Measurement Of Elastic Modulus Research Articles

Monitoring Compliance and Elastic Modulus in a Bioreactor for Optimal Control of Vascular Tissue Growth

Functional vascular tissue engineering aims to produce blood vessels in vitro in a controlled environment named bioreactor. In order to control the growth and remodeling of vascular tissues, suitable measurements should be made on the construct in situ, i.e. during the growth. These measurements will feed the controller with information in order to take efficient control decisions. The non-destructive measurement of compliance or elastic modulus in vitro is a potential indicator of the vascular construct maturity. This work shows that compliance and elastic modulus are related: they can be estimated during the growth of constructs in a bioreactor, and thus provide useful feedback information to the controller.

Preparation and characterization of the simulated burnup americium-containing uranium–plutonium mixed oxide fuel

In order to investigate the effect on fuel thermophysical properties when adding americium and selected fission products to uranium–plutonium mixed oxide (MOX) fuel, simulated low decontamination MOX fuel with high burn-ups to 250 GWd/t, has been prepared and subjected to characterization tests, elastic moduli measurements and melting temperature measurement. Elastic moduli for the simulated low decontamination MOX fuel were almost the same level as fuel without americium and fission products and decrease in the moduli was slight with increasing simulated burn-up. The melting temperature of high burn-up, low decontamination MOX fuel may be estimated by using the findings on the effect of americium, plutonium addition and fission products accumulation.

Morphological and physical evolutions of aramid fibers aged in a moderately alkaline environment

AbstractThe recent use of aramid fibers in geotextiles for ground reinforcement raises fundamental durability issues, in particular in alkaline soils where they are subjected to hydrolysis. To study the degradation mechanisms in such an environment, accelerated aging at pH 9 and at pH 11 has been carried out for up to one and a half years. This work describes the morphological evolutions that occur and the morphology‐properties relationship during aging in moderately alkaline environments. The decreases in apparent density are larger at pH 9 than at pH 11, whereas the bulk chemical degradation is more extensive at pH 11 than at pH 9. Scanning electron microscopy micrographs of chemically etched fibers and the measurements of the local elastic modulus by nanoindentation support these results. Finally, this study has indicated an inverse correlation between the porosity level and the tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Ventricular Fold Phonation: Viscoelastic Properties and HSDI

Objective: Determine the functional biomechanical properties of the human false vocal fold mucosa at phonatory frequencies, in comparison with those of the true vocal fold cover; and to quantify the vibration patterns of ventricular fold phonation with HSDI (high speed digital imaging). Method: Viscoelastic shear properties of false fold specimens were quantified as functions of frequency, with measurements of elastic shear modulus (G′) and dynamic viscosity (h′) at up to 250 Hz using a simple-shear rheometer. Ventricular fold phonation of three subjects was analyzed by HSDI (high speed digital imaging) through kymography and laryngotopography. Results: All specimens showed similar frequency dependence of their viscoelastic properties, with G′ gradually increasing with frequency and h′ monotonically decreasing with frequency. G′ and h′ of the false fold mucosa were generally higher than those of the true vocal fold cover, although the differences did not reach statistical significance. Kymographic and laryngotopographic analysis of high speed digital images revealed vibration of the false fold mucosa for subjects undergoing ventricular fold phonation. The vibratory frequencies were lower than typical fundamental frequencies for phonation. Conclusion: These findings showed false folds could function as a secondary sound source. These preliminary data suggested that the false fold mucosa could serve as replacement material for patients with unrepairable vocal fold cover damage.

Understanding the Soil Contact Problem for the LWD and Static Drum Roller by Using the DEM

The estimation of the elastic soil modulus from many in situ field test devices currently rely on the continuum theory and assumptions about linear elasticity that are somewhat ill-posed. To improve the understanding of in situ field measurement of elastic modulus using intelligent roller compactors and light-weight deflectometers (LWDs), a complete understanding of the contact problems formed through the use of these devices is needed for a wide range of soils. The varying material properties of cohesionless and cohesive soils can have dramatic effects on the assumed stress distributions, contact areas, and surface deformations. Investigations are conducted by using the discrete-element method (DEM) to investigate the relationships between soil properties and the mechanical responses for both plate (simulated LWD) and drum-roller loading. Simulations of purely cohesionless granular soils are shown to exhibit substantially different stress and strain fields compared to simulations of cohesive soils. This ...

Silicon nitride based nanocomposites produced by two different sintering methods

This research explores the use of a variety of carbon nanostructures as reinforcing agents for Si 3N 4 matrix composites. We have chosen highly promising families of carbon materials: multiwall, singlewall carbon nanotubes (MWCNTs, SWCNTs), graphene, carbon black nanograins and graphite micrograins for use as fillers. These materials were dispersed with a concentration of 3 wt% in silicon nitride matrices. A high efficiency attritor mill has also been used for effective dispersion of second phases in the matrix. In the present work the development of sintering processes (hot isostatic pressing (HIP) and spark plasma sintering (SPS)) has been performed to consolidate and tailor the microstructure of Carbon nanotube (CNT)-reinforced silicon nitride-based ceramic composites. The silicon nitride nanocomposite systems retained the mechanical robustness of the original systems. Elastic modulus measurements and micro-indentation investigations of the hardness and fracture toughness have been performed as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction in order to characterize the composites produced by the two sintering methods.

Assessment of chemo-mechanical couplings in polymer matrix materials exposed to thermo-oxidative environments at high temperatures and under tensile loadings

The present paper is concerned with the experimental assessment of chemo-mechanical couplings in a polymer matrix material exposed to thermo-oxidative environments at high temperatures and under pure tensile loadings. A model developed within the thermodynamics of irreversible processes (TIP) states that oxygen reaction–diffusion in the polymer matrix should be affected by the strain tensor and its spatial gradient; the model motivates the design and the development of the experimental assessment, which is done by ultra micro-indentation (UMI) elastic modulus (EIT) measurements carried out – at room temperature – on unnotched and notched 977-2 polymer samples thermo-oxidized under tensile loadings. For the material and the loading conditions of the present research the EIT profiles are not influenced by the applied strain or by the strain gradients which develop close to the sample notches.

Mechanical Property Control of Polyacrylamide Gel Application for Cell Culture in Vitro

In order to construct the in vitro cell culture model occurring in biochemical and biophysical environment in vivo, and to establish quantitative detection and control of mechanical properties of substrate, a low modulus material polyacrylamide hydro-gel (PAHG) was synthesized and used as the substrate material for in vitro cell culture. Using a modified tensile device based on the principles of buoyancy for balance out gravity deformation and by detecting the minor deformation with the aids of computer graphic processing software, the measurement of low elastic modulus (E) of PAHG was established. By analyzing a large number of experimental data, the effect of two key factors (molar ratio of cross-linker/monomer and water content) on elastic modulus was investigated, and the influence of cross-linker/monomer (d) on saturated water content (w) was also discussed. Mathematical model for d, w and E of water saturated gel in vitro cell culture state was built up by regression analysis of experimental data. Based on the model, the d for PAHG with a given elastic modulus in water saturated state was calculated and applied to the synthesis of PAHG. The results showed that the elastic modulus of thus-obtained PAHG in water saturated state is in agreement with the given value with a relative error of 0.025-0.12, suggesting that the mathematical model is applicable for the prediction of properties of low modulus materials.

Wear behaviour and rolling contact fatigue life of Ti/TiN/DLC multilayer films fabricated on bearing steel by PIIID

In order to improve the friction and wear behaviours and rolling contact fatigue (RCF) life of bearing steel materials, Ti/TiN/DLC (diamond-like carbon) multilayer hard films were fabricated onto AISI52100 bearing steel surface by plasma immersion ion implantation and deposition (PIIID) technique. The micro-Raman spectroscopy analysis confirms that the surface film layer possess the characteristic of diamond-like carbon, and it is composed of a mixture of amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds. Atomic force microscope (AFM) reveals that the multilayer films have extremely smooth area, excellent adhesion, high uniformity and efficiency of space filling over large areas. The nanohardness (H) and elastic modulus (E) measurement indicates that the H and E of DLC multilayer films is about 32 GPa and 410 GPa, increases by 190.9% and 86.4%. The friction and wear behaviours and RCF life of DLC multilayer films specimen have also been investigated by ball-on-disc and three-ball-rod fatigue testers. Results show that the friction coefficient against AISI52100 steel ball decreases from 0.92 to 0.25, the longest wear life increases nearly by 22 times. In addition, wear tracks of the PIIID samples as well as wear tracks of the sliding steel ball were analyzed with the help of optical microscopy and scanning electron microscopy (SEM). The L10, L50, La and mean RCF life L of treated bearing samples, in 90% confidence level, increases by 10.1, 4.2, 3.5 and 3.4 times, respectively. Compared with the bearing steel substrate, the RCF life scatter extent of Ti/TiN/DLC multilayer films sample is improved obviously.

Preparation and characterization of Ti-15Mo alloy used as biomaterial

With the increase in life expectancy, biomaterials have become an increasingly important focus of research because they are used to replace parts and functions of the human body, thus contributing to improved quality of life. In the development of new biomaterials, the Ti-15Mo alloy is particularly significant. In this study, the Ti-15Mo alloy was produced using an arc-melting furnace and then characterized by density, X-ray diffraction, optical microscopy, hardness and dynamic elasticity modulus measurements, and cytotoxicity tests. The microstructure was obtained with β predominance. Microhardness, elasticity modulus, and cytotoxicity testing results showed that this material has great potential for use as biomaterial, mainly in orthopedic applications.

Towards a reliable procedure for the measurement of elastic modulus in instrumented indentation

Unloading stiffness is a critical magnitude when extracting elastic modulus in instrumented indentation. Any phenomenon which interacts with its measurement may affect the final calculation of the modulus. Analytical and numerical calculations have been carried out to determine the influence of thermal drift and creep response on its measurement, and the predictions were in good agreement with experimental results. Since the influence of thermal drift is depth-dependent, it determines the effective resolution of an indentation device for a given material. In contrast, indentation creep significantly alters unloading stiffness even for weakly rate-sensitive materials (sensitivity exponent, m < 0.05) but its effect could be smoothed down due to measurement artefacts (unloading curve fitting strategy). For instance, for an ultra-fine grained (UFG) pure niobium at room temperature (m ∼ 0.015 and H/Er ∼ 0.02), the error in the measurement of elastic modulus with a typical nanoindentation procedure (5 s of holding time and 65 s of unloading time) can be as high as 15%. This paper proposes simple rules for a reliable experimental procedure to avoid both thermal drift and creep effects on the measurement of elastic modulus, which are especially relevant for the new generation of high temperature instrumented indentation facilities.

Effect of pressure on the formation of superelastic hard particles in a metal-fullerene system and the tribological properties of composite materials reinforced with such particles

Raman spectroscopy, X-ray diffraction, and microhardness and modulus of elasticity measurements are used to study the influence of compacting pressure (5, 8 GPa) on the structure and properties of the phases prepared from fullerene soot extract (mixture of C60 and C70 crystallites) in a mixture with a cobalt powder. Carbon particles synthesized during high-temperature treatment at a pressure of 5 or 8 GPa and reinforcing composite samples have a universal hardness H u (hardness measured from the total (elastic and plastic) strain under loading) of 12 or 25 GPa, respectively. After heating of samples to 900°C, the values of H u of the particles decrease to 9–11 GPa at elastic recovery of the phase more than 85%. The dry friction coefficients of iron- and cobalt-based composite materials in contact with tool steel are 0.08 and 0.04, respectively.

A multifunctional mechanical Fourier spectrometer

A multifunctional instrument for measuring viscoelastic characteristics of polymeric materials is described. The operational principle of this instrument is based on the method of mechanical Fourier spectrometry. An incoming signal represents white noise that, like an outgoing signal, is expanded into a Fourier series in frequency. The use of a highly sensitive displacement transducer and a high-precision electromagnetic actuator makes it possible to collect spectral functions in a broad frequency range with a fair level of reliability. For the tests of flowable media, deformation is performed so that the test sample is compressed between two plane-parallel plates. In the tests of rubbery and solid samples, loading is accomplished via a three-point bending procedure or deformation of a membrane. The instrument makes it possible to perform tests on small samples (a volume less than 0.25 μl) and solid films with a thickness of 10–300 μm. The interval of complex elastic-modulus measurements ranges from 10 Pa to 50 MPa in the regime of a rheometer and from 10 kPa to 100 GPa in the regime of a solid-body spectrometer. The frequency interval is 0–1 Hz, and the temperature interval ranges from −100 to +300°C under the isothermic regime or under scanning at a heating rate from 0.1 to 10 K/min. Examples of the experimental results are presented.

Ambient and high temperature in situ damage evolution in nickel based IN 718 super alloy

In the present work, Lemaitre's damage assessment methodology has been applied to predict evolution of damage during tensile test at ambient temperature and at 823 K in nickel based IN 718 super alloy. The damage has been evaluated through apparent elastic modulus measurement from each unloading step during the test. Marked difference was found in damage evolution and operative damage micromechanisms at these test temperatures. Critical points have been identified on the damage evolution curves for room temperature loading condition. Based on these parameters, the damage has been predicted using Lemaitre's damage model for high temperature specimen. The damage predicted is found to be in good agreement with experimental curve.

Protein-Directed Assembly of Arbitrary Three-Dimensional Nanoporous Silica Architectures

Through precise control of nanoscale building blocks, such as proteins and polyamines, silica condensing microorganisms are able to create intricate mineral structures displaying hierarchical features from nano- to millimeter-length scales. The creation of artificial structures of similar characteristics is facilitated through biomimetic approaches, for instance, by first creating a bioscaffold comprised of silica condensing moieties which, in turn, govern silica deposition into three-dimensional (3D) structures. In this work, we demonstrate a protein-directed approach to template silica into true arbitrary 3D architectures by employing cross-linked protein hydrogels to controllably direct silica condensation. Protein hydrogels are fabricated using multiphoton lithography, which enables user-defined control over template features in three dimensions. Silica deposition, under acidic conditions, proceeds throughout protein hydrogel templates via flocculation of silica nanoparticles by protein molecules, as indicated by dynamic light scattering (DLS) and time-dependent measurements of elastic modulus. Following silica deposition, the protein template can be removed using mild thermal processing yielding high surface area (625 m(2)/g) porous silica replicas that do not undergo significant volume change compared to the starting template. We demonstrate the capabilities of this approach to create bioinspired silica microstructures displaying hierarchical features over broad length scales and the infiltration/functionalization capabilities of the nanoporous silica matrix by laser printing a 3D gold image within a 3D silica matrix. This work provides a foundation to potentially understand and mimic biogenic silica condensation under the constraints of user-defined biotemplates and further should enable a wide range of complex inorganic architectures to be explored using silica transformational chemistries, for instance silica to silicon, as demonstrated herein.

OS11-1-2 Measurement of Elastic Modulus over Wide Range of Temperature by Impact Sound

OS11-1-2 Measurement of Elastic Modulus over Wide Range of Temperature by Impact Sound

Laboratory Determination of Direct Tensile Strength and Deformability of Intact Rocks

Abstract The direct tensile strength and deformability are determined from dog-bone shaped specimens of intact sandstone, limestone, and marble by using a compression-to-tension load converter. The device allows a measurement of the rock elastic modulus and Poisson’s ratio under uniaxial tensile and compressive stresses on the same specimen. A series of finite difference analyses is performed to obtain a suitable specimen configuration that provides unidirectional tensile stresses at the mid-section of the specimen. The results indicate that the direct tensile strengths are clearly lower than the Brazilian and ring tensile strengths. The elastic moduli and Poisson’s ratios under uniaxial tension are lower than those under uniaxial compression. The discrepancy probably relates to the amount and distribution of the pore spaces and micro-fissures and the bond strength of cementing materials. The porous and relatively poor-bonding sandstone shows a greater difference between the tensile and compressive elastic moduli and Poisson’s ratios compared to those of the dense and well-bonding marble and limestone.

OS11F032 Measurement of Elastic Modulus over Wide Range of Temperature by Impact Sound

OS11F032 Measurement of Elastic Modulus over Wide Range of Temperature by Impact Sound

Evaluation of fibrinogen self-assembly: role of its αC region.

Exposure of cryptic, functional sites on fibrinogen upon its adsorption to hydrophobic surfaces of biomaterials has been linked to an inflammatory response and fibrosis. Such adsorption also induces ordered fibrinogen aggregation which is poorly understood. To investigate hydrophobic surface-induced fibrinogen aggregation. Contact and lateral force scanning probe microscopy, yielding topography, image dimensions and fiber elastic modulus measurements were used along with transmission and scanning electron microscopy. Fibrinogen aggregation was induced under non-enzymatic conditions by adsorption on a trioctyl-surface monolayer (trioctylmethylamine) grafted onto silica clay plates. A more than one molecule thick coating was generated by adsorption on the plate from 100 to 200 μg mL⁻¹ fibrinogen solutions, and three-dimensional networks formed from 4 mg mL⁻¹ fibrinogen incubated with uncoated or fibrinogen-coated plates. Fibrils appeared laterally assembled into branching and overlapping fibers whose heights from the surface ranged from approximately 3 to 740 nm. The elastic modulus of fibrinogen fibers was 1.55 MPa. No fibrils formed when fibrinogen lacking αC-domains was used as a coating or was incubated with intact fibrinogen-coated plates, or when the latter plates were sequentially incubated with anti-Aα529-539 mAb and intact fibrinogen. When an anti-Aα241-476 mAb was used instead, fine, long fibers formed. Similarly, sequential incubations of fibrinogen-coated plates with recombinant αC-domain (Aα392-610 fragment) or αC-connector (Aα221-372 fragment) and fibrinogen resulted in distinctly fine fiber networks. Adsorption-induced fibrinogen self-assembly is initiated by a more than one molecule-thick surface layer and eventuates in three-dimensional networks whose formation requires fibrinogen with intact αC-domains.

Rheometric properties of canine vocal fold tissues: Variation with anatomic location

Objective To evaluate the in vitro rheometric properties of the canine vocal fold lamina propria and muscle at phonatory frequencies, and their changes with anatomic location. Methods Six canine larynges were harvested immediately postmortem. Viscoelastic shear properties of anterior, middle, and posterior portions of the vocal fold cover (lamina propria) as well as those of the medial thyroarytenoid (TA) muscle (vocalis muscle) were quantified by a linear, controlled-strain simple-shear rheometer. Measurements of elastic shear modulus ( G′) and dynamic viscosity ( η′) of the specimens were conducted with small-amplitude sinusoidal shear deformation over a frequency range of 1–250 Hz. Results All specimens showed similar frequency dependence of the viscoelastic functions, with G′ gradually increasing with frequency and η′ decreasing with frequency monotonically. G′ and η′ of the canine vocalis muscle were significantly higher than those of the canine vocal fold cover, and η′ of the canine vocal fold cover was significantly higher than that of the human vocal fold cover. There were no significant differences in G′ and in η′ between different portions of the canine vocal fold cover. Conclusion These preliminary data based on the canine model suggested that the vocalis muscle, while in a relaxed state in vitro, is significantly stiffer and more viscous than the vocal fold cover during vibration at phonatory frequencies. For large-amplitude vocal fold vibration involving the medial portion of the TA muscle, such distinct differences in viscoelastic properties of different layers of the vocal fold should be taken into account in multi-layered biomechanical models of phonation.