Estimation Of Elastic Modulus Research Articles

Improved estimation of uniaxial compressive strength and elastic modulus for carbonate rocks using back propagation neural network and buckingham pi theorem

Improved estimation of uniaxial compressive strength and elastic modulus for carbonate rocks using back propagation neural network and buckingham pi theorem

Constrained amorphous interphase in plasticized poly(lactic acid): Composition and tensile elastic modulus estimation

The study investigates the distribution of the plasticizers acetyl triethyl citrate (ATEC) and acetyl tributyl citrate (ATBC) in the mobile amorphous (MAF) and rigid amorphous (RAF) fractions of semi-crystalline plasticized poly (lactic acid) (PLA) containing 5 wt% of plasticizer. During crystallization, the ATEC and ATBC concentration in the MAF increases from 5 to about 8 wt%. At the end of crystallization, the plasticizers concentration in the RAF is lower than that in the MAF. The progressive decrease of the ATEC and ATBC concentration in the RAF region could be linked to the growth of subsidiary lamellae in more restricted amorphous areas. The study also introduces an estimation of the tensile elastic modulus of the RAF (ERAF) in semi-crystalline pure and plasticized PLA containing α-crystals. The mechanical model with crystalline lamellae perpendicular to the stress direction turned out to be the most appropriate arrangement to represent the morphological organization in PLA samples prepared by injection-moulding processing at high pressure. The mathematical procedure led to a crystal elastic modulus (EC) of the α-phase in excellent agreement with the theoretical value reported in the literature (EC = 14 GPa), and to an ERAF value around 5.5 GPa, for both pure and plasticized PLA, thus suggesting that both ATEC and ATBC do not exert plasticizing action on the RAF.

Estimation of elastic modulus of recycle aggregate concrete based on hybrid and ensemble‐hybrid approaches

AbstractThe utilization of recycled aggregate concrete (RAC) within the construction sector has the potential to prevent irreversible harm to the environment and reduce the depletion of natural resources. Nonetheless, it is essential to scrutinize the quality of RAC before utilizing it in practical applications. RAC's most significant design parameter is its elastic modulus, typically determined through time‐consuming and costly experiments. Machine learning (ML) techniques can be a feasible solution to reduce the number of experiments required and obtain accurate estimates. This article employs two robust ML techniques, namely Xtreme Gradient Boosting (XGB) and Adaptive Boosting regression, in three distinct modes, namely individual, hybrid, and ensemble‐hybrid methods. Furthermore, phasor particle swarm optimization (PPSO) and chaos game optimization (CGO) have been utilized in hybrid and ensemble‐hybrid modes to optimize final results, minimize errors, and obtain highly precise outcomes. As mentioned earlier, several evaluators were employed to identify the most appropriate model to compare the modes. The findings suggest that the relevant optimizers significantly contributed to achieving superior metric values. Specifically, the results indicated that PPSO exhibited greater efficacy than CGO in optimizing outputs and enhancing accuracy. The hybrid models, particularly XGB in conjunction with PPSO, yielded the most favorable correlation coefficient and root mean square error values equal to 0.996 and 0.336 and can serve as an effective ML method to determine elastic modulus of recycle aggregate concrete for time and energy storage.

A novel relationship between elastic modulus and void ratio associated with principal stress for coral calcareous sand

Elastic moduli, e.g. shear modulus G and bulk modulus K, are important parameters of geotechnical materials, which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical materials. In this study, a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloading-reloading tests are conducted to study several typical mechanical properties of coral calcareous sand (CCS), and the void ratio evolution during loading, unloading and reloading. The test results show that the stress-strain curves during multiple unloading processes are almost parallel, and their slopes are much greater than the deformation modulus at the initial stage of loading. The relationship between the confining pressure and the volumetric strain can be defined approximately by a hyperbolic equation under the condition of monotonic loading of confining pressure. Under the condition of confining pressure unloading, the evolution of void ratio is linear in the e-lnp′ plane, and these lines are a series of almost parallel lines if there are multiple processes of unloading. Based on the experimental results, it is found that the modified Hardin formulae for the elastic modulus estimation have a significant deviation from the tested values for CCS. Based on the experimental results, it is proposed that the elastic modulus of soils should be determined by the intersection line of two spatial surfaces in the G/K-e-p'/pa space (pa: atmosphere pressure). “Ye formulation” is further proposed for the estimation of the elastic modulus of CCS. This new estimation formulation for soil elastic modulus would provide a new method to accurately describe the mechanical behavior of granular soils.

On the variants of SVM method for the estimation of soil elastic modulus from TSD model: Numerical parametric study

The accurate estimation of the subgrade resilient modulus MR is a crucial element in designing durable and resilient pavements as it quantifies the soil’s bearing capacity to withstand traffic loads without excessive deformation or failure. Conventional methods and devices that are used to estimate MR, such as the Falling Weight Deflectometer (FWD) have several limitations due to operational and security constraints when measuring at the network level. To overcome these limitations, Traffic Speed Deflectometer (TSD) has been developed, which can continuously assess the pavement bearing capacity without requiring traffic control. However, processing the massive amounts of data generated by TSD requires specialized processing techniques such as Machine Learning (ML). Therefore, the primary objective of this paper is to develop an efficient and effective model that can accurately estimate MR by combining two techniques: (TSD + ML). The study uses numerical simulations of deflection velocity slope SV under TSD as the forward model. The research employs Support Vector Machine (SVM) algorithm for ML to classify and estimate MR modulus values from a synthetic and controlled dataset. SVM model exhibits robust performance in both classification and regression analysis, whereas, 95% of the discrepancies between estimated and tested values did not exceed ±15MPa. Advanced numerical validation, sensitivity analysis and parameter estimation methods were also conducted to optimize the model’s performance. Overall, the approach proposed in this paper has the potential to make a significant impact in the field of subgrade evaluation and can facilitate the development of better road infrastructure.

Estimation of yield strength and elastic modulus of aerospace-grade aluminum 7075 composite reinforced with silicon carbide and graphite

This study aims to find a suitable theoretical model to estimate yield strength and elastic modulus of the AA7075 base cast and hybrid composite reinforced with silicon carbide and graphite (micron-sized) to attain high quality, high performance, and low-cost metal matrix composite. Compared to AA7075 base cast CM1 (AA7075 base cast) ultimate tensile strength, yield strength, and flexural strength of hybrid composite CM4 (AA7075 + 15 wt% SiC + 5 wt% Graphite), CM3 (AA7075 + 10 wt% SiC + 5 wt% Graphite), and CM2 (AA7075 + 5 wt% SiC + 5 wt% Graphite) increased (29%, 24%, and 19%), (36%, 35%, and 27%), and (19%, 13%, and 6%) respectively. Micro-mechanics contributed higher, followed by other strengthening mechanisms like load transfer, grain refinement, and thermal mismatch with respect to the volume fraction of the reinforcement particle in the aluminum metal matrix. In the yield strength model, Ramakrishnan-Modified Shear Lag-Mirza and Chen model, Li model, sum of contribution model, and proposed model estimated closer values. They agreed with experimental data at all values up to 7.34% of reinforcement volume fraction. In the elastic modulus model, Hashin-Shtrikman – average, upper, and lower bound and the proposed model estimated well and agreed with experimental data at lower and higher volume fractions of reinforcement.

Estimation of elastic modulus, fracture toughness and strength of 47.5B-derived bioactive glass-ceramics for bone scaffold applications: a nanoindentation study

The knowledge of the mechanical properties of glass–ceramic materials used in bone scaffolds is the key to the optimal design of tissue engineering devices. In this paper, the elastic properties and fracture toughness of silicate bioactive glass-ceramics based on the 47.5B parent composition were quantified for the first time through nanoindentation. Specifically, the effect of sintering temperature was investigated by testing samples sintered at six different temperatures. The samples sintered at higher temperatures exhibited elastic modulus and fracture toughness higher than those of the lower temperature samples. Both properties are comparable with those shown by similar bioactive glasses available in literature, supporting the mechanical suitability of the materials for bone applications. An estimation of tensile strength as a function of flaw size is also provided by means of fracture mechanics approaches.

Tissue Viscoelasticity Quantification Using Smartphone Tactile Imaging Probe With an Indenter and Viscoelastic Pitting Recovery Model

Viscoelasticity of human tissue often carries important physiological information linking to many fatal diseases, such as heart failure, renal impairment, and liver failure. Fluid retention due to these diseases cause swelling of body parts (edema) and changes the viscoelastic characteristic of the tissue. We hypothesize that the viscoelastic behavior change of the tissue can be estimated by creating and quantifying the pit on the swelled body parts. Here, we present a smartphone tactile imaging probe with an indenter (STIP-I) system that measures the pitting parameters and characterizes the viscoelastic behavior. This system consists of tactile imaging sensing that utilizes a light diffusion in a polydimethylsiloxane (PDMS)-based optical waveguide and a Viscoelastic Pitting Recovery (VPR) computation model. The prototype STIP-I system is tested using edematous tissue phantoms, which show a moderate measurement error of 29.5% for the pitting parameters and excellent performance of 7.60% error in elastic modulus estimation. The STIP-I system is expected to bring a new approach to understanding viscoelasticity changes due to various diseases.

Evaluation of local changes in radio-frequency signal waveform and brightness caused by vessel dilatation for ascertaining reliability of elasticity estimation inside heterogeneous plaque: a preliminary study.

To diagnose plaque characteristics, we previously developed an ultrasonic method to estimate the local elastic modulus from the ratio of the pulse pressure to the strain of the arterial wall due to dilatation in systole by transcutaneously measuring the minute thinning in thickness during one cardiac cycle. For plaques, however, some target regions became thicker as the vessel dilates, resulting in false elasticity. Therefore, a method to identify a reliable target for the elastic modulus estimation is indispensable. As a candidate for an identification index of plaques that become thicker during one cardiac cycle, the correlation of the radio-frequency (RF) signals remains high and it is not sufficient to obtain the elasticity. In this study, we thoroughly observed the target with a high correlation but positive strain in the plaque and characterized it by the property of the surrounding area. For the plaque formed in the right carotid sinus of a patient with hyperlipidemia and the wall of the right common carotid artery of a young healthy male, (1) the correlation value as the similarity between the RF signals, (2) change in brightness obtained from the log-compressed envelope signals, and (3) strain obtained between the time of the R-wave and that of the maximum vessel dilatation were observed to characterize the region in the plaque. In the plaque, it was found that the region with high correlation and positive strain and its surrounding area could be classified into one of the three typical patterns. As a preliminary study, this study provides a clue to assert the reliability of elasticity estimates for a region with high correlation and positive strain in the plaque based on measurable properties.

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.

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

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.

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)

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.

Experimental determination of higher order elastic moduli of metallic glasses

We studied the effect of uniaxial compression on longitudinal and transverse ultrasonic resonant vibrations (8–10 MHz) in Zr57Nb5Al10Cu15.4Ni12.6 (VIT106) metallic glass in the initial and relaxed states. On this basis, the 3rd- and 4th-order elastic moduli are determined. We also corrected previous calculations of the parameters of sound propagation vs the applied load and re-examined earlier estimates of higher order elastic moduli in other metallic glasses. To our knowledge, any other estimates of the 4rd-order elastic moduli of metallic glasses based on experimental observations are absent in the literature. The obtained data are discussed in the framework of available theoretical predictions.

Theoretical models for stiffness prediction of short fibre composites

The short natural fibre reinforced polymer matrix composites are a good cost-effective option in a multitude of non-structural applications. The estimation of elastic moduli of such composites is important during the initial design phase. In this work, a brief introduction to the theoretical models to determine elastic moduli of short fibre composites is presented. Various theoretical models like Halpin-Tsai model, Mori-Tanaka model with fibre orientation averaging, alongwith the rule-of-mixtures and the Hashin-Shtrikman bounds are employed to obtain the elastic properties of composites. Although some of these models have been used for short glass fibre composites, in this study, the applicability of these models to natural fibre composites has been explored. The elastic properties obtained from the theoretical model are compared with experimentally obtained values of injection moulded short jute fibre-polypropylene composites from our other work. The model which satisfactorily results in better elastic property predictions of short fibre composites amongst the presented theoretical models has been highlighted. It has been observed that the fibre orientation averaging is imperative to account for random fibre orientation and yield better elastic property predictions.

Estimation of modulus of elasticity of compacted loess soil and lateritic-loess soil from laboratory plate bearing test

In this paper, the moduli of elasticity of compacted loess and lateritic-loess soils on-site were estimated from the laboratory test. These were coarse grain soils used for the construction of base course and embankment of the railway line. The knowledge of the soil properties on-site such as the compacted elastic moduli is essential for the design and selection of materials. A total of 108 samples consisting of 36 samples of compacted soils on-site and 72 samples of compacted soils in laboratory were tested using plate bearing tests. The water contents of the compacted soil on-site were controlled to be within ± 2% of optimum water content. The water content and density of compacted soil on-site were determined and used for the compaction of soils in the laboratory. For the testing in laboratory, two loading types viz., point load and uniform load were performed using the compacted 15-cm diameter mold (California Bearing Ratio). The results showed that the point load test gave a slightly better estimation of elastic modulus with R2 of 0.977 than the uniform load test with R2 of 0.970. The experiment showed that the on-site elastic moduli of loess and lateritic-loess soils could be accurately estimated from the laboratory load tests.

Multiscale Assessment of Caprock Integrity for Geologic Carbon Storage in the Pennsylvanian Farnsworth Unit, Texas, USA

Leakage pathways through caprock lithologies for underground storage of CO2 and/or enhanced oil recovery (EOR) include intrusion into nano-pore mudstones, flow within fractures and faults, and larger-scale sedimentary heterogeneity (e.g., stacked channel deposits). To assess multiscale sealing integrity of the caprock system that overlies the Morrow B sandstone reservoir, Farnsworth Unit (FWU), Texas, USA, we combine pore-to-core observations, laboratory testing, well logging results, and noble gas analysis. A cluster analysis combining gamma ray, compressional slowness, and other logs was combined with caliper responses and triaxial rock mechanics testing to define eleven lithologic classes across the upper Morrow shale and Thirteen Finger limestone caprock units, with estimations of dynamic elastic moduli and fracture breakdown pressures (minimum horizontal stress gradients) for each class. Mercury porosimetry determinations of CO2 column heights in sealing formations yield values exceeding reservoir height. Noble gas profiles provide a “geologic time-integrated” assessment of fluid flow across the reservoir-caprock system, with Morrow B reservoir measurements consistent with decades-long EOR water-flooding, and upper Morrow shale and lower Thirteen Finger limestone values being consistent with long-term geohydrologic isolation. Together, these data suggest an excellent sealing capacity for the FWU and provide limits for injection pressure increases accompanying carbon storage activities.

Evaluation of the Diametrical Core Deformation and Discing Analyses for In-Situ Stress Estimation and Application to the 4.9\xa0km Deep Rock Core from the Basel Geothermal Borehole, Switzerland

The in situ state of rock mass stresses is a key design parameter, e.g., for deep engineered geothermal systems. However, knowledge of the stress state at great depths is sparse mostly because of the lack of possible in situ tests in deep boreholes. Among different options, core-based in situ stress estimation may provide valuable stress information though core-based techniques have not yet become a standard. In this study we focus on the Diametrical Core Deformation Analysis (DCDA) technique using monzogranitic to monzonitic rock drill cores from 4.9 km depth of the Basel-1 borehole in Switzerland. With DCDA the maximum and minimum horizontal stress (SHmax and Shmin) directions, and the horizontal differential stress magnitudes (∆S) can be estimated from rock cores extracted from vertical boreholes. Our study has three goals: first, to assess photogrammetric core scanning to conduct DCDA; second, to compare DCDA results with borehole breakout and stress-induced core discing fracture (CDF) data sets; and third, to investigate the impact of rock elastic anisotropy on ∆S. Our study reveals that photogrammetric scanning can be used to extract reliable core diametrical data and CDF traces. Locally aligned core pieces showed similar SHmax orientations, conform to borehole breakout results. However, the variability of core diametrical differences was large for the Basel-1 core pieces, which leads to a large spread of ∆S. Finally, we demonstrate that core elastic anisotropy must be considered, requiring robust estimates of rock elastic moduli, to receive valuable stress information from DCDA analyses.