Estimation Of Modulus Research Articles

Water influence on micro and homogenized modulus of shale

By using the outcrop shale of Longmaxi-3, a series of experiments including in-situ AFM Force Map, SEM-EDS before and after water vapor saturation and uniaxial/triaxial compression tests are conducted to discover the changing pattern of shale mechanical properties from micro and macro level. The current research first measures the micro elastic modulus distribution changes of shale under water condition, also verifying the water-softening effects. Expectation Maximization algorithm programmed by C language is utilized to define Gaussian Mixture Model of micro elastic modulus under different moisture. Self-Consistent Scheme by C program and Mori-Tanaka Scheme is adopted to upscale the micro modulus based on the results of EM. In the comparison with compression test results, M-T scheme behaves better on estimating modulus of originally dry shale core than SC scheme, however, the homogenization technique cannot achieve the accurate estimation of core sample modulus based on micro modulus. The combination of AFM morphology and SEM-EDS verifies the component CaSO4 of newborn particles when moisture is low. Due to strong heterogeneity of shale, the relationship between elastic modulus and water saturation is negative and non-linear, homogenization technique is not proper to upscale micro modulus of sample processed by water or other factors.

Estimation of deformation modulus of coals using artificial neural networks (ANN)

In this study, the Young modulus (E) of different coals was investigated using artificial neural networks (ANN). For this purpose, a comprehensive literature survey was carried out to compile such datasets available for the ANN analyses. As a result of the literature survey, a database composed of 81 datasets was formed. In the ANN analyses, uniaxial compressive strength (UCS) and dry density (ρd) of coals were adopted as input parameters. The ANN analysis results demonstrated that the predictive model established in this study could be reliably used to estimate the E for different coals. The correlation of determination value (R2) for the developed model is 0.85, which shows its relative success. In this context, this study can be declared a case study showing the applicability of ANN for the evaluation of E for a wide range of coal types. However, the number of samples and independent variables should be increased to obtain more comprehensive models in future studies.

Shear wave elastography of the brachioradialis spastic muscle and its correlations with biceps brachialis and clinical scales

BackgroundShear wave elastography technique estimates biological tissue shear elastic modulus (μ[kPa]), which can be used as an objective, muscle-specific indicator of stiffness increase caused by spasticity. We measured both the brachioradialis and biceps brachialis μ in hemiparetic post-stroke patients (n = 11). The spastic arm was compared with the supposedly non-affected contralateral limb and correlated with Fugl-Meyer Assessment and Modified Ashworth Scales. MethodsShear elastic modulus was estimated using an Aixplorer V.9 ultrasound device with the elbow at full extension. Average shear elastic modulus t-test, effect sizes, correlation matrix, spider plots and factor analysis were used to check for differences between spastic and nonspastic sides and explore relationships among the variables. FindingsSpastic brachioradialis μ (22.54 ± 11.59 kPa) and biceps brachialis (26.86 ± 12.07 kPa) were significantly greater than the non-spastic counterparts (13.13 ± 2.81 kPa, p = 0.031, ηp2 = 0.3846 for brachioradialis and 15.25 ± 5.00 kPa, p = 0.007, ηp2 = 0.5345 for biceps brachialis). Significant correlations were observed between the spastic brachioradialis and biceps μ and Modified Ashworth Scales, but no correlation with Fugl-Meyer Assessment. InterpretationElastography can provide muscle-specific shear elastic modulus estimations of spastic brachioradialis and biceps brachialis, which are distinct from the nonspastic side. In some patients, there was no clear correspondence of the Fugl-Meyer Assessment functional scale with Modified Ashworth Scales and μ, suggesting that spasticity is not the only determinant of arm function. Additionally, shear wave elastography of brachioradialis and biceps brachialis muscles may guide the spasticity treatment, for instance, selecting the preferable candidate for botulinum toxin therapy.

Accurate measurement of elasticity of the radial artery wall considering changes in cross-sectional shape of artery caused by pushing pressure applied by ultrasound probe

For the early diagnosis of atherosclerosis, our group developed an ultrasound probe that can simultaneously measure blood pressure and vessel diameter at the same position. However, because the developed probe requires the blood vessel to be deformed by pushing to measure the blood pressure, it affects the estimation of the vessel’s elastic modulus. In the present study, we derived a series of equations to estimate the elastic modulus of a blood vessel considering the pushing pressure applied by the ultrasound probe and the resultant deformation of the blood vessel. The validity of the proposed method was verified by numerical calculations, and then the method was applied to in vivo measurements. The proposed method resulted in fewer variations in the elastic modulus estimates with different pushing pressures compared with the conventional method.

Empirical estimation of rock mass deformation modulus of rocks: comparison of intact rock properties and rock mass classifications as inputs

Deformation modulus of rock mass (Em) is an important parameter for the analysis and design of mining engineering projects. However, field tests for measuring deformation modulus of rock mass are difficult, time-consuming, and capital intensive. This has led to the development of numerous empirical models for estimating rock mass deformation modulus, which are in different forms and scattered in the literature. The numerous models available in the literature use different types of inputs. Therefore, this study provides a comprehensive compilation of different empirical models for estimating the deformation modulus of rock masses. The compiled models are grouped based on their type of input parameter(s) into three categories such as those using intact rock properties, rock mass classification indices, and combination of intact rock properties and rock mass classification indices. Then, a comparative analysis was performed using absolute average relative error percentage (AAREP) and variance accounted for (VAF) to assess the reliability of using different types of inputs for estimation of deformation modulus of rock masses using data from two sites. The results of the analyses show that rock mass classification indices are the most reliable indices for estimating the deformation modulus of rock masses among the categories considered for analyses. For AAREP analyses in the two illustrative examples considered in this study, models (7 out of 10) using rock mass classification indices in the estimation of Em have the best performances with AAREP values ranging from 24.07 to 55.15%. For VAF analyses in the two examples, models (8 out of 10) using rock mass classification indices in the estimation of Em have the best performances with values ranging from 59.81 to 88.11%. The lowest errors and highest deviation similarities from models using rock mass classification indices indicate that they produce the most reliable estimations of Em. It is important to note that the reliability of deformation modulus estimated from empirical models depends on the quality of input data as the models performed differently across the sites used in this study. This study therefore provides a compilation of available models for estimating deformation modulus, performance evaluation of available models for estimating deformation modulus, and guidelines for selecting appropriate model for estimating deformation modulus of rock mass.

Nanomechanical Characterization of Bacterial Polyhydroxyalkanoates Using Atomic Force Microscopy

Polyhydroxyalkanoates are a promising class of biopolymers that can allow the production of sustainable plastic materials. The mechanical properties of such materials are very important for possible industrial applications, but the amount of polymer required for common mechanical testing can be orders of magnitude more than what is possible to achieve with a lab-scale process. Nanoindentation with the Atomic Force Microscope allows an estimation of the Elastic Modulus that can be used as a preliminary measurement on PHA when only a limited amount of material is available. Poly(hydroxybutyrate-co-hydroxyvalerate) copolymers were analyzed, with moduli ranging from 528 ± 62 MPa to 1623 ± 172 MPa, according to both the composition and the crystallization kinetics.

Viscoelastic Characterization of Soft Tissue-Mimicking Gelatin Phantoms using Indentation and Magnetic Resonance Elastography.

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the biomechanics-related mechanisms of disease, injury, and development. The mechanical testing method is the most straightforward way for tissue characterization and is considered as verification for in vivo measurement. Among the many ex vivo mechanical testing techniques, the indentation test provides a reliable way, especially for samples that are small, hard to fix, and viscoelastic such as brain tissue. Magnetic resonance elastography (MRE) is a clinically used method to measure the biomechanical properties of soft tissues. Based on shear wave propagation in soft tissues recorded using MRE, viscoelastic properties of soft tissues can be estimated in vivo based on wave equation. Here, the viscoelastic properties of gelatin phantoms with two different concentrations were measured by MRE and indentation. The protocols of phantom fabrication, testing, and modulus estimation have been presented.

Non-invasive measurement of nuclear relative stiffness from quantitative analysis of microscopy data

The connection between the properties of a cell tissue and those of the single constituent cells remains to be elucidated. At the purely mechanical level, the degree of rigidity of different cellular components, such as the nucleus and the cytoplasm, modulates the interplay between the cell inner processes and the external environment, while simultaneously mediating the mechanical interactions between neighboring cells. Being able to quantify the correlation between single-cell and tissue properties would improve our mechanobiological understanding of cell tissues. Here we develop a methodology to quantitatively extract a set of structural and motility parameters from the analysis of time-lapse movies of nuclei belonging to jammed and flocking cell monolayers. We then study in detail the correlation between the dynamical state of the tissue and the deformation of the nuclei. We observe that the nuclear deformation rate linearly correlates with the local divergence of the velocity field, which leads to a non-invasive estimate of the elastic modulus of the nucleus relative to the one of the cytoplasm. We also find that nuclei belonging to flocking monolayers, subjected to larger mechanical perturbations, are about two time stiffer than nuclei belonging to dynamically arrested monolayers, in agreement with atomic force microscopy results. Our results demonstrate a non-invasive route to the determination of nuclear relative stiffness for cells in a monolayer.Graphic abstract

Estimation and Comparison of Effective Elastic Modulus of Different Scaffolds Using Curve Fitting Method for Additive Manufacturing Field

Estimation and Comparison of Effective Elastic Modulus of Different Scaffolds Using Curve Fitting Method for Additive Manufacturing Field

Mechanical Behavior of GFRP Laminates Exposed to Thermal and Moist Environmental Conditions: Experimental and Model Assessment.

This paper presents an experimental and analytical study about the mechanical response at a different temperature on glass fiber-reinforced polymer laminates. The effect of different environmental conditions on compressive, tensile, stiffness, and viscoelastic behavior (storage modulus, loss modulus and damping ratio) of laminates were investigated. Before testing, laminates were preserved in a deep freezer at −80 °C, −20 °C, 0 °C, and room temperature (25 °C) for up to 60 days. Results confirmed that temperatures ranging from −80 to 50 °C, which were below the glass transition temperature of the epoxy resin, did not significantly affect the compressive, tensile, and stiffness performance of all laminates. When the testing temperature increased to 100 °C, the properties were decreased significantly due to the damaging of the fiber/matrix interface. Additionally, results obtained from dynamic mechanical analyses tests showed a drop-in storage modulus, high peaks in loss modulus and high damping factor at the glass transition region of the epoxy resin. The highest storage modulus, two phases of glassy states and highest damping ratio on the −80/G group of laminates were obtained. The accuracy of experimental results was assessed with empirical models on the storage modulus behavior of laminates. The empirical model developed by Gibson et al. provided accurate estimates of the storage modulus as a function of temperature and frequency. The remaining empirical models were less accurate and non-conservative estimations of laminates stiffness.

Discussion on the paper entitled “Estimating elasticity modulus and uniaxial compressive strength of sandstone using indentation test” by E. Mousavi, A. Cheshomi and M. Ashtari [Journal of Petroleum Science and Engineering 169 (2018) 157–166

A discussion on the paper by Mousavi et al. (2018) is presented. The paper is focused on the estimation of elastic modulus (E) and uniaxial compressive strength (UCS) of sandstone using indentation test. The authors concluded that the thickness effect of samples on the indentation indices (critical transition force (CTF) and indentation modulus (IM)) was negligible. They proposed a dimensionless surface parameter (S) to eliminate the size effect on the E and UCS. On the basis of the test results and analysis method presented in the paper by Mousavi et al. (2018), three aspects of indentation test need to be clarified: the methods to prevent the movement of rock specimens, the results obtained from indentation test and the effect of specimen sizes on the CTF and IM. Meanwhile, the present discussion paper proposed some references for the methods to prevent the movement of rock specimens and the methods to eliminate the size effect in indentation test.

Influence of anisotropic fiber properties on tensile elastic modulus estimation for carbon fiber reinforced thermoplastics

The influence of anisotropic fiber properties on estimation of the elastic modulus of carbon fiber-reinforced polyamide 6 (CFRPA6) was studied using two kinds of micromechanics models; Nairn et al. and Hashin (N–H) models, and Mori–Tanaka (M–T) model. First, these models’ accuracy was verified by comparison with an elastic modulus measured for injection molded dumbbell specimens of CFRPA6. Although there was a slight difference between the elastic moduli estimated from the N–H models and the M–T model, the difference was discussed in terms of model properties. Next, estimation errors caused by assuming carbon fiber (CF) as isotropic were calculated under several conditions. The maximum error occurred in the condition that the tensile direction was perpendicular to the fiber axis. Despite CF had large anisotropy, it was approximately 10% for both models. We infer that the small error was caused by a specific stress field.

Modulus of elasticity predictions through LSBoost for concrete of normal and high strength

In the past, empirical equations and some statistical regression approaches have been developed to estimate the modulus of elasticity of concrete. These methods aim at facilitating the application and design of concrete. But the accuracy and stability of these equations and models need further improvements. In this study, the least-squares boosting model is developed to predict the elastic modulus based on compressive strength for normal- and high-strength concrete. The model is highly accurate and stable, generates better predictions than other models reported in the literature, and thus is promising as a fast, robust, and low-cost tool for elastic modulus estimations.

Understanding the Geodetic Signature of Large Aquifer Systems: Example of the Ozark Plateaus in Central United States

AbstractThe continuous redistribution of water involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by the loading imposed by hydrological mass variations and can be quantified to first order with space‐based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well‐instrumented Ozark Plateaus Aquifer System (OPAS) in the central United States. We begin by characterizing the most important sources of groundwater level variations in the spatially heterogeneous piezometer dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for hydrological loading effects onto the dominant groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of aquifer layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.

Effects of bacterial exopolysaccharide on rheological properties of acid milk curd and its correlates

Exopolysaccharide (EPS) is a general term for the forms of bacterial polysaccharides found outside the cell wall of bacteria. The industrial microbiologist has become interested in exploiting microbial exopolymer production due to an increasing interest and need for novel polysaccharides. The use of bacterial EPS in acid milk curd (AMC) production accounts for a quality improvement of the milk curd in terms of stability during the normal operations of storage and transportation. On the other hand, EPS have been used as prebiotic because of its health-promoting effects in human beings. The objective of this study was to evaluate the rheological properties (RP) and their statistical correlations in acid milk curd (AMC) samples added with bacterial EPS. Rheometric properties are suitable parameters to evaluate food quality such as AMC. Some of the RP normally used in this evaluation include elastic modulus (EM), hardness (HR), breaking energy (BE), viscosity (VIS) and stress. Correlation between pairs of these parameters are important to understand in order to predict statistically other parameters in case they cannot be easily determined. Acid milk curd samples were formulated using 10, 15, and 20 % of reconstituted skim milk (RSM), to which 0, 0.2, 0.4, 0.6, 0.8, and 1 % level of EPS were added, respectively. Samples were pasteurized at 60 o C for 30 min, and at 85 oC for 30s. Afterwards, AMC samples were tempered to 40 °C inoculated with Lactobacillus delbrueckii subsp. bulgaricus B-5b, and incubated at 37 °C for 16 h. Results indicated that viscosity and hardness showed the strongest and highest correlation among all the parameters evaluated (r=0.9272) and it was comparable to that between viscosity and breaking energy (r=0.8349) and breaking energy and hardness (r=0.7694). However, elastic modulus and viscosity showed a rather low correlation (r=0.5394) and very low correlation (r=0.1830), respectively, suggesting that estimation of elastic modulus from viscosity values would be inaccurate. In general, rheometric properties of acid milk curd increased with higher EPS concentrations until 1 % level of EPS addition. Therefore, it is recommended to use BE and HR values, and BE and VIS values to predict accurate measurements of other RP values. Key words: Exopolysaccharide (EPS), acid milk curd (AMC), rheometric properties (RP), statistical correlation (SC)

Analysis of thin layers using surface acoustic wave-photonic devices in silicon-on-insulator.

The analysis of thin layers deposited on various substrates is widely employed in thickness monitoring, materials research and development and quality control. Measurements are often performed based on changes to acoustic resonance frequencies of quartz micro-balance devices. The technique is extremely sensitive, but it is restricted to hundreds of MHz frequencies and requires electrical connectivity. In this work we propose and demonstrate the analysis of elastic properties of thin layers deposited on surface acoustic wave-photonic devices in standard silicon-on-insulator. The devices operate at 2.4 GHz frequency, and their interfaces are fiber-optic. The radio-frequency transfer functions of the devices are modified by sub-percent level changes to the group velocity of surface acoustic waves following deposition of layers. Layers of aluminum oxide and germanium sulfide of thickness between 10-80 nm are characterized. The analysis provides estimates for Young's modulus of the layers.

Determination of the mechanical properties of gelatinized starch granule from bulk suspension characterization

Gelatinized starch granules are soft and deformable particles that are commonly used in food products as texture modifiers. Modelling the flow behavior of such suspensions during industrial processes requires the knowledge of the mechanical properties of the swollen granules; however, such data is usually lacking because of the difficulties inherent to the determination of mechanical properties of particles that are heterogeneous in terms of size and shape. We investigate here the rheological properties of dense suspensions prepared at different volume fractions and by different means (centrifugation, limited water swelling, osmotic compression) to estimate the mechanical properties of an “averaged” starch granule. Results show that starch granule exhibits a rough surface and behave as frictional particles. We compare the shear modulus value determined assuming either frictionless (previous model) or frictional interactions (as suggested by our results), the latter giving shear modulus lower by about one order of magnitude. This study also allows the first estimate of the starch granule bulk modulus, which value is corresponding to a Poisson ratio of 0.47, close to the maximum value of 0.5. The swollen granule shear modulus is also shown to be temperature independent in the range commonly found in industrial processes (20–90 ∘C). These results pave the way toward multiscale mechanistic modelling of the flow of starch suspensions, to derive macroscopic rheological properties from the description of the microscopic granule properties. Estimating starch granule mechanical properties from bulk suspension characterization

Backcasting and forecasting stabilized soil mechanical properties for mechanistic-empirical pavement design

The ability to reliably forecast or backcast mechanical properties of chemically stabilized soils to use as design inputs (e.g. Mechanistic-Empirical Pavement Design Guide) is not readily available. In this paper, seven data sets comprised of 1642 laboratory specimens and 206 field cores were used to calibrate numerical relationships from literature to backcast and forecast mechanical properties of chemically stabilized soil commonly used in Mississippi pavements. When relationships from literature were compared to Mississippi materials, unconfined compressive strength (UCS) was underpredicted; however, when regression parameters were optimized to the data sets, prediction accuracy increased and were on average within 89–99% of actual UCS values. Equations were also shown to provide reasonable estimates of elastic modulus (E) and indirect tensile strength (IDT) when parameters were optimized. Accelerated curing to replicate later life pavement properties in laboratory specimens as well as field cores were compared to relationships from literature to determine their applicability to later life mechanical properties. Literature equations calibrated using laboratory cured specimens predicted mechanical properties within the range of properties reported from cores. Based on this analysis, a set of recommended regression parameters are given that are optimized for common Mississippi materials.

Optical coherence elastography for assessing the influence of intraocular pressure on elastic wave dispersion in the cornea

The cornea is a highly specialized organ that relies on its mechanical stiffness to maintain its aspheric geometry and refractive power, and corneal diseases such as keratoconus have been linked to abnormal tissue stiffness and biomechanics. Dynamic optical coherence elastography (OCE) is a clinically promising non-contact and non-destructive imaging technique that can provide measurements of corneal tissue stiffness directly in vivo. The method relies on the concepts of elastography where shear waves are generated and imaged within a tissue to obtain mechanical properties such as tissue stiffness. The accuracy of OCE-based measurements is ultimately dependent on the mathematical theories used to model wave behavior in the tissue of interest. In the cornea, elastic waves propagate as guided wave modes which are highly dispersive and can be mathematically complex to model. While recent groups have developed detailed theories for estimating corneal tissue properties from guided wave behavior, the effects of intraocular pressure (IOP)-induced prestress have not yet been considered. It is known that prestress alone can strongly influence wave behavior, in addition to the associated non-linear changes in tissue properties. This present study shows that failure to account for the effects of prestress may result in overestimations of the corneal shear moduli, particularly at high IOPs. We first examined the potential effects of IOP and IOP-induced prestress using a combination of approximate mathematical theories describing wave behavior in thin plates with observations made from data published in the OCE literature. Through wave dispersion analysis, we deduce that IOP introduces a tensile hoop stress and may also influence an elastic foundational effect that were observable in the low-frequency components of the dispersion curves. These effects were incorporated into recently developed models of wave behavior in nearly incompressible, transversely isotropic (NITI) materials. Fitting of the modified NITI model with ex vivo porcine corneal data demonstrated that incorporation of the effects of IOP resulted in reduced estimates of corneal shear moduli. We believe this demonstrates that overestimation of corneal stiffness occurs if IOP is not taken into consideration. Our work may be helpful in separating inherent corneal stiffness properties that are independent of IOP; changes in these properties and in IOP are distinct, clinically relevant issues that affect the cornea health.

The validation of elastic modulus models: Code models and their modified versions

AbstractElastic modulus (E) estimation forms an important element in the methods used to predict concrete creep deformation, which is an important structural design consideration. A variety of differentEestimation models for concrete exist but there is uncertainty as to which of the models is the most accurate. This research study assesses the performance of models namely, the ACI 318, ACI 318 Simplified, Mendis et al., Rüsch et al., Carrasquillo et al., ACI 363, AS 3600, Omar et al., AS 3600, BS 8110, Alexander and Davis, SANS 10100, CEB‐FIP, and the EC 2. The included list of models is taken from national codes and includes their superseded and modified versions. TheEvalues of 108 specimens, whose properties differed (in aggregate type, cement type, concrete strength, and curing age), were measured. The actualEvalue was compared to each model's estimations to determine which were most accurate statistically using the coefficient of variation (ωj). The ACI 363 model was the most accurate out of the 16 models assessed, yielding an overallωjof 16%. The CEB‐FIP model was found to be the least accurate showing an overallωjof 31.8%. From the 16 models considered, it was recommended that the ACI 363 model be utilized by creep prediction models. In addition, it was found that not all modified estimate models produced better estimates.