Showing papers on "Strain hardening exponent published in 1984"
TL;DR: In this article, a phenomenological treatment of plastic deformation is proposed which makes it possible to describe in a unified way the plastic behavior of a material both under dynamic loading and in creep.
1,310 citations
TL;DR: In this paper, the role of the strain and strain rate gradients in raising the apparent torsion peak strain ep above the ep values obtained from homogeneous tension or compression testing is clarified.
917 citations
TL;DR: In this article, the validity of using an equivalence criterion to describe the plastic properties of polycrystals at large strains is addressed from the point of view of the microscopic properties of the constituent grains.
497 citations
TL;DR: In this paper, the estimation procedures for materials which strain harden according to the simple power law used in finite-element caclulations are expressed in terms of the material stress-strain curve by using reference stress techniques common in creep analysis.
429 citations
TL;DR: In this paper, it was shown that the occurrence of such an "anomaly" is not restricted to anisotropic plasticity, but also in the case of hypoelasticity and classical isotropic hardening plasticity theory.
153 citations
TL;DR: In this article, the authors characterized the dislocation structures in the ferrite of a C-Mn-Si dual-phase steel intercritically annealed at 810°C by transmission electron microscopy.
Abstract: Dislocation structures in the ferrite of a C-Mn-Si dual-phase steel intercritically annealed at 810°C were characterized at various tensile strains by transmission electron microscopy At strains which corresponded to the second stage on a Jaoul-Crussard plot of strain hardening behavior, the dislocation density in the ferrite is inhomogeneous, with a higher density near the martensite. The third stage on a Jaoul-Crussard plot corresponds to the presence of a well-developed dislocation cell structure in the ferrite. The average cell size during this stage is smaller than the minimum size reported for deformed iron, and the cell size was inhomogeneous, with a smaller cell size near the martensite.
145 citations
TL;DR: In this article, the authors apply Hill's self-consistent method to finite elastic-plastic deformations and estimate the overall moduli of polycrystalline solids, showing that small second-order quantities such as shape changes of grains and residual stresses have a first-order effect on the overall response, as they lead to a loss of the overall stability by localized deformation.
Abstract: Applying Hill's self-consistent method to finite elastic-plastic deformations, the overall moduli of polycrystalline solids are estimated. The model predicts a Bauschinger effect, hardening, and formation of vertex or corner on the yield surface for both microscopically non-hardening and hardening crystals. The changes in the instantaneous moduli with deformation are examined, and their asymptotic behavior, especially in relation to possible localization of deformations, is discussed. An interesting conclusion is that small second-order quantities, such as shape changes of grains and residual stresses (measured relative to the crystal elastic moduli), have a first-order effect on the overall response, as they lead to a loss of the overall stability by localized deformation. The predicted incipience of localization for a uniaxial deformation in two dimensions depends on the initial yield strain, but the orientation of localization is slightly less than 45 deg with respect to the tensile direction, although the numerical instability makes it very difficult to estimate this direction accurately.
137 citations
TL;DR: In this article, the authors considered the shear wave propagation in a half-space of a nonlinear material, where the surface of the halfspace is subjected to a time dependent but spatially uniform tangential velocity.
Abstract: O ne-dimensional shear wave propagation in a half-space of a nonlinear material is considered. The surface of the half-space is subjected to a time dependent but spatially uniform tangential velocity. The half-space material exhibits strain hardening, thermal softening and strain rate sensitivity of the flow stress. For this system, a well-defined band of intense shear deformation can develop adjacent to the loaded surface, even though the material has no imperfections or other natural length scale. Representative particle velocity and strain profiles, which have been obtained numerically, are described for several different models.
122 citations
TL;DR: In this article, a detailed dislocation model is developed for the evolution of plastic resistance to large strain monotonie deformation of polycrystalline single phase, subgrain forming cubic metals.
120 citations
TL;DR: In this article, the effect of strain hardening on the flow behavior of superplastic copper alloy Coronze 638 has been analyzed and it was shown that grain growth at low strain rates causes sufficient hardening to compensate for the low strain rate sensitivity, thus preventing the development of sharp necks.
111 citations
TL;DR: In this article, a hardened steel wedge was indented vertically into the horizontal surface of an aluminium alloy specimen with subsequent horizontal movement of the specimen in a direction normal to the edge of the wedge with the vertical force held constant.
Abstract: Experiments are described in which a hardened steel wedge was indented vertically into the horizontal surface of an aluminium alloy specimen with subsequent horizontal movement of the specimen in a direction normal to the edge of the wedge with the vertical force held constant. Forces were recorded during a test and observations made of the plastic deformation of the specimen at the end of a test. Experimental results for a range of wedge angles and different lubricants are compared with results predicted from a slipline field analysis of asperity deformation in which the frictional force is considered to be the force needed to push waves of plastically deformed material ahead of wedge shaped asperities on the harder surface. Although the slipline field results are for an assumed non-hardening material, allowance is made in the calculations for the strain hardening of the actual test material by using average values of flow stress obtained from a stress-strain curve for the material.
01 Sep 1984
TL;DR: In this paper, the plane state of stress in a rotating circular disk of elastic-plastic material with linear strain hardening is studied based on Tresca's yield condition and its associated flow rule.
Abstract: The plane state of stress in a rotating circular disk of elastic-plastic material with linear strain hardening is studied based on Tresca's yield condition and its associated flow rule. The plastic core consists of two parts with different forms of the yield condition. By specializing the results to perfectly plastic material, the usual statically determinate stress distribution is recovered but, since the plastic strain at the axis becomes infinite, these stresses are not meaningful.
TL;DR: In this article, the elastic limits of the steels (the stress at a strain of less than 5 × 10 −5 and the stress-strain curves at small plastic strains were measured using balanced electrical resistance strain gauges of high sensitivity.
TL;DR: In this paper, it was shown that the size and orientation of an imperfection is critical in determining whether or not localized necking is initiated along the imperfection, and the influence of strain hardening, strain rate hardening and plastic anisotropy on the occurrence of local necking of imperfect sheet is also examined.
Abstract: Localized necking in sheet metal has been examined for strain paths between uniaxial tension and plane strain (ie, the negative minor strain region of a forming limit diagram) The behavior of sheet with preexisting imperfections has been analyzed and is contrasted to that free of imperfections In particular, it is shown that the size and orientation of an imperfection is critical in determining whether or not localized necking is initiated along the imperfection The influence of strain hardening, strain rate hardening, and plastic anisotropy on localized necking of an imperfect sheet is also examined One of the most significant conclusions obtained from present analysis and from a reexamination of Hill’s theory is the prediction of a critical thickness strain criterion for the onset of localized necking at negative minor strains, regardless of whether or not an imperfection is present The critical thickness strain criterion is observed in Ti alloys, Al alloys, steels, and brass
TL;DR: In this paper, a general equation for the plane-stress yield condition of orthotropic sheet material that is isotropic in its plane is given, and a set of constitutive relations for planar-isotropic strain hardening is formulated on the basis of the usual normality rule for strain rates, together with the assumption of a scalar relation between an effective stress and a work-equivalent effective strain.
Abstract: A general equation is written for the plane-stress yield condition of orthotropic sheet material that is isotropic in its plane. A set of constitutive relations for planar-isotropic strain hardening is then formulated on the basis of the usual normality rule for strain rates, together with the assumption of a scalar relation between an effective stress and a work-equivalent effective strain. It is shown how particular laws proposed earlier for sheet-metal plasticity fit into the general scheme. Solutions to the problem of balanced biaxial stretching of a sheet containing a circular hole illustrate a wide range of effects produced by various realizations of the general constitutive relations.
TL;DR: In this article, critical lateral fluid pressure for suppression of plastic buckling of annular plates during deep drawing by hydroforming process is examined and the theoretical prediction, utilizing the energy method, is accompanied by experiments.
TL;DR: In this article, Parkes et al. re-examine a classical problem of rigid-plastic structural dynamics solved by Parkes, namely that of finding the deformations of a beam carrying a mass at its tip which is subjected to a short pulse loading.
TL;DR: In this paper, a shear punch test was developed to extract strength and ductility information from thin sheet samples as small as transmission electron microscopy (TEM) disc specimens, based on driving a cylindrical punch through a clamped specimen, and instrumenting the punch to obtain a load-displacement curve of the punching process.
TL;DR: In this article, the authors show that grain-scale shear bands should form and should be inclined to the rolling direction preferentially at angles of 23° and 37°.
TL;DR: In this paper, the authors present some experimental results on 316 L stainless steel at room temperature and show that the additional hardening due to multiaxiality is present every time that the strain (or stress) path is non-proportional.
TL;DR: In this paper, the influence of the strain path upon the formability of the sheet is investigated using different types of forming limit diagrams under complex strain paths, and the effect of material strain hardening and strain-rate hardening is examined for several strain paths.
Abstract: Forming limit diagrams (FLDs) in simple and complex deformation paths are determined using a theoretical model of localized necking due to an initial heterogeneity of the sheet. The influence of the strain path upon the formability of the sheet is investigated using different types of FLDs under complex strain paths.The effect of material strain hardening and strain-rate hardening is examined for several strain paths. The influence of the imperfection level on the FLDs is presented. Computer simulation of the evolution of rheological parameters during deformation and their dependence on the strain path is carried out.The model is compared with previous experimental works, and a good agreement is obtained between theoretical results and experimental forming limit diagrams.The mathematical model developed in this work is shown to be a powerful tool to understand and predict the plastic behaviour of metal under simple and complex strain paths.
TL;DR: In this article, the efffect of stacking fault energy on solid particle erosion and the observed behaviour on the basis of existing erosion models were studied. But the results indicate that the erosion rate correlates well with the stacking fault energies and the strain hardening exponent.
TL;DR: In this article, the authors studied the stress dependence of the activation volume of polycrystalline alpha brasses over a range of strains in various grain sizes containing 10, 15, 20, and 30 at.-%Zn, and in poly crystalstalline Cu of 4N and 5N purities at 77, 200, and 290 K.
Abstract: The stress dependence of the activation volume was studied over a range of strains in polycrystalline alpha brasses of various grain sizes containing 10, 15, 20, and 30 at.-%Zn, and in polycrystalline Cu of 4N and 5N purities at 77, 200, and 290 K. The data show that solute atoms are effective obstacles to dislocation glide only up to small percentage values of uniaxial strain; conventional work hardening, i.e. forest cutting, determines the flow stress at higher strains.
TL;DR: In this paper, nonlinear axisymmetric finite element analyses are performed on the uniaxial compressive test of concrete cylinders with height-to-diameter ratios (h/d) ranging from 1-3.
Abstract: Nonlinear axisymmetric finite element analyses are performed on the uniaxial compressive test of concrete cylinders. The models include thick steel loading plates, and cylinders with height-to-diameter ratios (h/d) ranging from 1–3 are treated. A simple constitutive model of the concrete is employed, which accounts for the strain hardening and softening in the pre- and postfailure regions, respectively. When h/d = 2, the failure mode is found to consist of undisturbed end cones and the occurrence of strain softening, especially in the outer region of the cylinder middle. For shorter cylinders the strain softening is more pronounced along the surface of the cylinder middle, whereas longer cylinders exhibit a more uniform distribution of strain softening. The failure modes for force and displacement controlled tests are found to be similar. If long cylinders are to provide the true uniaxial strength the use of geometrically matched loading plates seems to be advantageous. Finally, it is observed that for variations of the element size within limits otherwise required to obtain a realistic analysis, the results are insensitive to the element size.
TL;DR: In this article, the steady state crack propagation problems of elastic-plastic materials in Mode I, plane strain under small scale yielding conditions were investigated with the aid of the finite element method.
Abstract: Steady state crack propagation problems of elastic-plastic materials in Mode I, plane strain under small scale yielding conditions were investigated with the aid of the finite element method. The elastic-perfectly plastic solution shows that elastic unloading wedges subtended by the crack tip in the plastic wake region do exist and that the stress state around the crack tip is similar to the modified Prandtl fan solution. To demonstrate the effects of a vertex on the yield surface, the small strain version of a phenomenological J2, corner theory of plasticity (Christoffersen, J. and Hutchinson, J. W. J. Mech. Phys. Solids, 27, 465 C 1979) with a power law stress strain relation was used to govern the strain hardening of the material. The results are compared with the conventional J2 incremental plasticity solution. To take account of Bauschinger like effects caused by the stress history near the crack tip, a simple kinematic hardening rule with a bilinear stress strain relation was also studied. The results are again compared with the smooth yield surface isotropic hardening solution for the same stress strain curve. There appears to be more potential for steady state crack growth in the conventional J2 incremental plasticity material than in the other two plasticity laws considered here if a crack opening displacement fracture criterion is used. However, a fracture criterion dependent on both stress and strain could lead to a contrary prediction.
TL;DR: In this article, the tensile behavior of plane-strain specimens having a central hole with axis in the zerostrain direction has been examined based on the contrasting behavior of two materials, one with a relatively high strain hardening rate (an HSLA steel) and the other with a low rate (Ti-6Al-4V).
Abstract: The tensile behavior of plane-strain specimens each having a central hole with axis in the zero-strain direction has been examined. The study is based on the contrasting behavior of two materials, one with a relatively high strain hardening rate (an HSLA steel) and the other with a low rate (Ti-6Al-4V). Deformation of the holes, associated necking of the ligaments, as well as the overall force-elongation response exhibit excellent agreement with predictions from a large-strain elastoplastic finite-element model. Failure of the high strain-hardening material occurs by ductile tearing across the ligaments, whereas failure of the low-hardening material occurs by shear localization. This is consistent with the predicted incremental plastic strain distributions as calculated by the finite element method. The experimental results and predictions of the finite-element models indicate the importance of work hardening in diffusing plastic flow in the presence of a geometric inhomogeneity in the form of a hole.
TL;DR: In this article, the axisymmetric bifurcation and post-bifurcation behavior of circular tubes subjected to the combined action of axial tension and internal pressure are investigated numerically using the finite element method.
TL;DR: In this paper, the nature of dislocation slip in interstitial free Ti-gettered iron and type 304 stainless steel has been examined through tests for plastic strain rate continuity based on load relaxation experiments.
TL;DR: In this paper, the effects of grain size, temperature, and interstitial content on ductility at low temperatures have been investigated and attributed to the occurrence of twinning in titanium.