Showing papers on "von Mises yield criterion published in 1974"

The yield-point loads of singly-notched pin-loaded tensile strips

Abstract: P lane stress and plane strain yield-point loads have been calculated for single-edge notched strips when tensile loading is applied through pins. These yield-point loads are lower than those for fixed-grip loading, and the percentage drop is larger in plane stress than in plane strain. The calculations were required for assessing various creep and fatigue crack propagation tests. Excellent agreement was found between experimental yield-point loads and the plane stress calculations based on the von Mises yield criterion. However, no such agreement was found when further tests were carried out on doubleedged notched specimens. Possible reasons for this discrepancy are discussed. The plane strain calculations may also be used for the ‘double cantilever bend’ specimen by a simple substitution.

The Influence of State of Stress on Low-Cycle Fatigue of Structural Materials. A Literature Survey and Interpretive Report

Abstract: A literature survey was made on the influence of state of stress on the deformation and fracture behavior during low-cycle fatigue Only the phenomenological aspects of fracture and deformation in the low-cycle range (< 10 5 cycles) are considered Most of the materials investigated are shown or are assumed to have isotropic fatigue properties so that anisotropy was generally not considered For the isotropic case correlation formulas between uniaxial and multiaxial states of stress (strain) are stated in Appendix 1 Individual papers are reviewed to see which formula can best correlate uniaxial and multiaxial data No single criterion was found which consistently correlates the data Of all the correlation formulas the von Mises or distortion energy or octahedral shear stress criterion showed the highest degree of acceptance However, some papers show no good correlation on the basis of this criterion and serious objections are voiced against this criterion on principal grounds- The von Mises criterion gives the same value for two states of stress which differ only by a hydrostatic pressure, it is pressure insensitive Fatigue fracture is shown to be affected by the superposition of a hydrostatic pressure and therefore a preassure sensitive criterion should be used for correlation In future work a clear distinction of the influence of multiaxial states of stress (strain) on crack initiation and crack growth is necessary Crack initiation and propagation studies are urgently needed For isotropic fatigue properties pressure sensitive criteria should be incorporated into the constants of a generalized Coffin-Manson law In the case of anisotropic fatigue properties, new correlation procedures have to be developed

Nonlinear Thermo-Elastic-Plastic and Creep Analysis by the Finite-Element Method

Abstract: Consistent with a Lagrangian displacement formulation, an incremental constitutive relation for uncoupled thermoelastic-plastic and creep deformations is presented. The nonisothermal von Mises yield function and its associated flow rule are utilized, together with both isotropic and kinematic hardening rules. Steady-state creep deformations are considered using Norton-Odqvist's power law. This development is particularly applicable to the nonlinear finite element analysis of three-dimensional structures with timeand temperature-dependent material properties. Using a nonlinear general-purpose computer program which has been developed on the basis of this formulation, a number of numerical examples are solved and the results compared with the closed-form solutions.

A comparison of the dislocation structures at small strains in copper deformed in tension and in torsion

Abstract: OFHC copper specimens of 39 μm grain size were deformed in tension (to 8 pct tensile strain) and in pure torsion (to 8 pct shear strain) at 300 K and the resulting dislocation Burgers vectors, distributions and densities were determined using transmission electron microscopy. Employing the von Mises yield criterion and the total plastic-work hypothe-sis, good agreement was obtained between the tension and torsion test results for: (a) equivalent stress •σ versus equivalent strain •∈P curves, (b) the dislocation Burgers vec-tors, distribution and density as a function of the equivalent strain and (c) the equivalent stress as a function of the square root of the dislocation density. These results imply that in the unidirectional straining of copper there results a constant dislocation struc-ture for a given amount of plastic work, irrespective of whether the deformation is in tension or torsion. However, equally good correlations were obtained on the basis of maximum shear stress and maximum shear strain and therefore a positive decision be-tween the two yield criteria could not be made.

The yield-point loads of symmetrically-notched metal strips

Abstract: T heoretical plastic yield-point loads are calculated for symmetrically-notched metal strips in plane stress, assuming that the material obeys the von Mises yield criterion. Deep-notch solutions due to R. Hill are extended to cover all notch depths. The numerical results are presented in simple empirical formulae. The purpose of the work is to provide a way of discriminating between metals that obey the Tresca or the von Mises yield criteria.

Influence of machining temperature on the surface damage, residual stress, and texture of hot-pressed beryllium

Abstract: The effect of lathe machining temperature ranging from room to 400°C on the depth of twinning, extent of microcracking, residual stress, and texture of hot-pressed, S200-type beryllium was investigated. It was shown that twinning, microcracking, and residual stress were essentially eliminated when machining was performed above the ductile-to-brittle fracture transition range at 400°C. This behavior has been related to the operation of multiple slip systems, which, in terms of the von Mises criterion, satisfies the condition for uninhibited deformation. Minimization of residual stress was attributed to recovery resulting primarily from dislocation annihilation and climb, the latter giving rise to the formation of welldefined low-angle boundaries and stable hexagonal networks adjacent to the machined surface.

The Yield Criterion in the General Case of Nonhomogeneous Stress and Deformation Fields

Abstract: The transition of a material into the plastic state is connected with a change of its structure. It is obvious that, even within the framework of a continuum theory, one has to take into account the fact that the notion of structure does make sense only if it is related to a finite region (and not to a single point), and also, in an analogous way, to a finite interval of time.

Design of beams with off-center web openings

Abstract: Frozen stress photoelastic model techniques were used to determine the validity of using a Vierendeel truss analysis for analyzing wide flange beams having off-center unreinforced rectangular openings in their webs. Excellent correlation exists between experimental results and theoretical calculations. Results of this analysis were used with the von Mises yield theory to obtain interaction curves for use in design of such structural members.

Analyses of Solid State Extrusion Process of Polymeric Materials by Pressure Dependent Yield Criteria

Abstract: Among various methods to estimate extrusion pressure in solid state extrusion, Sachs's method1 is one of the most convenient and widely used ones. According to this method the equation for extrusion pressure is derived by taking accounts of the equilibrium of the forces in the tapered die part and of the yield criterion of the material being extruded. Analytical solutions have easily been obtained in the cases that the yielding behavior of the material obeys Tresca or von Mises yield criterion and where the yield stress does not depend on strain or the strain dependence of yield stress is represented in a simple analytical form. The yielding behavior of metallic materials satisfies these conditions.

Characterization of 2014-T651 Aluminum Alloy

Abstract: : The mechanical properties of 2014-T651 aluminum alloy were determined at room temperature under various strain rates and stress states. Uniaxial tension and compression tests were performed at strain rates ranging from 0.00001 to 1000 sec-1. Biaxial stress tests were conducted at rates of 0.0001 and 1 sec-1. The biaxial stress states were obtained with thin walled tubular specimens loaded with a combination of axial tension/compression, internal pressure, torsion and external pressure with any two loads superimposed for any given test. The experimentally observed yield agrees with the von Mises yield condition. Strain to failure exhibited a high degree of anisotropy; ductility being minimum in the thickness direction. Fracture toughness and pin bearing strength properties were also determined.

The Correlation between the Properties of Sintered Iron and the Cutting Phenomena

Abstract: In this paper, the correlation between the properties of sintered iron and the cutting phenomena is reported. For this purpose, the compressive stress-strain diagram in high-strain region of the sintered iron is found and the application of von Mises' yield condition to it is investigated, considering the relation between the compressive strain and the yield shear stress. Moreover, the cutting mechanism during high cutting speed and the average shear stress on the shear plane were also investigated.The results obtained are as follows:(1) The stress in the lower yield point of the sintered iron is extremely small and is about a half of the stress in a metal of the same component. This is brought about by the reduction of the effective sectional area and the strength of the grain boundary.(2) The Poisson ratio in the plastic region approaches a value of 0.5 relative to an increase of the compressive strain.(3) The shear zone at a cutting speed of 180 m/min is extremely large and is of the width about 0.08 mm, which is about twice that of the mild steel.(4) The mean shear stress is 50-55 kg/mm2.(5) The correlation between the properties of the sintered iron and the cutting phenomena is extremely higher after the effect of friction is compensated.

Computing laminar boundary layers with the von Mises equation

Abstract: There is much current interest in numerical methods of solution of the laminar boundary-layer equations. Methods used to date may generally be classified as (i) explicit finite-difference methods (e.g. Refs. 1, 2, 3); (ii) implicit finite-difference methods (e.g. Refs. 4, 5, 6, 7); (iii) difference-differential methods (e.g. Ref. 8). A method based on converting the boundary-layer problem into an integral equation and solving the latter by iteration has been developed by one of the present authors.