Showing papers on "Tensile testing published in 1978"
TL;DR: In this paper, a dynamic finite-difference computer program is used to calculate the quasi-static necking deformation of a round tensile bar to 71 per cent reduction in area.
Abstract: A dynamic finite-difference computer program is used to calculate the quasi-static necking deformation of a round tensile bar to 71 per cent reduction in area. Finite strain and rotation are accounted for. We modelled the behavior of A-533 Grade B Class 1 nuclear-pressure-vessel steel as elastic work-hardening plastic material, using J2-flow theory and a flow curve obtained from a simple tensile test. Up to the time of fracture, computed results of neck radius vs load and elongation, load vs elongation, and neck profile vs neck radius compare favorably with experimental results. We present the macroscopic stress and strain state at fracture and compare these results with those of Bridgman and other calculators. Our calculated neck stress shows monotonically decreasing stress in the radial direction and does not show the sharp stress peaks on the axis or the rounder stress peaks off the axis that these earlier calculations show. We find considerable differences from the Bridgman solution. An iterative computer method is introduced to allow correction of simple tension-test data to a universal flow-stress curve valid for large strain.
151 citations
TL;DR: In this article, an experimental study was carried out to investigate the effects of titanate coupling agents on the rheological properties of p articulate-filled polyolefin melts, and it was found that the addition of the coupling agent TTS to the PP-CaCO3 and PP-fiberglass systems reduced the melt viscosity considerably.
Abstract: An experimental study was carried out to investigate the effects of titanate coupling agents on the rheological properties of p articulate-filled polyolefin melts. Inorganic fillers used were CaCO3, talc, and fiberglass, and polyolefins used were high-density polyethylene (HOPE) and polypropylene (PP). It was found that the addition of the coupling agent TTS to the PP-CaCO3 and PP-fiberglass systems reduced the melt viscosity considerably, whereas the addition of the coupling agent ETDS-201 to the PP-talc and HDPE-talc systems affected the melt viscosity very little. Also carried out was an injection molding study to investigate the effects of different inorganic fillers and the titanate coupling agents used on the mechanical properties of the injection molded specimens. It was found that addition of titanate coupling agents generally resulted in reduced modulus and tensile strength, and increased elongation and impact strength of the filled systems. The PP-CaCO3-TTS and HDPE-talc-ETDS 201 systems were found to have impact strength improved by approximately 100 percent with the addition of a titanate coupling agent. The PP-CaCO3-TTS samples have ultimate tensile elongation approaching that of virgin PP.
121 citations
01 Jul 1978
85 citations
TL;DR: The theoretical background for the two most common indirect rock tensile strength measurements, namely the point load test and the Brazilian test, is discussed in this article, where the exact theoretical stress field variation within the loaded specimens has not been evaluated earlier in the literature, strangely enough.
80 citations
TL;DR: In this article, a novel technique has been developed to produce a laminate of Al/AlxOy by a pulsed gas process in an electron beam gun system, which obeys a Hall-Petch relation for yield strength.
69 citations
TL;DR: In this paper, a long-term strength test was performed on glass fibres drawn from both Suprasil rods and graded index pre-forms in a laser furnace and in a graphite resistance furnace and coated in both cases with a u.v.-curable epoxy acrylate.
Abstract: Long-term strength tests have been performed on glass fibres drawn from both Suprasil rods and graded index pre-forms in a laser furnace and in a graphite resistance furnace and coated in both cases with a u.v.-curable epoxy acrylate. Results of stress-free ageing tests in humid environments over a period of 18 months show that the fibres weaken at a rate that depends not only upon humidity level but also upon which heating source is used for fibre drawing. The weakening phenomenon has been ascribed to stress-induced reactions between silica and adsorbed water at the glass-polymer interface which occur spontaneously during the tensile test (dynamic fatigue). Static fatigue tests in 90% r.h. show that the fatigure behaviour deviates from that predicted by the theories of Charles and of Charles and Hillig for uncoated glasses; specifically plots of log (stress) versus log (time-to-failure) and stress versus log (time-to-failure) show downward curvatures which become more pronounced as the applied stress is lowered. In the absence of fatigue data for uncoated fibres, however, it is not possible to determine whether such non-linear behaviour is brought about by the presence of the organic coating layer.
67 citations
TL;DR: In this paper, various methods for the shear stress-strain characterization of composite laminates are examined and their advantages and limitations are briefly discussed, and the necessary accompanying analysis are then presented and compared for three simple shear characterization procedures.
44 citations
01 Jan 1978
TL;DR: In this article, an exact linearized solution is produced for the velocities and stresses due to a small nonuniformity in the radius which varies sinusoidally in the axial direction.
Abstract: Neck development in bars of strain-rate dependent materials under tensile load is analyzed in several ways. For a circular bar of a power-law creeping material, an exact linearized solution is produced for the velocities and stresses due to a small nonuniformity in the radius which varies sinusoidally in the axial direction. This solution is used to assess the accuracy of a long wavelength approximation commonly used to analyze neck development. The long wavelength approximation is then adopted to study the growth of nonuniformities in bars of a general class of strain-rate dependent materials. This analysis, together with two illustrative examples, elucidates Hart's stability criterion for such materials. Attention is drawn to the connection between the criterion and experimental observation in tension testing and the closely parallel situation in creep buckling of compressed columns.
29 citations
TL;DR: A review of the literature on testing of notched specimens is provided with empkasi-1 on short-term notched bar tension tests as discussed by the authors, where the effects of notch geometry, stress state, oni! smooth-bar tensile properties on notched ductility, notch sensitivity, and mode of fret lure are discussed.
Abstract: A review of the literature on testing of notched specimens is provided with empkasi-1 on short-term notched bar tension tests. The effects of notch geometry, stress state, oni! smooth-bar tensile properties on notched ductility, notch sensitivity, and mode of fret- j lure are discussed. For design against failure due to notch weakening, a simple cri. \ terion based on a limiting value of notched ductility is proposed. Notched ductility I for the metals considered in this study, can be approximated by the reduction in am; from a smooth tension test divided by a tensile stress triaxiality factor that is propor tional to the ratio of hydrostatic to octahedral shearing stresses associated with the notch.
28 citations
TL;DR: In this paper, the effects of strain, strain rate and deformation heating in tensile testing of sheet steel are numerically analyzed. And the results show that the stretchability of sheet metals can be improved by using very low forming speeds or more economically by using an effective cooling system.
Abstract: The effects of strain, strain rate and deformation heating in tensile testing of sheet steel are numerically analyzed. An experimentally determined strain-hardening formula is used as a basis of the calculation. The effects of heat conduction and free or forced con-vection during the test are taken into account by using the approximate solution method originally given by Bishop for metal extrusion. The calculated values agree well with the experimental data. It is shown that deformation heating considerably affects the uni-form strain. Consequently the stretchability of sheet metals can be improved by using very low forming speeds or more economically by using an effective cooling system.
28 citations
TL;DR: In this paper, the effect of superposition of a high power ultrasonic and a "static" strain on the microstructure of commercial aluminium containing 1% Si and 0.6% Mg was investigated.
01 Apr 1978
TL;DR: The relation between the uniaxial tensile strength of Bohus granite and the sample size of the sample has been investigated in this paper, where it was shown that the strength of the Bohus granite is independent of sample size within a very large range of volume.
Abstract: The Relation Between the Uniaxial Tensile Strength and the Sample Size for Bohus Granite
An experimental investigation has shown that the uniaxial tensile strength of Bohus granite is independent of the sample size within a very large range of volume. An indirect measurement of the tensile strength such as the point load test does, however, yield the well-known decrease in strength with increasing sample volume. The reasons for these results are discussed and a theoretical extension of Weibull's statistical theory for the tensile strength of materials is used to indicate that the uniaxial tensile strength test may be a measurement of the minimum tensile strength of the bonding between the grains in the rock.
TL;DR: In this article, the effect of purity level, dispersoid type, and heat treatment on fracture toughness was investigated in ten different alloys based on the 7075 composition. And the results showed that the smaller dispersoid and hardening particles become increasingly important in controlling the fracture toughness as the large intermetallic particles are eliminated by increasing the purity of these aluminum alloys.
Abstract: Ten different alloys based on the 7075 composition were used to study the effect of purity level, dispersoid type, and heat treatment on fracture toughness. Five purity levels ranging from 0.03 to 0.30 wt pct Fe + Si and two dispersoid types were investigated. Each alloy was given two heat treatments: the standard T651 heat treatment or a special thermomechanical treatment (TMT). Fracture toughness was measured using notched round tensile specimens taken from both the longitudinal and long-transverse directions. The notched round tensile test was modified to give the “plastic energy per unit area”. This fracture toughness parameter gave the same ranking for corresponding alloy/heat treatment combinations as the total energy per unit area measured on precracked Charpy specimens. The fracture toughness ranking for the ten alloys was the same in the longitudinal and long-transverse directions. This suggests the elongated distribution of constituent particles in the rolling direction does not change the failure mechanism. Fractographic evidence showed a bimodal distribution of ductile dimple size in all ten alloys. The number of large ductile dimples decreased with increasing purity level while the number of small ductile dimples increased. This is interpreted to mean that the smaller dispersoid and hardening particles become increasingly important in controlling the fracture toughness as the large intermetallic particles are eliminated by increasing the purity of these aluminum alloys. Since thermomechanical processing controls the amount and type of these smaller particles, it is a useful means for increasing fracture toughness in high purity aluminum alloys.
TL;DR: In this article, the role of strain in the fracture of low strength steel in the temperature range of −196 to 28°C and at the crack tip strain rate range of 10 −5 to 10°/sec.
TL;DR: In this paper, the influence of Si on the impact and tensile behavior of steels has been examined, and the effect of grain-boundary segregation on tensile strength has been investigated.
Abstract: The influence of Si on the impact and tensile behavior of steels has been examined. Analy-sis of the data in the literature shows that there is reasonable agreement on the affect of Si on tensile strength. However, the influence of Si on impact behavior seems to depend on an interrelationship with Mn and N, and also, on whether the steels are normalized or hot rolled. An explanation of this has been given in terms of varying degrees of grain-bound-ary segregation of N, dependent on the Si, Mn and matrix free N contents, and the effect of these variations onK
y value, and through this on impact properties. Atom probe, strain-aging and internal friction data are presented which give some support to this ar-gument. However, direct evidence to support a grain-boundary segregation theory is still awaited and further atom probe work is required.
TL;DR: In this paper, ultra-oriented high density polyethylene was extruded at an extrusion (draw) ratio of 26 and subsequently irradiated under vacuum by a cobalt-60 source at doses of 10,15, 20, 40, 60 megarads (MRad).
Abstract: Filaments of ultra-oriented high density polyethylene were solid-state extruded at an extrusion (draw) ratio of 26 and subsequently irradiated under vacuum by a cobalt-60 source at doses of 10,15, 20, 40 and 60 megarads (MRad). Several identically prepared but unirradiated strands were also tested. One set of samples at each dose was immersed in a silicone oil bath for one half hour at 128°C and one set was given no post-irradiation thermal treatment. Characterization of the resultant morphologies included differential scanning calorimetry (DSC), birefringence, thermomechanical analysis (TMA), and tensile testing. Results from DSC measurements indicate that initial radiation crosslinking only slightly disrupts the crystal lattice, but on subsequent melting and re crystallization, the chains are unable to recrystallize effectively in their former habit. In all cases, melting point and crystallinity decrease with increasing radiation dose. Birefringence and TMA results indicate that orientation is not disrupted by irradiation. For unannealed samples, Young's modulus increases slightly then levels off while tensile strength and elongation at break increase initially, then drop, For annealed irradiated samples, Young's modulus rises at first, then levels off at higher doses. Tensile strength and elongation at break increase significantly with increasing radiation treatment, then essentially reach constant values at highest doses.
TL;DR: In this article, the authors show that the stress-strain behavior of copper at large strains is similar to B.C. material in terms of linearity and the workhardening modulus is less than for iron and copper and appears to show a saturation in hardening at strains above 2.2.
TL;DR: In this paper, experimental data for three types of carbon fiber and two epoxy resin formulations are presented for checking prediction models for the longitudinal tensile strength of unidirectional fibrous composites.
TL;DR: In this article, a measure of the critical strain rate at which the two competitive effects balance allows for the determination of both the longitudinal viscosity coefficient and the related relaxation time of a metallic solid.
Abstract: When a metallic solid is strained below its elasticity limit, in any locally dilated zone two competitive effects take place: thermoelastic cooling and heating due to internal friction phenomena. During an adiabatic tensile test, a measure of the critical strain rate at which the two effects balance allows for the determination of both the longitudinal viscosity coefficient and the related relaxation time.
TL;DR: A tensile testing technique utilizing a powder-cushion between the specimen/grip surfaces has been devised and tested as mentioned in this paper, and bending strains associated with this gripping technique have been determined as a function of load with a buttonhead specimen instrumented with nine strain gages.
Abstract: A tensile testing technique utilizing a powder-cushion between the specimen/grip surfaces has been devised and tested. Bending strains associated with this gripping technique have been determined as a function of load with a buttonhead specimen instrumented with nine strain gages. Experiments with eight different powders showed that lubricating powders such as graphite and boron nitride are more effective in producing good alignment, with graphite considered superior. Alignment obtained with the graphite powdercushion is comparable with that obtained with more complex devices and procedures.
TL;DR: In this article, the effects of hydrogen absorption upon mechanical properties have been studied for ASTM A533B and A542 steels, and the results show that with an increase of hydrogen concentration, the ductility such as reduction in area and total elongation decreases remarkably.
TL;DR: In this article, the mechanisms controlling hot ductility in 70-30 wrought commercial cupronickel alloys were investigated by measuring hot tensile testing and tests were conducted over a range of temperatures and strain rates and for materials of different initial grain sizes.
Abstract: An investigation is described into the mechanisms controlling hot ductility in 70–30 wrought commercial cupronickel alloys. Ductilities were measured by hot tensile testing and tests were conducted over a range of temperatures and strain rates and for materials of different initial grain sizes. Ductilities were found to change in a complex manner with all these variables. In all cases, failure was due to grainboundary cavitation, but good ductility could be achieved if dynamic recrystallization occurred at grain boundaries during testing. Cavities were found to nucleate at manganese sulphide inclusions, and the distribution of cracked boundaries with respect to the tensile axis was far from uniform. Analysis of the metallographic observations suggests that more than one mechanism of cavity growth operated in the material.
TL;DR: A pressure vessel for tensile testing has been developed to measure tensile stress in high-pressure up to 50.5 MPa at elevated temperatures up to 773 K.
Abstract: A pressure vessel for tensile testing has been developed to measure tensile stress in high‐pressure up to 50.5 MPa at elevated temperatures up to 773 K. The vessel is designed to facilitate the measurement of the actual tensile load on the specimen by an external load cell without the influence of axial stress due to high pressure in the vessel and the effect of friction at sliding seals where the load rod enters the vessel. Application of the vessel to tensile testing of a steel in hydrogen atmosphere is briefly described.
TL;DR: In this article, a one-dimensional finite element model is used to relate the constitutive equation of a thermoplastic with the phenomena observed when it is tensile tested, and predictions are made of the temperature distribution in a propagating neck, and in particular PVC is shown to be liable to thermal fracture in fast tensile tests.
Abstract: A one-dimensional finite element model is used to relate the constitutive equation of a thermoplastic with the phenomena observed when it is tensile tested. Predictions are made of the temperature distribution in a propagating neck, and in particular PVC is shown to be liable to thermal fracture in fast tensile tests. The neck geometry is shown to be an important factor in stable, high speed, neck propagation.
TL;DR: In this paper, different methods used to measure the strain-rate sensitivity parameter by a strain rate change experiment are analyzed in terms of the variables that influence the tensile test, and it is shown analytically and by some calculations performed on data taken in Zry-4, in the superplastic range, that there is a unique way of obtaining the strain rate sensitivity parameter from the experimental load vs. time curves.
TL;DR: In this article, a tensile testing of two samples of 3Ni-Cr-Mo-V steel, differing significantly in carbon and manganese content and hence in strength after heat treatment, has been carried out in a gaseous hydrogen environment.
Abstract: Tensile testing of two samples of 3·5Ni-Cr-Mo-V steel, differing significantly in carbon and manganese content and hence in strength after heat treatment, has been carried out in a gaseous hydrogen environment. The ductility observed was found to be dependent on both strength level and heat treatment. Treatments that produced 0·2% flow strength levels below about 1700 MN/m2 appeared to induce resistance to embrittlement by gaseous hydrogen, except where heat treatments were carried out in what appeared to be a critical range for temper embrittlement. A tendency towards temper brittleness resulted in a ductility trough around 400°C that was greatly accentuated by testing in hydrogen. This appears to substantiate a cooperative action of temper embrittlement and hydrogen embrittlement. Very different failure modes are associated with the two conditions giving rise to lowstrain, hydrogen-induced failures: quenched or lightly tempered structures give rise to quasi-cleavage, whereas materials tempered ...
TL;DR: An approximate mathematical description of the tensile test for a material that is strain hardening and strain rate sensitive is given in this paper, where three phases of deformation are distinguished: (I) nearly homogeneous deformation up to maximum load, (II) gradual localization of the deformation at nearly constant load, and (III) necking.
Abstract: An approximate mathematical description of the tensile test is given for a material that is strain hardening and strain rate sensitive. Three phases of the deformation are distinguished: (I) nearly homogeneous deformation up to maximum load, (II) gradual localization of the deformation at nearly constant load, and (III) necking. The analysis realistically approximates: load, extension curves; post-uniform elongation; incipient neck size; and neck profiles.
TL;DR: In this article, the spindle false-twist method was used to texture a Cummerciat polyethylene terephthalate multifilament yarn with various tension and twist levels.
Abstract: Cummerciat polyethylene terephthalate multifilament yarn was textured using the spindle false-twist method over a range of heater temperatures and contact times and at various tension and twist levels. The decrimping extension, initial modulus, tenacity, and fiber clongation of the various samples were measured on a tensile tester. The changes in these mechanical properties as functions of the texturing parameters are described and their structural dependence dis cussed in this paper.