Measurement Of Elastic Modulus Research Articles

Collaborative Research on Adhesion Strength of Thermal Barrier Coatings in JSMS

This paper introduces the brief summary of the recent collaboration test results on thermal barrier coatings (TBCs) in the JSMS Subcommittee, which covers the measurements of elastic modulus, tensile strength, residual stress and thermal conductivity of the TBC specimens. Here, the round-robin TBC specimens consisting of 8% yttria stabilized zirconia, CoNiCrAlY alloy bond coat and Ni-base superalloy were prepared by plasma spraying method. The isothermal exposure and the thermal cycles were applied to the TBC specimens by several conditions at high temperatures, to measure both the residual stress and the remaining adhesion strength of the ceramic top, as well as to characterize the thermally grown oxide at the top coat/bond coat interface. The round-robin test results clearly demonstrated that the adhesion strength was significantly changed by the application of thermal cycles and the isothermal exposure. Of particular important results was found in the remaining adhesion strength that were strongly dependent on the testing method to give the thermal cycles.

MICROSTRUCTURE AND PHYSICAL PROPERTIES OF QUARG CHEESE AS AFFECTED BY DIFFERENT HEAT TREATMENTS

ABSTRACT The effects of different heat treatments on the rheological properties, microstructure and yield of production of quarg cheese were investigated. Three levels of time–temperature combination were used: 72C–16 s, 82C–5 min, 90C–5 min. Rheological properties were studied by means of frequency sweep experiment with the measurement of elastic modulus (G′). Microstructures of samples were observed by scanning electron microscopy (SEM). Maximum and minimum G′ and cheese yield were obtained at 90 and 72C, respectively (P < 0.05). Yield at 82 and 90C was higher than 72C but difference between heat treatment at 82 and 90C was not significant (P < 0.05). G′ values at 82 and 90C were higher than that at 72C. The difference between 82 and 90C was initially low; subsequently increase in frequency made G′ at 90C higher than 82C. SEM micrographs of samples at 82 and 90C were closely similar and no differences were observed between them. Micrographs showed the regular microstructure with branched clusters and numerous small pores at 82 and 90C, whereas micrographs of heat treatment at 72C had larger protein aggregates and fewer but larger pores. This study showed that heat treatments at 82 and 90C were more suitable for quarg cheese making than that at 72C. PRACTICAL APPLICATIONS Quarg cheese is one of the most popular acid-coagulated cheeses. This study shows that heat treatment at 82C–5 min is preferred for quarg production compared with other heat treatments. Contribution of denatured whey proteins in gel network led to higher cheese-making yield as well as high nutrition value. Heat treatment at 82C is also suggested in economic and energy consumption aspect.

Mechanical damping in nanostructured Nd 60Fe 30Al 10 magnetic alloys

Nanostructured Nd 60Fe 30Al 10 magnetic alloys were obtained by melt spinning at a tangential wheel speed of 5 m/s. Magnetic and stress relaxation processes were investigated in the as cast condition. Low frequency mechanical spectroscopy studies (dynamic elastic torsion modulus and internal damping measurements) were conducted at fixed frequencies between 0.1 and 1 Hz, in the range [150–480 K]. The low temperature internal damping and dynamic elastic modulus exhibited a large heating–cooling hysteresis and two damping peaks: one due to a stress induced relaxation mechanism operating near 200 K [1 Hz] and another one, at about 260–270 K, which could not be correlated with any step in the modulus, indicating that it is not anelastic in origin. The high temperature damping was described by an exponential background and a broad peak contribution centered at about 400 K (1 Hz). The resulting maximum is frequency dependent, but it is little sensitive to applied fields up to 30 mT. On contrary, the elastic modulus behavior associated to this maximum resulted largely affected by frequency, the external fields and the magnetic state of the sample.

Formation of nanocomposites during annealing of amorphous Fe-P-V alloys

Annealing-induced nanocrystallization in amorphous Fe79.3P18.2V2.5 and Fe76.8P18.2V5 alloys has been studied using Mossbauer spectroscopy, X-ray diffraction, and elastic modulus and internal friction measurements. The annealing temperature has been optimized for producing nanocomposites. The alloy containing 2.5 at % V, free of paramagnetic phases, is shown to possess better magnetic properties in comparison with the alloy containing 5 at % V, in which a large percentage, up to 22 vol %, of paramagnetic phases was found.

Influence of visco-elasto-plastic properties of magnetite on the elastic modulus: Multicyclic indentation and theoretical studies

In the present work, we study the indentation behaviour of the magnetite coexisting with hematite in a natural dual-phase crystal. In particular we show the influence of cycling indentation conditions on the elastic modulus measurement in relation to the visco-elasto-plastic properties of the material. Elastic properties of Fe 3O 4 are investigated using Oliver and Pharr's technique, which is based on depth-sensing indentation (DSI) analysis. Depending on the visco-elasto-plastic properties of the material, the indentation test conditions ( monotonic, cyclic, loading and unloading rates, dwell time at peak load, …) can modify the shape of the load–depth curve and, subsequently, the results. Molecular dynamics simulation based on shell model potential, is used to determine elastic quantities including elastic modulus, bulk modulus and Young modulus.

Surface dilatational rheology measurements for oil/water systems with viscous oils

This work presents an application of the capillary pressure tensiometry (CPT) for accurate measurements of the surface dilatational elastic and loss moduli of the interface between water and transparent oil phases with viscosities up to 10,000 mPa s. Surface rheological studies involving viscous oils are not possible with other available methods due to the considerable bulk viscous forces. Theoretical estimations show that successful measurements with such systems are possible by using a suitable frequency range of the oscillating spherical drop method by CPT. Measurements with oils having viscosities between 5 and 10,000 mPa s at a frequency smaller than 1 Hz were performed using the oil as outer phase and the aqueous surfactant solution as inner (drop) phase. As predicted by the theory the measured surface elastic modulus did not depend on the viscosity (within experimental accuracy). Three different approaches to account for the contribution of the bulk shear viscosity to the measured pressure signal were analyzed and applied. The results showed that if exact numerical corrections are used the calculated loss modulus also did not depend on the viscosities of the bulk phases. The two other methods used lead to errors, sometimes significant.

High temperature shear modulus determination using a laser-ultrasonic surface acoustic-wave device

For radioactive thin specimens in high pressure or high temperature environments, the conventional approach for high precision elastic modulus measurements is not easy. Radiation damage to transducer’s bonds or the substantial changes in specimen dimensions induced by temperature, pressure, and phase transitions, reduce the intrinsic accuracy of the time-of-flight acoustic measurements. We describe here an alternative approach in which the surface acoustic-wave (SAW) velocity is measured directly with a fixed propagation distance, independent of specimen dimensions. Then, using the known relationship between SAW and shear velocities, it is possible to obtain the shear modulus with a high accuracy without measuring the bulk shear wave. Laser ultrasonics was used combining a pulsed laser source with a heterodyne interferometer. The proposed technique is validated for Al, Au, Ta, and Pb 0.8% Ca, TA6V4 without phase transitions, and for Sn and Co through the phase transitions.

The solid–fluid transition in a yield stress shear thinning physical gel

We present an experimental investigation of the solid–fluid transition in a yield stress shear thinning physical gel (Carbopol® 940) under shear. Upon a gradual increase of the external forcing, we observe three distinct deformation regimes: an elastic solid-like regime (characterized by a linear stress–strain dependence), a solid–fluid phase coexistence regime (characterized by a competition between destruction and reformation of the gel), and a purely viscous regime (characterized by a power law stress-rate of strain dependence). The competition between destruction and reformation of the gel is investigated via both systematic measurements of the dynamic elastic moduli (as a function of stress, the amplitude, and temperature) and unsteady flow ramps. The transition from solid behavior to fluid behavior displays a clear hysteresis upon increasing and decreasing values of the external forcing. We find that the deformation power corresponding to the hysteresis region scales linearly with the rate at which the material is being forced (the degree of flow unsteadiness). In the asymptotic limit of small forcing rates, our results agree well with previous steady state investigations of the yielding transition. Based on these experimental findings, we suggest an analogy between the solid–fluid transition and a first-order phase transition, e.g., the magnetization of a ferro-magnet where irreversibility and hysteresis emerge as a consequence of a phase coexistence regime. In order to get further insight into the solid–fluid transition, our experimental findings are complemented by a simple kinetic model that qualitatively describes the structural hysteresis observed in our rheological experiments. The model is fairly well validated against oscillatory flow data by a partial reconstruction of the Pipkin space of the material’s response and its nonlinear spectral behavior.

Thickness dependence of nanofilm elastic modulus

Young’s modulus is a fundamental physical parameter that determines not only the mechanic but also the electronic properties of a solid thin film. In here, we show that the elastic modulus is not a constant as that of conventional treatment but varies with film thickness. Scaling behavior is found based on the theoretical analysis of the free energy of surface-to-volume ratio of the film and results of the elastic modulus measurement. It has been shown that there exists some film thickness hb when the surface energy of the film comes into play. The hb is inverse proportional to the bulk Young’s modulus and depends strongly on the in-plain strain ε0 as ε0−2. For Si nanofilms, the variation of dimensionless elastic modulus Ψ=E/Ebulk with the dimensionless film thickness η=h/hb can be represented in the following form: Ψ=η0.226. The present investigation illustrates the importance of the effect of dimensionality on the basic parameter of a thin film as well as providing important implications for electronic devices, in particular for the Si-based strained nanodevices.

Measurement of the hyperelastic properties of 44 pathological ex vivo breast tissue samples

The elastic and hyperelastic properties of biological soft tissues have been of interest to the medical community. There are several biomedical applications where parameters characterizing such properties are critical for a reliable clinical outcome. These applications include surgery planning, needle biopsy and brachtherapy where tissue biomechanical modeling is involved. Another important application is interpreting nonlinear elastography images. While there has been considerable research on the measurement of the linear elastic modulus of small tissue samples, little research has been conducted for measuring parameters that characterize the nonlinear elasticity of tissues included in tissue slice specimens. This work presents hyperelastic measurement results of 44 pathological ex vivo breast tissue samples. For each sample, five hyperelastic models have been used, including the Yeoh, N = 2 polynomial, N = 1 Ogden, Arruda–Boyce, and Veronda–Westmann models. Results show that the Yeoh, polynomial and Ogden models are the most accurate in terms of fitting experimental data. The results indicate that almost all of the parameters corresponding to the pathological tissues are between two times to over two orders of magnitude larger than those of normal tissues, with C11 showing the most significant difference. Furthermore, statistical analysis indicates that C02 of the Yeoh model, and C11 and C20 of the polynomial model have very good potential for cancer classification as they show statistically significant differences for various cancer types, especially for invasive lobular carcinoma. In addition to the potential for use in cancer classification, the presented data are very important for applications such as surgery planning and virtual reality based clinician training systems where accurate nonlinear tissue response modeling is required.

Wrinkle-Based Measurement of Elastic Modulus of Nano-Scale Thin Pt Film Deposited on Polymeric Substrate: Verification and Uncertainty Analysis

Wrinkle-based measurement of elastic modulus for a nano-scale thin film was analyzed. As a demonstrative example, the wrinkles of Pt films on a Polydimethylsiloxane (PDMS) substrate under compressive loading were formed with a well-defined wavelength, corresponding to the difference of elastic moduli between the films and substrates. The elastic modulus of the Pt nano-scale thin film measured with the wrinkle-based measurement was found to be consistent with that independently measured with micro-tensile test. Uncertainty of the wrinkle-based measurement was analyzed to figure out the main uncertainty components for the evaluation of elastic modulus measurement, and guidelines for the reliable wrinkle-based measurement were suggested.

Contact-resonance atomic force microscopy for nanoscale elastic property measurements: Spectroscopy and imaging

Quantitative measurements of the elastic modulus of nanosize systems and nanostructured materials are provided with great accuracy and precision by contact-resonance atomic force microscopy (CR-AFM). As an example of measuring the elastic modulus of nanosize entities, we used the CR-AFM technique to measure the out-of-plane indentation modulus of tellurium nanowires. A size-dependence of the indentation modulus was observed for the investigated tellurium nanowires with diameters in the range 20–150 nm. Over this diameter range, the elastic modulus of the outer layers of the tellurium nanowires experienced significant enhancement due to a pronounced surface stiffening effect. Quantitative estimations for the elastic moduli of the outer and inner parts of tellurium nanowires of reduced diameter are made with a core–shell structure model. Besides localized elastic modulus measurements, we have also developed a unique CR-AFM imaging capability to map the elastic modulus over a micrometer-scale area. We used this CR-AFM capability to construct indentation modulus maps at the junction between two adjacent facets of a tellurium microcrystal. The clear contrast observed in the elastic moduli of the two facets indicates the different surface crystallography of these facets.

Preparation and mechanical characterization of dense and porous zirconia produced by gel casting with gelatin as a gelling agent

A modified gel casting procedure based on a natural gelatin for food industry and commercial polyethylene spheres as pore formers was successfully exploited to produce dense and porous ceramic bodies made of yttria stabilized tetragonal zirconia polycrystal (Y-TZP). Vickers and Knoop microhardness, elastic modulus and fracture toughness measurements on dense samples obtained by experimental investigation closely matched results found in the literature for similar materials. However, after a careful analysis of obtained results, no indentation size effect and a lower scattering of experimental data from low load indentations were observed, in comparison with literature. Mechanical testing of porous samples (with reproducible values of porosity of about 40%) evidenced a high scattering of compressive strength values, suggesting that the uneven distribution of cavities in the material or the presence of defects from the agglomeration of pore forming agents could have a more direct influence on the mechanical properties of such materials than the absolute value of porosity.

Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS

This article focuses on the rheological, mechanical and optical properties of polydimethylsiloxane (PDMS) relevant for microelectromechanical systems (MEMS). In view of the limited amount of published data, we analyzed the two products most commonly used in MEMS, namely RTV 615 from Bayer Silicones and Sylgard 184 from Dow Corning. As far as rheological parameters are concerned, the viscosity and spin curves were measured. With regard to mechanical properties, we focused on the measurement of the inconstant elastic modulus up to 115% strain. For the optical characterization we concentrate on the optical dispersion and the wavelength-dependent damping coefficient.

Critical issues in making small-depth mechanical property measurements by nanoindentation with continuous stiffness measurement

Experiments were performed on a (100) copper single crystal to examine the influences that small displacement oscillations used in continuous stiffness measurement techniques have on hardness and elastic-modulus measurements in nanoindentation experiments. For the commonly used 2-nm oscillation, significant errors were observed in the measured properties, especially the hardness, at penetration depths as large as 100 nm. The errors originate from the large amount of dynamic unloading that occurs in materials like copper that have high contact stiffness resulting from their high modulus-to-hardness ratios. A simple model for the loading and unloading behavior of an elastic–plastic material is presented that quantitatively describes the errors and can be used to partially correct for them. By correcting the data in accordance with model and performing measurements at smaller displacement oscillation amplitudes, the errors can be reduced. The observations have important implications for the interpretation of the indentation size effect.

Novel techniques for nanomechanical characterization

Due to increased resolution in experimental capabilities and the development of materials at small geometric and microstructural length scales, novel techniques for mechanical characterization at the micrometer and submicrometer length scale have been a major focus of many experimental and computational studies in recent years. Perhaps the most widely used nanomechanical characterization technique of the past 20 years is nanoindentation. Conventionally used to make elastic modulus and hardness measurements at depths at the nanometer length scale, this technique has been applied to thin fi lms and bulk structures of various material classes, from hard ceramics to biological tissues. New methodologies beyond nanoindentation have been developed in order to better mimic classical mechanical tests at the micrometer scale, specifi cally microtensile and microcompression testing. Furthermore, the development of coupling these micro-mechanical measurements to other characterization techniques applied at equivalent length scales has allowed a more comprehensive picture of deformation behavior of materials. It is not always clear, however, how such techniques can be appropriately applied to outstanding questions within the materials community. Sometimes a new technique becomes popular and is applied to problems without careful examination of the inherent artifacts of the method and the assumptions used in the subsequent analyses. In turn, it is important for the materials community to debate the applicability of such techNovel Techniques for Nanomechanical Characterization

Digital recordings of gas-vesicle collapse used to measure turgor pressure and cell–water relations of cyanobacterial cells

The gas vesicles of the cyanobacterium Microcystis sp. collapse under pressures ranging from 0.65–1.10 MPa, determined from turbidity changes in a pressure nephelometer. In turgid cells, collapse occurs at a lower range of pressures; the difference is equal to the cell turgor pressure. The turgor pressure decreases, however, as gas vesicles collapse; this decrease is minimised by calculating the turgor pressure in samples with few of their gas vesicles collapsed. Previously, pressure and turbidity were measured in discrete steps, using analogue meters, or continuously, using chart recorders: turgor pressure was calculated from the mean or median collapse pressures. We describe modifications allowing continuous digital recording; the output was modelled with polynomial or sigmoid functions, the latter providing the best fit over the full collapse-pressure curve; turgor pressure could then be calculated for any point on the collapse-pressure curve. The shape of the collapse-pressure curve was affected by the rate of pressure rise; curves were similar to those from step-wise methods when the pressure was raised at approximately 4 kPa s − 1 . Under a rapid, almost instantaneous, rise in pressure there was a larger initial decrease in turgor and from the subsequent recovery the hydraulic conductivity of the cell surface could be calculated; the new method gave improved measurements of the cell volumetric elastic modulus. Following collapse of half the gas vesicles, cells recovered their full turgor pressure after 3 h. This suggests turgor homeostasis. These methods are applicable to other bacteria with gas vesicles, including Escherichia coli, if it could be genetically modified to express transgenic gas vesicles.

Hybrid theoretical, experimental and numerical study of vibration and buckling of composite shells with scatter in elastic moduli

Hybrid theoretical, experimental and numerical method is proposed for free vibration and buckling of composite shell with unavoidable scatter in elastic moduli. Based on the Goggin’s measurement techniques, the elastic moduli for material T300-QY8911 are measured, and a set of experimental points are obtained. The measurements of elastic moduli are quantified by either (1) the smallest ellipsoid and (2) the smallest four-dimensional uncertainty hyper-rectangle. Then uncertainty propagation in vibration and buckling problems of composite shell by ellipsoidal analysis and interval analysis are, respectively, studied from the theoretical standpoint. Comparison between these analyses is performed numerically.

A particle-based model for the transport of erythrocytes in capillaries

Abstract This paper presents a two-dimensional (2D) particle-based model for the red blood cell, and uses it to compute cell deformation in simple shear and pressure-driven flows. The cell membrane is replaced by a set of discrete particles connected by nonlinear springs; the spring law enforces conservation of the membrane area to a high accuracy. In addition, a linear bending elasticity is implemented using the deviation of the local curvature from the innate curvature of the biconcave shape of a resting red blood cell. The cytoplasm and the external liquid are modeled as homogeneous Newtonian fluids, and discretized by particles as in standard smoothed particle hydrodynamics (SPH) solution of the Navier–Stokes equations. Thus, the discrete particles serve not only as a numerical device for solving the partial differential equations, but also as a means for incorporating microscopic physics into the model. Numerically, the fluid flow and membrane deformation are computed, via the particle motion, by a two-step explicit scheme. The model parameters are determined from experimental measurements of cell viscosity and elastic moduli for shear, areal dilatation and bending. In a simple shear flow, the cell typically deforms to an elongated shape, with the membrane and cytoplasm undergoing tank-treading motion. In a Poiseuille flow, the cell develops the characteristic parachute shape. These are consistent with the experimental observations. Comparison with prior computations using continuum models shows quantitative agreement without any fitting parameters, which is taken to be a validation of the particle-based model and the numerical algorithm.

Determination of elastic modulus of a beam by using electronic speckle pattern interferometry

This paper proposes a sonic resonance test for an elastic modulus measurement which is based on the electronic speckle pattern interferometry. Previous measurement technique of elastic constant has the limitation of application for thin film or polymer material because contact to specimen affects the result. It has been developed as a non-contact optical measurement technique which can visualize resonance vibration mode shapes with whole field. The maximum vibration amplitude at each vibration mode shape is a clue to find the resonance frequencies. The dynamic elastic constant of test material can be easily determined from vibration of a beam equation using the measured resonance frequencies. The proposed technique is able to give high accurate elastic modulus of materials through a simple experimental set-up and analysis. The experimental result also compared to the theoretical result.