Variation Of Elastic Modulus Research Articles

Effects of h-BN additives on tensile mechanical behavior of Fe matrix: A molecular dynamics study

In this paper, the effect mechanism of h-BN size, strain rate and tensile direction on tensile mechanical properties of Fe matrix in the presence of h-BN inclusions was investigated by molecular dynamics simulations. The results showed that the existence of h-BN inclusions diminished the tensile mechanical properties of Fe, which was attributed to the large variation in Elastic modulus between the inclusions and matrix as well as stress concentration near the interface. When the h-BN inclusions was 1 nm in radius, the results of the CNA analysis showed that the crystal structure changes from ordered to disordered to partially ordered, and the DXA analysis indicated that the dislocation length increased, then decreased, and then increased again. The stress–strain curve showed a double-peak phenomenon. The first peak was caused by the change in the crystal structure, and the second peak aroused due to the regrowth of dislocations. By analyzed the stress–strain curves at different strain rates, it was found that the tensile strength increased with increasing strain rate, while the Elastic modulus was almost unaffected, from the perspective of potential energy, the conclusion was confirmed. The findings of different tensile directions indicated that the material’s tensile strength was affected by the tensile direction. When the h-BN inclusions are parallel to tensile direction, the h-BN inclusions hindered the plastic deformation and a second peak appeared in the stress–strain curve. This study is essential to comprehend the influence of h-BN inclusions on mechanical properties of free-cutting steel.

A comprehensive quantitative bottom-up analysis of fiber-reinforced recycled-aggregate concrete behavior

This study provides a more profound understanding of the influence of the phases of fiber-reinforced recycled-aggregate concrete (FRRAC), on its elastic properties, in particular Young’s modulus and Poisson’s ratio. Multi-scale modeling analyses of mortar and FRRAC were conducted to assess the effect of variations in the fiber content, fiber elastic modulus, RA content, and water-to-cement ratio (w/c) on the elastic properties at each scale. Thus, the analytic Mori–Tanaka (MT) homogenization algorithm developed in Python programming language and the three-dimensional finite element (FE) homogenization scheme were applied to evaluate the elastic properties of FRRAC. As such, different fiber types including steel, basalt, glass, and propylene, at a volume fraction range of 0–2%, along with the variations in fiber elastic modulus, and different RA replacement levels ranging from 0 to 100% were incorporated in the modeling process at different w/c ratio. Based on the results, the Poisson’s ratio of steel FRRAC in the MT approach surges with increasing fiber content. Furthermore, the elastic modulus of FRRAC is highly susceptible to an increase in Young’s modulus of polypropylene fiber, among other fiber types. The elastic modulus of concrete experiences a sharp decrease with increasing w/c for all fiber types in both FE and MT approaches.

Dynamic Elastic Modulus Variability in Anisotropic and Isotropic Materials: Comparison by Acoustic Emission

This study compared the variation of the dynamic elastic modulus (E) of three types of composite pipes made by the filament winding process and a steel alloy specimen, according to signal source changes. The specimens were produced with three different winding angles, i.e., ±50°, ±52.5°, and ±55°. The moduli were obtained through a known signal source and the angular variation, according to two sensors positioned over the specimen's surface. In a previous article, the variation in the velocity of acoustic emission (AE) signals, performed in the same type of pipes, was discussed based on the standards for glass fiber-reinforced epoxy (GFRE) filament wound specimens. This work took these preliminary findings to compare with the results found for steel alloy pipes (SAE 1020). This data was used with appropriate equations to determine the dynamic elastic moduli of each material. It was found that, even for small angular differences, the modulus changes position concerning the lamination angle. Thus, the lower the quality control, the lower the final product with composite materials. As expected, for isotropic materials such as steel alloys, the modulus remains constant along the angles, while for anisotropic ones, it is dependent on the principal directions of stress and strain, or on the other hand, dependent on the correlation between the angular wave velocity of the AE signals.

Impacts of Drained Conditions and Degree of Reconsolidation on Postcyclic Mechanical Behaviors of Laterite Clay

The mechanical behaviors of subgrade soils will change after cyclic loading, resulting in a modification of foundation bearing capacity and the development of additional settlement. Recognizing this, cyclic triaxial tests were conducted to remolded laterite clay, and reconsolidation was allowed. During the process, the cyclic loading was applied under undrained and partially drained conditions, respectively. Results show that the variations of both postcyclic undrained strength and elastic modulus versus degree of reconsolidation are different: the postcyclic elastic modulus increases with an increase of the degree of reconsolidation, while the undrained strength decreases a little under the condition of the large degree of reconsolidation. Furthermore, there are specific degrees of reconsolidation, making the postcyclic undrained strength and elastic modulus equal to the corresponding test results of the specimen without reconsolidation. Moreover, the greater the number of cycles, the larger the elastic modulus of the specimens with full reconsolidation, and the lower the elastic modulus of the specimens without reconsolidation. The undrained strengths of the specimens with full reconsolidation are all higher than those of the specimens without cyclic loading, whereas those of the specimens without reconsolidation are all lower. In addition, both postcyclic undrained strength and elastic modulus between cyclic loading under undrained and partially drained conditions are compared: the elastic moduli of the specimens under partially drained conditions are greater than those obtained under undrained conditions, while the undrained strengths obtained under partially drained conditions are equal to that under undrained conditions at a certain number of cycles.

Designing Interfacial Reactions for Nanometer-Scale Surface Patterning of PDMS with Controlled Elastic Modulus

Control over the surface chemistry of elastomers such as polydimethylsiloxane (PDMS) is important for many applications. However, achieving nanostructured chemical control on amorphous material interfaces below the length scale of substrate heterogeneity is not straightforward, and can be particularly difficult to decouple from changes in network structure that are required for certain applications (e.g., variation of elastic modulus for cell culture). We have recently reported a new method for precisely structured surface functionalization of PDMS and other soft materials, which displays high densities of ligands directly on the material surface, maximizing steric accessibility. Here, we systematically examine structural factors in the PDMS components (e.g., base and cross-linker structures) that impact efficiency of the interfacial reaction that leads to surface functionalization. Applying this understanding, we demonstrate routes for generating equivalent nanometer-scale functional patterns on PDMS with elastic moduli from 0.013 to 1.4 MPa, establishing a foundation for use in applications such as cell culture.

Interphase elastic modulus characterization in glass/epoxy composite using combined peridynamics and experimental method

This paper introduces a novel combined technique to characterize the elastic modulus gradient for glass/epoxy interphase. The developed procedure is applicable to all fiber-reinforced polymer (FRP) composites. Interphase in FRP composites plays a vital role in the mechanical performance of the material. Scientists almost characterized this region using nanoscale test methods such as atomic force microscopy (AFM) and scratch tests. These local methods characterize the elastic properties at a specific region near the fiber and, usually, are utilized for all regions around the fiber. This paper proposes a combined peridynamic and single-fiber micro tensile test method to characterize the overall elastic modulus gradient at the interphase region. The advantages of peridynamic as a non-local method are used to model the multiscale regions of interphase, fiber, and matrix. Single-fiber micro tensile tests are performed by the authors, and variations of displacements and strains are measured by the digital image correlation method. The obtained displacements are used as target values in the developed peridynamic code, and by performing peridynamic analyses, the elastic modulus variation along the interphase is automatically extracted. Furthermore, the variations of stresses and strains are investigated at the specimens’ cross-section using different hypotheses for the interphase region.

Analysis of structural and elastic properties of Kapok fibre and hybrid cottons for textile applications

ABSTRACT The damage that has been caused to the environment due to the extensive usage of synthetic fibres has prompted the improvement and usage of natural fibre materials. This study is an attempt to explore the structural, physical, and mechanical properties of a few selected natural fibres which are grown across India and Yemen. The powder X-ray diffraction data of 3 distinct fibres, namely DCH-32, Zabid, and Kapok, were obtained and used along with different statistical tools to obtain their physico-mechanical properties. The selected fibres belong to the monoclinic crystal system with lattice parameters a = 7.350Å, b = 8.220 Å, c = 10.370 Å, α=β = 90° and γ = 96.28°. A novel method has been introduced to obtain the 3-dimensional ordered region of fibre materials, and the obtained results reveal that the DCH-32 and Zabid cottons have a uniform distribution in their ordered regions, whereas the Kapok fibre has a nonuniform distribution in its ordered region. The existence of anisotropy in selected materials is also reported by studying the spatial variation of elastic moduli in different axes.

Intrinsic Mechanical Compliance of 90° Domain Walls in PbTiO3

AbstractFunctionality of domain walls and other topological defects in ferroelectrics is being widely investigated for applications in electronic devices. While the intrinsic electronic properties of a wall have been considered, its inherent mechanical properties remain explored very little, despite the fact that coupling between strain and polarization is prevalent in many of these materials. Herein, an in‐depth study of variations in nanomechanical properties at 90o domain walls and their adjacent domains in single‐crystalline lead titanate (PbTiO3) is presented as a prototypical ferroelectric material using a combination of various atomic force microscopy (AFM)‐based methods. Considerable variations of elastic moduli are found at 90o domain walls extending up to ~100 nm into the domain areas. AFM nanoindentation also allows to extract local domain wall hardness and plastic and elastic deformation energies. These findings have implications for the design of ferroelectric domain wall functionality that incorporates the intrinsic elastic compliance of a domain wall.

Estimation of the stress state of a cylindrical shell by analogy with a beam

The analysis of the stability and strength criterion of reinforced concrete shells during deformation according to the harmonic law under the action of axial compression is carried out. A method for determining the criterion of durability of reinforced concrete according to the momentless theory is presented. Options for estimating the stress-strain state of shells at a constant and variable modulus of elasticity are considered. An analogy is given between the behavior of quantities in the semi-momentless and momentless theories of zero-curvature shells. A method for calculating reinforced concrete structures of coatings under conditions of rheological deformation is presented, reflecting their real work, as well as taking into account the random nature of the values taken in the calculation.

Correlation of mineral density and elastic modulus of dog dentin using μ-CT and nanoindentation

This study sought to 1) investigate the spatial distribution of mineral density of dog dentin using µ-CT and 2) characterize the relationship between the elastic modulus and mineral density of dog dentin using nanoindentation and µ-CT. Maxillary canine teeth of 10 mature dogs were scanned with a µ-CT then sectioned in the transverse and vertical planes and tested using nanoindentation. Spatial distribution of mineral density and elastic modulus was quantified. Results demonstrated significant spatial variation in mineral density and elastic modulus. Mineral density and elastic modulus generally increased from the dentin-pulp interface to the dentino-enamel junction and from the crown base to the crown tip. Significant site dependent correlations between mineral density and elastic modulus were determined (0.021 > R2 > 0.408). The results of this study suggest that while mineral density is a mediator of elastic modulus, other mediators such as collagen content may contribute to the mechanical behavior of dog dentin.

Effect of radiation-induced damage of trabecular bone tissue evaluated using indentation and digital volume correlation

Exposure to X-ray radiation for an extended amount of time can cause damage to the bone tissue and therefore affect its mechanical properties. Specifically, high-resolution X-ray Computed Tomography (XCT), in both synchrotron and lab-based systems, has been employed extensively for evaluating bone micro-to-nano architecture. However, to date, it is still unclear how long exposures to X-ray radiation affect the mechanical properties of trabecular bone, particularly in relation to lab-XCT systems. Indentation has been widely used to identify local mechanical properties such as hardness and elastic modulus of bone and other biological tissues. The purpose of this study is therefore, to use indentation and XCT-based investigative tools such as digital volume correlation (DVC) to assess the microdamage induced by long exposure of trabecular bone tissue to X-ray radiation and how this affects its local mechanical properties. Trabecular bone specimens were indented before and after X-ray exposures of 33 and 66 h, where variation of elastic modulus was evaluated at every stage. The resulting elastic modulus was decreased, and micro-cracks appeared in the specimens after the first long X-ray exposure and crack formation increased after the second exposure. High strain concentration around the damaged tissue exceeding 1% was also observed from DVC analysis. The outcomes of this study show the importance of designing appropriate XCT-based experiments in lab systems to avoid degradation of the bone tissue mechanical properties due to radiation and these results will help to inform future studies that require long X-ray exposure for in situ experiments or generation of reliable subject-specific computational models.

Effect of loading-path on the elastic modulus degradation of high strength steels

Experiments of repetitive uniaxial tension are performed for DP590, TRIP590, TRIP780, and BH220 steels. Variation of chord modulus of the four materials with accumulated plastic strain is discussed. Large specimens of uniaxial tension, wide plate tension and cruciform tension are prestrained in different plastic strain. Uniaxial tension of sub-size samples which are machined from the prestrained large specimens is performed. Dependence of the normalized chord modulus of the four metals on strain path is discussed in detail. The results show that elastic modulus degradation is dependent on the material strength, accumulated plastic strain and strain path. At the same equivalent strain, the chord modulus degradation of TRIP780, TRIP590, DP590, BH220 steels decreases in turn. The chord modulus of TRIP780 steel at 0.24 equivalent strain reaches 20.5%. The chord modulus of DP590 steel is more sensitive to strain path change than the other three metals. The path of biaxial stretching combined with uniaxial tension provides the greatest chord modulus degradation among the six loading paths. Each material should have the most suitable loading path under which the elastic modulus variation can be minimized so springback can be easily controlled.

Size effects in the uniaxial compressive properties of 3D printed models of rocks: an experimental investigation

Transparent physical models of real rocks fabricated using three-dimensional (3D) printing technology are used in photoelastic experiments to quantify the evolution of the internal stress and deformation fields of rocks. Therefore, they are rendered as an emerging powerful technique to quantitatively reveal the intrinsic mechanisms of rock failure. The mechanical behavior of natural rocks exhibits a significant size effect; however, limited research has been conducted on whether transparent physical models observe similar size effects. In this study, to make the transparent printed models accurately demonstrate the mechanical behavior of natural rocks and reveal the internal mechanism of the size effect in rock mechanical behavior, the size effect in 3D printed models of fractured and porous rocks under uniaxial compressive loading was investigated. Transparent cylindrical models with different sizes that contained different fractured and porous structures were printed using the fracture and porous characteristics extracted from natural coal and sandstone. The variation in uniaxial compressive strength and elastic modulus of fractured and porous models for increasing model sizes were obtained through uniaxial compression experiments. Finally, the influence of internal discontinuous structural features, such as fractures and pores, on the size effect pertaining to the mechanical behavior of the model was analyzed and elaborated by comparing it with the mechanical properties of the continuous homogeneous model without fractures and pores. The findings provided support and reference to analyze the size effect of rock mechanical behavior and the effect of the internal discontinuous structure using 3D printed transparent models.

Effect of interfacial transition zone on creep behavior of steel fiber-reinforced concrete

• A SFRC creep prediction model considering ITZ was established. • The role of ITZ in SFRC was revealed. • The effects of relevant factors on SFRC creep were analyzed. • The key factors affecting SFRC creep were determined. To explore the interface transition zone (ITZ) effect on the creep behavior of steel fiber-reinforced concrete (SFRC), this study proposed a three-phase creep prediction model based on the mesomechanical shear lag theory. The model verification was performed using available creep data, and three influencing factors were analyzed. The proposed creep prediction model well described the creep behavior of SFRC, revealing the ITZ's role in it. The specific creep values of SFRC at the loading age of 365d with 1, 2, and 3% steel fiber contents exceeded those assessed without the ITZ effect account by 9.8, 6.3, and 54.0%, respectively. The effects of the ITZ elastic modulus and thickness, as well as the steel fiber length-to-diameter ratio on the SFRC creep, were analyzed via the proposed model. The grey relational analysis theory can characterize the correlation between related factors and various variations, so as to determine the key factors. Through this theory, it was revealed that the ITZ elastic modulus variation had the most significant effect on the SFRC creep.

Structural, morphological and mechanical properties of Dy3+ doped Sr2MgSi2O7 nanocomposites

Dysprosium (Dy3+) doped Sr2MgSi2O7 nanocomposites (NCs) were synthesised by low temperature solution combustion technique using Aloe Vera gel as fuel. Dy3+ has been doped to Sr2MgSi2O7 with different concentrations, such as 5%, 7%, and 11%. The prepared NCs were subjected to powder X-ray diffraction (PXRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The crystallite size has been determined and its ordered region is plotted using an in-house mathematical program. Employing General Utility Lattice Program (GULP) and Elastic Tensor Analysis (ELATE) tool, the physico-mechanical properties of synthesised NCs were determined and the spatial variation of elastic moduli has been plotted. The 3-dimensional graphical representation of various elastic moduli has shown that the linear compressibility is isotropic, while Young's modulus (E), shear modulus (G), and Poisson's ratio (υ) are highly anisotropic. The ordered region has significantly improved for the 11% concentration due to the stability attained in the unit cell. The correlation between Dy3+ concentration and Young's modulus was also determined using Functional Data Analysis (FDA). The G/K ratio was also obtained and results suggest that the compound exhibit brittle nature. These results show that the prepared nanocomposites have got wide applications in the design and strain engineering fields.

Effects of content and size of aggregate on the mechanical responses of concrete at cryogenic temperatures

The meso-structure of concrete, which determines its apparent performance, is closely related to the maximum aggregate size (MAS) and aggregate volume. At cryogenic temperatures, due to the freezing of pore water, the internal structure of concrete is changed, leading to some difference in the role of coarse aggregate particles. In this study, the meso-mechanical modeling method was adopted based on the continuous grading aggregate model to investigate the influence of content and size of aggregate at cryogenic temperatures. The uniaxial compressive and uniaxial tensile behavior of concrete cubic specimens (sized by 150 × 150 × 150 mm3) with various aggregate volumes (15 % ∼ 45 %) and MAS values (12 mm ∼ 36 mm) were simulated with consideration of cryogenic temperatures effects. The variation of compressive strength, tensile strength, elastic modulus, and fracture to energy with maximum aggregate size and aggregate volume fractions at cryogenic temperatures was investigated, and the related influencing mechanism was analyzed. The numerical results demonstrated that the failure patterns of specimens at cryogenic temperature show some differences compared with those at ambient temperature. Besides, it was indicated that the effect of maximum aggregate size and aggregate volume on the elastic modulus and the energy to fracture is consistent with those at ambient temperature. At cryogenic temperatures, the compressive strength is improved with the increase of maximum aggregate size. For the smaller aggregate volume fraction (15 % ∼ 30 %), the tensile strength at cryogenic temperatures tends to increase as the increase of maximum aggregate size, while an opposite trend appeared at larger aggregate volume. Additionally, as the increase of aggregate volume fractions, the compressive strength decreases first and then increases at cryogenic temperatures, while the tensile strength and elastic modulus exhibit a trend of increase. It is concluded that cryogenic temperatures can enhance the influence of maximum aggregate size on tensile strength, but weaken the influence of aggregate volume fractions on strengths.

Preparation of gradient hydrogel for pressure sensing by combining freezing and directional diffusion processes

Gradient ionic gels have received extensive attention in the field of pressure sensing due to their gradient variation of structure and elastic moduli, which can achieve a broad-range pressure response. However, designing and fabricating gradient gels with good mechanical and sensing properties remains a challenge. In this study, a physically cross-linked PVA ionic hydrogel with gradient structure is successfully synthesized by a directional ion diffusion process in NaCl solution at low temperature (–15 °C). Along the direction of ion diffusion, the gradient gel exhibits a continuous change from dense to porous structure, which is attributed to the synergy of freezing and salt-out effect. Cyclic compression test proves the good fatigue resistance of the gradient gel. The gradient ionic gel is applicated as a flexible capacitive pressure sensor, which exhibits high sensitivity of 1.09 kPa−1 (<100 kPa) and a broad sensing range (400 Pa to 0.8 MPa), while the response times can achieve to 92 ms. The gradient gel sensor demonstrates the signal stability in a long-term loading-unloading process and independence to the test frequency, as well as high sensitivity and instantaneous response under repeated tiny compressive strains and water droplets. Moreover, the excellent sensing capability enable the gradient hydrogel to be a versatile platform for flexible wearable sensors to monitor subtle vital signal and human movement. This strategy provides an innovative route to fabricate gradient hydrogels and develops the applications in flexible pressure-responsive smart materials.

Enhanced sustained responsive-systems based on anionically modified gelatin-containing hybrid gels: A route to correlate physico-mechanical and swelling properties

Anionically modified gelatin-based multi-responsive hybrid gels were prepared by free radical copolymerization of acrylamide (AAm) and itaconic acid (IA) in varying amounts of gelatin (GLN). Influence of composition on physicochemical and mechanical properties was assessed. Maximum degradation temperatures of hybrids increased with addition of GLN to PAAm/IA network. Equilibrium swelling of hybrid PAAm/IA-GLNs was studied in water as a function of GLN content in the range of 0.075–0.750% (w/v). By examining the variation of the compression elastic modulus of hybrids with GLN, a correlation was obtained for the dependence of the effective crosslink density on the GLN content. pH sensitive swelling of hybrids exhibited a double-step increase with the S-shaped curve around pH 4.7 and 8.0. In studies evaluating the swelling tendency in various solvents, Hofmeister series and various swelling temperatures, it was found that swelling kinetics in NaNO3 solutions proceeds by Fickian diffusion and Schott's pseudo-second order model can be effectively used to evaluate swelling kinetics. Hybrid gels were applied to adsorption of cationic methylene blue (MB) and malachite green (MG) as model contaminating dyes from aqueous solutions. Accordingly, GLN-based hybrid gels could be a good adsorbent for the removal of cationic dyes from the contaminated waters.

Structure-function relationships in dog dentin

Investigations into teeth mechanical properties provide insight into physiological functions and pathological changes. This study sought to 1) quantify the spatial distribution of elastic modulus, hardness and the microstructural features of dog dentin and to 2) investigate quantitative relationships between the mechanical properties and the complex microstructure of dog dentin. Maxillary canine teeth of 10 mature dogs were sectioned in the transverse and vertical planes, then tested using nanoindentation and scanning electron microscopy (SEM). Microstructural features (dentin area fraction and dentinal tubule density) and mechanical properties (elastic modulus and hardness) were quantified. Results demonstrated significant anisotropy and spatial variation in elastic modulus, hardness, dentin area fraction and tubule density. These spatial variations adhered to a consistent distribution pattern; hardness, elastic modulus and dentin area fraction generally decreased from superficial to deep dentin and from crown tip to base; tubule density generally increased from superficial to deep dentin. Poor to moderate correlations between microstructural features and mechanical properties (R2 = 0.032–0.466) were determined. The results of this study suggest that the other constituents may contribute to the mechanical behavior of mammalian dentin. Our results also present several remaining opportunities for further investigation into the roles of organic components (e.g., collagen) and mineral content on dentin mechanical behavior.

Introduction to this special section: Potential fields

This special section of The Leading Edge is dedicated to recent advances in potential field methods of geophysical exploration. In their broadest sense, these methods are rooted in data whose origins are compatible with solutions to the Laplace equation such as gravity, magnetics, and electrostatics, each responding to distinct and complementary material properties of the subsurface such as mass density, magnetic susceptibility, and electrical conductivity. These proxies for the real targets of geologic interest (lithologic boundaries, fluid-saturated zones, regions of mineral alteration, etc.) have proven themselves indispensable, for example, through joint inversion of seismic data and their direct reflection — no pun intended — of subsurface variations in seismic wavespeed. Indeed, joint inversion seismic and gravity data yield a direct path toward inference and constraint of the elastic moduli variations within the subsurface — variations that, themselves, can reveal changes in rock porosity or fracture density.