoelectronic devices. Under shear strain, the bandgap size and type of monolayers MoS2, WS2, and MoS2/WS2 vdWHs were effectively modulated, along with the interlayer charge redistribution in the MoS2/WS2 vdWHs. This work reveals the tunability of the electronic properties of monolayers MoS2, WS2, and MoS2/WS2 vdWHs under shear strain, offering new possibilities and solutions for developing optoelectronic devices, sensors, and related fields. Methods: This work employed the CASTEP module within the Materials Studio software package for first-principles calculations. Ultrasoft pseudopotentials were employed during geometry optimizations to account for ion–electron interactions using the GGA-PBE functional for exchange–correlation potentials. The electronic configurations of the S, Mo, and W atoms were chosen as their typical arrangements: (3s2p4), (4s2p6d55s1), and (5s2p6d46s2), respectively. A vacuum layer of 20 Å was added to avoid interactions between the atomic layers. A cutoff energy of 500 eV was set for structural optimization and self-consistent calculations, with k-point grids of 6 × 6 × 1 and 9 × 9 × 1. During the structural optimization process, the energy convergence criterion was set to 1 × 10−5 eV, and the thresholds for interatomic forces and stresses were set to 0.01 eV/Å and 0.01 GPa, respectively. Grimmer’s DFT-D2 correction accounted for the interlayer vdW interactions in the MoS2/WS2 vdWH, while the phonon dispersion was calculated using the linear response method. [ABSTRACT FROM AUTHOR]

The current research work investigates the static, buckling, and free vibration behavior of carbon nanotube-reinforced composite (CNTRC) beam using the inverse hyperbolic shear deformation theory. This theory is based upon the shear strain shape function yielding a nonlinear distribution of transverse shear stresses and inherently satisfies the traction-free boundary conditions at the upper and lower surfaces of the beam structures omitting the requirement of the shear correction factor. The governing differential equations are developed using Hamilton's principle, and the closed-form solutions are obtained using Navier's approach. The rule of mixture is adopted to estimate the material characteristics of CNTRC beams. The four different ways of CNT's reinforcement distribution are used such as uniform distribution, O-beam, X-beam, and V-beam for the analysis. The analytical results in terms of deflection, stresses, critical buckling load as well as natural frequencies of the CNT-reinforced composite beam are obtained for various span thickness ratios, CNT volume fractions, and CNT reinforcement distributions. The result shows that the present theory predicts the responses of the CNTRC beam quite accurately as compared to the existing theories. Some new results are also included for the benchmark solutions of the new research. [ABSTRACT FROM AUTHOR]

The bulk production of fly ash from the primary source requirement brings the attention of the geotechnical engineers for the recommendation of mass utilization in a different area of civil engineering. The application of waste materials is normally done in stratified form, and their performance must be examined in static as well as dynamic conditions. The behavior of the waste material under static condition has been done in considerable amounts; therefore, in the present study, the shear modulus assessment of the homogeneous and stratified soil-ash deposits has been carried out. In addition, the strain energy per unit volume required for the liquefaction has also been investigated for the present combinations. The stratified soil shows higher shear modulus than that of the fly ash and local soil for shear strain of 0.3% and 0.6% and beyond 0.6%; it shows a comparable shear modulus as compared to the homogeneous one. The shear modulus versus shear strain variation of the present materials was comparable with the sand having higher fine content (or categorized as SP). The energy required for liquefaction is dependent on all the considered parameters, whereas it is independent of the cycle needed to liquefy. In addition to that, the excess pore pressure model has been developed for the homogeneous and stratified soil-ash deposit using a strain energy ratio as an independent parameter. [ABSTRACT FROM AUTHOR]

Shear strains during processing affect the agglomerate size of nanoparticles in nanocomposites and their final behavior in various applications. In this study, dielectric characterization technique as a novel and well-effective method is applied for quantitative measurement of average agglomerate size in polymer nanocomposites under shear strain sweep, combining with an existing analytical model. Examining how changes in filler content, surface energy and polarity of particles and the matrix control the strain-dependency of agglomerates size, two different nanoparticles, namely, titanium dioxide (TiO2) and carbon black (CB), with same average diameters and volumes were added to polystyrene (PS). It was found that larger agglomerates were present in the PS/CB nanocomposite prior to shearing and the CB agglomerates were less prone to deagglomeration under shear strain. This behavior was attributed to higher polarity of CB nanoparticles, leading to higher tendency for agglomeration and higher resistance to shear, in respect to TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

Evaluation of the characteristic behaviour of clay under cyclic loading is desirable and essential for an optimised monopile design of offshore wind turbines (OWTs). In current design practice, an irregular storm history is transformed into an idealised regular cyclic history with loading packages of uniform amplitude in ascending order. This paper investigates the effects of load representations by performing a series of load-controlled cyclic triaxial tests. The load histories investigated consist of a calculated 1 h storm loading on an OWT monopile foundation in the North Sea and its representations with different orders of the idealised load packages. The role of the average shear stress is discussed by comparing the shear strain evolution, pore water pressure accumulation, soil stiffness and strength. Cyclic degradation obtained with and without average shear stress components is studied. The experimental investigations in this paper indicate that the current design practice of load idealisation may not necessarily be conservative. The average shear stress affects the strain accumulation significantly but has relatively minor effects on the evolution of pore water pressure. It is suggested that the soil element response subjected to irregular load history should be investigated further from both experimental and numerical perspectives to develop an improved procedure for monopile design. [ABSTRACT FROM AUTHOR]

High-quality rotary core samples of natural London Clay were taken during installation of subsurface instrumentation to monitor the ground response at Hyde Park, London, to the construction of Crossrail tunnels. An extensive programme of advanced triaxial tests was performed on specimens from London Clay divisions A3 to C. Detailed analysis of their response to undrained shearing in compression from their estimated in situ stress state provides new insights into the magnitude of and changes in stiffness at small- and medium-strain levels. A consistent trend in the variation of small-strain stiffness with depth and lithological division is established for the Hyde Park research site. Differences between the stiffness magnitudes from this investigation and those reported earlier by others are shown to be a result of the conditions before and during undrained shearing, particularly the ratio of shearing axial strain rate to the preceding creep strain rate. This provides an explanation for significant discrepancies in small-strain stiffness values reported in recent years, which have led to uncertainties regarding which values to adopt, particularly for numerical analysis applications. Understanding the relevance of the axial shearing to creep rate ratio allows for improved triaxial testing techniques and the subsequent interpretation of the test data. [ABSTRACT FROM AUTHOR]

During glass production, phase separation can result in the formation of suspended liquid droplets, which can cause changes in the system rheology. In nuclear waste vitrification context, some new glassy matrices may present this phase separation matter, but the mechanisms controlling the viscosity changes have not yet been determined. Here, we measure the viscosity of a sodium‐borosilicate melt containing dissolved MoO3 at different temperatures and subject to different applied shear strain rates. We observe that (i) the viscosity increases sharply as the temperature decreases and (ii) at any constant temperature below 1000°C, the system presents non‐Newtonian response. Using transmission electron microscope observations coupled with viscosity calculations, we interpret the cause of the observed changes as the result of phase separation. We show that the viscosity increase on cooling is in excess of the predicted temperature dependence for a homogeneous melt of the starting composition. The increase is due to the formation of a second phase and is controlled by chemical and structural modifications of the matrix during the loss of the elements that form the droplets. This work provides insights into the rheology of a system composed of two composition sets due to a miscibility gap. [ABSTRACT FROM AUTHOR]

In this paper, the shear strain-dependent dynamic response properties of a retaining wall model made of mechanically stabilized earth (MSE) with polymeric geostrip material are investigated in a 1-g shaking table test. The values of lateral displacements and accelerations measured at different points along the MSE wall surface were used to evaluate the equivalent hysteris loops. The effect of reinforcement stiffness and backfill slope angle on the equivalent shear stiffness modulus (G e) and damping ratio (D) were investigated. The experimental results show that the variation of shear stiffness modulus and damping ratio as a function of shear strain (γ) is affected by vertical pressure (σ v), but the effect of the stiffness of the polymeric geostrip on the damping ratio is negligible. The variations of the G e , G e / σ v , G e / G max , and D as a function of γ are expressed in exponential equations with high least squares values in this study. • Shaking table tests on the physical model of polymeric geostrip reinforced MSE wall. • Analytical investigation of dynamic response parameters (D , G e) of polymeric geostrip reinforced wall. • The effect of slope angle of backfill soil and stiffness of geostrip on the shear stress-shear strain hystresis loops. • The effect of reinforced soil location on the dynamic parameters. [ABSTRACT FROM AUTHOR]

The stress-induced martensitic transformations and superelasticity behavior in the NiTi alloy with a single crystal model and a twist grain boundary bicrystal model at different temperatures are studied using molecular dynamics simulations. An atomic tracing method is proposed to identify specific numbers of B19′ martensite variants. Under uniaxial compressive loading, the stress-induced martensitic transformation takes place accompanied by the formation of <011>M type II twins, and the deformation process can be divided into three distinct stages based on microstructure evolution and average atomic total energy. It is found that the twist grain boundary induces an increase in the martensite start temperature, which is consistent with the experimental results. There is no residual B19′ martensite at the end of the unloading process, and the irrecoverable strain mainly results from plastic deformation at the grain boundary through the analysis of atomic local shear strains and has hardly changed with increasing deformation temperature. Remarkably, the grain boundary brings about the acceleration of martensite nucleation and an earlier occurrence of stress plateau. Further simulation results manifest that the presence of the twist grain boundary leads to weakened temperature dependence of martensitic transformation stress and a reduction in the hysteresis loop area. [ABSTRACT FROM AUTHOR]

The coronavirus pandemic (COVID-19) has led to a surge in disposable mask waste, posing an urgent environmental challenge. This study explores a sustainable solution by using mask chips as reinforcement material in geotechnical engineering, simultaneously improving ground strength and recycling waste. The mechanical behavior of Fujian sand reinforced with mask chips under plane strain biaxial shear condition was examined. Biaxial shear tests were performed on dense pure sand and sand samples containing three mask chip sizes (20 mm × 5 mm, 10 mm × 10 mm, and 12 mm × 3 mm) at a 0.5% mass ratio, under effective lateral pressures of 50 and 100 kPa. The test results show that incorporating mask chips improved strength and delayed stress peak, with the 20 mm × 5 mm chips demonstrating the best performance. Within the tested lateral pressure range, the sample dilates along the minor principal strain direction during shearing. The volumetric strain of mask–sand mixtures exhibits more significant contraction before the dilation compared with pure sand. Moreover, two distinct shear band shapes were observed through imaging technique where the thickness of the shear band decreases as the lateral pressure rises. Additionally, the Roscoe solution was found to provide the closest approximation of the inclination angle of the shear band in mask-reinforced sand. [ABSTRACT FROM AUTHOR]

The secant shear modulus is an important parameter in several geotechnical engineering models and calculation approaches. The characteristics of this parameter are very complex due to the hysteretic behavior of cyclically loaded soils. Its characteristics primarily depend on the mean effective confining stress and the void ratio. In this paper, the characteristics of the secant shear modulus of sand under large shear strain amplitude are investigated in detail based on the results of several cyclic triaxial and simple shear tests under drained and undrained conditions. The evaluation of the secant shear modulus based on the shape of the open stress–strain hysteresis loop is then discussed. Under certain loading conditions, the secant shear modulus defined from the reloading and unloading branches of the loop obviously differ. The evolution of the stiffness index, which measures the change in the secant shear modulus due to cyclic loading, shows that the drainage conditions play an essential role in the behavior of the secant shear modulus. [ABSTRACT FROM AUTHOR]

Shanghai clay exhibits overconsolidation, soil structural, and small-strain characteristics. While there have been several studies on the effects of small-strain characteristics on the deformation caused by deep excavation, the effects of overconsolidation and structural behaviors on this deformation remain unexplored. Therefore, in this study, a constitutive model considering the aforementioned three characteristics is developed and then implemented in the commercial software program FLAC3D (version 7.00) to investigate the effects of overconsolidation and structural behaviors. Initially, validation and parametric study of the constitutive model are conducted based on a cylindrical numerical model. Subsequently, the constitutive model is validated by a well-documented case history of a deep excavation in Shanghai. Thereafter, the effects of overconsolidation and structural behaviors on wall deflection and ground settlement induced by deep excavation are investigated. It is observed that overconsolidation has a significant effect on the deformation induced by deep excavation, while the effect of soil structure is negligible. With an increase in excavation depth, the effect of overconsolidation on the deformation increases, and its effect on ground settlement is more significant than that on wall deflection. According to the results of the parametric study, it is revealed that by the time the shear strain induced by deep excavation reaches a maximum value, overconsolidation has partially degraded while soil structure has not yet collapsed, which accounts for the magnitude of the aforementioned effects induced by deep excavation. [ABSTRACT FROM AUTHOR]

Diamane superlattice generated by the interlayer bonding of twisted bilayer graphene (IB-TBG) has attracted much attention thanks to its excellent properties inherited from bulk diamond, as well as the versatile modulation of physical and mechanical properties, which may open up novel electronic applications. In this work, we have systematically studied the in-plane and interlayer mechanical behaviors of IB-TBG through molecular dynamics simulations and theoretical analysis by considering different structural parameters, such as the twisted angle, stack pattern, and interlayer bonding density. It is found that interlayer bonding density plays a crucial role in determining the in-plane and interlayer shear mechanical properties of IB-TBG. Both the in-plane tensile modulus and strength follow the same linear attenuation relationship with interlayer bonding density for different twisted angles and stacked patterns, while the interlayer shear modulus increases with interlayer bonding density following the same power law, and the critical shear strain of failure linearly decreases with interlayer bonding density. Furthermore, two failure modes are observed under shear deformation, i.e., the failure of interlayer bonding (mode I) and fracture of graphene sheets (mode G). Then, theoretical prediction is carried out by considering the balance of in-plane tension and interlayer shear, which can identify the two failure modes well. The results presented herein yield useful insights for designing and tuning the mechanical properties of IB-TBG. [ABSTRACT FROM AUTHOR]

The double wedges sliding along the weak layer of the foundation can be observed on the slope of the waste dump and the sliding body is divided into the active wedge and passive wedge by the weak foundation and the failure surfaces of the waste dump. Because the conventional limit equilibrium slice method cannot reflect the polygonal slip surface of the slope of the waste dump with weak foundation, this study proposed a double wedge calculation method for the slope of the waste dump with weak foundation. The limit equilibrium analysis is performed on double wedges by considering the direction and values of the interaction force between double wedges to obtain the safety factor of the slope of the waste dump. Meanwhile, the quasi-3D double wedges stability analysis method of the waste dump slope with weak foundation is proposed by considering the influence of the geometry and sliding direction of the slope surface on the slope stability. The safety factor of the inverted dump slope is 0.82, the volume of the sliding body is 6.43 million m3, and the main sliding direction is 20° south by east. The shear strain rate cloud diagram of the section is 'y' type distribution, and the sliding body is divided into two independent blocks. The safety factor of the sliding body section obtained by the double wedge method is between 0.76 and 0.92, and the closer to the boundary of the sliding body, the greater the safety factor of the section. The quasi-three-dimensional safety factor obtained by theoretical analysis is 0.817. The results show that the calculation results of quasi-3D double wedge are basically consistent with the calculation results of strength reduction method, while the proposed method is simpler. It can be used as a quick method to evaluate slope stability in engineering practice. [ABSTRACT FROM AUTHOR]

A severe plastic deformation (SPD) process known as linear corrugation and straightening (LCS) was employed to deform 4-mm-thick plates made of a twin-rolled cast magnesium alloy (AZ31). The cross section (through the thickness, top edge to the middle) of two of the processed plates was examined under an optical microscope and by using electron backscatter diffraction. A 2D finite element model (FEM) was then developed for the push-press-release cycle of the LCS process for all four processed specimens up to three presses. FEM of the LCS revealed that overall strain accumulation was highest in the regions of the specimen with the smallest grain sizes. Images obtained from some processed specimens were correlated with the plastic (PEEQ) and shear (P12) strain distribution results obtained from FEM. This demonstrates that a relatively simple deformation model successfully predicts the formation of fine and coarse grain development in certain regions with higher and lower shear strains. Moreover, FEM showed the formation of dead zones within the plate specimens where plastic and shear strains were very small. These dead zones retained the original coarse grains within the processed plates. [ABSTRACT FROM AUTHOR]

Extensive research has shown that nanolayered structures are capable of suppressing the shear banding in metallic glass in nanoindentation experiments. However, the specific mode and mechanism of the shear banding underneath the indenter remains unknown. Also, the quantification of shear banding-induced strain localization is still a challenge. Herein, the size-dependent shear banding behavior of a CuTiZrNb high-entropy alloy-based nanolayered glass with individual layer thicknesses (h) ranging from 5 to 80 nm was systematically investigated by nanoindentation tests. It was found that the hardness of the designed structure was almost size-independent. Yet, a clear transition in the deformation modes from the cutting-like shear bands to the kinking-like ones was discovered as h decreased to 10 nm. Moreover, multiple secondary shear bands also appeared, in addition to the primary ones, in the sample with h = 10 nm. The transition leads to an obvious strain delocalization, as clearly illustrated by the proposed theoretical model, which is based on the assumption of a pure shear stress state to quantify the shear banding-induced strain localization. The strain delocalization results from the higher density of amorphous/amorphous interfaces that exhibit the change in morphology with a refined layered glass structure. [ABSTRACT FROM AUTHOR]

This paper deals with the use of viscoelastic composite material (VECM) for the constrained layer of an active constrained layer damping (ACLD) treatment for enhanced damping characteristics due to contributions of extensional strains in addition to transverse shear strain. The proposed VECM layer is composed of graphite fibers reinforced in a conventional viscoelastic matrix. The bending analysis of the overall beam is carried out and contributions of extensional and shear strains for damping behavior are found out. The effects of changing various geometric parameters of the present VECM layer on the control performance of the ACLD treatment have also been evaluated and presented. [ABSTRACT FROM AUTHOR]

The viscoelasticity of a carbon nanotube (CNT)-laden air–water interface was characterized using two different experimental methods. The first experimental method used a Langmuir-Pockels (LP) trough coupled with a pair of oscillating barriers. The second method is termed the Bicone-Trough (BT) method, where a LP trough was custom-built and fit onto a rheometer equipped with a bicone fixture to standardize the preparation and conditioning of a particle-laden interface especially at high particle coverages. The performance of both methods was evaluated by performing Fast Fourier Transform (FFT) analysis to calculate the signal-to-noise ratios (SNR). Overall, the rheometer-based BT method offered better strain control and considerably higher SNRs compared to the Oscillatory Barriers (OB) method that oscillated barriers with relatively limited positional and speed control. For a CNT surface coverage of 165 mg/m2 and a frequency of 100 mHz, the interfacial shear modulus obtained from the OB method increased from 39 to 57 mN/m as the normal strain amplitude increased from 1 to 3%. No linear viscoelastic regime was experimentally observed for a normal strain as small as 0.5%. In the BT method, a linear regime was observed below a shear strain of 0.1%. The interfacial shear modulus decreased significantly from 96 to 2 mN/m as the shear strain amplitude increased from 0.025 to 10%. [ABSTRACT FROM AUTHOR]

In order to optimize the efficiency and safety of gas hydrate extraction, it is essential to develop a credible constitutive model for sands containing hydrates. A model incorporating both cementation and damage was constructed to describe the behavior of hydrate-bearing cemented sand. This model is based on the critical state theory and builds upon previous studies. The damage factor Ds is incorporated to consider soil degradation and the reduction in hydrate cementation, as described by plastic shear strain. A computer program was developed to simulate the mechanisms of cementation and damage evolution, as well as the stress-strain curves of hydrate-bearing cemented sand. The results indicate that the model replicates the mechanical behavior of soil cementation and soil deterioration caused by impairment well. By comparing the theoretical curves with the experimental data, the compliance of the model was calculated to be more than 90 percent. The new state-dependent elasto-plastic constitutive model based on cementation and damage of hydrate-bearing cemented sand could provide vital guidance for the construction of deep-buried tunnels, extraction of hydrocarbon compounds, and development of resources. [ABSTRACT FROM AUTHOR]

The Tyennan Domain of western Tasmania is a structurally emplaced, complexly deformed lithotectonic sheet (allochthon). It comprises stacked, isoclinally folded slabs of allochthonous high-grade schist including garnet schist and quartzite, amphibolite and rare eclogite (uppermost unit), overlying low-grade pelite, overlying low-grade quartzite and platy quartzite (middle unit), overlying parautochthonous low-grade dolomitic pelite, quartzite and dolostone (lowermost unit). It is a product of Cambrian continental margin subduction, rebound and exhumation coupled with ophiolite obduction. Tyennan rocks were transported to maximum depths of ∼60–80 km sufficient to generate high-P metamorphism. Their deformation involved progressive shear, large shear strains and large shear displacements with a bulk west-over-east sense of shear related to the direction of subduction and buoyant exhumation. The Tyennan Domain shows a unique crustal architecture, including: (1) metamorphic sheets with 100 km lengths, 50 km widths and 5–10 km structural thicknesses, (2) a leading edge fold nappe with ∼200 km axial surface trace length, (3) megasheath folds with 20–25 km dimensions, and (4) asymmetric folds within regional scale shear lozenges as macro-augen. It provides an unparalleled window beneath the now, largely eroded, obducted ophiolite sheet and provides structural insight into the mechanics of continental margin subduction–obduction. Deformation has been partitioned through the composite exhumed 'slab' with domains of isoclinal macrofolds transitioning into regional scale sheath folds bounded by zones of higher strain. The higher strain zones are characterised by transposition foliation, rootless mesoscopic isoclinal folds, small-scale sheath folds, overprinting crenulation cleavages and platy mylonitic to schistose zones in quartzite. The uppermost, high-grade part of the Tyennan allochthon is clearly a composite, ∼1 km thick 'sheet' made up of a 'welded' amalgam of largely pelitic fragments that had been subducted to different depths, assembled and deformed during buoyant ascent to the current structural level. The Tyennan Domain represents the subducted part of a microcontinent during a Cambrian arc–microcontinent collision outboard of the eastern Pacific margin of Gondwana. The Tyennan Domain consists of stacked, recumbent and isoclinally folded slabs of allochthonous high-grade schist and low-grade pelite-quartzite, overlying parautochthonous low-grade dolomitic marl, quartzite and dolostone. Isoclinal, asymmetric, macrofold 'wave trains', megasheath folds and a 'leading edge' fold nappe with ∼200 km length scale dominates the structure of the Tyennan Domain. [ABSTRACT FROM AUTHOR]