Measurement Of Elastic Modulus Research Articles

In Vivo Optical Coherence Elastography Unveils Spatial Variation of Human Corneal Stiffness.

The mechanical properties of corneal tissues play a crucial role in determining corneal shape and have significant implications in vision care. This study aimed to address the challenge of obtaining accurate in vivo data for the human cornea. We have developed a high-frequency optical coherence elastography (OCE) technique using shear-like antisymmetric (A0)-mode Lamb waves at frequencies above 10 kHz. By incorporating an anisotropic, nonlinear constitutive model and utilizing the acoustoelastic theory, we gained quantitative insights into the influence of corneal tension on wave speeds and elastic moduli. Our study revealed significant spatial variations in the shear modulus of the corneal stroma on healthy subjects for the first time. Over an age span from 21 to 34 (N = 6), the central corneas exhibited a mean shear modulus of 87 kPa, while the corneal periphery showed a significant decrease to 44 kPa. The central cornea's shear modulus decreases with age with a slope of -19 +/- 8 kPa per decade, whereas the periphery showed non-significant age dependence. The limbus demonstrated an increased shear modulus exceeding 100 kPa. We obtained wave displacement profiles that are consistent with highly anisotropic corneal tissues. Our approach enabled precise measurement of corneal tissue elastic moduli in situ with high precision (<7%) and high spatial resolution (<1 mm). Our results revealed significant stiffness variation from the central to peripheral corneas. The high-frequency OCE technique holds promise for biomechanical evaluation in clinical settings, providing valuable information for refractive surgeries, degenerative disorder diagnoses, and intraocular pressure assessments.

Controlling diurnal flower-opening time by manipulating the jasmonate pathway accelerates development of indica-japonica hybrid rice breeding.

Inter-subspecific indica-japonica hybrid rice (Oryza sativa) has the potential for increased yields over traditional indica intra-subspecies hybrid rice, but limited yield of F1 hybrid seed production (FHSP) hinders the development of indica-japonica hybrid rice breeding. Diurnal flower-opening time (DFOT) divergence between indica and japonica rice has been a major contributing factor to this issue, but few DFOT genes have been cloned. Here, we found that manipulating the expression of jasmonate (JA) pathway genes can effectively modulate DFOT to improve the yield of FHSP in rice. Treating japonica cultivar Zhonghua 11 (ZH11) with methyl jasmonate (MeJA) substantially advanced DFOT. Furthermore, overexpressing the JA biosynthesis gene OPDA REDUCTASE 7 (OsOPR7) and knocking out the JA inactivation gene CHILLING TOLERANCE 1 (OsHAN1) in ZH11 advanced DFOT by 1- and 2-h respectively; and knockout of the JA signal suppressor genes JASMONATE ZIM-DOMAIN PROTEIN 7 (OsJAZ7) and OsJAZ9 resulted in 50-min and 1.5-h earlier DFOT respectively. The yields of FHSP using japonica male-sterile lines GAZS with manipulated JA pathway genes were significantly higher than that of GAZS wildtype. Transcriptome analysis, cytological observations, measurements of elastic modulus and determination of cell wall components indicated that the JA pathway could affect the loosening of the lodicule cell walls by regulating their composition through controlling sugar metabolism, which in turn influences DFOT. This research has vital implications for breeding japonica rice cultivars with early DFOT to facilitate indica-japonica hybrid rice breeding.

High-throughput measurement of elastic moduli of microfibers by rope coiling

There are many fields where it is of interest to measure the elastic moduli of tiny fragile fibers, such as filamentous bacteria, actin filaments, DNA, carbon nanotubes, and functional microfibers. The elastic modulus is typically deduced from a sophisticated tensile test under a microscope, but the throughput is low and limited by the time-consuming and skill-intensive sample loading/unloading. Here, we demonstrate a simple microfluidic method enabling the high-throughput measurement of the elastic moduli of microfibers by rope coiling using a localized compression, where sample loading/unloading are not needed between consecutive measurements. The rope coiling phenomenon occurs spontaneously when a microfiber flows from a small channel into a wide channel. The elastic modulus is determined by measuring either the buckling length or the coiling radius. The throughput of this method, currently 3,300 fibers per hour, is a thousand times higher than that of a tensile tester. We demonstrate the feasibility of the method by testing a nonuniform fiber with axially varying elastic modulus. We also demonstrate its capability for in situ inline measurement in a microfluidic production line. We envisage that high-throughput measurements may facilitate potential applications such as screening or sorting by mechanical properties and real-time control during production of microfibers.

Determination of Young’s Modulus of PET Sheets from Lamb Wave Velocity Measurement

BackgroundThe elastic modulus of polyethylene terephthalate (PET) sheets is typically measured through destructive tests that require specific sample preparation and time-consuming testing procedures.ObjectiveTo improve the efficiency of measuring the elastic modulus of PET sheets, research on a non-destructive measurement approach using guided Lamb waves was conducted.MethodsIn this approach, the group velocity of the zero-order symmetric Lamb wave mode (S0 mode) at a single frequency is first measured from PET sheets. The semi-analytical finite element method (SAFEM) is used as the forward model to calculate the corresponding numerical group velocity. Particle swarm optimisation (PSO) is used to update the elastic modulus in the SAFEM model until the numerical group velocity from the model matches the experimental results.ResultsThe results show that measuring the group velocity data at a single frequency is sufficient for elastic modulus measurement while the material thickness can be assumed as a constant, which improves the efficiency of the measurement. The identified modulus differs from the tensile modulus of the material due to the frequency dependence of the elastic modulus. However, this discrepancy could be eliminated by using a linear regression model.ConclusionsThe method mentioned above can achieve non-destructive and efficient measurement of the elastic modulus of PET sheets, which can potentially be applied for in-line quality inspection in PET bottle production processes.

Icephobic Coating Based on Epoxy/Polydimethylsiloxane Interpenetrating Polymer Network Gel

Ice accretion endangers the safety and reliability of equipment operation in frigid regions. Silicone polymer icephobic coatings present themselves as an effective strategy. However, they face durability challenges, which is a crucial foundation for expanding their application. In this work, a durable icephobic coating was prepared based on an epoxy/polydimethylsiloxane (PDMS) interpenetrating polymer network (IPN) gel. In the process, epoxy was used to improve mechanical performance. IPN technology was used to integrate PDMS and epoxy. Low-molecular-weight silicone oil was used to adjust the elastic modulus of the coating by reducing crosslinking. The mechanical properties, icephobicity and durability of the coatings were characterized through elastic modulus measurements, ice adhesion strength tests, and icing/deicing cycle tests, respectively. Results shows the ice adhesion strength of the epoxy/PDMS IPN gel coating was approximately 8 kPa when the elastic modulus was 0.18 MPa. Additionally, the epoxy/PDMS IPN gel has good durability, weather resistance, and substrate adhesion. After 25 icing/deicing cycle tests, the coating remained undamaged, and the ice adhesion strength was stable in the range of 3–14 kPa. Within the range of −5 to −30 °C, the ice adhesion strength of the coating was stable and less than 20 kPa. After 168 h of salt spray aging test, the ice adhesion strength of the coating was maintained at 48.72 ± 5.27 kPa. This can provide a reference for an icephobic coating design.

An intravascular optical coherence tomography technique for in vivo carotid intima-media thickness measurement and mechanical characterization

Arterial characteristic parameters including the intima-media thickness (IMT), strain, strain rate, elastic modulus, and compliance may be unevenly distributed due to local lesion growth. Thus, a combination of the full-field distribution of these parameters may provide more effective guidance for the diagnosis and treatment of vascular diseases than either one of them. Here, we develop an intravascular coherence tomography (IVOCT) based full-field measurement method to characterize the mechanical properties of carotid artery in vivo. Image processing methods are proposed based on U-Net model and centroid detection for accurate IMT measurement. The strain, strain rate, incremental elastic modulus and volumetric compliance are obtained based on the geometric changes of intima-media. Ex vivo silica gel phantom tests demonstrate the accuracy of the vascular wall segmentation by the U-Net based method is greater than 92%, and the error for elastic modulus measurement is less than 2%. A porcine carotid artery was imaged by IVOCT in vivo, and the IMT and the mechanical characteristics during cardiac cycle were measured. The proposed method facilitates the study of the uneven pathological evolution of the vascular wall and provides an effective measurement method for the study of vascular mechanical properties in vivo.

Mechanical Properties and High Temperature Performance of Sustainable Reactive Powder Concrete Containing Waste Glass

At present, it is a challenge to produce a high performance reactive powder concrete (RPC) from local available materials due to the least costly components of a conventional concrete are eliminated by more expensive elements such as the silica fume and steel fibers. In the other hand, million tons of glass is being dumped every year all over the world. More than 75% of glass composition is basically silica and reported to having a pozzolanic reaction. Thus, glass is potentially suitable material as replacement materials for the RPC mixture. In our work, waste glass powder (WGP) was used to completely replace silica fume. Compressive strength, splitting tensile strength, flexural strength and elastic modulus measurements were reported along with the density and colour of the RPC produced. The highlight of this study is on the assessment of the RPC at high temperature tested by direct burning at 600˚C. This had addressed to a very limited reported finding on the high temperature performance of RPC utilizing waste materials. It was found that, RPC containing waste glass powder changes the colour of RPC from darkish grey to light grey. Adding waste glass powder had reduced the density of RPC by (0.05) gm/cm3. Using waste glass powder instead of silica fume had also improves the mechanical properties of RPC. However, there is no effect of adding waste glass powder in solving the spalling problem of RPC at high temperature up to 600˚C. This paper reports finding on the mechanical properties and high temperature performance of sustainable RPC that utilize waste glass powder in total replacement for the silica fume. This is carried out as an effort to address the high cost of the material used in the ordinary RPC and to enhance the recycling of local waste glass.

High strain rate mechanical behavior of Ti-6Al-4V with micro–macro correlation under compressive loading

The application of Ti6Al4V in lightweight structures subjected to impact loads necessitates a comprehensive understanding of its dynamic response under high strain rates to ensure the safety and reliability of these components. In this paper, the macroscopic compressive mechanical behavior of Ti6Al4V under high strain rates was investigated through the split-Hopkinson pressure bar (SHPB) technique at both room temperature and 200 °C, followed by microstructure analysis of the compressed specimens, carried out employing a combination of optical microscopy (OM) and electron backscatter diffraction (EBSD), and elastic modulus and hardness measurements, performed by a nanoindentation instrument. At room temperature, both the modulus and strain hardening exponent of Ti6Al4V exhibited an initial increase before the strain rate reached 1000s-1, after which they decreased at 3400s-1. Meanwhile, the flow stress continued to rise with increasing strain rate. Microscopic observations revealed that twinning played a substantial role in the strain hardening effects. Notably, the basal slip system of the hcp (hexagonal close packed) α phase did not display a more favorable trend, while the c+a type slip systems became more active. Under a strain rate of 5000s-1, discontinuous dynamic recrystallization emerged as the dominant mechanism, resulting in an increased frequency of low-angle grain boundaries, as well as a reduction in grain size and dislocation density. These results provide a basis for explaining the mechanical behavior of Ti6Al4V under high strain rates and offer insights for the establishment of material models that take into account microstructure deformation mechanisms.

Evaluation of heat resistance of SiC-based ceramic fibers via in situ elastic modulus and electrical conductivity measurement at elevated temperatures

SiC-based ceramic fibers have numerous applications as reinforcement materials. Herein, the in situ thermal stability of four types of SiC-based ceramic fibers from three generations was investigated in terms of elastic modulus and electrical conductivity at temperatures up to 1800 °C in a vacuum under low pressure (<10–4 Pa). A specific tensile test device (MacaSiC) for single fibers was used. Mechanical and physical properties were monitored during heating and cooling at 1200, 1500, and 1800 °C for 10 min. Fibers exposed at 1200, 1500, and 1800 °C for 10 min were evaluated by measuring tensile strength retention, and correlating them with fiber crystallinity and microstructural evolution. Third-generation fibers exhibited excellent thermal stability at temperatures up to 1800 °C. The strength degradation of the third-generation SiC fibers was associated with the enlargement of apparent β-SiC crystallites and carbonization caused by the release of Si in the annular region of the fibers.

Numerical analysis of bending property of bi-modulus materials and a new method for measurement of tensile elastic modulus

Numerical analysis of bending property of bi-modulus materials and a new method for measurement of tensile elastic modulus

Investigation of the surface layer of wheel steel by indentation method

The article considers methods of measurement of microhardness and modulus of elasticity of plasma hardened wheel steel by kinetic indentation method. It provides features of measurement of microhardness, modulus of hardness, elastic recovery, influencing on wear resistance of surface layers of steel. Measurement of these characteristics of material allows estimating and choosing optimum technology of surface modification by surface plasma hardening. It is confirmed that objectivity of determination of microhardness, modulus of elasticity, elastic recovery and flow stress depends on strict observance of imprint depth requirements depending on thickness of hardened layer. It is noted that in spite of the increased amount of factual information, obtained by indentation method, the physical substantiation of hardness micro-mechanisms remains poorly understood, which necessitates substantiation of physical representations of the nature of hardness of metallic materials. It is established that the measurement of microhardness, elastic modulus and elastic recovery by the kinetic indentation method is expedient to use for certification of the surface layer of plasma-hardened wheel steel according to the parameters of physical and mechanical characteristics.

Microscopic computed tomography aided finite element modelling as a methodology to estimate hygroexpansion coefficients of wood: a case study on opposite and compression wood in softwood branches

Abstract Microscopic X-ray computed tomography (XµCT) aided finite element (FE) modelling is a popular method in material science to relate material properties to heterogeneous microstructures. Recently, a methodology was developed for the XµCT aided FE modelling of wood, which characterises the process from specimen preparation to estimation of material properties. In the current research, this methodology is tested on branches of Norway spruce (Picea abies (L.) Karst.) to estimate the hygroexpansion coefficients of opposite (OW) and compression wood (CW). These properties are largely unknown and have engineering implications. The study is complemented by measurements of density, moisture content (MC) and elastic moduli. Results showed that the methodology assisted in the design of an integrated process and the identification of bottlenecks. It was seen that the level of detail of the numerical model had a strong influence on the obtained hygroexpansion properties. CW from branches showed higher density and longitudinal shrinkage coefficients, and elastic moduli less affected by MC. These differences are unlikely caused by MC, but more likely by the characteristics of the microstructure.

Acute brain slice elastic modulus decreases over time

A common benchmark in the brain tissue mechanics literature is that the properties of acute brain slices should be measured within 8 h of the experimental animal being sacrificed. The core assumption is that—since there is no substantial protein degradation during this time—there will be no change to elastic modulus. This assumption overlooks the possibility of other effects (such as osmotic swelling) that may influence the mechanical properties of the tissue. To achieve consistent and accurate analysis of brain mechanics, it is important to account for or mitigate these effects. Using atomic force microscopy (AFM), tissue hydration and volume measurements, we find that acute brain slices in oxygenated artificial cerebrospinal fluid (aCSF) with a standard osmolarity of 300 mOsm/l experience rapid swelling, softening, and increases in hydration within the first 2 hours after slicing. Reductions in elastic modulus can be partly mitigated by addition of chondroitinase ABC enzyme (CHABC). Increasing aCSF osmolarity to 400 mOsm/l does not prevent softening but may hasten equilibration of samples to a point where measurements of relative elastic modulus are consistent across experiments.

Mechanical Properties of Uncured Thermoset Tow Prepreg: Experiment and Finite Element Analysis

This paper presents an experimental analysis of the tensile behavior of unidirectional carbon/epoxy prepreg, focusing on the nonlinearity observed at the beginning of the stress–strain curve. Due to the material’s high viscosity, securely holding specimens during testing was challenging, prompting modifications in the gripping method to ensure reliable data. By using a longer gauge length, the slippage impact on elastic modulus measurement was minimized, resulting in good repeatability among the test samples. Experimental findings highlighted the significant interaction between fiber waviness and the viscous matrix, leading to stiffness reduction. The linear stiffness of the samples closely matched that of the fibers and remained unaffected by temperature variations. However, at higher temperatures, the epoxy matrix’s decreased viscosity caused an upward shift in the stiffness plot within the non-linear region. To support the experimental findings, a micromechanical model of prepreg tow with fiber waviness was proposed. An RVE model of periodically distributed unidirectional waved cylindrical fibers embedded within the matrix was developed to predict effective material stiffness parameters. The simulation outcomes aligned well with the uniaxial tensile test of the prepreg tow, demonstrating the proposed RVE model’s capability to accurately predict elastic properties, considering factors like fiber arrangement, waviness, and temperature.

The Effect of Zirconia Nanoparticles on Thermal, Mechanical, and Corrosion Behavior of Nanocomposite Epoxy Coatings on Steel Substrates.

Zirconia (ZrO2) nanoparticles (1-3 wt.%) were incorporated into the epoxy matrix using the ultra-sonication mixing method of dispersion to manufacture nanocomposite coatings. An automatic applicator was used to prepare the coating samples on a stainless steel substrate. The influence of ZrO2 nanoparticles on the physicochemical characteristics of epoxy coatings was evaluated using energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), thermos-gravimetric analysis (TGA), elastic modulus, and micro-hardness measurement with the nano-indentation technique. The corrosion stability during immersion in 3.5% NaCl solution was monitored using electrochemical impedance spectroscopy (EIS). All ZrO2-containing coatings showed better corrosion stability and adhesion than pure epoxy coating. Epoxy coating incorporated with 2% ZrO2 exhibited the greatest values of corrosion resistance and adhesion due to the effect of nanoparticle properties and their better de-agglomeration in the epoxy matrix than pure epoxy coating.

Development of a low-cost non-destructive test system for measurement of elastic modulus

Conventional measurement processes to determine elastic modulus of samples such as tensile or flexural test and bending test are typically unidirectional and destructive in nature for the measured samples. The industrial grade and commercially available Non-Destructive Test (NDT) measurement instrument based on the impulse excitation technique is meanwhile expensive. This project involves designing and developing a low-cost NDT system for the measurement of elastic modulus based on the impulse excitation technique. Secondly, it is to compare the performance of the measurement system with the tensile test. The performance of the NDT prototype will be put to test by using different type of specimens such as aluminium alloy, copper, brass, and carbon steel. Each type of specimen will carry be tested three times to get the average of the data. After all the data collection of the NDT measurement system, the tensile test will be carried out. A comparison for the measurement of the elastic modulus will be conducted between the NDT system, tensile test, and theoretical results. The expected outcome for this project is to develop a NDT for the measurement of the elastic modulus. This project also aims to reduce the industrial waste, reduce the cost of the sample test and maintain the accuracy and the performance of the NDT system compared with the tensile test.

Thermal-Related Stress-Strain Behavior of Alkali Activated Slag Concretes under Compression.

In this paper, the thermal-related stress-strain behavior of alkali-activated slag (AAS) concretes, with different alkali concentrations and moduli, was studied under compression. After exposure to high temperatures (200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C), a compression test was carried out on the specimens. The stress-strain relationship, axial compressive strength, and elastic modulus were expressed using both a displacement extensometer and the digital image correlation (DIC) technique. It was mainly determined that: (1) With the increase in temperature, the stress-strain curves of the AAS concretes tended to be flattened, indicating reductions in both axial compressive strength and elastic modulus. After 1000 °C, only 2.5-3.7% axial compressive strength and 1.4-3.9% elastic modulus remained, respectively. (2) The DIC technique was used for thermal strain measurements of the AAS concrete. Compared to the traditional extensometer, DIC yielded a small error of 4.5% and 7.2% for axial compressive strength and elastic modulus measurements, respectively. The strain cloud chart obtained from DIC was helpful for monitoring the damage process of the specimens. The findings of this paper refined scientific systems of AAS concrete under thermal action, and also provided a newly non-contact approach for thermal strain measurements of AAS concrete under compression.

Continuous Monitoring of Elastic Modulus of Mortars Using a Single-Board Computer and Cost-Effective Components

The Elastic Modulus Measurement through Ambient Response Method (EMM-ARM) is designed to continuously monitor the elastic modulus of hardening construction materials such as concrete, cement paste, mortars, stabilized soils, and epoxy resin. In practice, a composite beam, made of the tested material in its mould, is induced to vibration by means of environmental or controlled excitation, and its resonant frequency is identified. The material’s elastic modulus can then be calculated based on the vibration equation of structural systems. The traditional system to conduct EMM-ARM experiments is based on specialized equipment and on proprietary licensed software, which results in a considerable cost, as well as limited options for customization. The paper hereby presented proposes a delve into the development and validation of a cost-effective and open-source system that is able to conduct EMM-ARM experiments. By using a Raspberry Pi for the computing device and cost-effective electronic components, the cost of the system was one-twentieth of the traditional one, without compromising the measurement reliability. The composite beam’s excitation is generated, while the vibration response is recorded by the proposed system simultaneously, since the Raspberry Pi supports multiprocessing programming techniques. The flexibility earned by the exclusive use of open-source and cost-effective resources creates countless application possibilities for the proposed system.

Multiwell-Pressure History Matching in Delaware Play Helps Optimize Fracturing

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204162, “Multiwell-Pressure History Matching in Delaware Play Helps Optimize Fracturing for Subsequent Pads,” by Roberto Suarez‑Rivera, SPE, and Rohit Panse, W.D. Von Gonten Laboratories, and Javad Sovizi, Baker Hughes, et al. The paper has not been peer reviewed. _ Because hydraulic fracture models include complex physics and uncertainties defined by many variables, the problem of calibrating modeling results with field responses is ill-posed. It is always possible to find a calibrated model that reproduces field data; however, such a model is not unique and multiple matching solutions exist. The objective and scope of the complete paper is to define a work flow for constraining these solutions and obtaining a more-representative model for forecasting and optimization. Introduction In this project, a work flow is presented that uses an ultrafast hydraulic fracturing model with well-known physics and high-confidence rock-property inputs to conduct sensitivity analysis for pad-scale field development. Based on a study of uncertainty on the model variables, the two most-uncertain variables (tectonic strain and leakoff multiplier) are selected for model calibrations. Model results are compared with the field response for all wells and all stages to better understand the discrepancies between the field and the model. Pressure history matching (PHM) is then conducted by adjusting the selected two variables until the global error of all stages and all wells is minimized. The results are nonunique, and uncertainty in the fracture geometry remains high. This can only be reduced by including geometrical constraints from appropriate field measurements. The authors propose that the global response represents the behavior of the entire pad and is unbiased by the behavior of single specific stages. Pad Layout and Model Development The pad in question is in the Delaware Basin and targets two landing zones in the Wolfcamp A formation. The cored well used to generate the geomodel is approximately 2 miles from this pad. Rock-properties modeling was conducted at centimeter-scale resolution using core measurements and petrophysical measurements. These measurements subsequently were integrated with depth-specific measurements of static elastic properties and ultrasonic velocity measurements conducted at elevated stress conditions, representative of the in-situ effective stress. Combining the P- and S-wave velocity and elastic moduli measurements at in-situ stress conditions with the corresponding centimeter-scale resolution velocity measurements along the core surface allowed later correction of in-situ conditions for static-to-dynamic effects and acquisition of centimeter-resolution profiles of anisotropic velocities and corresponding static anisotropic elastic properties along the length of the core. A detailed interface geologic study also was conducted to identify the presence, type, geologic origin, and density of all interfaces present in the core. The core-based measurements provide a high-confidence, high-resolution vertical representation of the reservoir (at the core location). Using multiple wells with consistent field logs and consistent formations tops in the region, a regional geomodel was created for hydraulic fracture modeling. This model possessed a high-confidence representation of the structural geometry of the dominant formations represented in the model. Using these as geometrical boundaries, rock properties were propagated homogeneously along the lateral extent of the model. The authors aim to maintain the model as simply as possible, particularly when no information exists to do otherwise. Their strategy is to start with a simple model, verify the differences between the model and the field measurements, and make changes when necessary if the differences are unacceptable, but not before.

Measurement of Dynamic Elastic Modulus and Poisson’s Ratio of Sugarcane Core by Cantilever Beam Vibration Method

Measurement of Dynamic Elastic Modulus and Poisson’s Ratio of Sugarcane Core by Cantilever Beam Vibration Method