Showing papers on "Stress–strain curve published in 1969"
TL;DR: In this article, a variational principle is established to characterize the flow field in an elastically rigid and incompressible plastic material containing an internal void or voids, and an approximate Rayleigh-Ritz procedure is developed and applied to the enlargement of an isolated spherical void in a nonhardening material.
Abstract: The fracture of ductile solids has frequently been observed to result from the large growth and coalescence of microscopic voids, a process enhanced by the superposition of hydrostatic tensile stresses on a plastic deformation field. The ductile growth of voids is treated here as a problem in continuum plasticity. First, a variational principle is established to characterize the flow field in an elastically rigid and incompressible plastic material containing an internal void or voids, and subjected to a remotely uniform stress and strain rate field. Then an approximate Rayleigh-Ritz procedure is developed and applied to the enlargement of an isolated spherical void in a nonhardening material. Growth is studied in some detail for the case of a remote tensile extension field with superposed hydrostatic stresses. The volume changing contribution to void growth is found to overwhelm the shape changing part when the mean remote normal stress is large, so that growth is essentially spherical. Further, it is found that for any remote strain rate field, the void enlargement rate is amplified over the remote strain rate by a factor rising exponentially with the ratio of mean normal stress to yield stress. Some related results are discussed, including the long cylindrical void considered by F.A. McClintock (1968, J. appl. Mech . 35 , 363), and an approximate relation is given to describe growth of a spherical void in a general remote field. The results suggest a rapidly decreasing fracture ductility with increasing hydrostatic tension.
4,156 citations
TL;DR: The mechanical behavior of OFHC copper at strain rates from 10−3 to 103 sec−1 at 300°, 420°, and 590°K was investigated in this paper.
Abstract: The mechanical behavior of OFHC copper at strain rates from 10−3 to 103 sec−1 at 300°, 420°, and 590°K was investigated. The strain rate behavior of copper can be divided into two regions. Below 10 sec−1 the dislocation motion is thermally activated over forest dislocation barriers. Above 103 sec−1, a linear relationship between stress and strain rate was observed indicating the presence of a viscous damping mechanism. The stress level τB that must be exceeded in order to obtain viscous behavior depends on the work‐hardened state of the copper. The mobile dislocation density in the viscous damping region was found to be (1) independent of strain rate, (b) only a small fraction (10−5) of the total dislocation density, (c) independent of strain, and (d) increased with increasing temperature. These deductions are discussed in terms of the dislocation multiplication and annihilation mechanism.
130 citations
TL;DR: In this article, the authors made careful measurements of the stress-strain curves of tungsten wires of 10 μ and 20 μ diameter and of aligned composites of the same wires in copper at strains greater than the yield strain of the copper.
Abstract: Careful measurements have been made of the stress-strain curves of tungsten wires of 10 μ and 20 μ diameter and of aligned composites of the same wires in copper At strains greater than the yield strain of the copper the apparent stresses in the matrix, evaluated from the law of mixtures, are very high The effect appears to be due to the mutual constraint of the two phases caused by their different lateral contractions, since it disappears when the fibres yield and hence the transverse contractions become the same The experimental results are compared with those predicted for a completely plastic matrix and the stresses are found to be higher than calculated This is interpreted to mean that the yield of the copper is gradual, and that during stage II of the stress-strain curve of the composites an appreciable portion of the copper continues to deform elastically
111 citations
TL;DR: In this paper, the Cottrell-Petch formulation was used to predict the probability distribution of crack orientation angles, and from these the distribution of the surface trace angles that should be observed experimentally.
47 citations
TL;DR: In this paper, tension and compression tests were conducted on single crystal samples of tantalum and tantalum-rhenium-base solid solutions as a function of temperature and strain rate.
43 citations
TL;DR: In this article, a brief summary of the structure of keratin fibres is followed by a review of their mechanical and allied properties, including tensile stress-strain properties, stress relaxation, and creep, and torsional stress strain properties and stress relaxation.
Abstract: A brief summary of the structure of keratin fibres is followed by a review of their mechanical and allied properties. Among these properties are tensile stress–strain properties, stress relaxation, and creep, and torsional stress–strain properties and stress relaxation. The mechanism of supercontraction, properties of set fibres and disulphide-reduced fibres, and thermal transitions in keratin are also discussed. Finally, the various theoretical attempts that have been made to explain these properties are critically reviewed.
43 citations
43 citations
TL;DR: In this paper, the low endurance fatigue behavior of commercial purity aluminium, Nylon 66 and an epoxy resin is examined and compared, and both aluminium and nylon obey a plastic strain criterion for failure and this behaviour is independent of frequency.
Abstract: The low endurance fatigue behaviour of commercial purity aluminium, Nylon 66 and an epoxy resin is examined and compared. Both aluminium and nylon obey a plastic strain criterion for failure and this behaviour is independent of frequency. No satisfactory criterion for failure could be found for the epoxy resin whose behaviour is strongly frequencydependent.
33 citations
25 citations
TL;DR: In this paper, the deformation mechanism in polyblends of polypropylene with ethylene-propylene rubber having different compositions was clarified by simultaneous measurements of the infrared dichroism with stress and strain under a constant rate of strain of 1.64%/min.
Abstract: To clarify the deformation mechanism in polyblends of polypropylene with ethylene–propylene rubber having different compositions, simultaneous measurements of the infrared dichroism with stress and strain under a constant rate of strain of 1.64%/min have been carried out. The orientation function of the crystallographic c axis of polypropylene in the blends has been obtained as a function of strain ranging from 0 to 20% and of polypropylene content ranging from 0.3 to 1.0. These results have been compared with the temperature dependences of the dynamic Young's modulus and of the loss modulus, as well as of stress–strain curves for the same blends. The modulus data analyzed by Kerner's equation reveal the occurrence of phase inversion at polypropylene contents higher than about 0.5, and this is supported by the infrared dichroism data. The strong effect of quenching on crystalline structure and mechanical properties of pure polypropylene has also been elucidated.
25 citations
01 Jun 1969
TL;DR: In this article, the authors studied the stress-strain behavior at notch roots in sheet specimens under constant amplitude loading and showed that the stress strain at the notch roots at sheet specimens is linear in the length of the root.
Abstract: Elastoplastic stress-strain behavior at notch roots in sheet specimens under constant amplitude loading
TL;DR: In this paper, the results of a theoretical investigation of the stress-strain properties of tight brittle rock undergoing local failure (microcracking) during regions III and IV are discussed.
TL;DR: In this paper, a triaxial compression test was carried out on specimens of Bunter Sandstone at confining pressures of 0,150 and 500 psi and the nonlinearity of the compressibility was found to be much greater than that of the modulus of rigidity.
TL;DR: In this paper, the authors examined the impact of metallurgical variables on the fracture behavior of polycrystalline beryllium and found that the fracture is predominantly intergranular up to 6 kilobars and then becomes transgranular with a corresponding increase in the pressure dependence of fracture stress.
Journal Article•
TL;DR: In this paper, the authors investigate the physical behavior of OSAKA MARINE CLAY under the stress relaxation test and show that for a given given increase in the strain, both the initial stress and the fully relaxed stress relaxations decrease with increasing temperature.
Abstract: THE MECHANICAL BEHAVIOR OF CLAY IS INVESTIGATED FROM THE THERMAL BEHAVIOR OF ITS ELASTICITY AND VISCOSITY. THE MECHANICAL BEHAVIOR OF THE CLAY SKELETON WHOSE STRESS AND STRAIN ARE EXPRESSED BY A LINEAR RELATION WITH A PARAMETER OF TIME HAS BEEN SIMULATED BY A MATHEMATICAL MODEL. VISCOSITY OF CLAY IS INFLUENCED BY TEMPERATURE AS SUGGESTED IN THE FLOW BEHAVIOR AT VARIOUS TEMPRATURES. THE EFFECT OF TEMPERATURE ON THE ELASTICITY OF CLAY CAN BE INVESTIGATED BY THE BEHAVIOR ON THE STRESS RELAXATION TESTS AT VARIOUS TEMPERATURES. THE EFFECT OF TEMPERATURE ON THE ELASTIC MODULI IN THE MODEL IS INVESTIGATED. RESULTS OF THE STRESS RELAXATION TESTS SHOW THAT FOR A GIVEN INCREMENT OF STRAIN BOTH THE INITIAL STRESS AND THE FULLY RELAXED STRESS RELAXATION DECREASES WITH INCREASING TEMPERATURE. THE BEHAVIOR OF OSAKA MARINE CLAY UNDER THE STRESS RELAXATION TEST IS WELL PREDICTED BY THE MECHANICAL MODEL. ELASTIC MODULI DECREASE WITH THE INCREASE IN TEMPERATURE.
TL;DR: In this paper, a suggested method is described to provide data relating to the admissible strength of rocks in engineering, and the calculated stress distribution in cylindrical specimens under uniaxial a and triaxial loading, and deduced strain distribution in these specimens are shown to be useful working guides to the prediction of strength behaviour in the rocks concerned.
01 Feb 1969
TL;DR: In this article, the authors studied the stress-strain relationship of CONCRETE under UNIAXIAL TENSILE STRESS and discussed the factors that may influence the relationship.
Abstract: THE STRAIN PROPERTIES OF CONCRETE UNDER UNIAXIAL TENSILE STRESS ARE STUDIED AND FACTORS INFLUENCING THE STRESS-STRAIN RELATION ARE DISCUSSED. THE INFLUENCE OF SIX FACTORS: AGGREGATE-CEMENT RATIO, AGGREGATE GRADING, WATER-CEMENT RATIO, CURING CONDITIONS, SPECIMEN LENGTH, AND LOADING RATE ARE EXAMINED. THE TEST DATA SHOW THAT WITH THE EXCEPTION OF AGGREGATE GRADING, ALL THE ABOVE FACTORS INFLUENCE TO SOME DEGREE THE STRESS-STRAIN RELATION OF CONCRETE UNDER UNIAXIAL TENSION. /AUTHOR/
TL;DR: The physical significance of the sign conventions for stress and strain components, in particular, shear stress and shear strain, are discussed in this paper, where illustrative examples are provided.
Abstract: The definition and physical significance of the sign conventions for stress and strain components, in particular, shear stress and shear strain, are of vital importance in studying the response of anisotropic composite materials. Designers and analysts who must predict the strength and stiffness characteristics of laminated systems should be thoroughly familiar with the physical interpretations of these signs. In this paper we elaborate on these sign conventions and demonstrate their importance with several illustrative examples.
TL;DR: In this article, the variation of stress and strain in metals as they are subjected to shock impulses of up to 200 kb and released is presented. But the results of these measurements are not consistent with a simple elasto-plastic model for metal behaviour.
Abstract: Measurements are presented of the variation of stress and strain in metals as they are subjected to shock impulses of up to 200 kb and released. Results have been obtained for a magnesium alloy and for two grades of aluminium of very different yield strengths. The release characteristics of these metals are shown to be broadly consistent with a simple elasto-plastic model for metal behaviour. Elasto-plastic Hugoniots are fitted to published shock data for the metals used; a revised calibration is given for the manganin stress transducer employed, and a new method of construction is illustrated. Stress relaxation is observed in magnesium and is associated with the easy slip on the basal plane in hexagonal close-packed materials.
TL;DR: In this paper, the effects of strain on Young's modulus and Poisson's ratio for a composite propellant (86% solids, 14% polymeric binder) were evaluated from constant-strain-rate dilatation tests at temperatures from −60° to 160°F.
Abstract: Effects of strain on Young's modulus E and Poisson's ratio v for a composite propellant (86% solids, 14% polymeric binder) are evaluated from constant-strain-rate dilatation tests at temperatures from —60° to 160°F. Linear and nonlinear viscoelastic response are separated, and the nonlinearities found are accounted for by extensive volume change at low temperatures and strain hardening at elevated temperature because of high solids loading. Data from stress-relaxation tests at four strain levels at -60° and 80°F confirm the nonlinearities measured in the constant-strain-rate tests. Dewetting and subsequent volume change at low temperatures cause approximately a 50% change in E and a decrease in v (Cauchy relation) from 0.50 to 0.27. The significance of these E and v variations is assessed by a finiteelement computer analysis with typical grain designs subjected to cooldown arid pressurization loading conditions. The results show that neglect of nonlinearitie s in propellant modulus and v would yield high (conservative) predictions of stress and strain during cooldown in a steel-case motor but low predictions of strain because of the pressurization in fiberglass motor. Fortunately, in the latter case, the pressure would tend to reinforce E and v and reduce their nonlinearities. Nomenclature a, b = grain bore and outside diameters, respectively ar — time-temperature shift factor B = bulk modulus D = grain diameter E = Young's modulus E(t) = [\a(t)/€o]T Q/T = stress-relaxation modulus F(t) = [\cr(t)/e(t)]TQ/T = constant-strain-rate modulus L, I = grain length and gage length, respectively P = pressure T — temperature t = time V = volume e = A/// = strain; e = strain rate X = 1 -j- e = extension ratio v — Poisson's ratio o- = stress Subscripts
Patent•
04 Aug 1969
TL;DR: In this article, a transducer is equipped with a STRESSSENDITIVE BODY CONDITIONED to RENDER ADDITIVE the RADIAL and TANGENTIAL STRESSES imposed on the body.
Abstract: PRESENTED IS A TRANSDUCER ASSEMBLY INCLUDING A STRESSSENDITIVE BODY CONDITIONED TO RENDER ADDITIVE THE RADIAL AND TANGENTIAL STRESSES IMPOSED ON THE BODY.
TL;DR: The mechanism of stress and strain concentration at fatigue loading is governed by two fundamental effects: macro-support and micro-support as discussed by the authors, which is a nonlinear theory derived by the author.
Abstract: The mechanism of stress and strain concentration at fatigue loading is governed by two fundamental effects. Within the yield range of ductile materials the macro-support effect predominates, which can be represented by the results of a nonlinear theory derived by the author [1, 2, 4]. Within the high-cycle fatigue range the micro-support effects predominate, which can be described by the author's theory of mean stress value originally derived in connection with the calculation of sharply curved notches [1, 3, 4]. This theory introduces a material constant of length dimension. Taking the two effects into account, an approximate preliminary calculation of the fatigue strength of notched construction parts is possible [4].
TL;DR: In this paper, the constraint ratio was introduced as a measure of deformation behavior of each grain and basic relations between stress and strain were deduced in terms of the constraint ratios, and an energetic consideration was made on the deformation characteristics of polycrystals.
Abstract: It is a basic problem in the deformation of polycrystalline aggregates composed of anisotropic crystals, whether the stress or the strain is constant in the polycrystals. In order to treat the problem analytically, the idea of constraint ratio was introduced as a measure of deformation behaviour of each grain. Basic relations between stress and strain were deduced in terms of the constraint ratio. On the basis of the relations acquired, energetic consideration was made on the deformation characteristics of the polycrystals. It was found that, if the mutual restriction between the grains is absent, the constant stress condition is energetically stable. In real polycrystals, however, the strain is to be continuous through the grain boundary during deformation. It was concluded that, the mode of deformation changes gradually from constant stress to constant strain in proportion to the increase in strained region around the grain boundary.
TL;DR: In this paper, a non-linear form of viscoelasticity in terms of logarithmic strain is given together with a correction factor, and the results are compared with the theoretical predictions.
Abstract: A description of a simple non-linear form of viscoelasticity in terms of logarithmic strain is given together with a correction factor. Apparatus is described for determining relaxation data in simple tension and results are given for a low density polyethylene. These results are then used in conjunction with the theory to predict behaviour in simple tension at various strain rates, at various constant strain ratios in loading only, stress relaxation under complex stress and in tests with varying strain ratios. An apparatus is described to obtain such data and the results are compared with the theoretical predictions.
TL;DR: In wrinkling tests based on angular recovery from a fixed deformation, constraints imposed on the fibres by virtue of yarn or fabric construction are of secondary importance as mentioned in this paper, and when ageing effects have been eliminated, this results in similar wrinkleratings for all fabrics.
Abstract: In wrinkling tests based on angular recovery from a fixed deformation, constraints imposed on the fibres by virtue of yarn or fabric construction are of secondary importance. When ageing effects have been eliminated, this results in similar wrinkle-ratings for all fabrics. Any performance differences subjectively assessed during wear arise from either fabric deformability or optical effects caused by differences in curvature.
01 Jul 1969
TL;DR: In this paper, the authors developed a method based on USING a "LEAST SQUARES" FIT of a POLYNOMIAL EXPRESSION to EXPERIMENTAL data from reinFORCED or PRESTRESSED CONCRETE BEAM TESTS.
Abstract: AN ANALYSIS IS DEVELOPED FOR THE DETERMINATION OF THE COMPRESSIVE STRESS-STRAIN CURVE OF CONCRETE IN FLEXURE. THE METHOD IS BASED ON USING A "LEAST SQUARES" FIT OF A POLYNOMIAL EXPRESSION TO EXPERIMENTAL DATA FROM REINFORCED OR PRESTRESSED CONCRETE BEAM TESTS. IT IS SHOWN THAT THE METHOD GIVES BETTER CORRELATION WITH EXPERIMENTALLY MEASURED MOMENTS THAN THE FINITE DIFFERENCE ANALYSIS AND CAN BE EASILY ADAPTED TO THE COMPUTER. /ACI/
01 Jul 1969
TL;DR: In this article, the authors dealt with the stress and strain distribution around a circular bar embedded in a matrix and subjected to a mechanically applied triaxial load The three-dimensional 'freezing' technique of photoelasticity was used.
Abstract: : The report deals with the stress and strain distribution around a circular bar embedded in a matrix and subjected to a mechanically applied triaxial load The three-dimensional 'freezing' technique of photoelasticity was used The results obtained correspond to the case of a rigid circular bar embedded in an homogeneous, elastic matrix Two models were analyzed; in one the axis of the circular bar was parallel to the direction of the loading and in the other the axis of the circular bar was normal to the direction of loading By combining the results obtained independently for these two cases, stress and strain distribution around the circular bar for various ratios of triaxial load can be obtained (Author)
TL;DR: Differences exist between and within breeds in the initial modulus, the stress at 15% extension, and the slopes of the curves in the yield and post-yield regions.
Abstract: Stress–Strain data for wool fibres of different origin are presented, the tests having been made under different moisture conditions. Small differences exist between wool fibres from primary and secondary follicles from the same animal, the secondary being easier to stretch both initially and finally under wet conditions. However, the relative yield slope is markedly higher for secondary than for primary fibres. Differences exist between and within breeds in the initial modulus, the stress at 15% extension, and the slopes of the curves in the yield and post-yield regions.