Showing papers on "Strain hardening exponent published in 1969"
TL;DR: In this paper, data from tensile tests at three temperatures on copper single crystals strengthened by fine dispersions of BeO particles, produced by internal oxidation, are discussed with reference to recent developments in the theories of dispersed particle strengthening.
44 citations
TL;DR: In this paper, the Ni-12 at. % Ti alloy was studied by means of thin foil transmission electron microscopy and electron diffraction technique, which showed two stage age-hardening at 500°C and 600°C.
Abstract: Precipitation behaviour in Ni-12 at. % Ti alloy was studied by means of thin foil transmission electron microscopy and electron diffraction technique. Hardness measurements showed two stage age-hardening at 500°C and 600°C. Thin foil observations revealed that the initial rapid increase in hardness was associated with the presence of superlattice. Slower second hardening was caused by the formation of modulated structure or periodic ordered structure. The increase in hardness by these periodic structures was found to be due to the internal strain hardening as originally suggested by Mott and Nabarro.
37 citations
TL;DR: In this article, the plane strain behavior of an clasto-plastic cracked plate in tension is examined at two levels of work-hardening, and the results are compared to similar data for the case of plane stress.
Abstract: The plane strain behavior of an clasto-plastic cracked plate in tension is examined at two levels of work-hardening. The results are compared to similar data for the case of plane stress
35 citations
TL;DR: In this article, microstructures of impulse-loaded regions were correlated with the stress levels effecting them, and strain profiles beneath the impact position for the type-200 nickel were determined metallographically and correlated with microhardness profiles.
Abstract: Plastic deformation in typical bcc, fcc and hcp metals has been studied as a function of initial impact energy (up to about 4200 J). Materials included 1100-F aluminium, 2024-T3 aluminium, lead, OFHC copper, type-200 nickel, columbium, tantalum, vanadium, molybdenum, and cadmium. Macroscopic deformation resulting from projectile impacts at velocities up to 8 km/sec was recorded by sub-microsecond photography and flash X-radiography. A correlation was established between homologous test temperature (T/Tm) and size of craters resulting from impact, as was a relationship between the relative increase in microhardness in the impact affected region beneath the target crater and impact stress over the square root of compressibility. The microstructures of impulse-loaded regions were correlated with the stress levels effecting them. Strain profiles beneath the impact position for the type-200 nickel were determined metallographically and correlated with microhardness profiles.
26 citations
TL;DR: In this article, a vanadium modification of 4340 alloy was used for stress corrosion testing of precracked specimens in a cantilever beam apparatus, and the effect of these plastic zones on the fracture paths was demonstrated.
Abstract: Stress corrosion testing of a vanadium modification of 4340 alloy was conducted using precracked specimens in a cantilever beam apparatus. Plastic zones at the crack tip were determined using optical interference measurements, and the effect of these plastic zones on the fracture paths was demonstrated. Crack propagation rates were measured for steels of varying yield strengths (140–205 ksi). Electron fractographs and photomicrographs associated with the fracture through plastic zone are presented. Crack propagation rates were shown to vary inversely with the yield strength of the steel with the overall failure time being related to both the propagation rate and the fracture toughness of the material.
24 citations
TL;DR: In this paper, the influence of the constitutive relation on the transient and final responses of elastic-plastic structures is investigated for uniformly expanding rings and long cylinders, and a solution based upon a rigidplastic material assumption is developed.
19 citations
TL;DR: In this article, the authors assume that the waviness of slip is governed by the ease of cross slip of screw dislocations, and the conditions for cross slip are analytically related to the applied stress, strain range, stacking fault energy and other material parameters.
18 citations
18 citations
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.
17 citations
TL;DR: In this paper, the effect of room temperature first order transition on the plastic yield behavior of polytetrafluoroethylene (PTFE) has been investigated, and the experimental observations suggest a model of the solid-state structure of PTFE which could be described as an "elastic-plastic network", in which crystalline domains are connected by elastic amorphous regions, and in which the crystaline domains can flow plastically at sufficiently high stress or temperature.
Abstract: : The effect of the room temperature first order transition on the plastic yield behavior of polytetrafluoroethylene (PTFE) has been investigated. Stress-strain curves were measured at different strain rates and temperatures. Tensile creep under constant dead load was also measured as a function of temperature and stress level. The effect of degree of crystallinity was investigated by using both a rapidly quenched and slow cooled polymer. The curve of yield stress vs temperature in the temperature range from -50 to +68C was found to be almost identical with the curve of elastic modulus vs temperature: the yield stress shows a marked local decrease at the first order transition. The experimental observations suggest a model of the solid-state structure of PTFE which could be described as an 'elastic-plastic network', in which crystalline domains are connected by elastic amorphous regions, and in which the crystalline domains can flow plastically at sufficiently high stress or temperature. (Author)
TL;DR: In this article, the plastic behavior of metals is studied, taking into account the strain bardening and the Bauschinger effect, in order to understand the plastic properties of metals.
Abstract: The plastic behaviour of metals is studied, taking into account the strain bardening and the Bauschinger effect.
TL;DR: In this article, a method for the analysis of a round bar carrying genera combinations of axial force and torque is presented, and the analysis is based on the Prandtl-Reuss incremental stress-strain laws and the von Mises yield criterion.
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
01 Jan 1969
TL;DR: In this article, a review of the nature of fracture processes occurring in high-strength materials is presented, including the level of stored elastic energy, component geometry, fracture toughness, and environment.
Abstract: This chapter presents a review of the nature of the fracture processes occurring in high-strength materials. Important parameters affecting fracture behavior of such materials are the level of stored elastic energy, component geometry, fracture toughness, and environment. Because of the occurrence of low-energy tear fracture in high-strength materials, there is no well-defined brittle-ductile transition, and temperature is therefore a less important variable than in the case of materials of lower strength. Knowledge of the characteristics of stable crack growth in high-strength materials permits a rational approach to safe design procedures to be made. Examples of design procedures are given. The metallurgical structure, particularly particle spacing and strength, together with consideration of strain hardening, are discussed in relation to fracture toughness of high-strength steels, aluminum, and titanium alloys. The influence of cyclic loading and environment on fracture of high-strength materials is also reviewed.
Patent•
28 Jan 1969
TL;DR: In this article, it is believed that the striated roughness of the resulting extrusion is minimized by grain elongation in the rolling direction and grain elongations in the extruding (axial) direction.
Abstract: Elongated extrusions of titanium base metal are produced from billets in the form of coils of titanium base metal. In such a coil, the rolling direction of the sheet and the axis of the convolutions of the sheet are at right angles to each other. It is believed that striated roughness of the resulting extrusion is minimized because grain elongation in the rolling direction and grain elongation in the extruding (axial) direction are such that strain hardening is neutralized.
TL;DR: Sliding friction tests of Cu and Cu-Be alloy plates in contact with various alloy sliders in air and vacuum were performed by as discussed by the authors, showing that they can be used to test the elasticity of the plates.
Abstract: Sliding friction tests of Cu and Cu-Be alloy plates in contact with various alloy sliders in air and vacuum
01 Jan 1969
TL;DR: In this paper, a survey on the use of digital computers for elastic-plastic analysis of pressure vessel components is presented and a review of linear incremental stress strain relations for a strain hardening Prandtl-Reuss material with a von Mises yield criterion is presented.
Abstract: : The report presents a survey on the use of digital computers for elastic-plastic analysis of pressure vessel components Included is a review of linear incremental stress strain relations for a strain hardening Prandtl-Reuss material with a von Mises yield criterion and the formation of generalized stress strain relations Case studies are given of axisymmmetric elastic- plastic analysis of a torispherical pressure vessel, a flush cylindrical nozzle in a sphere and a thick-walled cylinder under internal pressure
01 Aug 1969
TL;DR: In this article, the evolution of the yield locus of metals in the strain-hardening range is analyzed in the σ - τ plane by applying the theory of slip and by taking into account the Bauschinger effect.
Abstract: The evolution of the yield locus of metals in the strain-hardening range is analytically studied in the σ - τ plane. The problem, of theoretical and technical interest, is completely solved by applying the theory of slip and by taking into account the Bauschinger effect.
TL;DR: In this article, a complete solution for the enlargement of a circular hole in a disk of initial thickness h 0 = αr n 0, where α and n are constants, using Prager's kinematic hardening law with Tresca's yield function and its associated flow rule was obtained.
TL;DR: In this article, the propagation of plane elastic-plastic waves due to combined two shear loadings is studied in which the materials are assumed to be elastic, isotropic work hardening.
31 Oct 1969
TL;DR: In this paper, the authors investigated parameters affecting low-cycle fatigue life of AlSl 304, 316, and 348 and found that the mode of crack initiation was intergranular for all conditions except for the highest strain rate at 650 deg C.
Abstract: Parameters affecting low-cycle fatigue life of AlSl 304, 316, and 348 were investigated. Test parameters were temperature, strain amplitude, strain rate, and length of hold times at peak strain in each cycle. Metallographic and fractographic analysis of 348 and 304 stainless tested at 650 and 816 deg C and strain rates of 4 x 10{sup -3}, 4 x 10{sup -4} and 4 x 10{sup -5} sec{sup -1} showed that the mode of crack initiation was intergranular for all conditions except for the highest strain rate at 650 deg C. At these conditions, the 304 exhibited a transgranular type crack initiated at the highest and lowest strain range evaluated. The 348 exhibited better strain fatigue resistance for a given total axial or plastic strain level. Fatigue resistance at 316 to 650 deg C is less than 304 or 348. The 316 exhibited strain hardening followed by softening over the entire range (F.S.)
TL;DR: In this article, a linearization of the relationship between stress concentration factor and the reciprocal of strain hardening exponent for geometrically similar pressure vessels made of materials within the family has enabled a view of shakedown in vessels of strain-hardening materials to be formulated.
Abstract: A power law, well known in creep analysis, embodies a family of curves which express the stress-strain relations for a family of materials ranging from linear elastic to rigid perfectly plastic. A linearization of the relationship between stress concentration factor and the reciprocal of strain hardening exponent for geometrically similar pressure vessels made of materials within the family has enabled a view of shakedown in vessels of strain hardening materials to be formulated. The absence of discontinuities in the power law, except at the rigid plastic end point, results in shakedown loads dependent on strain hardening exponent and previous loading history.
01 Jan 1969
TL;DR: Dynamic plastic response of finite bar subject to axial impact load noting reflected waves, stress- strain-time histories and residual strain this paper. But this is not the case for all finite bars.
Abstract: Dynamic plastic response of finite bar subject to axial impact load noting reflected waves, stress- strain-time histories and residual strain