Young's modulus of lignin from a continuous indentation test

The deformation of lignin in a continuous ball indentation test was almost entirely elastic up to a stress of 2.2 × 10⁸ Pa (22 kg mm^–2). The load versus depth of indentation curve of the lignin followed closely the classical Hertz equation thus enabling the Young's modulus of lignin to be calculated. From these results a stress-strain curve for lignin was drawn.Visitor from Mechanical Engineering Department, University of Maryland, College Park, Md 20742, USA.     

Elastic properties of silicon oxynitride

Silicon oxynitride is a refactory material which appears to exhibit good mechanical and thermal properties. This work studies the elastic properties of hot-pressed samples with an addition of 5 wt% MgO. The samples are isotropic and homogeneous, and the three different methods of measurement used, operating in the frequency range 20 kHz to 10 MHz, give similar results. Young's modulus and shear modulus are low (about 22×10¹⁰ Pa and 9×10¹⁰ Pa, respectively), which leads to small thermal stresses and thus allows a good thermal shock resistance. The elastic moduli decrease linearly when the porosity increases over the range of 0 to 27%. Poisson's ratio is sensibly a constant equal to 0.2, and the rate of variation is the same for both moduli: 2.5, this value being superior to what could be expected from the usual theories.     

Stress-strain curve for aluminium from a continuous indentation test

Continuous indentation tests using a 6.35 mm diameter steel ball were carried out on polycrystalline aluminium (99.995%) at forces up to 942 N (96 kg) and a total displacement of 65m. On loading the results were observed to follow the classical Hertz equation until the elastic limit was reached at 4.6±0.2 N (0.47 kg), 1.02±0.05m. The unloading results after plastic indentation were found to fit the Hertz solution for an indenter in a spherical hole. Using the Hertz theory it was possible from the unloading results to determine the mean stress and strain under the ball, together with the indentation diameter, plastic strain, Meyer stress and ratio of elastic to total strain, enabling a stress-strain curve for hardness to be drawn. The elastic limit of aluminium occurred at a stress of 4.7±0.2×10⁸Pa (46kg mm^–2) and a strain of 1.27±.05%. At a total strain of 11.25% the stress was 11.7±0.2×10⁸Pa (115 kg mm^–2).     

Study of the mechanical properties of CeO2 layers with the nanoindentation technique

The mechanical properties of CeO₂ layers that are undoped or doped with other elements (e.g. Zr and Ta) are a topic of special interest specially in the manufacturing of superconductor buffer layers by pulsed electron deposition. Nowadays, the trend is to produce small devices (i.e. coated conductors), and the correct mechanical characterization is critical. In this sense, nanoindentation is a powerful technique widely employed to determine the mechanical properties of small volumes. In this study, the nanoindentation technique allow us determine the hardness (H) and Young's modulus (E) by sharp indentation of different buffer layers to explore the deposition process of CeO₂ that is undoped or doped with Zr and Ta, and deposited on Ni–5%W at room temperature. This study was carried out on various samples at different ranges of applied loads (from 0.5 to 500 mN). Scanning electron microscopy images show no cracking for CeO₂ doped with Zr, as the doping agent increases the toughness fracture of the CeO₂ layer. This system, presents better mechanical stability than the other studied systems. Thus, the H for Zr–CeO₂ is around 2.75 · 10⁶ Pa, and the elastic modulus calculated using the Bec et al. and Rar et al. models equals 249 · 10⁶ Pa and 235 · 10⁶ Pa respectively.     

Deformation and fracture behavior of notched and unnotched unidirectional C/C-Mg composite with Young's modulus 520 GPa and tensile strength 1 GPa

Experimental study on tensile fracture behavior of the newly developed C/C-Mg composite, prepared by infiltration of Mg into the pores in the C/C composite heat-treated at 3000°C, was carried out. The volume fraction of the filled Mg was 9–10%. The composite had a specific density 2.1, Young's modulus 520 GPa and Poisson's ratio 0.26. The average tensile strength measured for the specimen with a nominal width 8 mm, gage length 40 mm and thickness 1 mm was 1 GPa. The Young's modulus was improved from 450 to 520 GPa and the strength from 0.9 to 1.0 GPa by Mg-infiltration. The specific Young's modulus and specific strength based on the average measured values were 2.5 × 10⁷ m and 5 × 10⁴ m, respectively, showing high potential as light-weight, stiff and strong structural material. The strength distribution of the composite was described by the two-parameter Weibull distribution function with a shape parameter 7.6 and scale parameter 1060 MPa. Prior to the overall fracture of the composite, the longitudinal cracking arose at the notch tip, due to which the notch tip was blunted and the ligament portion behaved like an unnotched specimen. As a result, the notched strength could be described by the net stress criterion. The apparent critical energy release rate at formation of the longitudinal crack was around 70–90 J/m².     

Spatial and structural dependence of mechanical properties of porcine intervertebral disc

Structure–function relationship of natural tissues is crucial to design a device mimicking the structures present in human body. For this purpose, to provide guidelines to design an intervertebral disc (IVD) substitute, in this study the influence of the spatial location and structural components on the mechanical properties of porcine IVD was investigated. Local compressive stiffness (LCS) was measured on the overall disc, also constrained between the two adjacent vertebrae: the dependence on the lumbar position was evaluated. The compliance values in the anterior position (A) were higher than both in the central posterior (CP) and in the lateral-posterior (RP, LP) locations. The values of Young's Modulus (74.67±6.03 MPa) and compression break load (1.36×10⁴±0.09×10⁴N) of the disc were also evaluated by distributed compression test. The NP rheological behavior was typical of weak-gels, with elastic modulus G always higher than viscous modulus G all over the frequency range investigated (G and G respectively equal to 320 and 85 Pa at 1 Hz) and with the moduli trends were almost parallel to each other.     

Measurement of Young's modulus and internal friction of an in situ Al-Al3Ni functionally gradient material

An in situ Al-Al₃Ni functionally gradient material (FGM) was produced by centrifugally casting an Al-20 mass% Ni alloy into a thick-walled tube. Four specimens, 90 mm long, with rectangular cross-sections (width × thickness) of 6 × 6, 6 × 5, 6 × 4 and 6 × 3 mm² were machined from the tube such that the thickness direction of the specimens was in the radial direction of the tube. The microstructure of the FGM tube consisted of granular morphology Al₃Ni as a second phase distributed within the aluminium matrix with an increasing volume fraction gradient from the inside to the outside of the tube. Thus, the thicker the specimen, the greater was the composition gradient and the thinner the specimen, the greater was the volume fraction of Al₃Ni. The dependence of the Young's modulus and internal friction on the composition gradient of the FGM was determined by a flexural forced-resonance technique from the resonant frequency and the resonance peak width, respectively, as a function of nominal specimen thickness. The Young's modulus of the Al₃Ni second phase was determined from a correlation plot of assumed Al₃Ni Young's modulus values against the calculated resonant frequency values corresponding to the associated FGM Young's modulus values. The latter were calculated using a rule of mixtures with a fixed matrix Young's modulus and a gradient volume fraction of Al₃Ni for each specimen thickness. By plotting the experimental FGM specimen resonant frequencies on this plot, the average Al₃Ni Young's modulus was found to be 140 GPa. The Young's modulus of the FGM was found to vary between 81.5 and 100.8 GPa across the 6 mm tube-wall thickness from the inner to outer surface, reflecting the 15.2 and 43.2 vol % Al₃Ni second phase, respectively. The measured internal friction increased with the volume fraction of Al₃Ni, and owing to the relatively large Al₃Ni particle size, was thereby dependent on the resultant increase in the second phase-matrix interface number density rather than the dislocation density.     

Effect of hardness on erosion of WC-Co composites

Erosion behaviour of a range of WC-Co composites is investigated using 200 to 500m Al₂O₃ grit normally incident at 140±40 m sec^–1. A simple relation is obtained linking erosion rateW(g g^–1) and hardnessH(M Pa), W = 1.44 × 10¹¹ H ^–3.5. Current erosion models based on indentation fracture mechanics are not found to apply; an explanation is suggested in terms of an indentation size effect.     

Precision tensile testing of small specimens of polysulphur nitride in the scanning electron microscope

Experiments have been carried out using a miniature tensometer in a scanning electron microscope to obtain high-precision mechanical tensile test data on needle-shaped crystals of (SN) _x . Extensions as low as 10 nm can be measured over a gauge length of varied size from a few millimetres down to a few microns. Loads were applied in a range of 0.1–10 N and measured with a sensitivity of 0.006 N. Young's modulus parallel to the chain axis of (SN) _x was measured as 1.3 × 10¹⁰ N m^–2, the crystals yielded at 1.3 × 10⁸ N m^–2 at a strain of 0.9%, tensile strength was determined at 2.1 × 10⁸ N m^–2.     

Methodology for the determination of the interfacial properties of brittle matrix composites

The interfacial properties of a glass-ceramic matrix composite (SiC/CAS) were determined from single-fibre push-out tests using the interfacial test system. The coefficient of friction, , the residual clamping stress, _c, and fibre axial residual stress, _z , were extracted by fitting the experimental stress versus fibre-end displacement curves using the models of Hsueh, and Kerans and Parthasarathy. Using Hsueh's model, the intrinsic interfacial frictional stress (=_c) was found to be 11.1±3.2 MPa, whereas by using Kerans-Parthasarathy's model it was found to be 8.2±1.5 MPa. Comparisons between these models are included, together with a discussion of data analysis techniques.Nomenclature _z Axial fibre residual stress (Pa) - ^* Effective clamping stress (Pa) - _c Residual clamping stress (Pa) - _p Poisson's effect-induced clamping stress (Pa) - _d ⁰ Debond stress in the absence of residual stresses (Pa) - _d Experimental debond stress (Pa) - Compressive applied stress (Pa) - Interfacial shear stress (Pa) - u Fibre-end displacement (m) - h Debond length (m) - r Fibre radius (m) - E _f Fibre Young's modulus (Pa) - E _m Matrix Young's modulus (Pa) - v _f Fibre Poisson's ratio (dimensionless) - v _m Matrix Poisson's ratio (dimensionless) - f Fibre volume fraction (dimensionless) - k Parameter (dimensionless) - D Parameter (dimensionless) - Interfacial coefficient of friction (dimensionless) - G _i Interface toughness (J m^–2) - C _m Load-train compliance (m N^–1)     

Determination of mechanical properties of thermally grown oxide on Fecralloy by nano-indentation

Nano-indentation was used to measure the mechanical properties of the thermally grown oxide (TGO) on a Fecralloy substrate. Due to the influence both of the substrate and the indenter size effect (ISE), the measured hardness and Young's modulus of the TGO system decreased with increasing indentation depth. Models were proposed to determine the mechanical properties of the TGO with consideration of both the substrate effect and the ISE. In addition, the ratio of hardness to Young's modulus (H/E) can be related to the ratio of irreversible work to total work (W_ir/W_t) during the indentation process.     

The distribution of carbonate in enamel and its correlation with structure and mechanical properties

The correlation of carbonate content with enamel microstructure (chemical and crystal structure) and mechanical properties was evaluated via linear mapping analyses by Raman microspectroscopy and nanoindentation. Mappings started at the outer enamel surface and ended in the inner enamel near the dentin-enamel junction (DEJ) in lingual and buccal cervical and cuspal regions. The carbonate peak intensity at 1070 cm⁻¹ gradually increased from outer to inner enamel. Moreover, the phosphate peak width, as measured by the full width at half maximum of the peak at 960 cm⁻¹, also increased, going from ~9 cm⁻¹ in outer enamel to ~13 cm⁻¹ in enamel adjacent to the DEJ, indicating a decrease in the degree of crystallinity of hydroxyapatite from outer to inner enamel. In contrast, Young’s modulus decreased from 119 ± 12 to 80 ± 19 GPa across outer to inner enamel with a concomitant decrease in enamel hardness from 5.9 ± 1.4 to 3.5 ± 1.3 GPa. There were also significant correlations between carbonate content and associated crystallinity with mechanical properties. As carbonate content increased, there was an associated decrease in crystallinity and both of these changes correlated with decreased modulus and hardness. Collectively, these results suggest that enamel carbonate content and the associated change in the crystal structure of hydroxyapatite, i.e., degree of crystallinity, may have a direct effect on enamel mechanical properties. The combination of Raman microspectroscopy and nanoindentation proved to be an effective approach for evaluating the microstructure of enamel and its associated properties.     

The molecular weight dependence of properties of [poly(n-butylamino)2−x (di-allylamino)x]n phosphazenes

Poly(n-butylamino) (di-allylamino) phosphazenes were prepared by the reaction of samples of (NPCl₂)_n having a molecular weight of either 5 × 10⁴ or 10 × 10⁶ with n-butylamine, and di-allylamine. Films were prepared by the casting method, and the molecular weight dependence of properties of the film were determined with an Erma refractometer, an oxygen gas permeater, and a tensilon and reho-vibron-orientec. It was found that the refractive index of the film did not depend on the molecular weight and n-butylamine or di-allylamine contents. Also, the glass transition temperature of the films decreased with increasing di-allylamine content. The oxygen gas permeability D_k value increased with increasing di-allylamine content. However, a plot of the Young's modulus values versus amine contents or D_k values did not produce a straight line. In order to make a film having the highest D_k value, the polymer has to have an antisymmetric structure.     

Solid-state extrusion of nylons 11 and 12: processing,morphology and properties

Monofilaments of poly(11-amino-undecanoic acid) (nylon 11), and poly(laurylactam) (nylon 12) have been produced using solid-state extrusion methods in an Instron capillary rheometer. The resulting morphology, physical and mechanical properties were investigated. For nylon 11, at an extrusion ratio (ER) of 12, the crystalline melting-point temperature increased by 16° C, over the undrawn material, while the per cent crystallinity,X _c, increased by 23%. Nylon 12, extruded to a maximum ER of 6, realized an increase inT _m of 4° C at ER=5 and anX _c increase of 14%. Young's modulus for nylon 11 increased from 3 GPa at an ER=3 to 5.5 GPa at an ER=7 and levelled off at greater ER. For nylon 12, the Young's modulus climbed from 2.5 GPa at ER=3 to about 3.3 GPa at E R=5.5. Conventionally melt-spun and cold-drawn nylon 11 and nylon 12 fibres exhibited Young's modulus values of 2.7 GPa and 2.9 GPa respectively. Atmospheric moisture loss was found not to affect solid-state extrusion of these higher nylons. Increases in extrusion temperature and/or pressure increased the extrusion rate. The flow activation energy of nylon 11 was 73 kcal mol⁻¹ at 0.24 GPa extrusion pressure, and 124 kcal mol⁻¹ at 0.49 GPa extrusion pressure. Calculated apparent viscosities were about 10¹⁴ poise and 10¹⁵ poise, respectively. The morphologies were shown by electron microscopy to be microfibrillar and the resulting monofilaments were transparent to visible light.     

Microhardness studies on calcium hydrogen phosphate (brushite) crystals

Vicker's and Knoop microhardness studies were carried out on grown calcium hydrogen phosphate dihydrate (CaHPO₄·2H₂O) crystals over a load range of 10-50 g. The Vickers (H_V) and Knoop (H_K) microhardness numbers for the above loads were found to be in the range of 94-170 kg/mm² and 28-35 kg/mm² respectively. It was also found that these numbers increased with increase in load. The Mayer's index (n) was found to be greater than 1.6 showing soft-material characteristics. The fracture toughness values (K_c), determined from measurements of crack length, were estimated to be 6 ± 0.5 × 10³ kg m^−3/2 and 4.5 ± 0.5 × 10³ kg m^−3/2 at 25 g and 50 g respectively. The brittleness indices (B_i) were found as 2.3 ± 0.1 × 10⁴ m^−1/2 for 25 g and 3.7 ± 0.1 × 10⁴ m^−1/2 for 50 g. Using Wooster's empirical relation, the elastic stiffness coefficient (c₁₁) has been calculated from Vicker's hardness values as 4.8 ± 0.5 × 10¹⁵ Pa for 10 g, 9.7 ± 0.5 × 10¹⁵ Pa for 25 g and 13.3 ± 0.5 × 10¹⁵ Pa for 50 g. The Young's modulus was calculated as 1.5 ± 0.1 × 10¹⁰ N m⁻² from Knoop microhardness values.     

Fabrication of C/SiC composites by an electrodeposition/sintering method and the control of the properties

Carbon fibre reinforced SiC matrix composites (C/SiC composites) were fabricated using an electrodeposition/sintering method and the control of properties such as flexural strength. Young's modulus and thermal expansion coefficient was investigated in order to fabricate C/SiC-based functionally gradient materials. By means of choosing the condition of electrodeposition and sintering, C/SiC composites with volume fraction of fibre (V _f) ranging from 45 to 78% were fabricated. Maximum flexural strength and Young's modulus were 185 MPa and 47.5 GPa with V _f of 75%, but both properties decreased with the decrease in V _f. Conversely, the thermal expansion coefficient increased with the decrease in V _f; the value varied from 0.2 to 2.75 × 10^–6K^–1.     

Composite materials reinforced with polyoxymethylene whiskers

Various composite samples reinforced with polyoxymethylene (POM) whisker crystals were prepared and their Young's moduli were measured and analysed, on a theoretical equation, to estimate the modulus of the filler itself. Good reinforcement was obtained with matrix resins such as an epoxide and an unsaturated polyester, the results giving the modulus of the whisker to be approximately 1×10¹¹ N m^–2, i.e., almost equivalent to the ideal crystal modulus of POM. Some acoustic properties were investigated for sheet composite materials prepared with a polyolefin polymer for matrix. The sonic velocity attained was more than twice that of the matrix polymer, at larger filler contents, while the internal dynamic loss was maintained at a reasonably high level. Loudspeakers carrying diaphragms of the composite sheets showed improved frequency characteristics in the high-frequency region. Some morphological observations were made for the crystals embedded in resins.     

Stability tests of quadrupole mass spectrometer by two-stage flow-dividing system

Stability tests of two quadrupole mass spectrometers (QMSs) were performed using a two-stage flow-dividing system from the following viewpoints: (1) fluctuation and drift of ion current, (2) repeatability of ion current, (3) change in ion current owing to prior conditions of use, (4) long-term stability of sensitivity, and (5) interference effect. These tests were performed at the pressure from 8 × 10⁻⁶ Pa to 8 × 10⁻⁴ Pa using N₂, Ar, He, and H₂.The fluctuation and drift of two QMSs over 1 h were within 2%. The repeatabilities at pressures of 8 × 10⁻⁶ Pa and 8 × 10⁻⁵ Pa were within 2% during eight cycles with an interval of 1 h between each cycle. However, the repeatability at 8 × 10⁻⁴ Pa increased to be within 4%. The changes in sensitivities of QMS-1 and QMS-2 for 757 days were less than ±15% and less than ±25%, respectively. The change owing to the interference effect was less than 2% while the partial pressure of the interference gas was under 2 × 10⁻⁴ Pa. However, both positive and negative changes were observed less than 60% with increasing the partial pressure of the interference gas until 8 × 10⁻³ Pa.     

Effects of annealing atmosphere on thermoelectric signals from ZnO films

Zinc oxide epilayer films were grown on vicinal cut sapphire substrates by pulsed laser deposition with in situ annealing oxygen pressures varied from 0 to 10 × 10³ Pa. The best crystalline quality was obtained for ZnO layer with annealing oxygen pressure of 6 × 10³ Pa. Laser induced thermoelectric voltage (LITV) were observed along the tilting angle orientation of the substrate when the pulsed KrF excimer laser of 248 nm were irradiated on the films. The largest LITV signal was measured for the film grown at 6 × 10³ Pa annealing oxygen pressure. According to the measured LITV signals, Seebeck anisotropy was evaluated and was found to range from 3 to 12 μV/K for ZnO films annealed at different oxygen pressures from 2 to 10 × 10³ Pa. It is suggested that oxygen ambient plays an important role in the electronic properties of the ZnO films.     

Evaluation method for the adhesion strength of vitreous enamel

A new quantitative evaluation method and the formula for vitreous enamel were proposed. The three-point bending strength was measured by loading on the superposition of test piece which sandwiched glass layer partly between two steel sheets. The adhesion strength () was calculated using the following equation, = 3PLh/2b·Eg/[Egh3 + Es(h3 – h3)]w here, P; bending strength, L; length of span, b; width of glass layer, Eg; Young's modulus of glass, Es; Young's modulus of steel, h; thickness of glass layer, h'; thickness of superposition of test piece. The evaluation method for vitreous enamel of this experiment agreed with the empirical evaluation and may be applied to an actual situation.