Biaxial Pressure Research Articles

Pressure-tuning of α-RuCl3 towards a quantum spin liquid

The layered material α-RuCl3 is a promising candidate to realize the Kitaev quantum spin liquid (QSL) state. However, at ambient pressure, deviations from the perfect Kitaev geometry prevent the existence of the QSL state at low temperatures. Here we present the discovery of a pressure-induced high-symmetry phase in α-RuCl3, which creates close to ideal conditions for the emergence of a QSL. Employing a novel approach based on Bragg and diffuse scattering of synchrotron radiation, we reveal a pressure-induced reorganization of the RuCl3-layers. Most importantly, this reorganization affects the structure of the layers themselves, which acquire a high trigonal symmetry. For this trigonal phase the largest ratio between the Kitaev (K) and the Heisenberg exchange (J) ever encountered is found: K/J = 124. Additionally, we demonstrate that this phase can also be stabilized by a slight biaxial pressure. This not only resolves the conflicting reports of low-temperature structures in the literature, but also facilitates the investigation of the high-symmetry phase and its potential QSL using a range of experimental techniques.

Load history dependency of stiffness properties of PTFE-coated glass fibre membranes

The aim of this contribution is to investigate whether the order of load ratios applied to a textile structure impacts the biaxial stiffness behaviour of the structural textile itself. These investigations are performed based on biaxial tests on an architectural woven glass fibre fabric, a representative of such membranes. The first part of the paper investigates the existence and extent of load history dependency in the material response. Biaxial test results show that effects of a previous load history on the weave geometry cannot be eliminated by further load cycling in all biaxial stress ratios. Moderate to strong effects are recognized in two stress ratios, although not in both weave directions.The second part of the paper examines how these effects influence material stiffness parameters and structural calculations. Two boundary value problems are investigated: a pressure chamber test and a roof structure. Parameters obtained by fitting biaxial tests with or without history are considered. By incorporating an adaptive load-ratio dependent scheme, highly predictive numerical results are obtained, showing that while the effect of load history may appear small in the biaxial tests and pressure chamber test, it can be significant in complex structural problems like roof structures.

Optical and Electrical Properties of SiO2 under Uniaxial, Biaxial, and Isotropic Pressure: a First Principles Study

Optical and Electrical Properties of SiO2 under Uniaxial, Biaxial, and Isotropic Pressure: a First Principles Study

Strain rockburst failure characteristics and mechanism of high stress circular hard rock tunnel triggered by dynamic impact load

Strain rockburst poses a great threat to the construction safety of deep engineering, especially induced by dynamic impact loads such as blasting from the adjacent tunnel excavation. Aiming to clarify the failure characteristics and mechanism of strain rockburst induced by the dynamic impact load, a series of dynamic impact tests under different biaxial prestress conditions were conducted on the sandstone cube specimens with prefabricated circular holes by using the new biaxial Hopkinson pressure bar equipment. The real-time rockburst process and fracture characteristics on both sidewalls were captured by the high-speed camera. The test results show that the strain rockburst process can be divided into: the calm stage, slab buckling and spalling stage, rock slabs ejection stage, and V-shaped notch formation stage. Ultimately, a symmetrical V-shaped notch failure zone was formed on the sidewall, similar to the site. The strain field evolution characteristics and displacement deformation characteristics around the circular hole during the rockburst process were further explained by using digital image correlation (DIC). The failure mechanism of sidewall strain rockburst was closely related to spalling failure, characterized by dynamic tensile failure. The static stress provides the initial compressive stress field and governing the stress distribution around the tunnel. Dynamic impact load disrupts the original stress equilibrium of the surrounding rock, inducing significant alterations in internal stresses and strains within the surrounding rock, consequently inducing spalling or rockburst failure. The influences of lateral pressure on rockburst were also analyzed in detail, while the lateral pressure influences the severity of strain rockburst, which determines the dynamic load response characteristics, influence range of strain concentration zone, displacement deformation characteristics of the tunnel surrounding rock, and the severity of strain rockburst decreases with the increase of lateral pressure.

Chloride ion diffusion and distribution characteristics in recycled coarse aggregate concrete under uniaxial and biaxial pressure

Under uniaxial compression, recycled coarse aggregate leads to complex internal stresses (simultaneous uniaxial, biaxial, and multiaxial tensile and compressive stresses at the micro scale) and even micro cracks in concrete, which poses difficulties in accurately predicting the chloride ion diffusion of recycled concrete. By changing the compressive stress level and bi-directional stress ratio of concrete, a self-developed biaxial compression device was used to test the chloride ion diffusion coefficient of recycled concrete under different stress states. In order to analyze the influence of various factors on chloride ion diffusion, DIC digital image technology and microcrack statistics technology were used to analyze the influence of concrete micro deformation on its chloride ion diffusion coefficient under load, and X-ray fluorescence technology was used to accurately analyze the concentration distribution of chloride element in different positions of concrete. The pore structure inside recycled concrete was characterized through experiments, and a real three-dimensional multi-scale model of concrete and the statistical characteristics of porosity at different scales were obtained. Finally, a theoretical model was established to predict the chloride ion diffusion coefficient under biaxial compressive loads, achieving accurate prediction of chloride ion diffusion coefficient close to practical engineering.

Experimental study on the influence of explosive stress wave on the dynamic crack propagation characteristics under biaxial confining pressure

The effect of biaxial confining pressure on dynamic crack and the interaction between explosive stress wave and dynamic crack are studied based on dynamic photoelastic method in this experiment. The experiment consists of five groups, primarily focusing on the angle at which the stress wave encounters the crack. The experimental results reveal two main fractures: mode I fracture and mixed-mode fracture. The influence of biaxial confining pressure on stress waves and dynamic cracks differs between these two fracture modes. Additionally, the Newton-Raphson iteration method is employed to analyze and calculate the fringe pattern of the crack tip at various stages. Subsequently, the calculation results are used to reconstruct the photoelastic fringe. To validate the accuracy of the calculation method, the reconstructed photoelastic fringe pattern is compared with the experimental results. The results show that the presence of confining biaxial pressure enhances the crack initiation toughness, propagation toughness and propagation speed. It also improves the crack's resistance to the impact of the incident stress wave from all directions. When the stress wave interacts with the crack, the photoelastic fringe patterns at the crack tip can be categorized into two main types. One is primarily influenced by the stress wave, while the other is primarily influenced by the stress field at the crack tip. To extract accurate crack tip information, it is essential to analyze the fringe pattern dominated by the stress field at the crack tip.

Modelling of GaAsSb/InAs type-II QW heterostructure and simulation of its optical gain characteristics under (100), (001) and (110) directional pressure

A multi band (particularly, six band) k. p approach has been adopted for modelling the GaAsSb/InAs/AlSb W-shaped quantum well (QW)-heterostructure (a type-II with broken bandgap band alignment) and simulation of behaviour of optical gain characteristics under uni- and bi-axial pressures. The motivation behind designing such QW heterostructure is its high optical gain in MIR (mid infrared region) with noteworthy tuneable optical characteristics. The tuneable characteristics under uni-axial (100) and (001) pressure and bi-axial (110) pressure have been studied through the simplification of a multiband band k. p Hamiltonian. For all the directional pressures, the pressure range was fixed from 1 GPa to 3 GPa (with the interval of 0.5 GPa). For the (100) directional pressure, a significant increase in the gain (from 3570 to 7800/cm) was noted showing the red shifted wavelength with increasing order of pressure; while (001) directed pressure has caused to reduce the gain (3550–1158/cm) with red shifted wavelength. The (110) directed pressure has also caused to enhance the gain considerably (2550–7597/cm) with change in wavelength towards high wavelength. The study of gain characteristics was performed considering 1.5 × 1012 cm−2 2-D charge carrier density, which proves the tunability of the designed heterostructure in various tuneable optoelectronic devices.

Terahertz Biaxial Strain Sensor Based on Double-Upright Cross Metamaterial

In this article, a terahertz metamaterial biaxial strain pressure sensor structure is proposed, which can address the problems of the low sensitivity, the narrow pressure measurement range, and the uniaxial-only detection of existing terahertz pressure sensors. The performance of the pressure sensor was studied and analyzed using the time-domain finite-element-difference method. By changing the substrate material and optimizing the structure of the top cell, the size of the structure that can simultaneously improve the range and sensitivity of the pressure measurements was determined. The simulation results show that the sensor has a pressure-sensing effect in the frequency range of 1.0–2.2 THz under the conditions of transverse electric (TE) and transverse magnetic (TM) polarization, and the sensitivity can reach up to 346 GHz/μm. The proposed metamaterial pressure sensor has significant applications in the remote monitoring of target structure deformation.

Research on the True Triaxial Mechanical Properties of Concrete under the Coupling Action of High Temperature and Biaxial Unequal Lateral Pressure.

Based on engineering practice and practical needs, this paper takes ordinary concrete specimens as the research object, and adopts a high-temperature true triaxial loading test system to carry out high-temperature uniaxial and true triaxial static compression tests of concrete under high-temperature conditions. By comparing with normal temperature conditions, this paper analyzes the influence of the coupling effect of high-temperature and biaxial unequal lateral pressure on the static mechanical properties of concrete. By analyzing the experimental data, we reached a series of conclusions and carried out theoretical research on this basis. High temperatures can significantly affect the uniaxial static pressure strength characteristics, deformation characteristics, and failure mode of concrete. When the temperature exceeds 400 °C, the compressive strength decreases significantly, the peak strain increases sharply, and the plasticity of concrete is further enhanced. The coupling effect of high-temperature deterioration and lateral pressure strengthening makes the true triaxial mechanical properties of concrete change significantly; 0.6:0.2 and 400 °C are the turning points of side pressure ratio and temperature that affect the change law of the true triaxial mechanical properties of concrete, respectively. Based on the study of the high-temperature deterioration factor and lateral pressure strengthening factor, this paper further puts forward a concrete strength formula under the coupling action of high temperature and biaxial unequal lateral pressure. It was verified that the formula has a high accuracy.

Bond behavior between recycled aggregate concrete and steel rebar subjected to biaxial lateral pressure

Eighty-four pull-out tests were carried out to study the bond behavior between recycled aggregate concrete (RAC) and steel rebar, considering different levels of recycled coarse aggregate (RA) substitution and biaxial lateral pressure. The effects of these two parameters on bond strength and peak slip were analyzed, the bond-slip constitutive relation between RAC and steel rebar under biaxial lateral pressure was established, and the energy of bonded interface was also analyzed. The results show that the failure patterns of specimens without lateral pressure were splitting failure, while the failure patterns of specimens with different biaxial lateral pressure can be classified as splitting-pull out failure. With an increase of lateral pressure, the relative bond strength, peak slip and bond energy gradually increased, whereas the relationship between RA replacement percentages and these parameters could not be clearly observed. In addition, the relative bond strength and peak slip approximately increased linearly with the increase of lateral pressure. Finally, based on the experimental results, a modified expression for bond-slip prediction was developed, taking into account damage, and the obtained results show that the predicted curves fit well with test data.

Aging and G Protein‐Coupled Estrogen Receptor Exacerbates Carotid Artery Structural Remodeling

Aging is a nonmodifiable risk factor for cardiovascular disease associated with arterial stiffening and cardiac dysfunction. We previously showed an important role for G protein‐coupled estrogen receptor (GPER) in modulating female protection from arterial stiffening. In this study, we hypothesized that aging would decrease vascular compliance in GPER knockout (ko) mice to a greater extent than wildtype (wt) mice. Adult (25 weeks) and middle‐aged (57 weeks) mice were subjected to high frequency ultrasound for pulse wave velocity (PWV), and structural remodeling in the carotid artery was assessed with biaxial pressure myography followed by constitutive modeling. Data was analyzed by 3‐way ANOVA and Sidak’s post hoc tests. As we previously showed, PWV was significantly lower in adult female wt mice versus their male counterparts (1.4 ± 0.05 vs. 1.1 ± 0.02 m/s; P=0.0004) but was not different in adult ko mice (1.6 ± 0.07 vs 1.4 ± 0.08, P=0.20). Interestingly, PWV increased with aging in female but not male wt mice, so that the sex difference was lost (1.7 ± 0.03 vs 1.7 ± 0.06, P=0.99). Despite the lower PWV, circumferential linearized material stiffness in passive conditions was elevated in adult female wt versus male wt (1.9 ± 0.2 vs. 1.4 ± 0.2 MPa; P=0.02), but this sex difference was lost in middle‐aged wt mice (1.3 ± 0.1 vs. 1.2 ± 0.1 MPa; P=0.87). Aging significantly increased the ratio of thick to thin collagen only in male wt and female ko groups. We found that females but not males experience an increase in PWV at middle‐age along with a decrease in circumferential stiffness. In contrast, female GPER mice already display a higher PWV as adults, indicating that GPER deletion in females is a model of accelerated vascular aging.

Abstract P170: Similarities And Differences In The Vascular Impact Of Estrogen Loss Versus G Protein-coupled Estrogen Receptor Deletion

Women in their postmenopausal years have an increased risk of cardiovascular disease, and recent research suggests that increased vascular stiffness can be detected within a year of the onset of menopause. We have previously demonstrated that the G Protein-Coupled Estrogen Receptor (GPER) protects the vasculature without noticeable changes in blood pressure, but little is known about the underlying structural changes that provide protection. In this study we assessed the impact of estrogen and the G protein-coupled estrogen receptor (GPER) on vascular health, with the hypothesis that loss of estrogen or deletion of smooth muscle cell (smc)-GPER would similarly increase vascular stiffness. Female mice were separated into three cohorts: intact wildtype, ovariectomized (OVX), and GPER smc-KO. OVX occurred at 8 weeks of age and 8 weeks later blood pressure was measured via tail-cuff plethysmography, arterial stiffness was measured as pulse wave velocity (PWV) via high resolution ultrasound, and carotids were excised for biaxial pressure myography and imaging. Uterine weight in OVX mice (0.03 g) was significantly lower than intact mice (0.1 g; p=0.0002) confirming the loss of estrogen. No difference was observed in systolic blood pressure, however, both the OVX (1.5 m/s) and smc-KO (1.9 m/s) groups had significantly higher PWV than intact controls (1.2 m/s; p=0.02 and p=0.03, respectively). Carotids of OVX (366 μm) and smc-KO (389 μm) mice had a smaller outer diameter versus controls (441 μm; p >0.05) without a difference in thickness. Despite the similar responses of OVX and smc-KO groups, Masson’s trichrome staining of carotid sections showed significantly more smooth muscle area fraction in OVX (p=0.005), but not KO mice, and no difference in collagen area fraction. These data indicate that while estrogen loss and smc-KO of GPER both increase arterial stiffness, increased smooth muscle due to estrogen loss is likely not modulated through GPER. Future experiments will aim to understand how other components, such as extracellular matrix genes, may be affected by loss of GPER.

The nonlocal parameter for three-dimensional nonlocal elasticity analyses of square graphene sheets: An exact buckling analysis

This paper studies buckling problem of square nano-plates under uniform biaxial pressure through using three-dimensional nonlocal elasticity theory. Equations of stability are solved analytically for square nano-plates with simple supports using a Navier-type method. Critical buckling stress is presented for nano square plates with different thickness-length and nonlocal parameter-length ratios. The critical buckling stress is also reported using different local (classical) and nonlocal two-dimensional plate theories constructed essentially based on some simplifying assumptions. Comparison of the results of two-dimensional and three-dimensional theories for both local and nonlocal cases shows that the nonlocal two-dimensional plate theories are not as accurate as the local two-dimensional ones. This issue however reveals importance of the nonlocal three-dimensional solutions. Finally, through comparison of the numerical results with those obtained from molecular dynamic simulations, the value of the nonlocal parameter is calibrated for square graphene sheets. This parameter can be also used for the other nonlocal three-dimensional mechanical analyses of square graphene sheets to find accurate solutions.

Non-local criteria for the borehole problem: Gradient Elasticity versus Finite Fracture Mechanics

Two nonlocal approaches are applied to the borehole geometry, herein simply modelled as a circular hole in an infinite elastic medium, subjected to remote biaxial loading and/or internal pressure. The former approach lies within the framework of Gradient Elasticity (GE). Its characteristic is nonlocal in the elastic material behaviour and local in the failure criterion, hence simply related to the stress concentration factor. The latter approach is the Finite Fracture Mechanics (FFM), a well-consolidated model within the framework of brittle fracture. Its characteristic is local in the elastic material behaviour and non-local in the fracture criterion, since crack onset occurs when two (stress and energy) conditions in front of the stress concentration point are simultaneously met. Although the two approaches have a completely different origin, they present some similarities, both involving a characteristic length. Notably, they lead to almost identical critical load predictions as far as the two internal lengths are properly related. A comparison with experimental data available in the literature is also provided.

Biaxial pressure pack carburizing method to modification local low carbon steel’s mechanical properties

The absolute requirement for steel material can be hardened directly is the carbon content of this material is more than or equals to 0.3 %. This steel material is recognized as medium carbon steel and above. Carburizing process is an effort to increase low carbon content in soft steel material which have less than 0.3 % it can be done by adding carbon content up to 0.3 % and above. The tool commonly used for this process called pack carburizing device and the process occur in furnace atmospheric pressure. In this research, carbon content adding process held on pressurized pack carburizing container, and the pressure was given mechanically from two axial direction named biaxial pressing carburizing process. The speciment material used in this research is local low carbon steel (ST.37) and coconut shell active charcoal powder. Process parameter The process parameter are pressure, temperature, and hoding time. The best result is achieving at a process temperature of 1000 ºC with 3 hour holding time and biaxial pressure of 2 MPa with 115.4 HRB, 823,6 N/mm2, and 0,41 % the incensement of carbon content from 0,27 % to 0,40 %.

Physical-property cutoffs of tight reservoirs by field and laboratory experiments: a case study from Chang 6, 8–9 in Ordos Basin

Tight sandstone reservoirs are generally characterized by complex reservoir quality, non-Darcy flow, and strong heterogeneity. Approaches utilized for evaluating physical property cutoffs of conventional reservoirs maybe inapplicable. Thus, a comprehensive investigation on physical property cutoffs of tight sandstone reservoirs is crucial for the reserve evaluation and successful exploration. In this study, a set of evaluation approaches take advantage of field operations (i.e., core drilling, oil testing, and wireline well logging data), and simulation experiments (i.e., high-pressure mercury injection-capillary pressure (MICP) experiment, oil-water relative permeability experiment, nuclear magnetic resonance (NMR) experiment, and biaxial pressure simulation experiment) were comparatively optimized to determine the physical property cutoffs of effective reservoirs in the Upper Triassic Chang 6, Chang 8 and Chang 9 oil layers of the Zhenjing Block. The results show that the porosity cutoffs of the Chang 6, Chang 8, and Chang 9 oil layers are 7.9%, 6.4%, and 8.6%, and the corresponding permeability are 0.08 mD, 0.05 mD, and 0.09 mD, respectively. Coupled with wireline well logging, mud logging, and oil testing, the cut-off of the thickness of single-layer effective reservoirs are approximately 3.0 m, 3.0 m, and 2.0 m, respectively. Depending on the cutoffs of critical properties, a superimposed map showing the planar distribution of the prospective targets can be mapped, which may delineate the effective boundary of prospective targets for petroleum exploration of tight sandstone reservoirs.

Spark plasma sintering of TiB2-based ceramics with Ti3AlC2

A TiB2–Ti3AlC2 ceramic was manufactured by spark plasma sintering at 1900 °C temperature for 7 min soaking time under 30 MPa biaxial pressure. The role of Ti3AlC2 additive on the microstructure development, densification behavior, phase evolution, and hardness of the ceramic composite were studied. The phase characterization and microstructural investigations unveiled that the Ti3AlC2 MAX phase decomposes at the initial stages of the sintering. The in-situ formed phases, induced by the decomposition of Ti3AlC2 additive, were identified and scrutinized by XRD and FESEM/EDS techniques as well as thermodynamics principles. The sintered TiB2–Ti3AlC2 ceramic approached a near full density of ~99% and a hardness of ~28 GPa. The densification mechanism and sintering phenomena were discussed and graphically illustrated.

Highly stretchable sensing array for independent detection of pressure and strain exploiting structural and resistive control

Stretchable physical sensors are crucial for the development of advanced electrical systems, particularly wearable devices and soft robotics. Currently available stretchable sensors that detect both pressure and strain are based on piezoelectric, piezoresistive, or piezocapacitive effects. The range of pressure sensing is 1–800 kPa with large deformations being within the range of deformations of parts of the human body, such as elbows and knees. However, these devices cannot easily allow simultaneous and independent detection of pressure and strain with sensor arrays at large tensions (> 50%) because strain affects the pressure signal. In this study, we propose a monolithic silicone-based array of pressure and strain sensors that can simultaneously and independently detect the in-plane biaxial tensile deformation and pressure. To realize these functionalities, the deformation of the device structure was optimized using a hetero-silicone substrate made of two types of silicone with different hardness characteristics and porous silicone bodies. In addition, the resistances of the sensors were controlled by adjusting a mixture based on carbon nanoparticles to improve the sensitivity and independence between the pressure and strain sensors. These concepts demonstrate the potential of this approach and its compatibility with the current architectures of stretchable physical sensors.

Impact of strain, pressure, and electron correlation on magnetism and crystal structure of Mn2GaC from first-principles

The atomically laminated Mn2GaC has previously been synthesized as a heteroepitaxial thin film and found to be magnetic with structural changes linked to the magnetic anisotropy. Related theoretical studies only considered bulk conditions and thus neglected the influence from possible strain linked to the choice of substrate. Here we employ first principles calculations considering different exchange–correlation functionals (PBE, PW91, PBEsol, AM05, LDA) and effect from use of + U methods (or not) combined with a magnetic ground-state search using Heisenberg Monte Carlo simulations, to study influence from biaxial in-plane strain and external pressure on the magnetic and crystal structure of Mn2GaC. We find that PBE and PBE + U, with Ueff ≤ 0.25 eV, gives both structural and magnetic properties in quantitative agreement with available experimental data. Our results also indicate that strain related to choice of substrate or applied pressure is a route for accessing different spin configurations, including a ferromagnetic state. Moreover, the easy axis is parallel to the atomic planes and the magnetocrystalline anisotropy energy can be increased through strain engineering by expanding the in-plane lattice parameter a. Altogether, we show that a quantitative description of the structural and magnetic properties of Mn2GaC is possible using PBE, which opens the way for further computational studies of these and related materials.

Material flow characteristics and deformation law during dual directional hot forging of the steel-aluminium spur gear

To study the material forming characteristic and deformation law during dual directional hot forging (DDHF) of the steel-aluminum spur gear, a thermo-mechanical coupled finite element model (FEM) was built using DEFORM-3D software. Billet was designed into two parts—core cylinder and outer ring. 20CrMnTi steel and pure aluminum are selected as the materials of the outer ring and core cylinder, respectively. The steel outer ring formed the teeth of the spur gear and heated 1000°C, while the aluminum core formed the center of the spur gear and heated 400°C. The heated steel-aluminum billet was deformed under biaxial forging pressure. The FE simulation was carried out and the metal forming characteristic and flow law were analyzed. The simulation results show that the core pure aluminum has bigger deformation in the middle part and extruding the steel ring forming part of the teeth. The final forging temperature of billet increases and the forming load decreases with the increasing the forging speed.