Showing papers on "Ultimate tensile strength published in 1970"

The strength of the menisci of the knee as it relates to their fine structure

Abstract: 1. The orientation of collagen fibres of the menisci of the knee has been demonstrated by polarised light microscopy. 2. As might be supposed from its fibre structure, the ultimate tensile strength of the meniscal tissue is dependent upon the axis of loading. 3. The tensile strength of the meniscus is similar to that of articular cartilage.

The strain-rate, temperature and pressure dependence of yield of isotropic poly(methylmethacrylate) and poly(ethylene terephthalate)

Abstract: The yield behaviour of poly(methylmethacrylate) (PMMA) has been investigated in tension and compression over a range of testing temperatures and strain-rates. Both tensile and compressive yield stresses were found to increase monotonically with increasing strainrate and decreasing temperatures. Compressive yield stresses were in general found to be more dependent on strain-rate. The results of this investigation have been correlated with previous published data for the dependence of the torsional yield stress of PMMA on hydrostatic pressure. This was done by a modification of a theory proposed by Robertson which uses the internal viscosity approach to yield in glassy polymers. The modified theory clearly explains the temperature and strain-rate dependence of the yield stress and provides a quantitative explanation of the differences in behaviour between tension and compression in terms of the dependence of yield on the hydrostatic component of the applied stress. The tensile yield behaviour of isotropic amorphous poly(ethylene terephthalate) (PET) sheets has also been investigated over a wide range of temperatures and strain-rates. No torsion or compressive yield stresses are available because of the sheet form of the PET, but the results obtained in tension are shown to be fully consistent with the above theory, and with other published work.

Ultimate longitudinal strength

Abstract: Literature related to recent work in predicting ultimate strength of a ship hull girder is reviewed and discussed. Instability factors are presented for determining the maximum load such a girder will sustain in the sagging mode. Two bibliography sections are included: one for ultimate load for box structures and the other for primary and secondary structure associated with ultimate strength.

Marginal Fracture vs Mechanical Properties of Amalgam

Abstract: The clinical marginal fracture characteristics of three commercial dental amalgams were evaluated and compared with a number of their mechanical properties to determine which properties would relate best to clinical performance. It was found that compressive strength, tensile strength, transverse strength, transverse deflection, and flow as determined by ADA Specification No. 1 were ineffective, whereas the rheological properties of dynamic creep, static creep, and slow compressive strength appeared effective in relating to marginal fracture.

On the strength and stiffness of planar reinforced plastic resins

Abstract: The recent history of planar reinforced plastic resins, including glass flake, high modulus ceramic flake, and continuous vapor coated film composites, is reviewed. The theoretical mechanics of both continuous (film) and discontinuous (flake and ribbon) reinforcements are summarized in simple form. A novel set of design curves is presented from which the lower bound requirements for the flake composite constitutents may be read directly. At the same time, the dependence of the composite ultimate strength on the shear strength of the plastic resin matrix is demonstrated. The mechanical properties of experimental film and flake composites representative of recent work are reported and compared with the theoretical predictions. In conclusion, the potential of planar reinforced plastic resin composites is discussed and found to be significant for applications where low weight and high isotropic stiffness are required, for example in aero-structural, airfoil, or blade components.

The effect of solidification rate on structure and high-temperature strength of the eutectic NiAl-Cr

Abstract: The eutectic NiAl-Cr, consisting of chromium rods in a NiAl matrix, was directionally solidified at rates varying from 1/4 to 30 in. per hr. The inter-rod spacing and elevated temperature tensile properties were measured and the structure determined for each solidification rate. The spacing, λ, obeyed the relation λ2V= Constant, whereV is the solidification rate. AtV greater than 1 in. per hr, a cell or colony structure formed and the cell size decreased with increasing solidification rate. At 600°C, the tensile strength increased substantially with decreasing inter-rod spacing, reaching 100,000 psi at the highestV. At 800° and 1000°C, the strength first increased then decreased at the highest solidification rates reaching maximum strengths of 63,000 psi and 47,000 psi, respectively. At 1200°C, the strength decreased slightly with increasing solidification rate. Fracture occurred by shear along grain boundaries and cell walls. The decreased strength at the highest solidification rates may be related to the increased cell boundary area.

Stress-strain characteristics of concrete confined in steel binders

Abstract: Synopsis The ductility of concrete can be increased by confinement in steel binders but, for a proper analysis of the ultimate strength of structures utilizing this gain, an undertsanding of the st...

Mechanical properties of engineering materials

Abstract: This chapter discusses the mechanical properties of engineering materials. The mechanical properties of those materials that are commonly used in engineering need to be understood to determine the size and shape of each member to carry its respective load. First, it is necessary to define some of these properties. When a direct force is applied to a structural member it tends to lengthen if the force is tensile, or to shorten if the force is compressive. Strain is a measure of the deformation, and direct strain is the deformation determined along the line of action of the direct force. If a length of mild steel bar is subjected to an axial tensile load the extension of the specimen is, at first, very small and would be undetectable by direct measurement, such as with a scale. It is necessary, therefore, to make use of an instrument known as an extensometer. This instrument is clamped over a known length of the specimen, and the elongation of that length is magnified so that it can be determined easily. As the tensile load increases so the extension increases until a point is reached where the extension increases rapidly and becomes measurable by dividers and a scale.

An evaluation of a carboxylate adhesive cement.

Abstract: Properties of a zinc phosphate and a carboxylate cement were measured and compared. Solubility, setting time, film thickness, and pH were similar, and tensile strengths were in the same range. The carboxylate cement was distinctly superior in its adhesion to both enamel and dentin under tensile loading, but little difference was observed when both cements were evaluated by measuring the tensile force needed to remove Class I inlays.

Curable polyepoxide compositions

Abstract: This application relates to curable compositions, based on cycloaliphatic epoxides in admixture with epoxy hardeners and polymers of butadiene, which can be cast into articles of desired configuration or used as binders in the preparation of laminates, and cured at elevated temperatures to form articles characterized by excellent physical properties such as tensile strength, toughness, resistivity to development and propagation of internal cracks, heat distortion temperatures and also characterized by excellent electrical properties.

Tensile Rupture of Rubber

Abstract: The dependence of tensile strength of a number of vulcanizates on temperature has heen studied. A critical temperature θc is found for natural rubber at which an abrupt change in strength occurs. This temperature depends on degree of crosslinking and also on the nature of the vulcanizing system. The presence of carbon black filler increases the strength above θc but has little influence on the value of θc or the strength at temperatures below it. The behavior can be explained qualitatively in terms of a change in mechanism of rupture from essentially a tear process above θc to a crack growth process below it. The influence of vulcanizing system is mainly due to changes in the nature of the crosslink rather than changes in regularity of the main chain as shown by the rate of low temperature crystallization.

Effect of Transformation Substructure on the Strength and Toughness of Fe-Mn Alloys

Abstract: Phase transformations in Fe−Mn alloys containing up to 9 pct Mn were studied by optical and electron transmission microscopy. Either equiaxed ferrite, massive ferrite, or massive martensite can form on cooling from austenite. The particular type of transformation product formed was found to depend on the alloy content, austenite grain size, and cooling rate. The mechanical properties of all the transformation products were evaluated using tensile and impact testing and are discussed in terms of the observed microstructural features. Yield strength and impact transition temperature were found to be relatively insensitive to manganese content but were strongly influenced by the transformation substructure and grain size of the transformed phase. In martensite it has been shown that the structural unit analogous to grain size in ferrite is the martensite packet size, which in turn is controlled by the prior austenite grain size. The fracture surface of broken impact specimens and the fracture profile were examined by means of electron and optical microscopy techniques. These fractographic observations were correlated with impact test data and microstructural observations of the various transformation products.

Cohesion of soil particles and the intrinsic resistance of simple soil systems to wind erosion

Abstract: Summary In a simple dry soil system in which erosion is taking place by virtue of the impact of saltating sand grains, the intrinsic variables affecting soil resistance can be investigated with the aid of a mathematical model The soil erodibility depends on the cohesiveness of the soil which is indicated by the tensile strength This is directly proportional to the packing density of the system, to the co-ordination number of the particles, and to the inter-particle bond strength Tensile strength is inversely proportional to the cube of the particle diameter In a cohesive material any decrease in the particle size produces a great increase in the tensile strength and hence the mechanical stability is improved, but because the particles are lighter they are easily eroded once they are disturbed

Structure‐Property relationships in polyacrylate‐poly(urethane‐urea) interpenetrating polymer networks

Abstract: Interpenetrating polymer networks of polyacrylate (A) and poly (urethane-urea) (U) were prepared by mixing lattices of self-curing polyacrylate and urethane-urea prepolymer followed by subsequent curing of each network. The structures of the mixtures were analyzed by the dynamic viscoelasticity and the electron microscopy. It was found that a phase inversion occurred from the “U-phase particles in A-phase matrix” to the “A-phase in U-phase matrix” at A/U ≑ 30/70 as the U-phase content increases. With increasing A-phase content, tensile strength started to increase and elongation-to-break becomes almost constant after the A-phase formed a continuous phase. This implies that the tensile properties are closely related to the morphological features.

Shear Test for Measuring Bonding in Cast Gold Alloy-Porcelain Composites

Abstract: A method of casting tensile rods, and a simplified method of fusing porcelain disks to the rods for measuring bond strength in a repeatable manner, are described. Bond strengths as high as 20,000 psi were recorded on oxidized rods. Both chemical depletion and a coating of gold reduced the bond.

Bending Behavior and Tensile Strength of Carbon Fibers

Abstract: The strength of anisotropic polycrystalline carbon fibers was investigated. Theoretical estimates of the strength of graphite are far higher than observed values for carbonized rayon fibers, and we have searched for an explanation. Internal ``grain boundaries'' in the fibers can account for the reduced strength inasmuch as the fracture appears to be intergranular. The ``grains'' are believed to be axially oriented fibrils, ap‐approximately 500‐A across. Experimental evidence for some inelastic behavior in carbon fibers at room temperature was obtained from bending experiments on single filaments. The results were interpreted in terms of local ``yielding'' or rupture of cross‐link bonds between adjacent fibrils. The stress at which such ``yielding'' takes place in bending is approximately equal to the failure stress in a tensile test. Although a Griffith model of completely brittle fracture in tensile tests was considered, the possibility that local ``yielding'' might precede tensile fracture seemed more likely. Consideration of the brittle failure model and the localized plastic flow model both lead to the same conclusion: The tensile strength of carbonized rayon fibers is limited by the fibrillar microstructure and cannot be expected to approach the theoretical estimates for graphite single crystals.

A theory of snow slab failure

Abstract: Existing theories of snow slab failure emphasize failure either in the tensile zone of the slab or along the slab base. The tensile zone theories do not explain measured fracture angles or the observed fact that a necessary condition for extensive fracturing is weakness in the basal plane. On the other hand, the basal theories do not explain where the tensile stress originates and why brittle failure commences in the tensile zone and propagates into the basal plane. A new model is proposed wherein the critical value of the maximum principal stress evaluated at the tensile zone is coupled to the inability of the slab to sustain basal stress. A scale analysis of the equilibrium equations shows that this model predicts the measured fracture angles and large values for the maximum principal stress.

A new glassy carbon fibre

Abstract: It is shown that phenol-hexamine polymers may be extruded from the melt to produce fibres which may be carbonised to form fine high-strength glassy carbon fibres with a tensile strength of up to 2 GNm−2 (300 000 Ib in−2) after 900° C heat-treatment. The fibres have a specific modulus of ∼5 Mm compared with ∼14 Mm for carbonised polyacrylonitrile fibres and ∼3 Mm for silica glass fibres. Both strength and modulus increase rapidly with decrease in diameter. The fibres are subjected to no special surface treatment after extrusion but electron microscopy indicates the presence of a thin textured sheath surrounding a true glassy carbon core in the final fibre. The fibres have the advantages of glassy carbon (inertness to chemical attack, resistance to abrasion) and give promise of a new range of cheap high-strength carbon fibres derived from coal tar fractions.

Thermomechanical properties of fibrous composites

Abstract: Basic composite properties can be related to those of their constituents by available theoretical results which are, on the one hand, relatively simple, and yet which are repre­sentative of the actual physical response of the materials. The present paper reviews recent developments in the theoretical analysis of the mechanical and thermal properties of fibrous composites. Comparisons with available experimental results are presented. Attention is focused on the properties of unidirectional fibrous composites. The definition of effective composite properties and methods for the analysis of the elastic moduli of such composites are reviewed. Theoretical results for composite thermal expansion coefficients and specific heats are presented. Tensile strength studies based on statistical failure models are then described. Effects of variations in fibre strength and of non-uniform stress distributions are treated. Finite length fibres and uniform strength fibres are also considered. Emphasis is placed upon demonstrating that the influence upon composite strength of the statistical nature of the strength of contemporary advanced filaments is susceptible to rational analysis.

Portland cement compositions reinforced with non-round filaments

Abstract: A reinforced composite of a castable matrix having discontinuous reinforcing filaments randomly distributed within the matrix which reinforce the matrix and which are bonded to the matrix chemically and/or mechanically. The filaments have a non-round cross sectional configuration with width and thickness dimensions and with a width-to-thickness ratio of not greater than about five. For maximum reinforcing strength, the filaments should have an ultimate tensile strength at least equal to the average tensile stress developed in the filament at bond failure. The characteristics of the filaments are such as to permit dry admixing with the castable matrix material. A method of making the reinforced composite and apparatus for and a method of coating the filaments are disclosed.

Filters comprising anisometric compressed and bonded multilayer knitted wire mesh composites

Abstract: Filters and filter units are provided which comprise as the filter sheet anisometric compressed and bonded knitted wire mesh composites composed of a plurality of sheets of knitted wire mesh, superimposed at random orientation with respect to each other, compressed or densified to a voids volume within the range from about 10 to about 90 percent, and bonded together The sheets are taken in sufficient number, usually at least five and preferably ten or more, and as much as 1,000 or more, to form a self-supporting relatively non-resilient composite of high tensile strength and high breaking strength having an average pore diameter of less than 200 microns, and preferably less than 100 microns, that is relatively uniform in any unit area of the surface, and having an anisometric porosity, the through pores extending crosswise of the sheet greatly exceeding in number the through pores extending laterally of the sheet, which latter pores can be reduced virtually to zero in a highly compressed composite The composite is formed by superimposing a plurality of knitted wire mesh sheets, annealing the composite to avoid wire breakage during later processing, compressing the composite to the desired density and anisometricity by application of pressure in a direction approximately perpendicular to the plane of the layers of the composite, and bonding the sheet layers and wire filaments of the sheets together at their points of contact and/or crossing The bonding holds the composite at the selected density, prevents relative movement of the wires in the composite, and in conjunction with the multilayer structure imparts the self-supporting nonresilient characteristic, together with high tensile strength and high breaking strength

38—the effect of spinning conditions on the tensile properties of core-spun yarns

Abstract: A critical assessment of the merits of core-spinning by means of comparisons of the strength and extension of core-spun yarns with all-staple-fibre yarns forms the basis of this paper. Core-spinning was done by introducing the filament under tension into the drafted strand as the latter entered the front rollers of the ring-frame. A 20-den (2.2-tex) nylon monofilament was used as core, and three types of staple-fibre covering were investigated. The effects of twist, pre-tension, and feeding arrangements on the geometrical disposition and tensile properties of the yarns were examined. Improvements in strength are, in general, realized at low twists by the incorporation of the filament and by further constraining it to occupy the core. The contribution of the components to the yarn strength and the process of breaking were also subjected to a detailed study. The studies reported provide an interesting insight into the extent of cohesion developed between the fibres during the straining of the yarn and its i...

Fracture Properties of Polyphenylene Oxide Composites

Abstract: The mechanical properties of glass bead, randomly oriented short glass fiber and randomly oriented short graphite fiber polyphenylene oxide composites were investigated. Fracture toughness measurements were made using double edge-notched tensile specimens and tensile strength, tensile strain and initial elastic modulus were measured in standard ASTM tensile tests. It was found that the fracture toughness was relatively independent of filler types and geometry (and nearly equal to that of the unfilled polymer) when no polymer-filler adhesion was present. When adhesion was promoted by surface treatment of the reinforcement, the fracture toughness of the treated fiber composites was greater than that of the untreated composites, while that of the treated particulate composites was below that of the untreated materials. The fracture toughness was also relatively independent of fiber concentration, but decreased sharply with increased glass bead concentration. The elastic moduli of the composites vari...