Showing papers on "Young's modulus published in 1990"

Characterization of Elastic Properties of Carbon-Black-Filled Rubber Vulcanizates

Abstract: A novel strain-energy function which is a simple cubic equation in the invariant (I1−3) is proposed for the characterization of the elastic properties of carbon-black-filled rubber vulcanizates. Conceptually, the proposed function is a material model with a shear modulus which varies with deformation. This contrasts with the neo-Hookean and Mooney-Rivlin models which have a constant shear modulus. The variation of shear modulus with deformation is commonly observed with filled rubbers. Initially, the modulus falls with increasing deformation, leading to a flattening of the shear stress/strain curve. At large deformations, the modulus rises again due to finite extensibility of the network, accentuated by the strain amplication effect of the filler. This characteristic behavior of filled rubbers may be described approximately by the proposed strain-energy function by requiring the coefficient C20 to be negative, while the coefficients C10 and C30 are positive. The use of the proposed strain-energy ...

Structural properties of ordered high-melting-temperature intermetallic alloys from first-principles total-energy calculations

Abstract: Intermetallic compounds which are ductile at high temperatures are of great technological interest; however, purely experimental searches for improved intermetallic materials are time consuming and expensive. Theoretical studies can shorten the experimental search by focusing on compounds with the desired properties. While current ab initio density-functional calculations cannot adequately determine material properties at high temperature, it is possible to compute the static-lattice equation of state and elastic moduli of ordered binary compounds. Known correlations between equilibrium properties and high-temperature properties such as the melting temperature can then be used to point the way for experiments. We demonstrate the power of this approach by applying the linear augmented-plane-wave method to the calculation of the equation of state and all of the zero-pressure elastic moduli for SbY in the B1 (NaCl) phase, CoAl and RuZr in the B2 (CsCl) phase, and NbIr in the L${1}_{0}$ (Au-Cu I) phase. The calculated equilibrium lattice constants are all within 2% of the experimentally determined values. The only experimentally known elastic moduli in these systems are the bulk and shear moduli for polycrystalline SbY, CoAl, and NbIr. The predicted bulk moduli are with 7% of experiment. Theory enables us to place limits on the experimental polycrystalline shear modulus. The experimental shear moduli of SbY and CoAl are within our theoretical bounds, but the experimental shear modulus of NbIr is 35% smaller than our lower bound. We stress that in the case of CoAl our calculations provided a prediction for the bulk and shear moduli that were subsequently confirmed by the experiments of Fleischer. We also discuss the band structures and electronic density of states for these materials.

Mechanical properties of nanophase TiO 2 as determined by nanoindentation

Abstract: Nanoindenter techniques have been used to determine the hardness. Young’s modulus, and strain rate sensitivity of nanophase TiO2, which is currently available only in very small quantities and which cannot be tested by most conventional techniques. Hardness and Young’s modulus both increase linearly with sintering temperature over the range 25–900°C but come to within only 50–70% of the single crystal values. Strain rate sensitivity, on the other hand, is measurably greater for this material than for single crystal rutile, and the value of strain rate sensitivity increases as the grain size and the sintering temperature are decreased. In its as-compacted form, the strain rate sensitivity of nanophase TiO2 is approximately a quarter that of lead at room temperature, indicating a potential for significant ductility in these ceramic materials. Finally, a significant scatter in hardness values has been detected within individual nanophase samples. This is interpreted as arising from microstructural inhomogeneity in these materials.

Braided catheter with low modulus warp

Abstract: An intravascular catheter comprises an elongated catheter body having a flexible plastic inner wall, a braided reinforcing mesh surrounding the inner wall and a flexible plastic outer wall surrounding the reinforcing mesh. The braided reinforcing mesh comprises helical members having a high modulus of elasticity and longitudinal warp members having a lower modulus of elasticity.

The structure and mechanical properties of sheets prepared from bacterial cellulose Part 2 Improvement of the mechanical properties of sheets and their applicability to diaphragms of electroacoustic transducers

Abstract: A sheet obtained from bacterial cellulose had a remarkably high modulus of elasticity as reported in Part 1 of this series. The Young's modulus of a sheet prepared by squeezing and drying a gel-like pellicle of bacterial cellulose was found to be >15 GPa. In addition, it has been found that treatment of the gel-like pellicles or dried sheets of bacterial cellulose with alkaline and/or oxidative solutions improves the mechanical properties significantly, and the Young's modulus of the resulting sheets approaches 30 GPa. In this paper, improvement of the mechanical properties of bacterial cellulose sheets by the removal of impurities is investigated and the applicability of bacterial cellulose to diaphragms of electroacoustic transducers is discussed

The yield stress of fibre suspensions

Abstract: Yield stresses were determined for commercial wood pulp suspensions and synthetic fibre suspensions of low and medium mass concentration. The yield stresses measured represent interfibre failure of the network rather than failure between the suspension and a solid surface. The measurements were carried out in a rotary viscometer at low yield stresses and in a concentric rotary shear tester at yield stresses in excess of 2500 Pa. The experimental results were correlated with the volumetric concentration Cv in equations of the form τy = aCbv where a and b are constant for a given fibre type. It was found that b ≃ 3, in agreement with the predictions of a theoretical model of fibre network strength based upon the interlocking of elastically bent fibres. The dependence of the yield stress on the fibre properties of aspect ratio and modulus of elasticity was not adequately predicted by the model, suggesting that fibre bending alone did not account for the network strength over the concentration range studied.

Limits to adherence of oxide scales

Abstract: Strains can cause oxide scales to fracture, often leading to loss of protectiveness and creation of spalling debris. Fracture mechanics is used to identify a number of criteria under which uniform scales may be expected to fail as a result of rapidly applied strains. The failure mode most frequently found occurs when the strain ɛ builds up in the scale until the strain energy density per unit area exceeds the fracture surface energy γ of the oxide. This produces spalling when ɛ>(2·8 γ/hE)1/2, where h is the scale thickness and E is the Young's modulus of the oxide. Two further regimes are identified in thin scales. First, as the external strain is applied to the oxide via the metal substrate, it is obvious that no further stress can be applied to the oxide if the substrate has itself been stressed beyond yield. This condition gives rise to a second regime, that of extended oxide adherence on substrates under external tensile strains in which the oxide cracks and forms a series of islands, but rema...

Correlating schmidt hardness with compressive strength and young’s modulus of carbonate rocks

Abstract: Schmidt hammer has increasingly been used world-wide as an index test for a quick rock strength and deformability characterization. The reason is mainly due to its rapidity and easyness in execution, non destructiveness, simplicity, portability and low cost.

Mechanical Properties of Hardened Cement Paste Exposed to Temperatures up to 700 C (1292 F)

Abstract: Temperatures of significance are identified in the range 20 to 700 C (68 to 1292 F) for changes in strength and elastic modulus both static and dynamic) of unsealed hardened cement paste measured at the various temperaturues as well as after cooling. These changes are correlated with chemical microstructural changes reported in the literature. The beneficial effects of thermal drying and loading, within limits, upon these mechanical properties are observed. It is concluded that these properties are dependent primarily on the maximum temperature of exposure as opposed to the temperature at testing.

The effect of cell size on the mechanical behavior of cellular materials

Abstract: The Young's modulus, strength and fracture toughness, of a brittle reticulated vitreous carbon foam, was measured as a function of cell size at a constant density and compared to a theoretical model Image analysis was used to characterize the macrostructure of the samples and provided a basis for evaluating the mechanical behavior It was determined that both the compressive and bend strength scale inversely with cell size The change in compressive strength is due to a change in the strut strength with cell size The bend strength behavior may be due to a reduction in the critical flaw size, as well as the increasing strut strength at smaller cell sizes The fracture toughness and elastic modulus were found to be independent of cell size Comparison of these results with previous work on open cell alumina clearly indicates a very different behavior and is attributed to a change in the microstructure of the solid phase with cell size in the alumina materials

Tensile properties of short fiber-reinforced SiC/Al composites: Part II. Finite-element analysis

Abstract: The tensile properties of aluminum matrix composites containing SiC whiskers or particulate were investigated analytically and compared to experimental results. Two finite-element models were constructed and used for elastoplastic analysis. In both models, the SiC fibers are represented as longitudinally aligned cylinders in a three-dimensional array. The cylinder ends are transversely aligned in one model and staggered in the other. Using the models, the sensitivity of the predicted composite properties to the deformation characteristics of the matrix alloy was examined, and the general behavior of the models was validated. It was determined that both models are necessary to predict the overall composite stress-strain response accurately. The analytic results accurately predict: the observed composite stress-strain behavior; the experimentally observed increase in Young’s modulus and the work-hardening rate with increasing fiber volume content and aspect ratio; and the decrease and subsequent increase in proportional limit as the SiC volume fraction is increased. The models also predict that the transverse material properties should be insensitive to fiber aspect ratio. In addition, the model predicts the location of initial yielding and the propagation of the plastic region. These results offer insights into the deformation mechanisms of short fiber-reinforced composites.

Prediction of process-induced residual stresses in thermoplastic composites

Abstract: Reference LTC-ARTICLE-1990-001 URL: http://jcm.sagepub.com/ Record created on 2006-06-26, modified on 2016-08-08

Effect of Coarse Aggregate Characteristics on Mechanical Properties of High-Strength Concrete

Abstract: An experimental study investigated the influence of 4 coarse aggregate types available in Northern California on the compressive strength and elastic behavior of a very high-strength concrete mixture. Using identical materials and similar mix proportions, it was found using diabase and limestone aggregates produced concretes with significantly higher strength and elastic modulus than those using granite and river gravel. The mineralogical differences in the aggregate types are considered to be responsible for this behavior.

Microhardness and Young's modulus in cortical bone exhibiting a wide range of mineral volume fractions, and in a bone analogue

Abstract: The relationships between microhardness and mineral content and microhardness and Young's modulus have been determined for cortical bone exhibiting a wide range of mineral volume fractions. These relationships have also been determined for a hydroxyapatite reinforced polyethylene composite which is considered to be an analogue material for bone. Strong nonlinear relationships were found between the variables for both materials. For a given volume fraction of mineral the hardness of the natural bone tissue was found to be considerably higher than that of the analogue material. This was attributed to the different ways in which the mineral phase is bound to the matrix in the two materials. The relationship between microhardness and Young's modulus was similar for both materials. The strength of the relationships found suggest that microhardness data is a viable means of estimating the Young's modulus of specimens that do not easily lend themselves to convential testing procedures.

Hardness, Young's modulus and yield stress in mammalian mineralized tissues

Abstract: The hardness, Young's modulus of elasticity, tensile yield stress, ultimate stress and calcium content of 65 specimens from mammalian long bones and dental tissues were determined. The hardness was a very good predictor of the Young's modulus and yield stress, but a less good predictor of ultimate stress. The relationship in each case was nearly linear. All of these properties have the same type of non-linear relationship to the calcium content of the specimens. Over the range of calcium contents used here, hardness would be a useful guide to the mechanical properties of mineralized tissues in situations where conventional test specimens could not be produced, or where variations in mechanical properties over small distances are of interest.

Young's modulus and damping of Ti6Al4V alloy as a function of heat treatment and oxygen concentration

Abstract: Young's modulus and damping of texture-free Ti6Al4V alloy were evaluated at room temperature by longitudinal resonance vibration tests on cylindrical bars of measured length and density. Damping was determined from the half-width Δf of the resonance peaks. The alloy's properties were evaluated as a function of solution heat treatments between 600 and 1200 °C with subsequent quenching, aging treatments between 200 and 550 °C, and plastic deformation of solution-treated and quenched alloy. The effects of oxygen concentration were determined on identically produced Ti6Al4V alloys but with systematic variation of oxygen concentration between 0.17 and 0.30 wt.% (0.50–0.88 at.%). Heat treatment alone accounts for variations in Young's modulus EO by as much as 10% of the nominal value and in damping by more than an order of magnitude. Interstitial oxygen increases Young's modulus in addition to and independent of heat treatment, according to Ealloy (GPa) = E0 + 13.5 (weight per cent of oxygen) Oxygen was found to have little effect on the damping capacity at room temperature. Low Young's modulus values are obtained when the second phase contains a vanadium enrichment of about 10 wt.% V. In the quenched state the second phase is actually a metastable (β + α″) phase mixture with a very low specific modulus values of about 74 GPa and a high specific damping capacity of 1 × 10−2. The largest damping capacity (Q−1 > 10−3) of the alloy is obtained after solution treatment and quenching (STQ) from 800 °C. High damping is also obtained after STQ from just below 1000 °C. The high damping is believed to arise from anelastic deformation of the second phase when it is present as metastable (β−α″) or (α″−α′) mixtures respectively. The damping capacity of STQ-treated alloys decreases rapidly on aging, even at low aging temperatures of 200°C, to Q−1 values of less than 1 × 10−4.

The effect of variation in structure on the Young's modulus of cancellous bone: a comparison of human and non-human material.

Abstract: The Young's modulus of cubes of human cancellous bone was measured in three orthogonal directions. Apparent density and mineral volume fraction were also measured, as were two architectural variables, fabric and connectivity, which were determined using image analysis techniques. Multiple regression was used to relate the Young's modulus to the four explanatory variables. The results from this study are compared with those obtained from a previous investigation using non-human cancellous bone. The relationships revealed by the two studies are very similar. It was possible to explain approximately 93 per cent of the variance in Young's modulus using the four variables in this present study. Apparent density is the major explanatory variable in both studies and shows a strong correlation with connectivity. In common with the non-human study the measure of fabric is a worthwhile explanatory variable; however, connectivity and mineral volume fraction are relatively unimportant. The four explanatory variables contribute to a successful model for the prediction of Young's modulus. Any other candidate variables are likely to be unimportant or be highly correlated with those already investigated.

Crosslinked biopolymers: Experimental evidence for scalar percolation theory

Abstract: Rheological measurements have been performed on pectin biopolymers close to the sol-gel transition. From these measurements scaling exponents were determined independently for the viscosity, s=0.82(5), for the elastic modulus, t=1.93(8), for the frequency-dependent modulus, \ensuremath{\Delta}=0.71(2), and for the relaxation times below and above the transition, \ensuremath{ u}z=2.67(12) and \ensuremath{ u}z'=2.65(9). The exponents satisfy the scaling relations predicted by the theory and their numerical values agree with those from scalar elasticity percolation. Universal scaling functions were constructed from the data for the complex modulus and the dynamic viscosity.

Laboratory Measurement of Small Strain Shear Modulus Under K0 Conditions

Abstract: A new device to measure the small strain shear modulus (Gmax) under a no lateral strain condition has been developed. The techniques for measuring Gmax are discussed, with emphasis on bender element techniques. The performance of the bender elements are compared with results from simultaneous resonant column tests. An in-depth description of the lateral stress measurement system, the Gmax determination technique, and the measurement of vertical strain is presented along with representative test results to demonstrate the performance of the device.

Tensile and fracture properties of epoxy resin filled with flyash particles

Abstract: The ultimate tensile strength, modulus of elasticity and fracture properties of epoxy resin filled with flyash particles have been evaluated by the tensile test. The tensile strength of epoxy resin filled with flyash particles decreases the fracture properties and the modulus of elasticity increases with increasing percentage of flyash. It is advisable to use flyash when the void formation cannot be controlled effectively.

Strain-rate sensitive behavior of cement paste and mortar in compression

Abstract: The strain-rate sensitivity of the cement paste and mortar constituents of concrete is studied experimentally. Saturated cement paste and mortar specimens are loaded in compression to 15,000 microstrains, 27 to 29 days after casting, using strain rates ranging from 0.3 to 300,000 microstrains/sec. Water-cement ratios of 0.3, 0.4, and 0.5 are used. Strain-rate sensitivity of the material is measured in terms of the initial elastic moduli, maximum stress, and corresponding strain. The initial elastic moduli and the strength of cement paste and mortar increase by 7% and 15%, respectively, with each order of magnitude increase in strain rate. The strain at the maximum stress is the greatest for the lowest strain rate. With an increase in strain rate, the strain at the maximum stress first decreases and then increases.

Effects of structural variation on Young's modulus of non-human cancellous bone.

Abstract: The modulus of elasticity of cubes of cancellous bone, tested in three orthogonal directions, was measured along with apparent density, fabric (measured using image analysis techniques), connectivity and mineral volume fraction. Multiple regression was used to relate Young's modulus and the explanatory variables. The most important explanatory variable was apparent density; fabric was also important. Connectivity was highly correlated with apparent density, and so it is difficult to assign relative weights to these two variables. However, both have a significant, and separate, effect on Young's modulus. The total variance in Young's modulus explained by these three variables was about 85 per cent. This implies that other explanatory variables are either unimportant or highly correlated with the variables listed above. Mineral volume fraction is shown to be an unimportant variable, and arguments are produced why this is to be expected, even though it is highly important in explaining the variation in Young...

Enhancements in Current Density and Mechanical Properties of Y-Ba-Cu-O/Ag Composites

Abstract: A liquid-phase processing method has been developed to manufacture bulk YBa2Cu3Ox/Ag superconducting composites with large current carrying capacity and enhanced mechanical properties. Transport critical current density of 10,000 A/cm2 is obtained in nominal 15 wt.% Ag composite using continuous direct current at 77 K and zero applied field. Using a pulsed current of 2 ms duration, a critical current density of 22,000 A/cm2 is obtained. This composite has a Young's modulus of 100 GPa and a fracture stress of 70 MPa, which are substantially higher than those of sintered 1-2-3 superconductor.

Dependence of the elastic moduli of porous silica gel prepared by the sol-gel method on heat-treatment

Abstract: The elastic moduli of silica gel monolith prepared by the sol-gel method from a tetramethoxysilane solution have been measured before and after heat treatment. The elastic moduli showed a drastic change with heat treatment; for example, Young's modulus changed from 0.95 GPa for the gel before heating to 72.5 GPa for the densified product after heating to 1050 ° C. The change in the Young's modulus of the gel with heating temperature is discussed on the basis of changes of porosity and strength of the silica skeleton.

Mechanical properties of a-C:H films prepared by plasma decomposition of C2H2

Abstract: Diamondlike a‐C:H films have been deposited by decomposition of C2H2. By the combination of Brillouin scattering and the ultralow load indentation technique, the following mechanical properties of the films were studied: the microhardness H, the Young’s modulus E, the shear modulus μ, and the Poisson’s ratio ν. From the measured data of mass density, hydrogen concentration, and the ratio of sp3/sp2 bonds the filling factors of these films were calculated. The results show that the hardness, Young’s modulus, and shear modulus of these films depend strongly on the volume concentration of voids and are directly proportional to the filling factor.