Modulus Ratio Research Articles

Stress distribution pattern in two different no-post systems in endodontically treated maxillary central incisors: A three-dimensional finite element analysis.

This study aimed to evaluate the stress distribution in an endodontically treated tooth restored with two different reinforcing fibers followed by direct composite restoration using a finite element analysis (FEA). FEA. Two three-dimensional models of endodontically treated maxillary central incisors were restored with two reinforcing fibers: the polyethylene fibers (PFs) and the short fiber-reinforced composite (SFRC), respectively. The restoration was carried out without any intraradicular preparation using direct composite restoration. The models were generated using SolidWorks. The elastic modulus and Poisson's ratio for various structures and materials were installed into the simulation software, Abaqus. A FEA was then conducted. Each model received a mixed-mode loading of 150 N as distributed pressure to the specified region, and stress distribution was evaluated using the von Mises criteria. Both the reinforcing materials, PF and SRFC, showed maximum concentration of stresses in the cervical third of the tooth. The calculated values of the von Mises stresses for the PF and the SFRC models were 1.7 Mpa and 1.9 Mpa, respectively. Moreover, the stresses generated were of low intensity and were uniformly distributed, suggesting that by using this technique, stresses may be very well tolerated by the remaining tooth structure without any fracture. This no-posttechnique, using the two reinforcing fibers, showed minimal stress concentration in the cervical region of the tooth. Thus, using this ultraconservative approach that aims to preserve and reinforce the pericervical dentin and restore the remaining tooth structure with direct composite restoration could be a promising treatment option for the rehabilitation of badly mutilated teeth.

First-principles study on electronic and mechanical properties of boron and nitrogen co-doped fluorinated diamane

Stimulated by the successfully synthesis of fluorinated diamane (F-diamane) [Nat. Nanotechnol., 2019, 15, 59], in this paper, first-principles calculations are performed to investigate the structural, electronic and mechanical properties of fluorinated diamane (F-diamane) co-doped with B and N atoms. The stable doped structures contain BN bonds, and the structure with N atom locating at internal substitution position with B atom at neighboring external positions is most stable. The thermal stability of the doped structures is verified by molecular dynamics simulation. B and N atoms co-doping could reduce the formation energy of bilayer graphene to diamane and effectively modulate the band gap. For mechanical performance, these doped configurations exhibit excellent elastic constants, Young's modulus, shear modulus, and Poisson's ratio with isotropy. This work would promote the synthesis and potential applications of diamane.

Exploring the design space of discontinuous metal matrix composites through domain-knowledge enhanced machine learning

Tailored reinforcement architectures in discontinuous metal matrix composites (DMMCs) offer superior mechanical performance with broad scientific and financial interests. This study presents a domain-knowledge enhanced machine learning approach to efficiently explore the design space of Al-SiC DMMCs for optimization. A substantial dataset containing 140,000 instances, resembling characteristic reinforcement configurations and variants, is generated using a series of algorithms. Employing high-throughput finite element analysis, the elastic properties of each configuration are estimated. Statistical analysis reveals that a more homogeneous distributed reinforcement contributes to mechanical stability, whereas configurations with extreme performance tend to have inhomogeneous reinforcement distribution. A deep residual neural network trained on this dataset accurately learns the structure-property correlations. Coupled with a genetic algorithm, the framework identifies optimal configurations across different volume fractions for maximizing/minimizing properties including tensile modulus, shear modulus, and Poisson's ratio. Comparative analysis shows the incorporation of domain knowledge improves data quality, facilitating more effective design space exploration. This study contributes to advancing composite materials design, particularly for next-generation high-performance DMMCs.

Mechanical characterization and constitutive modeling of additively-manufactured polymeric materials and lattice structures

Additively manufactured polymeric lattice structures are being extensively studied, primarily because their mechanical properties can be tailored by controlling the unit cell geometry, giving them higher designability than stochastic materials. However, the inherent layer-wise additive manufacturing process affects the base material properties related to the printing direction, which in turn affects the macroscopic responses of the entire lattice materials. A robust understanding and modeling of lattice structures' elastic and plastic yield behavior in a homogenized approach are essential to enhance their design and analysis efficiency in engineering applications. In pursuit of this goal, a unified printing angle-dependent constitutive model of base materials is proposed in line with the tensile experimental data. The elastic material properties (elastic modulus, shear modulus, and Poisson's ratio), obtained through numerical simulations of one unit-cell with periodic boundary conditions, exhibit anisotropic properties, with the degree of anisotropy determined by the angle of the constituent members and base materials. Furthermore, both experimental and numerical results of lattices demonstrate anisotropic mechanical response under horizontal and vertical compression. Virtual multiaxial experiments are conducted through multi-cell numerical simulations, enabling the determination of initial yielding points of two different lattice structures (Kelvin and Simple cubic and body-centered cubic hybrid structures) under various loading conditions using a dissipation energy-based criterion. Overall, the multiaxial yield surface of the investigated lattices under various stress states, except for the isotropic principal stress plane, can be properly depicted by the Extended-Hill anisotropic yield criterion.

Buckling Behavior of Laminated Shell Panels Under Linearly Variable Edge Load

This paper reports a detailed numerical investigation on the buckling aspects of laminated composite shell panels of three forms (cylindrical, spherical and hyperbolic paraboloid) with five support conditions exposed to linearly varying in-plane edge load employing eight nodded isoparametric finite element formulation. The impacts of different parameters including ply orientation, load factor, shell forms, aspect ratio, modulus ratio, curvature ratio, width-to-thickness ratio and angle of lamination on the buckling load of shell panels are examined. It is found that the various parameters addressed in this study have a remarkable impact on the buckling phenomena of laminated composite shell panels. Further, a comparison is made showing the effects of five types of compressive edge loads like uniform, triangular, parabolic, partial edge load and point load on the buckling phenomena of laminated shell panels with respect to five support conditions.

Effect of temperature on the uniaxial tensile properties of wood plastic composites: Experimental investigation and numerical analysis

Seven groups of uniaxial tensile experiments on wood plastic composites with a High Density Polyethylene (HDPE) matrix at different temperatures were completed in this paper. The test temperatures ranged from -60 °C to 60 °C, with a temperature difference of 20 °C for each group. All samples exhibited tensile brittle fracture. The test results showed that the tensile strength of the specimens decreased continuously with increasing temperature. Taking 0 °C as the reference temperature, the ultimate strength of the sample at -60 °C was 1.63 times that at 0 °C. When the temperature was 60 °C, this value was 0.41. Then, it can be calculated that the ratio of the strength of the sample at -60 °C to that at 60 °C was approximately 3.93, and the corresponding ratio of the elastic modulus was approximately 4.52. This shows that the mechanical properties of WPC are sensitive to changes in temperature. The variation coefficient of the average strength and elastic modulus of WPC for different specimens at different temperatures was less than 0.17, showing good stability due to the small dispersion of mechanical properties among different samples at any specific temperature.

First-principles predictions of the structural, dynamical, mechanical and thermal properties of MoGe2, Mo3Ge and Mo5Ge3

We have systematically investigated the structural, dynamical, elastic, and thermal properties of the C11b (tetragonal, space group I4/mmm) and C23 (orthorhombic, space group Pnma) for MoGe2 compound, A15 (cubic, space group Pm-3n) for Mo3Ge, D8m (tetragonal, space group I4/mcm) for Mo5Ge3. The simulated lattice constants exhibit strong agreement with both experimental and theoretical data. The results show that all the compounds have mechanical stability and dynamic stability. The anisotropy of some mechanical moduli was studied using several elastic anisotropy indexes and directional dependence of linear compressibility, Young's modulus, shear modulus and Poisson's ratio. At last, the thermal properties of MoGe2-C11b, MoGe2-C23, Mo3Ge-A15 and Mo5Ge3-D8m were studied and evaluated in detail.

Composite patch with negative Poisson's ratio mimicking cardiac mechanical properties: Design, experiment and simulation

Developing patches that effectively merge intrinsic deformation characteristics of cardiac with superior tunable mechanical properties remains a crucial biomedical pursuit. Currently used traditional block-shaped or mesh patches, typically incorporating a positive Poisson's ratio, often fall short of matching the deformation characteristics of cardiac tissue satisfactorily, thus often diminishing their repairing capability. By introducing auxeticity into the cardiac patches, this study is trying to present a beneficial approach to address these shortcomings of the traditional patches. The patches, featuring the auxetic effect, offer unparalleled conformity to the cardiac complex mechanical challenges. Initially, scaffolds demonstrating the auxetic effect were designed by merging chiral rotation and concave angle units, followed by integrating scaffolds with a composite hydrogel through thermally triggering, ensuring excellent biocompatibility closely mirroring heart tissue. Tensile tests revealed that auxetic patches possessed superior elasticity and strain capacity exceeding cardiac tissue's physiological activity. Notably, Model III showed an equivalent modulus ratio and Poisson's ratio closely toward cardiac tissue, underscoring its outstanding mechanical potential as cardiac patches. Cyclic tensile loading tests demonstrated that Model III withstood continuous heartbeats, showcasing outstanding cyclic loading and recovery capabilities. Numerical simulations further elucidated the deformation and failure mechanisms of these patches, leading to an exploration of influence on mechanical properties with alternative design parameters, which enabled the customization of mechanical strength and Poisson's ratio. Therefore, this research presents substantial potential for designing cardiac auxetic patches that can emulate the deformation properties of cardiac tissue and possess adjustable mechanical parameters.

Mechanical properties of tribofilms formed by metal dithiodiphosphates

Lubrication-based tribofilms are crucial in protecting contacting parts from wear and friction. A popular and well-studied additive commonly used in tribofilm formation is zinc dialkyldithiophosphate (ZDDP). While ZDDP has been shown to be an effective additive, the use of other metals in place of zinc may provide further benefits. Tribofilms were generated using fluids which contained DDPs neutralized with octylamine or different metals: magnesium, titanium, and zinc. Tribofilms were formed at 30 min, 60 min, and 120 min and were chemically and mechanically analyzed using EDS, AFM, and nanoindentation. Tribofilms were also analyzed based on property differences at the peak surface interactions. The metal used was found to have a significant effect on both tribofilms morphology and mechanical properties. Properties were further seen to change in the top 10% of the tribofilm surface as compared to bulk surface properties. Hardness and elastic modulus ratios were higher for the tribofilms formed by octylamine and MDDP as compared to TDDP and ZDDP tribofilms, but with the tradeoff of less tribofilm coverage of the substrate.

A comprehensive study on predicting the elastic modulus and Poisson ratio of hardened cement pastes via micro-scale cement hydration simulations

A comprehensive study was conducted to predict the elastic modulus and Poisson ratio of hardened cement pastes (HCPs), including numerical work, comparison of two modelling approaches, and experimental validation. Modelling approach 1 (M1) applied a continuum micromechanics model (CMM) whereas modelling approach 2 (M2) used finite element analysis (FEA). This study presents a reliable method for predicting the mechanical properties of HCPs by firstly employing the microstructures of HCPs, obtained by CEMHYD3D analysis with random distribution of cement particles as input parameters for both M1 and M2 approaches. The elastic modulus and Poisson ratio predicted by M1 and M2 approaches were verified through the experimental data obtained from compressive tests combined with digital image correlation analysis. The elastic moduli of HCPs were significantly affected by the input C-S-H modulus, with 90% of reported C-S-H elastic moduli falling within the range of 20.25 GPa and 30.4 GPa. The predicted elastic moduli of HCPs were well-matched with experimental data when assigning the elastic modulus, bulk modulus, and shear modulus, of C-S-H, as 20.25, 12.98, and 8.17 GPa, respectively. A sensitivity analysis demonstrated a linear increase in the elastic modulus of HCPs with increase of C-S-H modulus, with correlation coefficients R² of 0.9985 and 0.9996 for HCPs with water-to-cement ratios (w/c) of 0.3 and 0.5, respectively. Additionally, the predicted results showed greater consistency at later age (after 7 d) compared to earlier stages. The integral absolute error values of the elastic moduli obtained via M1 and M2 for HCPs with w/c of 0.3 were 6.32% and 6.23%, respectively while those for HCPs with w/c of 0.5 were 4.8% and 5.67%, respectively. M1 approach is more recommended since it is straightforward with time and cost efficiency compared to M2 approach in addition to the suitable prediction accuracy.

An automated design framework for composite mechanical metamaterials and its application to 2D pentamode materials

Until relatively recently most mechanical metamaterial classes being studied have been composed of a single solid constituent phase and design has focused almost exclusively on structural geometry. Additional design dimensions can be introduced by accepting heterogeneity and varying materiality, i.e., allowing mechanical properties to vary across the metamaterial's unit cells or even from cell to cell in the metamaterial domain, creating composite metamaterials. This higher dimensionality significantly expands the effective property envelope, but the additional complexity also presents a significant hurdle. To overcome the design challenge, an automated design framework is proposed that leverages modern evolutionary computation techniques, combined with finite element analysis for fitness evaluation, to a discretized or voxelated design domain. However, this approach introduces stochastic and statistical aspects to the design process, which requires additional processing to successfully extract useful solutions. A case study is presented in which the proposed automated design framework is used to generate 2D structures that exhibit pentamode-like behavior. Pentamode metamaterials, which are best known for extreme bulk-to-shear modulus ratios (B/G), offer unique control over effective elastic properties and make for a particularly interesting test case. The evolutionary objective was defined as maximizing B/G over a voxelated square 2D domain. It was found that the evolutionary process converges to a solution relatively rapidly, generally in less that a hundred generations. B/G ratio values of 10,000 and more were obtained, largely exceeding those commonly found in the literature for experimental pentamode metamaterials. These generated designs feature reduced stress concentrations due to the elimination of point-like connections between lattice struts, which addresses a key practical limitation of diamond lattice pentamodes. It was observed that whatever the initial variety of elastic moduli values across the voxels of the design domain, as evolution progressed this variety collapsed to a much smaller number, most often a binary composite of very stiff voxels with a limited number of much softer voxels at key locations that acted as hinges.

Analysis of Laminated Composite Porous Plate under Sinusoidal Load with Various Boundary Conditions.

Bending analysis was carried out for a laminated composite porous plate due to sinusoidal loading with various boundary conditions using improved third-order theory. Zero transverse shear stress provided a free surface at the top and bottom of the plate. Also, the authors developed a finite element formulation based on improved third-order shear deformation theory. To circumvent the C1 continuity requirement associated with improved third-order shear deformation theory, a C0 FE formulation was developed by replacing the out-of-plane derivatives with independent field variables. An in-house FORTRAN code was developed for the bending analysis of the laminated porous plate considering a 2D finite element model. The complete thickness of the plate was covered with different porosity patterns. The impacts of various modulus ratios, boundary conditions, thickness ratios, fiber orientation angles, and material parameters were examined for laminated porous plates. There was an 18.8% reduction in deflection in the case of the square plate as compared to rectangular plates, with a porosity value of 0.1, a thickness ratio of 10, and an orientation angle of 0°/90°/0°. According to the current research, adding porosities causes a relatively greater change in deflection rather than stress, thereby aiding in the development of a lightweight structure.

Quantitative study on fatigue characteristics of warm mix recycled asphalt

The warm mix recycling technology of asphalt pavement can improve the utilization rate of solid waste in highway construction industry on a large scale, and reduce the emission of harmful gases ( NOX, CO2, benzopyrene, etc.) in the process of road construction. It is one of the effective ways to realize carbon neutrality in highway construction industry. The main purpose of this study is to systematically analyze the fatigue characteristics of warm mix recycled asphalt (WMRA) from the perspective of quantitative research, and to provide scientific basis for the popularization and application of this technology. Therefore, this study mainly evaluated the anti-fatigue characteristics of WMRA under different conditions based on the linear amplitude sweeping test ( LAS test). Based on the calculation and analysis of the commonly used fatigue judgment indexes ( stress-strain curve, phase angle-strain curve, S×N curve ( S is the ratio of the instantaneous modulus to the initial modulus of the material, which is often replaced by the virtual modulus in the LAS test, and N is the number of cyclic loadings.), virtual strain storage energy-strain curve), the peak strain of virtual strain storage energy is recommended as the fatigue judgment standard from the perspective of reliability and accuracy, and the peak strain of damage factor is proposed as one of the new fatigue judgment standards. In this paper, the nucleation of microcracks and the coalescence of microcracks are distinguished in the process of fatigue damage evolution, and the peak strain of virtual strain energy storage and the peak strain of damage factor are used as the judging indexes respectively. Finally, based on the theory of continuum damage mechanics, the loss modulus of WMRA is selected as the representative value of material properties to calculate the virtual modulus and damage factor, and the fatigue damage evolution model of WMRA based on the viscoelastic continuum damage model ( VECD model) was constructed. Based on this model, the anti-fatigue characteristics of WMRA with the reclaimed asphalt pavement ( RAP) content were analyzed.

A comprehensive theoretical analysis on structural, electronic, optical, and mechanical properties of Sr2VRuO6 compound

In this paper, using the FP-LAPW technique as implemented in the Wien2k code, we have studied the structural, electronic, optical, and mechanical properties of strontium-based compound Sr2VRuO6. In this study, we explore the properties of Sr2VRuO6 using various approximations. We present the total energy versus energy, employing the Wu-Cohen-Generalized Gradients Approximation (WC-GGA) for both nonmagnetic and ferromagnetic states. To determine the stability of this material in cubic structure, the tolerance factor (t) and octahedral factor (μ) have been calculated. The lattice parameters of Sr2VRuO6 were determined, and subsequent calculations yielded the compressive modulus, Young's modulus, shear modulus, and Poisson's ratio in both two and three dimensions. Analyzing the band structure of Sr2VRuO6 within the mBJ-GGA approximation the half metallic character is observed with an indirect bandgap of 2.34 eV. In addition, the total and partial density of states, as well as charge density maps for Sr2VRuO6 have been calculated. Furthermore, we investigated the real and imaginary parts of the dielectric function as functions of energy for Sr2VRuO6. Additionally, the study delved into the variation of the refractive index, absorption coefficient, reflectivity, and energy loss with respect to energy for Sr2VRuO6.

Shear Modulus and Damping Ratio of a Calcite Cemented Gravelly Sand

Shear Modulus and Damping Ratio of a Calcite Cemented Gravelly Sand

A Constitutive Law Modeling the Mixed Hardening Behavior of Particle-Reinforced Composites

Abstract A homogenized elasto-plastic constitutive law (including both constitutive equations and inversed constitutive equations) is proposed in an incremental form for the particle-reinforced composites based on the flow theory of plasticity and the asymptotic homogenization method. The constitutive law can be used to predict the mixed hardening behavior of particle-reinforced composites under arbitrary loading conditions if the uniaxial tension test curve of matrix materials is known. It is found that the constitutive law of particle-reinforced composites is similar in form to the law of matrix materials. There is a simple proportional relationship between the yield stress, the plastic modulus, and the deviatoric back stress of particle-reinforced composites and the corresponding parameters of matrix materials, which is equal to the ratio of the shear modulus of composites to the shear modulus of matrix materials. The tangent modulus of particle-reinforced composites can be calculated using a simple arithmetic formula according to the tangent modulus of matrix materials. A numerical algorithm is suggested.

Uncertain stochastic vibration characteristic analysis of composite laminated rectangular plate based on improved kriging model

The stochastic vibration analysis of composite laminated structures has been conducted extensively in the field of structural dynamics. Existing studies in this field are primarily conducted based on deterministic structural parameters, whereas the effects of parametric uncertainties on the stochastic vibration characteristics of composite laminated structures are disregarded. This study investigates a composite laminated rectangular plate by considering the effect of interval uncertainty in the intrinsic parameters and load on its stochastic vibration characteristics. A rapid analysis model for the structural stochastic vibration characteristics is established based on an improved kriging model. Additionally, an innovative approach that combines the improved kriging model with intelligent optimization is proposed to solve problems pertaining to uncertainty-propagation analysis of structures. Based on this method, an uncertainty-propagation analysis of structural stochastic vibration responses is efficiently implemented. The effectiveness of the proposed method is demonstrated by comparing the results with those obtained from Monte Carlo simulation. The numerical results indicate that different uncertain factors exert varying degrees of effect on the stochastic vibration characteristics of the plate. Finally, the effects of density, elastic modulus ratio, fiber orientation and load on the interval fluctuation patterns of uncertain responses are discussed.

Novel, high throughput interface fracture testing method for thermal spray coatings: The modified cantilever bend technique

To measure the interfacial fracture toughness of ceramic/metal interfaces such as thermal spray coatings, a novel modified cantilever beam bending method is proposed. Finite element simulations are used to determine the energy release rate and phase angle for an interfacial crack in a bi-layered cantilever for varying modulus, thickness and beam aspect ratios. A high-throughput experimental procedure for the new test geometry is presented to extract a large number of measurements of interface fracture energy from the same sample, using digital image correlation. Interfacial fracture energies GC, determined using this method are compared for thermal spray coatings of Alumina and YSZ on steel substrates. GC of these coating-substrate combinations follow the same trend as measured from four-point bending or modified clamped beam bend techniques. Advantages and limitations of the technique in comparison to other methods in practice are discussed.

Physical, rheological and micro characteristics of ARA/Nano-TiO2 composite modified asphalt before and after short-term aging

This paper aims to investigate the composite application of nanomaterials and natural asphalt in order to enhance the road performance of asphalt pavement. The objective is to develop high-performance modified asphalt that improves the durability, reliability, and load resistance of asphalt roads while reducing resource waste and environmental pollution. The composite modified asphalt was prepared by adding different blends of Albanian natural rock asphalt (ARA) and 1% of nano titanium dioxide (Nano-TiO2), and the basic properties and rheological properties of the asphalt before and after aging were tested by using basic performance tests and temperature scanning tests. Subsequently, the microscopic morphological characteristics of the asphalt were observed by scanning electron microscope and atomic force microscope, and the number of bee structures, the area share of bee structures, root mean square roughness Rq, and arithmetic mean roughness Ra were used as microscopic quantitative indexes. The results indicate that the complex modulus and rutting coefficient of ARA/Nano-TiO2 composite-modified asphalt increase with an increase in ARA dosage when the dosage of Nano-TiO2 is 1%. The asphalt modified with Nano-TiO2 composite blended with 15% ARA exhibits higher residual needle penetration, composite modulus ratio, rutting coefficient ratio and lower softening point increment compared to 70# asphalt. The bitumen modified with titanium dioxide nanocomposite blended with 15% ARA exhibits higher Rq and Ra and a more stable phase structure before and after aging. 15% of ARA/Nano-TiO2 composite-modified asphalt has higher Rq and Ra before and after aging, and its phase structure is more stable. The results show that ARA/Nano-TiO2 composite-modified asphalt has better high-temperature deformation resistance and aging resistance than 70# and that 15% ARA is recommended as the optimum amount of composite-modified asphalt.

Assessment of the anisotropy development of mechanical properties of pitch-based carbon fibers

Carbon fiber XN-P9 derived from anisotropic pitch was heat treated at different temperatures (2000, 2500, and 3000℃) and the mechanical properties of those single filament in various directions were tested with some methods we have developed. The anisotropy of the mechanical properties of those pitch-based carbon fibers was evaluated to be developed by heat treatment. As a comparison, the properties of carbon fiber XN-05 derived from isotropic pitch were also tested. The ratio of the longitudinal tensile modulus to the shear modulus of XN-05 fiber was approximately 3. In contrast, for pristine XN-P9 fiber, the longitudinal tensile modulus was more than nine times greater than the shear modulus, and the difference between these moduli increased with the elevating heat treatment temperatures. It was suggested that the anisotropy of mechanical properties of pitch-based carbon fibers was developed by heat treatment. In compressive deformation in the transverse direction to the fiber axis, a yielding and a softening was clearly observed with the elevating heat treatment temperature. The effect of anisotropy development on the span-length dependence of flexural modulus obtained from the three-point bending test of the single filament was assessed.