Showing papers on "Tensile testing published in 1984"

Compatibility between carbon fibre and binary aluminium alloys

Abstract: Compatibility between carbon fibre and various binary aluminium alloys is investigated. Series of aluminium alloys are coated onto the fibre surface and the wetting behaviour of these alloys are observed by scanning electron microscopy after heating the coated fibres at 1073 K, well above the melting point of the alloys. It is found that the aluminium alloys containing such elements as indium, lead and thallium showed excellent wetting behaviour. These alloying elements have significantly smaller surface energies as compared to aluminium and they are practically insoluble with aluminium, even in the liquid states. Tensile test shows that the strength of carbon fibres is not degraded after heating at 1073 K when fibres are coated with an Al-1 at % Tl alloy. The reasons for these elements in aluminium to substantially improve the compatibility against carbon fibres are discussed from the thermodynamical point of view.

Improvement of Hot Ductility of Continuously Cast Carbon Steels

Abstract: To improve the quality of continuously cast carbon steels, the characteristics of the hot ductility were studied via in-situ melted and solidified tensile testing method. Special emphases were placed on the effect of C and P on the hot ductility in the temperature range between melting temperature and 700°C.It was found that zero strength temperature (ZSTc) and zero ductility temperature (ZDTc) have a linear relationship with the equilibrium solidus temperature in Fe-C binary alloys ranging from 0.003 to 1.6% C and does not have the singularity between 0.1 to 0.2% C content. The embrittlement due to P exists only in the carbon steels having C content higher than 0.25%, which are subjected to the melting thermal history. This embrittlement is caused by the segregation of P along the austenite grain boundary.Mild cooling in the secondary cooling stage is very effective to diminish the embrittlement resulting in producing defect free cast slabs.

Stiffness and strength of fracture callus. Relative rates of mechanical maturation as evaluated by a uniaxial tensile test.

Abstract: Mechanical evaluation of healing fractures in rabbits suggests that tensile testing both minimizes artifacts and permits direct intrinsic determinations of tissue quality. In healing osteotomies in the rabbit fibula, there is a rapid return of stiffness at 16 days, correlating with callus maturation. The failure mode proved to be a "delamination" fracture. Values for the strength of bone (3.3 N/m2) and fibrocartilage (0.2 N/m2) correlate well with the results of other studies but are probably values of maximum tissue adhesion strength.

Solid-state morphology and mechanical properties of Kevlar 29 fiber

Abstract: Kevlar 29 is an aromatic polyamide fiber spun from the polymer poly(p-phenylene terephthalamide). It has a paracrystalline structure with a lattice distortion parameter g = 5.9% and an a∗ constant = 0.51. The equatorial x-ray “crystallinity” is 68%; the microparacrystal (mPC) sizes are D 002 = 50 nm, D 110 = 4.4 nm, and D 200 = 3.6 nm. The mPCs are well oriented; the orientation parameter = 0.047. The small-angle x-ray diffraction pattern indicated that the fiber has nc chain folding. It has high tenacity (2.81 GNm−2), close to the tenacity of steel; high Young's modulus (63.9 GNm−2); small breaking strain (3.8%); and a very high melting point (600°C). Wide- and small-angle x-ray diffraction techniques, differential scanning calorimetry (DSC), and an Amsler tensile tester have been used to characterize the fiber and to assess the effect of annealing on its morphology and mechanical properties.

Tensile testing apparatus

Abstract: An improved mechanical extensometer for use with a constant load creep test machine 10, wherein the dead weight of the extensometer is counterbalanced by two pairs of weights 70,90 and 80,100 connected through a pulley system 68, 78, 88 and 98 to rod extension 55,56 and 59,60, leading into the furnace 20 where test sample S is undergoing elevated temperature (above 500° F.) tensile testing. Novel gripper surfaces, conical tip 119 and flat surface 122, are provided in each sample engaging platens 38 and 40 to reduce the grip pressure normally required for attachment of the extensometer to the specimen and reduce initial specimen bending normally associated with foil-gage metal testing.

The tensile testing of single wood pulp fibers in air and in water

Abstract: A technique for the tensile testing of single wood pulp fibers in air and in water is described. Successive loading-unloading tests with increasing loads showed that the immediate elastic recovery of the wood pulp fibers was a linear function of the removed load. The slope of the straight line is inversely proportional to the rigidity of the fibers. Creep curves were recorded at 50% relative humidity and in water. As the testing method involves the measurement of the elastic recovery, the effect on the strain of the irreversible extension of microcompressions and crimps is eliminated. The method presented in this paper may therefore be more accurate for the determination of rigidity than those which evaluate rigidity from stress-strain curves. The tensile testing technique was critically examined, with special emphasis on the reliability of the adhesive used in attaching the fibers to the testing apparatus. The calculated elastic moduli and the creep behavior agreed well with literature data.

The drawing behavior of polyethylene copolymers

Abstract: The tensile drawing behavior of a range of selected polyethylene copolymers has been studied. Sheets were prepared by quenching molten polymer into cold water. Two-centimeter-gauge-length samples were then drawn in air at 75 or 115°C in an Instron tensile testing machine at a crosshead speed of 10 cm/min. It was found that even at the very low concentration of one side branch per 1000 carbon atoms there was a very marked effect on the strain hardening behavior and the maximum draw ratio that could be achieved. The reduction in draw ratio increased with increasing branch concentration, and long branches were more effective than short branches in limiting the draw ratios achieved. The similarity between these effects and the effects of increasing Mw or radiation crosslinking is noteworthy. This suggests that even a very small concentration of branches can significantly reduces the moleculer motions required for the process of plastic deformation. The Young's modulus/draw ratio relationship follows a pattern virtually identical to that observed in the case of homopolymers.

Hot ductility of Nb and Al microalloyed steels follovving high-temperature solution treatment

Abstract: C–Mn–Al, C–Mn–Nb, and C–Mn–Nb–Al steels are known to exhibit troughs in their hot ductility behaviour. This paper attempts to explain the high-temperature brittleness of these steels by examining their hot deformation behaviour. Slow strain-rate, hot tensile testing of laboratory-melted and commercial C–Mn steels containing niobium and/or soluble aluminium following solution treatment at 1300°C for 1·5 h has been performed. The occurrence (or otherwise) of dynamic recrystallization, hot strength, and elongation to fracture were noted as a function of deformation temperature, and the austenite-ferrite equilibrium transformation temperature determined by slow-heating dilatometry. The addition of niobium and/or soluble aluminium to C–Mn–N steel produced a hot ductility trough, failure being intergranular when ductility was poor and by dimpled rupture and tensile necking when ductility was good. Poor ductility was associated with a fully austenitic microstructure. Small amounts of ferrite did not appe...

Effects of 50,000 h of thermal aging on graphite/epoxy and graphite/polyimide composites

Abstract: Thermal effects on tensile strengths of advanced composite systems have been determined for exposure times of 100 to 50,000 hours (5.7 years). Exposures were conducted at both ambient and reduced pressures at two temperatures for each composite. At the completion of the various aging periods, specimens were removed from the specially constructed aging furnaces, visually examined, and tensile tested at elevated temperature. After tensile testing, many of the thermal aging specimens were examined using a scanning electron microscope. Results of these studies are presented, and the changes in properties and the degradation mechanisms during high-temperature aging are discussed and illustrated using metallographic techniques.

Wet-dry indirect tensile test for evaluating moisture susceptibility of asphalt mixtures

Abstract: This report contains a description of the development and use of the Wet-Dry Indirect Tensile Test to evaluate stripping or moisture susceptibility of asphalt mixtures. Tests were performed on eight mixtures of which fiive had stripped in the field and three had not. Each mixture was tested to determine whether the results could be used to differentiate between stripping and nonstripping mixtures. Based on these tests and other fiield testing it was tentatively concluded thaatmixtures with less than 70 percent retained strength are moisture susceptible and require treatment. The results indicate the valuable information is provided by the Wet-Dry Indirect Tensile Test. The test can be performed either in the laboratory during mixture design or on thhe field-mixed materials. In general, the Wet-Dry Indirectly Tensile Test offers good potential for use in detecting moisture susceptible mixtures before they are placed in the field. (Author)

PART 2: The Influence of Solid Inclusions

Abstract: Solids in the form of colour pigments are commonly added to tablet film coats for the purpose of identification. This work examines the effect of their addition on certain mechanical properties of the films. Films were cast from aqueous solutions of hydroxypropylmethylcellulose (HPMC) in which the solids had been dispersed. Titanium dioxide was added in concentrations of up to 40% in the dried film. Two grades (regular and high tinting) of the following aluminium lakes (Colorcon Limited) were also investigated: Brilliant Blue FCF, Erythrosine and Tartrazine. A tensile test was performed on the films using an Instron test machine. In general, the addition of solid particles reduced the tensile strength of the film, shortened the elongation at break and increased the elastic modulus, i.e. the films became more brittle. The influence of storage humidity on these properties is also reported.Changes in these fundamental properties are correlated with practical problems associated with the addition of s...

Ultra-High Strength and Ultra-High Modulus Fibers from Polyethylene

Abstract: Using the method of hot drawing developed earlier, an attempt has been made to obtain ultra-high modulus and ultrahigh strength PE filaments from original filaments produced by the “surface growth” technique. The average tensile strength of the drawn fibers reaches 5.5 GPa and the value of modulus measured in a dead loading creep experiment is estimated to be 44 GPa. 13 % of the drawn specimens had extremely high tensile strength close to theoretical estimates. The great scatter of the tensile strength data is attributed to the kink-band formation in the specimens due to their bending during preparation or during drawing.

Polyphenylene ether resin compositions having improved ductile impact strength

Abstract: The ductile impact strength and tensile elongation of flame retardant compositions of a polyphenylene ether resin and a poly(alkenyl aromatic) are upgraded by the addition of only small amounts, typically from about 0.1 to about 10 parts by weight, of high molecular weight polyfunctional esters or low molecular weight saturated polyesters.

Modelling of cavitation in two phase superplastic alloys under uniaxial stress systems

Abstract: Superplastic materials are characterized by their ability to undergo exceptionally large deformation under low stresses. Many alloys, however, are prone to cavitation, which leads to premature failure even though deformation is within the superplastic regime. A model is presented which analyses the evolution of pre-existing cavities in two phase alloys subjected to uniaxial stress systems. It is seen that this model adequately describes the cavitation phenomenon of α–β brasses and microduplex Cu-Zn-Ni alloys in the tensile test. Closure of cavities in the compression test may also be described by this model. The results obtained thus enable the formation of an overall view of the behaviour of a two phase superplastic alloy subjected to the uniaxial tension test, and the difference in cavity evolution of different materials.

The effect of hot working on structure and strength of a precipitation strengthened austenitic stainless steel

Abstract: The development of microstructure and strength during forging in a γ′ strengthened austenitic stainless steel, JBK-75, was investigated by means of forward extrusion of cylindrical specimens. The specimens were deformed in a strain range of 0.16 to 1.0, from 800°C to 1080°C, and at approximate strain rates of 2 (press forging) and 2 × 103 s-1 (high energy rate forging), and structures examined by light and transmission microscopy. Mechanical properties were determined by tensile testing as-forged and forged and aged specimens. The alloy exhibited an extremely wide variety of structures and properties within the range of forging pzrameters studied. Deformation at the higher strain ratevia high energy rate forging resulted in unrecovered substructures and high strengths at low forging temperatures, and static recrystallization and low strengths at high temperatures. In contrast, however, deformation at the lower strain ratevia press forging resulted in retention of the well developed subgrain structure and associated high strength produced at high forging temperatures and strains. At lower temperatures and strains during press forging a subgrain structure formed preferentially at high angle grain boundaries, apparently by a creep-type deformation mechanism. Dynamic recrystallization was not an important restoration mechanism for any of the forging conditions. The results are interpreted on the basis of stacking fault energy and the accumulation of strain energy during hot working. The significance of observed microstructural differences for equivalent deformation conditions (iso-Z, where Z is the Zener-Holloman parameter) is discussed in relation to the utilization of Z for predicting hot work structures and strengths. Aging showed that the γ′ precipitation process is not affected by substructure and that the strengthening contributions, from substructure and precipitation, were independent and additive. Applications for these findings are discussed in terms of process design criteria.

An improved split-cell apparatus for the measurement of tensile strength of powders

Abstract: Measurement of the tensile strength of powder compacts is useful for determining the magnitude of the cohesive forces which cause powders to agglomerate. A split-cell apparatus has been developed which contains major improvements on previous devices, including separation of the split-cell from the base unit to allow higher packing densities. A piezoelectrically controlled translation device provides a means of vibration-free, variable speed application of the tensile load. A compact DC operated force transducer is used to measure the tensile load to an accuracy better than 0.1%. Several other design and procedural improvements also make the present method simpler and more efficient. Typical plots of tensile stress against time and tensile strength against packing density are shown for carbon black.

Blends of elastomeric polyetherester copolymers with thermoplastic polycarbonates

Abstract: Copolyetherester-containing blends having improved tensile strength together with high tear strength, tensile elongation and impact strength are prepared by creating an admixture of copolyetherester with a polycarbonate and, optionally, a polyester