Small Elastic Modulus Research Articles

Garnet-Based All-Ceramic Lithium Battery Enabled by Li2.985B0.005OCl Solder.

SummaryGarnet-based bulk-type all-ceramic lithium battery (ACLB) is considered to be highly safe, but its electrochemical performance is severely hindered by the huge cathode/electrolyte interfacial resistance. Here, we demonstrate an in situ coated Li2.985B0.005OCl as sintering solder, which is uniformly coated on both LiCoO2 and Li7La3Zr2O12. With the low melting point (267°C) and high ionic conductivity (6.8 × 10−5 S cm−1), the Li2.985B0.005OCl solder not only restricts La/Co interdiffusion, but also provides fast Li+ transportation in the cathode. A low cathode/electrolyte interfacial resistance (386 Ω cm2) is realized owing to the densification of the ACLB by hot-press sintering. The strain/stress of the LiCoO2 is also released by the small elasticity modulus of Li2.985B0.005OCl, leading to a superior cycling stability. The study sheds light on the design of advanced garnet-based bulk-type ACLB by exploring proper solders with higher ionic conductivity, lower melting point, and smaller elasticity modulus.

Experimental investigation on Stribeck curves of different elastic modulus materials under oil and water lubrication conditions

Purpose The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions. Design/methodology/approach Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system. Findings In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered. Originality/value The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

Effects of Magnesium-Calcium Alloys with Different Calcium Content on Their Mechanical Properties

Compared with traditional medical metal materials, magnesium alloys have the characteristics of small density, small elastic modulus and high specific stiffness. In order to study the effect of the addition of calcium on the mechanical properties of magnesium alloys, the tensile test and hardness test of magnesium-calcium alloy were carried out. The stress changes during the tensile test of magnesium alloy were discussed, and the microstructure of its section was further observed, so as to compare the effects of different calcium content on the mechanical properties of magnesium alloy. The results show that the addition of calcium content increases the hardness and tensile strength of the magnesium alloy, and it tends to rise first and then decrease.

Formability study on stamping an engine hood with aluminum alloy sheet

The formability of stamping an engine hood with aluminum alloy sheet was examined in the present study. In the stamping process, except that aluminum alloy would crack easily, a small elastic modulus makes the aluminum alloy easier to produce a significant springback defect, which would lead to variation of accuracy and is hard to grapple with. In the present study, the cyclic tension-compression reversal tests were first conducted to obtain the stress-strain relations and the Bauschinger effect exhibited in the aluminum alloy sheet was noted. The finite element simulations were then preformed for V-bending and U-hat drawing of aluminum alloy sheet, and the results of springback and side-wall curl were compared with those obtained from experiments. It is concluded from the comparison that the material model which includes the Bauschinger effect renders a more consistent result with the experimental data. In order to investigate the difference of forming characteristics between conventional steel and A6181-T4 in the stamping process of an engine hood, the effects of process parameters on the stamping formability were systematically analyzed by the finite element simulations. The finite element simulation results were validated by the production engine hood and the characteristics of A6181-T4 formability investigated in this study were confirmed.

A frost heaving mitigation method with the rubber-asphalt-fiber mixture cylinder

Severe frost heaving causes problems for heavy-haul railway embankments filled with lean clay during cold seasons in China. The anti-frost-heaving performance of a mixture, which consists of rubber particles, asphalt, and polypropylene fiber, was investigated by 1-D frost heaving tests and triaxial shear tests in the laboratory. The mixture cylinder embedded in the specimens can markedly reduce the frost heaving, and the increasing mass of tire granules plays a negative role in mitigating the frost heaving. The nonlinear elastic modulus for unfrozen soil decreases with the strain, while the constant elastic modulus for the mixture is independent of the strain. When the strain is <5%, the modulus of unfrozen soil is greater than that of the mixture. The water content in height for specimens with the mixture cylinder is lower than that for specimens without the cylinder. Therefore, both the smaller elastic modulus and capillary-break effect of the mixture were proven to contribute to the anti-frost-heaving performance.

The Impact of the Electronic Skin Substrate on the Robotic Tactile Sensing

The tactile sensing is of significant interest for coexisting-cooperative-cognitive robots (Tri-Co robots). In order to improve the tactile sensing performance of the robot via an electronic skin (e-skin), an auxiliary elastomeric substrate is required. This paper investigates the effect of the substrate including elastic modulus, thickness and location on the static sensing at first. It is found that thick substrate with small elastic modulus can even the force distribution effectively and improve the contact area sensing. But it brought noises and crosstalk on the e-skin when the substrate has the large deformation. In occasions of dynamic tactile sensing, the impact of substrate thickness and elastic modulus was also studied and it is found that smaller elastic modulus can help e-skin sense larger and higher frequency stimulus.

Small strain moduli of compacted silt by ultrasonic pulse velocity measurements

This study reported the investigation on the small strain modulus of compacted low plastic Mississippi River Valley silt under varying moisture contents and dry densities through ultrasonic pulse velocity testing method. Detailed procedures on filtering the ultrasonic pulse velocity signals and determining the wave arrival times were established. The variation of the small strain elastic moduli with bulk density, dry density as well as water content was also studied. The elastic properties of the compacted Mississippi River Valley silt were found to remain relatively constant with increasing moisture content and bulk density up to a point then decrease rapidly as moisture content increases wet of optimum water content and bulk density increases from around 2000 kg/m3 (bilinear model). The investigation of how pulse wave velocities and moduli vary with density, moisture content, and saturation was found to provide alternative tool for assessing soil characteristics, and based on the trends observed in this study, ultrasonic pulse velocity testing could provide insight on the stability of partially saturated compacted soils.

Experimental study of the influence of flexible boundaries with different elastic moduli on cavitation bubbles

Research on cavitation phenomena in various fields has shown that the mechanical properties of boundary materials have an important influence on the cavitation bubble. Here, an underwater low-pressure discharge method is used to induce a cavitation bubble, and a high-speed photography system is used to record the process of cavitation bubble collapse near different flexible boundaries. The results show that under a small elastic modulus, the cavitation bubble has a distinct “mushroom” shape during collapse. As the elastic modulus of the material increases, this shape evolves into a small cap and a large stalk until it disappears, thus increasing the critical condition of the bubble collapse to the boundary. There is a potential power relationship between the dimensionless deformation and elastic modulus. The dimensionless elastic modulus and distance can be used to determine whether a flexible boundary will be penetrated by a cavitation bubble. A cavitation bubble collapse shock wave near a flexible boundary will enter the boundary material with a propagation speed slightly slower than the shock wave velocity in the water body. Determining the collapse characteristics of cavitation bubbles near such flexible boundaries has important guiding significance for the utilization and prevention of cavitation near flexible boundaries.

Numerical simulation of borehole Stoneley wave reflection by a fracture based on variable grid spacing method

In this paper, the finite difference method is used to model the Stoneley wave reflection by a horizontal fracture in a borehole. The fracture shape is described by some finite difference grids. Therefore, the fracture aperture can be varied in the radial direction, thus extending previous researches on the assumption that the fracture aperture is constant throughout the fracture. Finite difference grids can also be used to describe a fracture which extends a finite distance in the radial direction. In addition, the finite difference algorithm can deal with the problem of inhomogeneous formation. Therefore, it allows the variation of formation elasticity in the model. Fine grids are needed to describe the small fracture aperture, and variable grid spacing is employed by finite difference method to improve computational efficiency. The Stoneley wave propagation is simulated by the variable grid spacing finite difference method in several models with variable fracture aperture, finite extension fracture and models with heterogeneous formation. The variable grid spacing finite difference method is validated through a comparison with real axis integration method and the analytical method. We get some conclusions by simulating and investigating effects of the variation of fracture aperture, the fracture of finite extension and inhomogeneity of formation on the Stoneley wave reflection. Although the fracture aperture changes along the fracture extension direction, the reflection coefficient of Stoneley wave is mainly controlled by the fracture aperture near the borehole. The Stoneley wave in the fracture is reflected back into the borehole, by the tip of finite extension fracture, which results in some notches in the reflection coefficient curve. If the Stoneley wave propagates from the formation with small elastic modulus to the formation with large elastic modulus, the reflection coefficient of Stoneley wave will be larger than that of homogeneous model with small elastic modulus. And if Stoneley wave propagates from the formation with large elastic modulus to the formation with small elastic modulus, the reflection coefficient of Stoneley wave will be smaller that of homogeneous model with large elastic modulus. These results provide some basis for the use of Stoneley wave to detect the fracture properties in formation.

Effects of material properties and geometric parameters on electromagnetic-assisted transfer printing

Flexible and stretchable electronics are rapidly evolving to be used in a wide range of applications, including wearable medical devices, implantable health monitoring devices, and bio-integrated systems. As an important method to integrate heterogeneous materials and functional components toward flexible and stretchable electronic systems, transfer printing technology has attracted increasing attention. Among the different approaches in transfer printing, electromagnetic-assisted transfer printing provides a versatile method that allows remote control. In order to investigate the effects of various materials and geometric parameters on the electromagnetic-assisted transfer printing process, a theoretical analysis is combined with the finite element method to investigate the underlying physics. The desirable ranges of parameters (e.g. thickness, radius, and elastic modulus of the upper and lower films in the design) are obtained for the optimized operation. The results indicate that the radii of the upper and lower films should be selected with large values and their upper limits are bound by the size of the functional components to be transferred. Moreover, the radii ratio between the upper to lower film should be within the range of 0.6–0.9. Though small thickness and elastic modulus are preferred in the upper and lower films, the values should be sufficiently large to ensure the strength. Meanwhile, the thickness ratio of upper to lower film should be within the range of 0.5–2. At the same time, the elastic modulus ratio and the height of the lower pickup cavity are shown to have little influence on the maximum displacement of the lower film. With the theoretical predictions validated by the finite element analysis, the results presented in this study are expected to provide useful guidelines for the experimental design.

Development and implementation of new triangular finite element based on MGE theory for bi-material analysis

Abstract Compared with the classical continuum theory, the modified gradient elastic theory (MGE theory) better explains the size effect, strain and damage localization of materials. In this paper, we constructed a C1 planar triangular finite element based on the MGE theory. We also derived its finite element format and compiled the corresponding finite element calculation program by the MATLAB software. The program was used to analyze the bi-material shear boundary layer problem with unidirectional infinite length. The results show that the change of the internal characteristic length of the material in the infinite direction (the same direction as the shear stress) has little effect on calculation results of the shear strain, while the change of the internal characteristic length in the finite direction has a certain impact on calculation results of the shear strain, and its impact is even greater on the material with small elastic modulus in the bi-material; when the size of the finite element mesh does not exceed the internal characteristic length of the material, the mesh dependence of calculation results can be eliminated. Compared with the MGE rectangular element, the triangular element constructed in this paper has higher calculation accuracy and better adaptability.

Guided waves in layered cylindrical structures with sectorial cross-section under axial initial stress

Due to mechanical loads, thermal fields and the limitation of the manufacturing technology, initial stresses in layered cylindrical structures are ineluctable. Accordingly, for the purpose of the guided wave nondestructive testing for the layered cylindrical structure with a sectorial cross-section, an analytical approach, the double-orthogonal polynomial method is utilized to investigate the influence of axial initial stress on wave characteristics. Based on Biot’s “Mechanics of Incremental Deformations”, the dynamic equations for the sectorial cylindrical structures in terms of displacements and axial initial stress are deduced. By virtual of the Heaviside function, the boundary conditions are automatically incorporated into constitutive equations and then into wave equations. The corresponding dispersion curves and displacement distributions of various sectorial cylindrical structures are calculated. Numerical results indicate that the influence of the initial stress applied on the outer layer is much significant at low frequencies, and the influence of the initial stress applied on the inner layer is much significant at high frequencies; the cut-off frequencies have negative relation with the area of the cross-section; the displacements at high frequencies are mainly distributed in the layer with smaller elasticity modulus, especially the layer simultaneously with bigger initial stress.

Rubber Material Properties of Several Rubber Tree Strains

：The rubber from rubber tree strain reyan 8-79 (hainan), zhanshi 218-6 (guangdong), yunyan 73-46 and yunyan 75-11 (yunnan) were tested to determine the physical and chemical properties, processing properties of raw rubber and physical and mechanical properties of vulcanized rubber. The results showed that raw rubber from different tree strains had different physical and chemical properties, processing properties,andthe physical and mechanical properties of vulcanized rubber were different as well. Yunyan 75-11 had the highest mooney viscosity, Reyan 8-79 had the highest protein content, Zhanshi 218-6 had the best tensile and tearing strength, Yunyan 73-46 had small elastic modulus, large loss factor and good processing properties.

Coupling effect of twin boundary and void on the mechanical properties of bulk nanotwinned copper: an atomistic simulation

Molecular dynamics simulations are performed to analyze the uniaxial tensile deformation behaviors of nanotwinned copper bulk containing pre-existing multiple spherical/ellipsoidal voids. The effects of twin-boundary spacing, initial void size, void fraction, void shape, void orientation angle and loading orientation on the mechanical properties are examined by considering the stress-strain response and dislocation activity. Results illuminate that the coherent twin boundary can significantly enhance the strength of bulk copper. The critical stress for dislocation emission in the copper specimen depends mainly on the size of voids, which can influence the yield stress of nanotwinned copper. Less stress is required to emit dislocations from larger voids than smaller ones. In general, the larger initial void porosity is accompanied by smaller elastic modulus and critical stress. Furthermore, it is found that different dislocation patterns can be triggered under different loading orientations.

METHODS OF IMPROVING ACCURACY OF MEASURING OUTPUT CHARACTERISTICS OF TENSOMETRIC ELEMENTS AND TESTMODULES

Over the past few years, thanks to the success of microprocessor technology, there has been a significant leap in the development and application of automated control systems. In such systems, information obtained from a set of sensors installed on the control object and giving complete information about it is used to form the control action. Improving the accuracy of measurement of their characteristics becomes an urgent task. This paper is considered to study of the processes of degradation of microelectromechanical structures of integral measuring tensometric elements, for example, pressure sensors, expressed in the obtaining of the output characteristics of the sensor for the regulations set forth in the technical specifications. The technique allowing to measure the parameters of the output signal of the strain cell with the help of a special installation is developed. The results of the experiments determined that when using material with a small modulus of elasticity can be used for the planting element, any substrate material of test module. The developed technique can be used in the production and design of the strain gauge, and the sensor as a whole.

An Elastic Interfacial Transistor Enabled by Superhydrophobicity.

Enabling mechanical responsiveness in field-effect transistors (FETs) offers new technological opportunity beyond the reach of existing platforms. Here a new force-sensing concept is proposed by controlling the wettability of a semiconductor surface, referring to the interfacial field-effect transistors (IFETs). An IFET made by superhydrophobic semiconductor nanowires (NWs) sandwiched between a layer of 2D electron gas (2DEG) and a conductive Cassie-Baxter (CB) sessile droplet is designed. Following the hydrostatic deformation of the CB droplet upon mechanical stress, an extremely small elastic modulus of 820 pascals vertical to the substrate plane, or ≈100 times softer than Ecoflex rubbers, enabling an excellent stress detection limit down to <10 pascals and a stress sensitivity of 36 kPa-1 is proposed. The IFET exhibits an on/off current ratio exceeding 3 × 104 , as the carrier density profile at the NW/2DEG interface is modulated by a partially penetrated electrostatic field. This study demonstrates a versatile platform that bridges multiple macroscopic interfacial phenomena with nanoelectronic responses.

Brownian Dynamics of Particles "Dressed" by Chiral Director Configurations in Lyotropic Chromonic Liquid Crystals.

We study Brownian dynamics of colloidal spheres, with planar anchoring conditions, suspended in the nematic phase of the lyotropic chromonic liquid crystal disodium chromoglycate (DSCG). Unlike typical liquid crystals, the unusually small twist elastic modulus of DSCG permits two energetically distinct helical distortions (twisted tails) of the nematic director to "dress" the suspended spheres. Video microscopy is used to characterize the helical distortions versus particle size and to measure particle mean-square displacements. Diffusion coefficients parallel and perpendicular to the far-field director, and their anisotropy ratio, are different for the two twisted tail configurations. Moreover, the crossover from subdiffusive to diffusive behavior is anomalously slow for motion perpendicular to the director (>100 s). Simple arguments using Miesowicz viscosities and ideas about twist relaxation are suggested to understand the mean-square displacement observations.

A comparison of small strain stiffness in till as measured by seismic refraction and barometric loading response

Soil stiffness can vary over several orders of magnitude depending on the actual range of strain imposed by testing, or as a result of operational strains in geotechnical structures. Soil stiffness changes rapidly with strain level at low strain levels (0.01–0.1%) and the variation with strain is not linear. Characterization of the in situ small strain stiffness of stiff soils is important in geotechnical design; however, analyses of the mechanical behaviour of these soils is confounded by stiffness values that vary with strain level. Stiff till cuttings are susceptible to progressive failure as a result of strain softening. As a consequence, the evolution of stiffness during progressive failure is both a key parameter in characterizing pre-failure slope deformations and a key diagnostic of softening. Changes in strength (due to softening) should be reflected in commensurate temporal and spatial changes in stiffness; consequently, real-time, in situ measurements of stiffness would better define the progression of softening. Seismic surveys, which create small compression and shear strains, have been used to estimate in situ small strain elastic moduli. These spatially extensive measurements can be correlated to temporal variations in stiffness from the monitoring of barometric loading efficiency. In this latter method, the pore pressure response of a grouted (sealed) piezometer to barometric pressure fluctuations is used to measure the compressibility (stiffness) of the formation. This article summarizes the results of field trials within a cutting in stiff till in Northern Ireland in which these two techniques were used to characterize small strain stiffness.

Strain sensing based on a microbottle resonator with cleaned-up spectrum.

In this Letter, a microbottle-resonator-based strain sensor with individual mode distribution and recognizable resonance spectrum was proposed and demonstrated. A cleaned-up spectrum was achieved by inscribing horizontal microgroove scars close to the bottle center. The inscribing parameters of these grooves were designed according to the field distribution of the modes, and the obtained spectrum showed excellent consistency with theoretical analysis. The shift in the resonance peak with increasing stretching force was investigated, and the corresponding strain sensitivities were 0.085pm/μϵ for transverse electric polarization and 0.136pm/μϵ for transverse magnetic polarization, which could be further increased by using materials with smaller elastic moduli.

Analytical investigation on the load-moment characteristics of GFRP bar reinforced circular NSC and HSC columns

In this study, the efficiency of Glass Fibre Reinforced-Polymer (GFRP) bar reinforced normal strength concrete (NSC) and high strength concrete (HSC) columns in sustaining axial and flexural loads was analytically investigated. Experimental data from available literature were used as benchmarks for the analytical investigations conducted in this study. In addition, a comprehensive parametric study was carried out to investigate the effect of different parameters (i.e., compressive strength of concrete, mechanical properties and reinforcement ratio of GFRP bars, and slenderness ratio of the columns) on the performance of concrete columns reinforced with GFRP bars. It was observed that under concentric axial load, the improvements in the axial load carrying capacity due to increasing GFRP longitudinal reinforcement ratio were more pronounced in GFRP bar reinforced NSC columns than in GFRP bar reinforced HSC columns. It was also observed that HSC columns reinforced longitudinally with GFRP bars with small longitudinal reinforcement ratio or low tensile modulus of elasticity might experience a tensile failure of the GFRP bars located on the tension side of the column cross-sections, especially if the columns are subjected to a high level of axial load eccentricity.