Showing papers on "Ultimate tensile strength published in 1998"

Design and mechanical properties of new β type titanium alloys for implant materials

Abstract: Pure titanium and Ti–6Al–4V alloy have been mainly used as implant materials. V-free titanium alloys like Ti–6Al–7Nb and Ti–5Al–2.5Fe have been then developed because toxicity of V has been pointed out. Al- and V-free titanium alloys as implant materials have been developed. Most of them are, however, α+β type alloys. β type titanium alloys with lower moduli of elasticity and greater strength have been developed recently. Design of new β type titanium alloys composed of non-toxic elements like Nb, Ta, Zr, Mo or Sn with lower moduli of elasticity and greater strength were, therefore, studied based on the d-electron alloy design method, and the basic mechanical properties of designed alloys of button ingots melted by tri-arc furnace in the laboratory were investigated in this study. β type alloys, Ti–Nb–Ta–Zr, Ti–Nb–Ta–Mo and Ti–Nb–Ta–Sn system alloys designed in this study are expected to have greater performance for implant materials. The Young's moduli of these alloys are lower compared with that of Ti–6Al–4V ELI which has been used as an implant material. The alloys on which some heat treatments have been conducted offer suitable tensile properties as implant materials. The tensile strength and elongation of designed alloys in this study are equivalent or greater than required values already reported.

Introduction to Composite Materials Design

Abstract: Introduction Basic Concepts The Design Process Composites Design Methods Design for Reliability Fracture Mechanics Materials Fiber Reinforcements Fiber-Matrix Compatibility Fiber Forms Matrix Materials Thermoset Matrices Thermoplastic Matrices Creep, Temperature, and Moisture Corrosion Resistance Flammability Manufacturing Processes Hand Lay-up Pre-preg Lay-up Bag Molding Autoclave Processing Compression Molding Resin Transfer Molding Vacuum Assisted Resin Transfer Molding Pultrusion Filament Winding Micro-mechanics Basic Concepts Stiffness Moisture and Thermal Expansion Strength Ply Mechanics Coordinate Systems Stress and Strain Stress-Strain Equations Off-axis Stiffness Macro-mechanics Plate Stiffness and Compliance Computation of Stresses Common Laminate Types Laminate Moduli Design Using Carpet Plots Hygro-thermal Stresses (*) Strength Lamina Failure Criteria Laminate First Ply Failure Laminate Strength Strength Design Using Carpet Plots Stress Concentrations (*) Damage Continuum Damage Mechanics Longitudinal Tensile Damage Longitudinal Compression Damage Transverse Tension and In-plane Shear Fabric-reinforced Composites Weave Pattern Description Analysis Tow Properties Element Stiffness and Constitutive Relationship Laminate Properties Failure Analysis Woven Fabrics with Gap Twill and Satin Randomly Oriented Reinforcement Beams Preliminary Design Thin Walled Beams Plates and Stiffened Panels Plate Bending Plate Buckling Stiffened Panels Shells Shells of Revolution Cylindrical Shells with General Loading Strengthening of Reinforced Concrete Strengthening Design Materials Flexural Strengthening of RC Beams Shear Strengthening Beam-column Appendices Bibliography

Stress-induced fragmentation of multiwall carbon nanotubes in a polymer matrix

Abstract: We report the observation of single nanotube fragmentation, under tensile stresses, using nanotube-containing thin polymeric films. Similar fragmentation tests with single fibers instead of nanotubes are routinely performed to study the fiber-matrix stress transfer ability in fiber composite materials, and thus the efficiency and quality of composite interfaces. The multiwall nanotube-matrix stress transfer efficiency is estimated to be at least one order of magnitude larger than in conventional fiber-based composites.

On the micromechanics of crushable aggregates

Abstract: This paper presents a study of the micromechanical behaviour of crushable soils. For a single grain loaded diametrically between flat platens, data are presented for the tensile strengths of particles of different size and mineralogy. These data are shown to be consistent with Weibull statistics of brittle fracture. Triaxial tests on different soils of equal relative density show that the dilatational component of internal angle of friction reduces logarithmically with mean effective stress normalized by grain tensile strength. The tensile strength of grains is also shown to govern normal compression. For a sample of uniform grains under uniaxial compression, the yield stress is related to the average grain tensile strength. If particles fracture such that the smallest particles are in geometrically self-similar configurations under increasing geotoscopic stress, with a constant probability of fracture, a fractal geometry evolves with the successive fracture of the smallest grains, in agreement with the a...

Axially Loaded Concrete-Filled Steel Tubes

Abstract: This paper presents an experimental and analytical study on the behavior of short, concrete-filled steel tube columns concentrically loaded in compression to failure. Fourteen specimens were tested to investigate the effect of the steel tube shape and wall thickness on the ultimate strength of the composite column. Confinement of the concrete core provided by the tube shape was also addressed. Depth-to-tube wall thickness ratios between 17

A characterization of first-generation flowable composites

Abstract: A plethora of new low-viscosity composite resin materials, or flowable composites, have been marketed during the last two years, but little has been published about them. The authors describe research in which they compared the properties--filler, depth or cure, flow, wear, compressive strength, diametral tensile strength, indented biaxial flexure strength and toughness--of flowable and hybrid composites. Mechanical property tests (ISO 4049, ISO/DIS 6872) of eight flowable composites and two hybrid composites were conducted. The flowable composite with the least flow was similar to traditional composites. Mechanical properties were generally about 60 to 90 percent of those of conventional composites. The authors conclude that flowable materials should be used with caution in high-stress applications for restorative dentistry.

Test environments and mechanical properties of Zr-base bulk amorphous alloys

Abstract: The mechanical properties of two Zr-base bulk amorphous alloys (BAA), Zr-10Al-30Cu-5Ni (BAA-10) and Zr-10Al-5Ti-17.9Cu-14.6Ni (BAA-11), were studied by both tensile and compressive tests at room temperature in various test environments. The BAA ingots up to 7 mm in diameter were successfully produced by both arc melting and drop casting and induction melting and injection casting. The BAA specimens deformed mainly elastically, followed by catastrophic failure along shear bands. Examination of the fracture region revealed ductile fracture features resulting from a substantial increase in temperature, which was attributable to the conversion of the stored elastic strain energy to heat. Surprisingly, “liquid droplets” located at major shear-band cracks adjacent to the fracture section were observed, indicating the occurrence of local melting during fracture. The angle orientation of shear bands, shear-band cracks, and fracture surfaces relative to the stress axis is quite different for BAA specimens tested in tension and compression. This suggests that both shear stress and normal stress may play a role in developing shear bands during plastic deformation. The tensile properties of BAAs were found to be insensitive to the test environment at room temperature. However, the reaction of BAAs with distilled water and heavy water was detected by laser desorption mass spectrometry (LDMS). These results suggest that moisture-induced hydrogen embrittlement in BAAs may be masked by catastrophic fracture following shear bands.

Brittle and Ductile Behavior in Carbon Nanotubes

Abstract: Large-scale molecular dynamics simulations were used to study the response of carbon nanotubes to a tensile load. Plastic or brittle behaviors can occur depending upon the external conditions and tube symmetry. All tubes are brittle at high strain and low temperature, while at low strain and high temperature armchair $(n,n)$ nanotubes can be completely or partially ductile. In zigzag $(n,0)$ tubes ductile behavior is expected for tubes with $nl14$, while larger tubes are completely brittle. In both cases the curvature determines the mechanical response.

Mechanical properties and morphology of impact modified polypropylene-wood flour composites

Abstract: The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene–ethylene/butylene–styrene triblock copolymer (SEBS–MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM–MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1–1 μm. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1503–1513, 1998

Porosity of Ceramics: Properties and Applications

Abstract: Introduction to the microstructural dependence of properties introduction to, and perspective on, the porosity dependence of properties porosity dependence of elastic properties at low to moderate temperatures porosity dependence of fracture energy and toughness, and related crack propagnation at 22C porosity dependence of tensile strength and reliability at low to moderate temperatures porosity dependence of hardness, compressive strength, wear and related properties at low to moderate temperatures porosity dependence of thermal and electrical conductivities and other nonmechanical properties at low to moderate temperatures porosity dependence of mechanical and other physical properties of related materials at 22C porosity dependence of properties at higher temperatures, including effects of porosity on thermal shock summary of porosity dependence, NDE, applications and engineering of porous ceramics.

High-strength alkali-resistant sintered SiC fibre stable to 2,200 °C

Abstract: The high-temperature stability of SiC-based ceramics has led to their use in high-temperature structural materials and composites1,2,3 In particular, silicon carbide fibres are used in tough fibre-reinforced composites Here we describe a type of silicon carbide fibre obtained by sintering an amorphous Si–Al–C–O fibre precursor at 1,800 °C The fibres, which have a very small aluminium content, have a high tensile strength and modulus, and show no degradation in strength or change in composition on heating to 1,900 °C in an inert atmosphere and 1,000 °C in air — a performance markedly superior to that of existing commercial SiC-based fibres such as Hi-Nicalon Moreover, our fibres show better high-temperature creep resistance than commercial counterparts We also find that the mechanical properties of the fibres are retained on heating in air after exposure to a salt solution, whereas both a representative commercial SiC fibre and a SiC-based fibre containing a small amount of boron were severely degraded under these conditions4 This suggests that our material is well suited to use in environments exposed to salts — for example, in structures in a marine setting or in the presence of combustion gases containing alkali elements

Material characterization of human medial collateral ligament

Abstract: The objectives of this study were to determine the longitudinal and transverse material properties of the human medial collateral ligament (MCL) and to evaluate the ability of three existing constitutive models to describe the material behavior of MCL. Uniaxial test specimens were punched from ten human cadaveric MCLs and tensile tested along and transverse to the collagen fiber direction. Using load and optical strain analysis information, the tangent modulus, tensile strength and ultimate strain were determined. The material coefficients for each constitutive model were determined using nonlinear regression. All specimens failed within the substance of the tissue. Specimens tested along the collagen fiber direction exhibited the typical nonlinear behavior reported for ligaments. This behavior was absent from the stress-strain curves of the transverse specimens. The average tensile strength, ultimate strain, and tangent modulus for the longitudinal specimens was 38.6 +/- 4.8 MPa, 17.1 +/- 1.5 percent, and 332.2 +/- 58.3 MPa, respectively. The average tensile strength, ultimate strain, and tangent modulus for the transverse specimens was 1.7 +/- 0.5 MPa, 11.7 +/- 0.9 percent, and 11.0 +/- 3.6 MPa, respectively. All three constitutive models described the longitudinal behavior of the ligament equally well. However, the ability of the models to describe the transverse behavior of the ligament varied.

Specimen size effect on tensile strength of surface-micromachined polycrystalline silicon thin films

Abstract: A new tensile tester using an electrostatic-force grip was developed to evaluate the tensile strength and the reliability of thin-film materials. The tester was constructed in a scanning electron microscope (SEM) chamber for in situ observation and was applied for tensile testing of polycrystalline silicon (poly-Si) thin films with dimensions of 30-300 /spl mu/m long, 2-5 /spl mu/m wide, and 2 /spl mu/m thick. It was found that the mean tensile strengths of nondoped and P-doped poly-Si are 2.0-2.8 and 2.0-2.7 GPa, respectively, depending on the length of the specimens, irrespective of the specimen width. Statistical analysis of these size effects on the tensile strength predicted that the location of the fracture origin was on the edge of the specimen, which was Identified by the SEM observation of the fracture surface of the thin films.

Short jute fiber‐reinforced polypropylene composites: Effect of compatibilizer

Abstract: Jute fibers were chopped to approximately 100 mm in length and then processed through a granulator having an 8-mm screen. Final fiber lengths were up to 10 mm maximum. These fibers along with polypropylene granules and a compatibilizer were mixed in a K-mixer at a fixed rpm, 5500, and dumped at a fixed temperature, 390°F, following single-stage procedure. The fiber loadings were 30, 40, 50, and 60 wt %, and at each fiber loading, compatibilizer doses were 0, 1, 2, 3 and 4 wt %. The K-mix samples were pressed and granulated. Finally, ASTM test specimens were molded using a Cincinnati injection molding machine. At 60% by weight of fiber loading, the use of the compatibilizer improved the flexural strength as high as 100%, tensile strength to 120%, and impact strength (unnotched) by 175%. Remarkable improvements were attained even with 1% compatibilizer only. Interface studies were carried out by SEM to investigate the fiber surface morphology, fiber pull-out, and fiber–polymer interface. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 329–338, 1998

Specimen Size Effect on Tensile Strength of Surface-Micromachined Polycrystalline

Abstract: A new tensile tester using an electrostatic-force grip was developed to evaluate the tensile strength and the reliability of thin-film materials. The tester was constructed in a scanning electron microscope (SEM) chamber for observation and was applied for tensile testing of polycrystalline silicon (poly-Si) thin films with dimensions of 30-300 m long, 2-5 m wide, and 2 m thick. It was found that the mean tensile strengths of nondoped and P-doped poly-Si are 2.0-2.8 and 2.0-2.7 GPa, respectively, depending on the length of the specimens, irrespective of the specimen width. Statistical analysis of these size effects on the tensile strength predicted that the location of the fracture origin was on the edge of the specimen, which was identified by the SEM observation of the fracture surface of the thin films. (283)

Bamboo fiber-reinforced polypropylene composites: A study of the mechanical properties

Abstract: A new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested. To enhance the adhesion between the bamboo fiber and the polypropylene matrix, maleic anhydride-grafted polypropylene (MAPP) was prepared and used as a compatibilizer for the composite. The maleic anhydride content of the MAPP was 0.5 wt %. It was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the tensile strength, and the impact strength all increased significantly. The new composite has a tensile strength of 32–36 MPa and a tensile modulus of 5–6 GPa. Compared to the commercially available wood pulp board, the new material is lighter, water-resistant, cheaper, and more importantly has a tensile strength that is more than three times higher than that of the commercial product. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1891–1899, 1998

A new conception on the toughness of nylon 6/silica nanocomposite prepared via in situ polymerization

Abstract: A novel method, in situ polymerization, was used for the preparation of nylon 6/silica nanocomposites, and the mechanical properties of the nanocomposites were examined. The results showed that the tensile strength, elongation at break, and impact strength of silica-modified nanocomposites exhibited a tendency of up and down with the silica content increasing, while those of silica-unmodified nanocomposites decreased gradually. It also exhibited that the mechanical properties of silica-modified nanocomposites have maximum values only when 5% silica particles were filled. Based on the relationship between impact strength of the nanocomposites and the matrix ligament thickness τ, a new criterion was proposed to explain the unique mechanical properties of nylon 6/silica nanocomposites. The nylon 6/silica nanocomposites can be toughened only when the matrix ligament thickness is less than τc and greater than τa, where τa is the matrix ligament thickness when silica particles begin to aggregate, and τc is the critical matrix ligament thickness when silica particles begin to toughen the nylon 6 matrix. The matrix ligament thickness, τ, is not independent, which related with the volume fraction of the inorganic component because the diameter of inorganic particles remains constant during processing. According to the observation of Electron Scanning Microscope (SEM), the process of dispersion to aggregation of silica particles in the nylon 6 matrix with increasing of the silica content was observed, and this result strongly supported our proposal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 789–795, 1998

Cell morphology and property relationships of microcellular foamed pvc/wood‐fiber composites

Abstract: Wood-fiber composites make use of cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness than neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and impact strength. Since microcellular plastics exhibit a higher impact strength, higher toughness, and increased fatigue life compared to unfoamed plastics, microcellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microcellular foamed PVC/wood-fiber composites with unique cell morphology and material composition are characterized. Microcellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO2 under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microcellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microcellular foamed PVC/wood-fiber composites are most sensitive to changes in the cell morphology and the surface modification of fibers.

Silkworm silk as an engineering material

Abstract: While silk exhibits high values of tensile strength and stiffness, these properties are compromised by their poor reproducibility. We present the results of experiments aimed at characterizing the variability of tensile properties exhibited by cocoon silk from Bombyx mori silkworms. Scanning electron microscopy is used to measure an average diameter for individual test specimens; the interspecimen variability of diameter is quantified and found to be inadequately represented by standard deviation. When load-extension data are converted into stress-strain curves, a marked improvement in reproducibility is realized if each specimen cross-section is calculated from diameter measurements specific to that specimen. Nevertheless, a significant variability in fracture stress remains; a Weibull analysis reveals that silkworm silk has a failure predictability comparable with that of glass and nonengineering ceramics. Unloading/reloading tests demonstrate that stiffness is not significantly affected by cumulative deformation, and the stress–strain relationship is not sensitive to strain rate. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2439–2447, 1998

Mechanical properties of silica aerogels

Abstract: Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes in the order of nanometers The mechanical behavior of silica aerogel was investigated with hardness, compression, tension and shear tests The influences of testing conditions, storage environment and age were examined, with particular attention paid to the effects of processing parameters, including fiber-reinforcement Good correlation was found between hardness and compressive strength over a wide range of processing parameters Increasing fiber reinforcement generally retarded shrinkage during fabrication and yielded smaller matrix densities for a given target density For a given fiber content, hardness, compressive strength and elastic moduli increased and strain at fracture decreased with increasing matrix density In the lower ranges of matrix density, fiber reinforcement increased strain at fracture and elastic moduli The mechanical response was also sensitive to environment and storage history With age, the compressive strength and elastic moduli increased while the strain at fracture decreased Tension and shear results indicate that shear strength of aerogels exceeds tensile strength which is consistent with brittle materials response