Evolution Of Modulus Research Articles

Hyperbolic Evolutionary Model for Equivalent Modulus of Sand and Characterization of Its Cyclic Hardening Properties

The cyclic hardening characteristics of soil hold significant importance for understanding its performance, and the evolution of the deformation modulus serves as a crucial indicator of the hardening properties. Deformations can be classified into elastic and plastic deformations and expressed in terms of modulus; however, their roles in the cyclic hardening process remain unclear. In this study, the elastic and plastic moduli were separated using the hyperbolic evolutionary model, which characterized the evolutionary properties of both to reflect the cyclic hardening process. A series of cyclic triaxial shear tests was conducted utilizing ISO sand and emery as test materials. A hyperbolic evolution model relating the equivalent modulus to the number of cycles was established, and the effect of various test conditions on the elastic modulus is discussed. The results indicate that: (1) the relationship between the equivalent modulus and the number of cycles is hyperbolic; and (2) the parameters k and b of the hyperbolic evolution model correspond to the elastic and plastic moduli, allowing for the separation of the evolution of both from that of the deformation modulus. The hyperbolic evolution model of the equivalent modulus proposed in this paper offers new insight into the cyclic hardening properties of sand.

Mechanical properties of (Ni, Fe)Cr2O4 polycrystal spinels studied by molecular dynamics simulations.

The elastic moduli and mechanical properties at the onset of crack in nanocrystalline and nanoporous (Ni, Fe)Cr2O4 compounds with a spinel structure are investigated by molecular dynamics simulations. The polycrystalline structures generated contain nanograins from 2.5 to 30nm in diameter. These structures are representative of the internal corrosion layer in nickel-based alloys. These simulations enabled us to establish the evolution of elastic moduli as a function of the composition, porosity, and grain size of the polycrystals. From this evolution, the initial database for the elastic properties of corrosion layers based on von Bertalanffy growth functions was determined. The onset of crack in polycrystals is also investigated via uniaxial tensile and shear deformation. Under shear deformation, flow stress as a function of grain size follows normal and inverse Hall-Petch regimes. The regime change occurs for grain sizes around 10nm. For grain sizes under this threshold, shear banding involving collective translation and rotation of nanograins dominates the plastic deformation. For grain sizes greater than 10nm, phase transition inside grains from a spinel to a post-spinel-like structure is observed as well. In that case, phase transition dominates the plastic deformation. Under uniaxial tensile deformation, intergranular decohesion occurs. The general law as a function of grain size for toughness, which is the material's capacity to absorb elastic and plastic energy prior to failure, is also established.

Hardness and Young's modulus evolution of low-power plasma sprayed Inconel 625 coatings exposed to high temperatures

Hardness and Young's modulus evolution of low-power plasma sprayed Inconel 625 coatings exposed to high temperatures

New impulse-based test method for early-age elastic modulus measurement in cementitious materials

Accurate monitoring of the elastic modulus evolution during the early-age fluid-solid transition in cementitious materials is crucial for understanding their mechanical behavior under early stresses. While existing methods, such as EMM-ARM, have proven effective, they are often associated with high costs or complex setups. This study presents the development of a low-cost, easy-to-implement system that employs impulse excitation applied to a composite beam, introducing the EMM-IRM method for the effective assessment of the elastic modulus of cement paste from the earliest stages of hydration. The use of impulse excitation is particularly advantageous in low-cost systems with accelerometers of lower sensitivity, as it enhances signal clarity and reduces interference from background noise, thereby improving measurement reliability. The system was validated through experimental comparisons with conventional EMM-ARM, cyclic compression, and traditional impulse excitation techniques, using Portland cement paste as the test material. The results show that EMM-IRM consistently estimates the elastic modulus, with a maximum deviation of 6.33% from other methods. Moreover, despite its cost-effectiveness, EMM-IRM demonstrates a higher signal-to-noise ratio compared to conventional EMM-ARM. This approach offers a practical solution for early-age characterization of cementitious materials, balancing cost, simplicity, and measurement accuracy.

Theoretical model to predict the fracture strength of fiber-reinforced ceramic matrix composites at elevated temperatures

The mechanical properties of ceramics and their composites in extreme environments, especially the fracture strength under high-temperature conditions, are key factors in assessing the safety and reliability of equipment. In this study, a temperature-dependent theoretical model is proposed with the aim of predicting the fracture strength for fiber-reinforced ceramic matrix composites at elevated temperature environments. This model encompasses not just the collective effects of various factors, including the Young's modulus of both fibers and matrix, the fiber volume fraction, and the melting point of the matrix, but also integrates the evolution of the Young's modulus of the fiber and matrix with temperature. Through the validation of multiple sets of experimental results, it is shown that the proposed model is able to predict the fracture strength of composites at elevated temperatures more accurately without conducting any high-temperature destructive tests. This model can help engineers and scientists to evaluate the mechanical properties of fiber-reinforced ceramic matrix composites at high temperatures more conveniently, thus guiding the optimal design and practical application of the materials, and thus improving the reliability and safety of the materials.

Moisture effects on the transverse compressive behaviour of single flax fibres

Studying the effects of moisture on the mechanical behaviour of single flax fibres, particularly in the transverse direction, is of key importance for the reliable use of biobased composites exposed to varying humidity levels. In this study, the apparent transverse Young’s modulus evolution of single flax fibres is recorded through repeated compressive load/unload cycles conducted at three Relative Humidity (RH) levels— 40%, 60%, and 80%. No significant changes in the apparent Young’s modulus, determined from the unloading, were observed during transverse compression cycling or under increasing humidity conditions. The absence of apparent softening with the rise in RH is attributed to the expression of two antagonistic mechanisms: wall softening due to plasticisation and structural stiffening linked to fibre compaction. Intriguingly, a noteworthy transverse stiffening is recorded at 40% RH following the humidification and drying of the fibre. This outcome is ascribed to a hornification phenomenon.

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

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

Oligo-cyclic loading-induced evolution of stress distribution and apparent amorphous modulus in lamellar stacks of high-density polyethylene

Assessing the resistance of high-density polyethylene (HDPE) against earthquake-like loads involves understanding the changes in structure and properties induced by oligo-cyclic loading at various length scales. To study the evolution of stress distribution and intrinsic properties within lamellar stacks from pristine to oligo-cyclic loading pre-conditioned materials, simultaneous in-situ SAXS/WAXS measurements were performed. During the elastic deformation of each pristine and preconditioned sample, crystal strain was tracked using the in-situ WAXS technique. Based on the established elastic tensor of the crystalline structure in polyethylene, we calculated the microscopic stress values within crystalline lamellae. In the pristine sample, lamellar stacks exhibit closely series-like coupling in the equatorial region and parallel-like coupling in the polar region of the spherulite. In the pre-conditioned sample, stress is primarily concentrated in the intra-fibrillar region, where the crystalline and amorphous phases are series-coupled, and strong strain concentration occurs in the inter-fibrillar region. By combining the local strain in the amorphous layer within the lamellar stacks in the equatorial region of the spherulite and the intra-fibrillar region with series-coupled lamellar stacks, measured by in-situ SAXS tests, the apparent amorphous modulus at the lamellar stack scale can be determined. This modulus changes from 71 to 106 MPa in the equatorial region of pristine spherulites to a notable 2000–7000 MPa in the intra-fibrillar region under the influence of oligo-cyclic pre-loading. Importantly, this apparent modulus is affected by both crystallization conditions and molecular structure, with molecular parameters exerting the primary influence.

Damage-based ion transport in recycled aggregate concrete under external sulfate attack

The utilization of recycled coarse aggregate (RCA) in replacement of natural coarse aggregate in the production of recycled aggregate concrete (RAC) may potentially lead to a reduction in the resistance of RAC to sulfate attack. In this study, the dynamic elastic modulus and sulfate ion transport of RAC was investigated by fully immersing RAC specimens produced with different water-to-cement ratios (W/C) and RCA volume fractions (VRCA) into sulfate (Na2SO4) solutions with different concentrations. The effects of W/C and VRCA on the initial damage velocity, damage acceleration, and service life of the RAC were analyzed by the defined damage evolution equations. The variation patterns of the ion diffusion coefficient and the surface ion concentration were discussed in detail, and a general equation was developed to describe the variation of surface ion concentration over time. A damage-based ion transport model was developed based on the damage evolution of the dynamic elastic modulus. The results demonstrated that the damage-based ion transport model exhibited excellent accuracy in predicting the ion transport behavior in the RAC. Furthermore, the mechanism of the effect of RCA on ion transport is more complex and requires a comprehensive study. This study provides theoretical support for the application of RAC in engineering construction and the calibration of important physical parameters in related numerical studies.

Hydro‐Mechanical Characterization of a Fractured Aquifer Using Groundwater Level Tidal Analysis: Effect of Pore Pressure and Seismic Dynamic Shear Stresses on Permeability Variations

AbstractGroundwater level tidal analysis is a powerful technique to monitor aquifer's permeability and hence its change over time. Earthquakes are known to affect aquifer's properties, in their vicinity through static stress changes but also further away through dynamic stresses. Most often changes are in the form of permeability increases, but sometimes decreases; the changes can be either permanent or transient. These observations are relatively well documented but the physical processes behind these changes are not well understood. By combining solid‐earth and barometric tidal groundwater level responses in a borehole in a coherent poroelastic theoretical framework, and a bi‐layer hydrogeological model, we recover a 15 years‐long time series evolution of aquifer transmissivity and shear modulus. This study showcases the full potential of the tidal analysis method, coupling pore pressure diffusion and rock deformation, at the frontier of hydrogeology and rock physics. This unprecedented measurement of permeability and shear modulus evolution by tidal analysis reveals, during interseismic period, high sensitivity of this shallow aquifer to effective stress, and thus to pore pressure. Thanks to additional finite element simulation of seismic wave propagation, we explore the different mechanisms affecting permeability and shear modulus in the studied fractured andesite aquifer. This study confirms the predominant role of seismic dynamic stresses, and more precisely of dynamic shear stresses, in the change of permeability following an earthquake.

Efficiency of layered double hydroxides in epoxy coating as corrosion inhibitor reservoirs for carbon steel

Layered double hydroxides (LDH) are considered as interesting containers for corrosion inhibitors, since they exhibit high ability to release inhibitor as well as to capture aggressive ions from aqueous solution. Epoxy containing organo-modified LDH filler intercalated with ethylenediamine-N,N′-disuccinate anions (EDDS), [Zn2Al(OH)6]+ [EDDS]4−0.25 . 2H2O (LDH-EDDS) with loading from 0% to 1.25% were coated onto carbon steel plates. The efficiency of these coatings against corrosion (barrier properties and release of inhibitors) was assessed by using electrochemical impedance spectroscopy. The evolution of the impedance modulus |Z| at low frequency range during time showed that the 0.75% organo-modified LDH-containing epoxy (thickness 80 μm) exhibited the highest corrosion resistance in the series and the associated value of |Z| at 3 mHz (1010 Ω cm2 after 21 days of immersion in 0.1 mol L−1 NaCl solution) placed it among the best solutions published so far using organo-modified LDH as cargo carrying a corrosion inhibitor. The behavior of this polymer composite was compared to the free-LDH coating by plotting the resistivity profiles along the coating thickness as a function of time. These results showed that (i) the presence of 0.75% LDH-EDDS in the epoxy coating delayed the penetration of water molecules, and (ii) limited corrosion of carbon steel. The efficiency of the organo-modified filler to inhibit the corrosion process was explained by an exchange between interleaved species occurring from released EDDS4− anions and aggressive Cl− ions being captured.

Multi-angle property analysis and stress–strain curve prediction of cementitious sand gravel based on triaxial test

In order to further promote the application of cementitious sand gravel (CSG), the mechanical properties and variation rules of CSG material under triaxial test were studied. Considering the influence of fly ash content, water-binder ratio, sand rate and lateral confining pressure, 81 cylinder specimens were designed and made for conventional triaxial test, and the influence laws of stress–strain curve, failure pattern, elastic modulus, energy dissipation and damage evolution of specimens were analyzed. The results showed that the peak of stress–strain curve increased with the increase of confining pressure, and the peak stress, peak strain and energy dissipation all increased significantly, but the damage variable D decreased with the increase of confining pressure. Under triaxial compression, the specimen was basically sheared failure from the bonding surface, and the aggregate generally did not break. Sand rate had a significant effect on the peak stress of CSG, and decreased with the increase of sand rate. Under the conditions of the same cement content, fly ash content and confining pressure, the optimal water-binder ratio 1.2 existed when the sand rate was 0.2 and 0.3. After analyzing and processing the stress–strain curve of triaxial test, a Cuckoo Search-eXtreme Gradient Boosting (CS-XGBoost) curve prediction model was established, and the model was evaluated by evaluation indexes R2, RMSE and MAE. The average R2 of the XGBoost model based on initial parameters under 18 different output features was 0.8573, and the average R2 of the CS-XGBoost model was 0.9516, an increase of 10.10%. Moreover, the prediction curve was highly consistent with the test curve, indicating that the CS algorithm had significant advantages. The CS-XGBoost model could accurately predict the triaxial stress–strain curve of CSG.

A new macro- and micro- coupling model of barrier dam soil

Barrier dams are widely distributed worldwide. It is highly important to accurately evaluate the safety and emergency response of barrier dams. However, the stressstrain relationship of barrier dam soil, which is an important issue for the safety evaluation of barrier dams, has not been elucidated clearly because of its complex composition and wide particle gradation. Based on the proposed macro- and micro- coupling modeling scheme, a series of CT triaxial tests were carried out on barrier dam soil to observe the macroscopic and microscopic behavior. Based on the particle displacement distribution, a fabric evolution rate was proposed as an index to describe the evolution of fabric behaviors. A significant correlation was detected between the shear band fabric evolution rate and the macroscopic mechanical properties of the soil. The fabric evolution equation, modulus evolution equation and Poisson's ratio evolution equation were proposed to set up a new macro- and micro- coupling model for barrier dam soil. The model has only five parameters that have definite physical meanings and can be easily determined by a series of triaxial tests. The validity of the proposed model was verified by different types of tests of barrier dam soil and soilrock mixtures. The model can reasonably describe the fundamental properties of barrier dam soil with wide particle gradation. The proposed model established by macro- and micro- coupling modeling considers the relationship between macroscopic mechanical properties and microscopic fabric behavior, which is suitable for barrier dam soils with wide particle gradations.

ПРИНЦИП НАЛОЖЕНИЯ ДЕФОРМАЦИЙ В ТЕОРИИ ЖЕЛЕЗОБЕТОНА

The work substantiates the correctness of applying the principle of the overlay of deformations when deriving equations of the mechanical state of concrete that are significant in the theory of reinforced concrete in linear and nonlinear formulations. This principle consists in the summation at some point in time of partial deformations corresponding to partial increments of non-decreasing stress at successive previous points in time. Strains are represented by the sum of instantaneous strains and delayed creep strains at the moment of application. The superposition of partial creep strains is implemented according to the Boltzmann superposition principle known in the linear theory of creep - each partial increment of creep strain depends only on the magnitude and duration of the generating partial stress increment and does not depend on its other increments. When taking aging into account, postulated by this principle the mutual independence of partial increments of creep strain takes place relative to partial increments of the stress level. Representing the deformation as the sum of the initial elastic deformation and the creep deformation with a measure that takes into account the evolution of the elastic modulus leads to a different type of equation of state, which is perceived as incorrect in some publications. This perception of a different type of equation of state together with constructions, not related to the principle of the overlay of deformations, led these authors to declare that the principle of the overlay of deformations in the theory of creep is erroneous. In contrast to the traditional approach, a material (concrete, steel, wood, plastic) is considered as a combination of fractions (fibers, layers) with statistically distributed strengths. The concept of strength structure makes it possible to substantiate the principle of superimposing deformations in a nonlinear formulation. In this case, the structure of the nonlinear equation of state turns out to be identical to the structure of the linear equation. This circumstance is significant in applications, for example, when solving relaxation problems that are important for the long-term safety of building structures.

Enhancing the stability of Li-Rich Mn-based oxide cathodes through surface high-entropy strategy

Li-rich Mn-based layered oxides (LMR) hold promise as cathode materials for lithium-ion batteries (LIBs) due to their high reversible capacity. However, issues such as oxygen release and structural degradation associated with oxygen redox cause voltage decay and capacity decline during cycling. In this study, a monodisperse Li1.2Ni0.13Co0.13Mn0.54O2 cathode material with surface high-entropy architecture (MZCN-LMR) was synthesized to enhance the overlap between the non-bonding orbitals of oxygen (|O2p) and the (TM-O)* occupied band. This enhancement enables regulation of the depth of oxygen oxidation, improving reversible oxygen redox and creating highly flexible structures, with mitigated anisotropic modulus and lattice strain evolution during (de)intercalation. Consequently, the developed MZCN-LMR cathode exhibits impressive capacity retention of 80.5 % after 400 cycles and minimal voltage decay of 0.7 mV per cycle with the voltage range of 2.1–4.6 V. This surface high-entropy strategy offers a universal approach to enhancing the redox stability of anions, contributing to the application of LMR.

Interfacial mechanics of β-casein and albumin mixed protein assemblies at liquid-liquid interfaces

Protein emulsifiers play an important role in formulation science, from food product development to emerging applications in biotechnologies. The impact of mixed protein assemblies on surface composition and interfacial shear mechanics remains broadly unexplored, in comparison to the impact that formulation has on dilatational mechanics and surface tension or pressure. In this report, we use interfacial shear rheology to quantify the evolution of interfacial shear moduli as a function of composition in bovine serum albumin (BSA)/β-casein mixed assemblies. We present the pronounced difference in mechanics of these two protein, at oil interfaces, and observe the dominance of β-casein in regulating interfacial shear mechanics. This observation correlates well with the strong asymmetry of adsorption of these two proteins, characterised by fluorescence microscopy. Using neutron reflectometry and fluorescence recovery after photobleaching, we examine the architecture of corresponding protein assemblies and their surface diffusion, providing evidence for distinct morphologies, but surprisingly comparable diffusion profiles. Finally, we explore the impact of crosslinking and sequential protein adsorption on the interfacial shear mechanics of corresponding assemblies. Overall, this work indicates that, despite comparable surface densities, BSA and β-casein assemblies at liquid–liquid interfaces display almost 2 orders of magnitude difference in interfacial shear storage modulus and markedly different viscoelastic profiles. In addition, co-adsorption and sequential adsorption processes are found to further modulate interfacial shear mechanics. Beyond formulation science, the understanding of complex mixed protein assemblies and mechanics may have implications for the stability of emulsions and may underpin changes in the mechanical strength of corresponding interfaces, for example in tissue culture or in physiological conditions.

Impacts of substitution of alkali by zinc on thermo-mechanical properties in borosilicate glasses

To decipher the effects of replacing alkali with zinc on thermo-mechanical properties, a series of borosilicate glasses with the molar compositions of 70.65SiO2·21.09B2O3·1.88Al2O3·1Li2O·(5.38-x)R2O·xZnO (x = 0, 0.34, 0.67, 1, 1.34, 2.69, 4.04, and 5.38) were prepared. Upon adding a slight quantity of ZnO, a local extreme point for glass transition temperature (Tg) appears. This behavior is deciphered to be originated from two opposite factors. On one hand, Tg reduces as a characteristic of the colligative properties for a dilute solution; in addition, Tg rises due to the higher field strength, bond energy and covalent characteristic of zinc cations compared to that of alkali ions. Otherwise, based on the evolution of intermediate-range clusters revealed by infrared, Raman and NMR spectra, we elucidate the atomic-scale structural origin, which leads to the nonlinear evolution of elastic moduli and coefficient of thermal expansion with the molar ratio of [ZnO]/([R2O]+[ZnO]).

Mechanical Properties of Twisted Cellulose Nanofiber-Reinforced Silk Yarns.

Silk has recently attracted considerable interest owing to its versatile properties as a natural fiber, especially in the medical sector. However, the mechanical properties of silk limit its potential applications. In our earlier work, the mechanical performance of silk filaments was enhanced owing to the insertion of cellulose nanofibers (CNFs). Nevertheless, silk filaments must be assembled and twisted to form a continuous yarn. In this study, the mechanical properties of CNF-reinforced silk yarns were evaluated to determine the optimal yarn structure. The evolution of the Young's modulus, ultimate tensile strength, toughness, and elongation at break was assessed as a function of the twist level in comparison with regular silk. The results demonstrated that the most favorable compromise of the mechanical properties was obtained at 1000 twists per meter.

Exploring the impact of solvent additives on dielectric properties in polymer photovoltaics: A deconvolution and in-depth study of electrical modulus, complex conductivity, and impedance responses

Impedance and dielectric spectroscopy is a well-known technique for characterizing interfaces, especially donor/receiver interfaces in bulk heterojunction (BHJ) solar cells. This technique was employed to investigate the interface of poly (4,8-bis-alkyloxybenzo(1,2-b:4,5-b0) dithio-phene-2,6-diyl-alt- (alkyl thieno (3,4-b) thiophene-2-carboxylate)-2,6-diyl) (PBDTTT-C): PC70BM in bulk heterojunction with DIO as additive. For this reason, a simulation was carried out to generate the complex impedance, modulus, and complex conductivity data based on the electrical parameters extracted from the equivalent circuit. Therefore, a new approach based on the coupling of complex functions such as impedance, modulus, and conductivity has been proposed. In addition, an extrapolation and deconvolution approaches are used to highlight the relaxation processes, the BHJ layer process, the two electrical contacts of the interfaces between PEDOT: PSS/PBDTTT-C: PC70BM and PBDTTT-C: PC70BM/Ca process, and the electrode polarization process. In the next step, the remove the low-frequency process enhances the visibility of other processes, particularly observable in the evolution of the electrical modulus and the conduction parameters associated with each process. In the complex functions, there was a good correlation between all parameters derived from both processes. The characteristics of the conduction processes, such as conductivity values at low and high frequencies and ionic strength were then extracted. All these parameters were evaluated and discussed as a function of the thickness of the active layer. Finally, we demonstrate that the electrical modulus and complex conductivity can be perfect tools to characterize the donor/acceptor interfaces.

Fabrication, microstructure and properties of 10Ti-5 Nb-1Sn biomedical β titanium alloy with low elastic modulus and high strength-ductility synergy

The new generation of β-type titanium alloy with low elastic modulus and high strength-ductility synergy has a good future in biomedical materials. In this paper, a 10Ti-5 Nb-1Sn alloy was designed by D-electron theory and fabricated by vacuum arc melting. Then the effect of cold-rolling and heat treatment on the evolution of microstructure, tensile properties and elastic modulus of 10Ti-5 Nb-1Sn alloy was systematically studied. The results have shown that the as-casted 10Ti-5 Nb-1Sn ingot consists of single β phase, the tensile strength is 473 MPa, the elongation is 35% and the elastic modulus is 36 GPa. The cold-rolling could obviously enhance the tensile strength to 823 MPa due to the high-density dislocation tangles and reduce the Young's modulus to 32 GPa due to the formation of {001}<110> texture, but the elongation significantly decreased. After annealing, the 10Ti-5 Nb-1Sn alloys could obtain a high strength-ductility synergy, i.e., tensile strength is 713 MPa and elongation is 23%, and low elastic modulus (33 GPa), which is close to human bone elastic modulus (10–30 GPa) and has the potential to be used as metallic biomedical materials.