Showing papers on "Tensile testing published in 1982"

Deformation modes of the α-phase of ti-6al-4v as a function of oxygen concentration and aging temperature

Abstract: The tensile properties of lamellar Ti-6A1-4V and the deformation modes of the α-phase of this alloy were investigated as a function of oxygen concentration and as a function of aging heat treatment. Oxygen affects the mechanical properties through microstructural modifications which depend on the choice of aging parameters. The variations in Young's modulus, yield strength, ultimate tensile strength, and ductility, are correlated with α/β volume ratio and with α-deformation characteristics. Homogeneityvs inhomogeneity of slip, change of the predominant slip modes from prismatic slip to fine planar slip on pyramidal planes, and the occurrence of Ti3Al precipitates influence the deformation behavior of the α-phase and thus influence the mechanical properties of the alloy. The deformation behaviors of the lesser β-phase regions were not investigated, and only speculations can be made on the extent of their influence on the alloy's mechanical properties.

Spun-bonded fabric of partially drawn polypropylene with a low draping coefficient

Abstract: The present invention provides for a soft, polypropylene spun-bonded fabric comprising continuous, i.e. endlessly spun, partially drawn polypropylene filaments which have a maximum tensile elongation of at least 200%.

Three-Parameter Failure Criterion for Concrete

Abstract: A general, three-dimensional failure criterion for plain concrete and mortar is proposed. This criterion is formulated in terms of the first and the third stress invariants of the stress tensor, and it involves only three independent material parameters. Although these parameters interact with one another, each parameter corresponds to each of three failure characteristics of concrete behavior. These material parameters may be determined from simple tests such as uniaxial compression and triaxial compression or biaxial tests. For the purpose of including reasonable values of tensile strengths in the failure criterion, it is advisable to include the uniaxial tensile strength in the parameter determination. A simple expression for evaluation of the uniaxial tensile strength on the basis of the uniaxial compressive strength is given. Twenty-two sets of good quality data for concrete and mortar have been included in this study, and comparisons between the proposed failure criterion and the experimental data are made in biaxial, triaxial, octahedral, and τ\N - σ\N planes. The ability of this criterion to capture the characteristics of failure in concrete and mortar appears to be quite good with accuracies generally within the natural scatter of the test data.

Concrete under Impact Loading, Tensile Strength and Bond

Abstract: Uniaxial impact tensile tests on plain concrete were carried out with the aid of Split Hopkinson Bar equipment with stress rates of up to 60000 N/mm2. s. Various concrete mixes were investigated under. dry and wet conditions. All the concretes showed an increase in strength with increasing stress rate. At very high stress rates the strength may attain twice the static tensile strength. Repeated impact tensile loading reduces the strength considerably more than cyclic loading does with conventional stress rates. The bond between reinforcing steel and concrete was studied in pull-out tests with short embedment length. The results showed the bond strength and stiffness of deformed bars to increase with the loading rate, whereas plain bars and prestressing strands were hardly affected by the loading rate. It proved possible to formulate the tensile strength and the bond behaviour as a function of stress rate by means of a power function. Relations between compressive strength and tensile strength are given for various stress rates.

Metal-thermoplastic-metal laminates

Abstract: Lightweight metal-thermoplastic-metal laminates exhibiting an improved combination of good formability and bending strength comprise a core layer of a thermoplastic material selected from certain partly crystalline polyamides and polyesters, and a metal layer of certain aluminum alloys laminated on each side of the core layer, said thermoplastic and metal layers having certain requirements with respect to thickness and tensile elongation, and, additionally for the metal, tensile offset yield strength.

The processing and static mechanical properties of metal fibre reinforced bioglass

Abstract: The development of bioglass composites is presented Stainless steel AlSl 316 L fibres are introduced into bioglass by immersion of premade porous fibre skeletons into molten bioglass It is shown that this technique is simple and effective in obtaining metal fibre reinforced bioglass Thermal shock, tensile tests and three-point bend tests all show a marked increase of strength of the composite over the parent glass and a substantial improvement of toughness

Influence of Grain Size and Age-Hardening on Dislocation Pile-Ups and Tensile Fracture for a Ti-AI Alloy

Abstract: In an aged Ti-8.6 wt pct Al alloy macroscopic embrittlement occurs with increasing grain size and degree of age hardening. The influence of the grain sizeL on the true fracture strain can be described by eF ∼L-1 Tensile crack nucleation is caused microscopically by strong dislocation pile-ups which crack the grain boundaries. Using transmission electron microscopy and equations from the dislocation theory, an experimental method was developed to determine quantitatively the shear stress concentrations at the grain boundaries which are produced by the dislocation pile-ups and cause crack nucleation. The experimental results show that for all investigated grain sizes and degrees of age hardening a critical local stress t* C ≈ 38 GPa leads to crack nucleation. Based on this result equations were derived which describe the combined influence of grain size and age hardening on the true fracture strain and on the true fracture stress. These equations show a good agreement with the tensile test results.

Plastic behavior of 70/30 brass sheet

Abstract: The plastic yield behavior of strip annealed 70/30 brass sheet has been investigated using several experimental techniques. Proportional path, stress-strain relations were measured in two strain states using a recently devised plane-strain test and a standard sheet tensile test. Based on these data, 70/30 brass exhibits a dramatic departure from Hill's plasticity models. Particularly notable is the lower work-hardening rate in plane strain. A second series of tests was carried out by deforming first in plane-strain tension and subsequently in uniaxial tension. The relative orientation of the principal strain directions in the two strain paths strongly affected the transient yielding behavior, but the original work-hardening pattern and plastic anisotropy were approached after an additional effective strain of ∼0.04. These observations are consistent with a two yield-surface model;i.e., one an underlying, proportional path yield surface and one an instantaneous, transient yield surface.

Hydrogen effects on the tensile properties of 21-6-9 stainless steel

Abstract: The effect of hydrogen on the mechanical properties of a series of nineteen experimental heats of 21-6-9 stainless steel was investigated. The nineteen material groups covered a variety of forging processes, strength levels, grain sizes, and microstructures. The data show that absorbed hydrogen acts as an interstitial strengthener which increases the flow stress of 21-6-9 similar to the effects of carbon, nitrogen, and other interstitial atoms. The true stress for tensile instability was observed to be ∼1130 MPa for both uncharged and hydrogen charged specimens and appeared to be independent of process variables. Thermal charging and/or tensile testing in high pressure hydrogen indicates this austenitic stainless steel is susceptible to hydrogen-induced cracking at grain boundaries, slip bands, and other interfaces. A lack of hydrogen-induced effects at true stresses below 1100 MPa indicates a lower limit for the hydrogen-induced reduction in interfacial strength. Above a true stress of 1100 MPa the extent of hydrogen induced reductions in interfacial strength is dependent on hydrogen concentration and increases as the hydrogen concentration increases. These observations are discussed in terms of several proposed hydrogen embrittlement theories.

Studies of the effect of titanate coupling agent on the performance of polypropylene–calcium carbonate composite

Abstract: Composites of polypropylene—CaCO3 coated with isopropoxy triisostearoyl titanate have been prepared on Buss Ko-Kneader. These composites have been evaluated for mechanical properties, melt index, dispersion, and adhesion of polymer to filler using the scanning electron microscope. Calcium carbonate being a platelike substance with low aspect ratio results in composites having inferior tensile properties but superior impact characteristics. Uniform dispersion of filler in the composite and long alkyl chains of the coupling agent provide additional advantages such as improved melt index, higher tensile elongation, and better optical properties.

A tensile technique for materials testing at high strain rates

Abstract: A method of tensile testing of materials under dynamic conditions has been developed involving little modification to the normal compressive split Hopkinson bar system. The specimens are of tapered shape enabling testing to be carried out at stresses in excess of the yield stress of the pressure bars, while the easy access to the specimens allows testing over a wide range of temperature. Virtually constant strain rates of up to 1500 s-1 have been achieved for stainless steel specimens. A constant effective specimen gauge length has been shown to apply for strain rates from quasi-static to dynamic.

Measurement of Tensile Strength of Natural Rubber Vulcanizates at Elevated Temperature

Abstract: The tensile strength of test pieces made from natural rubber vulcanizates drops abruptly at a critical temperature which can vary from 40 to 130°C. This variation in critical temperature is shown here to be a result of the variation in critical cut length with temperature. When the naturally occurring flaws in the test piece are smaller than the critical cut length, high tensile strength values occur, but when the flaws are longer than the critical cut length, low tensile strength values occur. The critical cut length decreases as the temperature increases, and the abrupt drop in tensile strength occurs as the critical cut length reaches the natural flaw size in the test piece. The natural flaw size in tensile test pieces depends on the sharpness of the cutter, and for tensile strength measurements at elevated temperature, it is shown that even a slightly blunt cutter may give markedly different results from a sharp one.

Mechanical behaviour of an amorphous metal ribbon reinforced resin-matrix composite

Abstract: Resin-matrix composites, reinforced with high aspect ratio 2826MB amorphous metal ribbon in a simple stacking pattern, were fabricated and evaluated. Typical composite properties at 60 vol% ribbon are a density of 5.27 g cm−3, a longitudinal tensile strength of 1740 MPa, a transverse tensile strength of 870 MPa, a near-isotropic in-plane modulus of 100 GPa and a fracture toughness similar to that of 6061-T6 aluminium alloy. These composites are also shown to have poor mechanical fatigue resistance. In comparison with other engineering materials, these composites are superior on a specific strength basis. However, they are not competitive with quasi-isotropic AS graphite-epoxy on a specific modulus basis. Because of this deficiency, it is concluded that amorphous metal ribbon reinforced composites would not be in a competitive position for most high performance composite applications. However, the high biaxial composite strength properties, potential low cost, and the unusual soft magnetic properties offered by the ribbons may result in some unique composite applications.

Influence of adhesion between filler and matrix on mechanical properties of filled polyethylene

Abstract: Young's modulus, yield stress, tensile elongation at break, and tensile impact strength of filled polyethylene have been studied as a function of the content of two types of filler: Kaolin and calcium carbonate. Scanning electron microscopy proved that the kaolin particles are bonded to the polyethylene by means of polymer links, while similar links for calcium carbonate have not been detected.

Hydrolysis of poly(butylene terephthalate)

Abstract: The hydrolytic stability of poly(butylene terephthalate) (PBT) resins and compounds was studied. Rates of reaction were determined by measuring changes in melt flow rate. Hydrolysis was slightly accelerated by contact of PBT with glass containers and reduced by incorporation of some flame retardant additives. Melt flow rates were related to tensile elongation ofunfilled PBT and tensile strength ofthe glass fiber reinforced polymer and used as failure criteria. Reaction rates were used to predict failure times at various conditions.

Tensile strength of filled polymers

Abstract: A model is developed to predict the ultimate tensile strength of a particulate-filled polymer which depends not only on the volume fraction of the filler and the elastic moduli of the two material phases, but also on the shape, size, and interfacial adhesion between the filler particle and the matrix. The effects of these parameters have been examined and attempts have been made to compare them with those available in the literature. Considering the complexity of fracture, the theoretical prediction is in reasonably good agreement with published experimental data.

Influence of structure on the resistance of 65G steel to fatigue crack growth

Abstract: (230-mm diameter) with a center crack, rectangular (width 25 mm) with an edge crack for axial tensile testing, and rectangular compact (width 81 mm) for off-center tensile testing~ The line of action of the forces always coincided with the rolling direction and the through crack developed perpendicular to it. To obtain different structures, the disk samples were normalized or hardened in oil from 810~ and tempered at 180, 320, 380, 440 and 5800C. After heat treatment the samples were ground to a thickness of 3 mm. Data on the microstructure and the mechanical properties in short-term static tension of standard flat samples is shown on Table i. To study crack growth in steel of a given structure from one to four samples were used and in individual cases up to seven rectangular samples, which were cut from test disks. The tests were made using the known method [2, 3] in a machine with an inertial load exciter [4] in laboratory air with a relative humidity of 40-60% using an almost from-zero (R = 0.05) sinusoidal tensile cycle with a loading frequency of 16-20 Hz and at high crack growth rate (more than i0-6 m/cycle), because of the difficulty in measuring its length, also at a frequency of 0.017 Hz on a machine with rigid loading [5]. In the i0"-i0 -" m/cycles range of rates the tests were repeated at the two frequencies in order to be convinced of their weak influence on the results. The rate of development of the original crack in growth of it to an initial length of 2 mm from an initiating notch was always greater than 10-9 m/cycle despite the low loads and the use of various methods easing origin of it [6]. Therefore, for investigations of crack resistance at lower rates the load was reduced in steps with observance of existing recommendations [2, 7]. The sample was tested in stages during which all parameters of the load cycle were maintained constant. In each stage the range of the stress intensity factor ~K = KmaX-Kminin the disk samples was constant if the crack length did not exceed 95 mm and in the remalning cases increased with crack length. The rate of crack development v in the stages with a constant AK was calculated from five to eight successive measurements of its length using the method of least squares [2] while with an increasing AK the value of v was determined as the ratio of the increase in the crack between two successive measurements to the corresondlng number of cycles. For determination of the characteristics of cyclic crack resistance and an analytical description of the full fatigue failure curves, use was made of the equation [8]

Compositional effects on the high temperature ductility of 1 Cr-1.25 Mo-0.25 V Steel

Abstract: This paper describes the results of slow strain rate (e = 4.4 × 10-5 s-1) tensile tests performed at temperatures between 25 and 700 °C on a high purity CrMoV steel containing various dopants. The materials all had a bainitic microstructure, a hardness of RC28, and a grain size of ASTM 0. Some samples were step cooled prior to tensile testing. Four different compositions were tested: undoped (HP), Mn + P doped (MnP), P doped (P), and Sn doped (Sn) materials. All four materials failed in a low ductility cleavage mode at low temperatures and by a low ductility grain boundary cavitation mode at high temperatures. At intermediate temperatures, around 500 °C, the MnP material showed the highest ductility, the HP and Sn materials showed the lowest, and the P material was intermediate. The beneficial effects of both Mn and P on the creep ductility are rationalized in terms of their control of the sulfur concentration on prior austenite boundaries. In addition, it is suggested that P on the grain boundaries can reduce the cavitation rate by reducing the grain boundary self diffusion rate.