Showing papers on "von Mises yield criterion published in 1985"

Direct Yield Stress Measurement with the Vane Method

Abstract: In the vane method for measuring the yield stress, the conventional analysis assumes that the stress is uniformly distributed on a cylindrical sheared surface to calculate the yield stress from the maximum torque and vane dimensions. By using two simple procedures, the present work shows that this assumption is justified at the moment of yielding. The yield stress calculated using the proposed methods compares favorably with that obtained with the conventional procedure. A comparison with the yield stress independently determined by other methods again confirms the usefulness of the vane technique as a simple but accurate method for direct yield stress measurement.

Effects of plastic strain amplitudes on non-proportional cyclic plasticity

Abstract: A series of plastic strain controlled cyclic tests was performed to facilitate the modelling of cyclic plasticity under general multiaxial loading conditions. The tests were carried out by applying combined axial force and torque to thin-walled tubular specimens of type 316 stainless steel at room temperature. Torsional and circular cycles of the equivalent plastic strain amplitude (von Mises type) ofΔep/2=0.1, 0.2 and 0.4% were specified.

The yield surface of textured polycrystals

Abstract: T he plastic anisotropy of a material is characterized in part by its yield surface. It is shown that conventional descriptions, based on extensions of the von Mises hypothesis for isotropic materials, are experimentally and theoretically inadequate in many instances. Symmetry arguments are used to derive the dimensionality and extent of the space necessary for representing the yield surface under various conditions of anisotropy. A useful concept is introduced: “closed” subspaces, in which sections and projections of the yield surface are identical and in which, therefore, normality is complete. Yield surfaces of heavily rolled or sheared sheets are derived from a computer simulation of polycrystal plasticity. It is found that even mild textures give rise to significant departures from “oval” yield surfaces: they develop sharp ridges and extensive flats. The anisotropy coefficients for in-plane tension of rolled sheets have been calculated. For torsion testing under fixed and free end conditions, respectively, the axial force and the length change have been calculated, as well as the change in the ratio of wall thickness to diameter.

Twin shear stress theory and its generalization

Abstract: Based on the twin shear stress yield criterion proposed by the author in 1961, a systematic theory of twin shear stress criterion is developed in the present paper. It includes twin shear stress yield criterion (in stress space), twin shear strain yield criterion (in strain space), generalized twin shear stress criterion considering the SD effect and the influence of hydrostatic stress, and a critical twin shear stress criterion of slip in crystal.

A curved quadrilateral element for static analysis of shells with geometric and material nonlinearities

Abstract: A 48 degrees-of-freedom quadrilateral element, including the effect of both material and geometric nonlinearities, is formulated and appropriate numerical procedures are adopted for the development of a systematic and efficient approach for the static nonlinear analysis of general shell structures. The element surface is described by a variable-order polynomial in curvilinear co-ordinates. The displacement functions are described by bicubic Hermitian polynomials in curvilinear co-ordinates. Without being confined to the assumption of axisymmetry, this formulation allows for the treatment of shells with a more general shape and with a complex spread of plastic zones. In the formulation for geometric nonlinearity, the total Lagrangian approach is adopted. Only small strains and small rotations are allowed. In the formulation for plastic deformation, the concept of a layered element model is used. In the inelastic range, the material is assumed to obey the Von Mises yield criterion and the Prandtl–Reuss flow rule. A tangential stiffness formulation is combined with the modified Newton–Raphson iteration method for the solution of nonlinear problems. A systematic choice of examples ranging from fiat plates to cylindrical panels and to spherical caps is solved and compared with available solutions to evaluate the recommended formulations and procedures in terms of their accuracy and efficiency.

Design of slender webs having rectangular holes

Abstract: The ultimate shear capacity of a plate girder having a central rectangular web‐hole is shown to be the sum of three contributing factors: (1) The elastic critical load of the web; (2) the load carried by the membrane tension in the web in the post critical stage; and (3) the load carried by the flanges. The elastic critical load in shear is evaluated by using an approximate formula derived from a finite element analysis. The load carried by membrane tension is calculated using the Von Mises criterion and a suggested mean value for the angle subtended by it with the longitudinal axis of the girder; the contribution of the flanges is calculated from their plastic moment capacities. The proposed method is shown to be satisfactory by comparing the predictions obtained from it with the corresponding test observations. An ultimate load method of designing flat strip reinforcement is proposed and is aimed at restoring the strength of the web to a value that would have been obtained had the hole not been cut. The...

Yield surface description of isotropic materials after cold prestrain

Abstract: A new procedure for the determination of the yield loci of prestressed materials is suggested. This procedure is based on the hypothesis of different isotropy center translations of the two stress deviator invariants. It also is based on the assumption that the yield loci equations are expressed by means of functions defined over the stress space which depend a) on the values of the translated invariants, calculated for the given stress tensor, and b) on the orientation in the stress space of the plane defined by the preloading tensor and the given stress tensor.

Adhesive Tensile Strengths of Scarf and Butt Joints of Steel Plates : 2nd Report, Relation between Mechanical Properties of Adhesive and Fracture Criteria of Joints

Abstract: For the investigation of fracture criteria, adhesive tensile strengths of scarf and butt joints bonded by a brittle and two ductile epoxy adhesives have been measure, and three-dimensional finite element analyses have been performed. Deformation of the Joints was influenced considerably by mechanical properties of adhesives. Fracture of the joints bonded by the brittle adhesive satisfied maximum principal stress criterion. At the scarf angles of 15° to 60°, fracture of the joints bonded by the ductile adhesives satisfied the von Mises criterion and at the scarf angles of more than 60°, a brittle (cleavage) fracture occurred in those joints by plastic constraint due to an increase of stress triaxiality in adhesive layer. Locations of fracture initiation and fracture modes of adhesive layers observed with an optical microscope and scanning electron microscope agreed with those expected from experimental results of deformation and adhesive tensile strength, and result of stress analyses.

Einfluß von Eigenspannungen auf Die Werkstoffanstrengung in wälzbeanspruchten Bauteilen

Abstract: Die Beanspruchung eines Werkstoffes in Hertz'schen Kontakten last sich z. B. mit der Gestaltanderungsenergie-Hypothese (Huber, von Mises, Hencky) als Vergleichsspannung berechnen. Diese Vergleichsspannung kann dann zu den lokalen Flieseigenschaften des Werkstoffes direkt in Beziehung gesetzt werden. Bei der Berechnung der Werkstoffanstrengung mus jedoch der Einflus der Reibung und der Eigenspannungen im Werkstoff berucksichtigt werden. Es wird gezeigt, das es unbedingt erforderlich ist, einen groseren Bereich des Halbraumes unter dem Kontakt zu betrachten, um das Maximum der Werkstoffanstrengung zu erfassen. Influence of Internal Stresses on the Stressing of Material in Components Subjected to Rolling-Contact Loads The stressing of a material in concentrated contacts can be calculated using f. e. the equivalent stress hypothesis by Huber, von Mises, Hencky (distortion energy hypothesis). The stress level can be directly related to the local yield properties of the material. For the calculation of the equivalent stress the influence of friction and internal stresses in the material have to be taken into account. The local stress level in the half space strongly depends on friction and internal stresses. It will be demonstrated, that it is necessary to have a look at a greater part of the full half space to find the maximum stress level.

Nonlinear analysis of thin-walled frames and members with arbitrary open cross sections.

Abstract: An incremental equilibrium equation for a beam-cloumn with arbitrary open cross sections is derived in a stiffness matrix form by using a moving element coordinate system and an incremental variational principle. A segmentation method for the cross section is used to analyze the development of plastic zones in the cross section and the effect of initial residual stresses arbitrarily distributed in the cross section. Yielding of the material is judged as a bi-axial stress problem under normal and shear stresses by using the flow theory of plasticity associated with von Mises yield criterion. Validity and efficiency of the present method are shown by illustrative examples.

Steel-pipe concrete core construction and its application

Abstract: The field of this invention relates to steel-pipe concrete core constructions. The prior art is generally used in such column as the load applied on it is much heavy and its compressed deformation is less semarkable. The consideration of prior art suggested that the stesses of steel-pipe follow Von Mises yield condition, and its theoretical analysis and calculating method of bearing strength of the axial compressed column is essentially based on the carrying capacity of concrete bore which is strengthened by the steel pipe.It is, therefore, a principal object of the present invention to provide a new method of force field equicibriam which method shows that the development of compression and tension stresses doesn't coincide with Von Mises yield condition during the deformation of steel-pipe under the application of axial loading. Accordingly, the steel-pipe concrete core construction may be used in a wide variety of application.

Biaxial Strength of HY 80 Steel

Abstract: The biaxial deformation behavior of HY 80 steel has been examined by testing thin wall tubes under combined axial tension and internal pressure. The effective stressstrain curves and the hardening response have been found to vary with the stress state. The plastic strain ratio at a given stress ratio deviates from the von Mises value except at the stress states near uniaxial tension, plane strain and equi-biaxial tension. Using Drucker theory, these deviations are eliminated and the resulting yield locus is in good agreement with both the Bishop-Hill theory and the experimental results. Influenced by the tube geometry, the instability strains at the onset of diffuse necking are decreased by an increase in hoop tension. The diffuse necking strains are reasonably predicted by the Swift and the LankfordSaibel/Mellor criteria.

Ultimate Strength of Rectangular Plates under Combination of Loads (Part 2)

Abstract: Interframe collapse of stiffened plate subjected to combined loading is investigated and empirical formulas for the ultimate strength are proposed based on the nonlinear finite element analysis in the present paper.The effects of existence of shear stress on the ultimate strength of plates is mainly investigated in the present paper. Reduction of ultimate strength by shear stress is more significant in the case of longitudinal compression than transverse one. Unified expression for the interaction of two direct and shear stresses is derived by modifying von Mises ellipsoid which is corresponding to in-plane crushing by yielding. In the formula the deviation from the ellipsoid is expressed as a function of plate slenderness ratio.

An experimental study of biaxial yield in modified 9Cr-1Mo steel at room temperature

Abstract: Described are two biaxial experiments which investigated yield, hardening, and flow behavior in modified 9Cr-1Mo steel at room temperature. The aim of these experiments was to determine whether the procedures recommended in NE Standard F9-5T for inelastic design analysis are applicable for this material in normalized and tempered condition. The first experiment investigated small offset yield behavior subsequent to radial preloads (sq rt of 3 sub sigma 12 = sub sigma 11) in tension-torsion stress space. The second experiment investigated yield behavior subsequent to nonradial preloads and also the time-dependent flow occurring during 0.5 hour periods at constant stress. The results of these experiments were qualitatively similar to those obtained earlier for types 304 and 316 stainless steel. Specifically, the von Mises yield criterion was found to provide a reasonable approximation of initial yield behavior. Although the subsequent yield surfaces suffered considerable distortion from their near-circular form after both radial and nonradial preloads, the hardening behavior was to the first order kinematic in nature. The strain-time data obtained during the 0.5 hr hold periods showed characteristics typical of creep curves. As in the case of earlier experiments, the high initial flow rates diminished more rapidly than would be estimated from elevated temperature data.

Prediction of the Service Behaviour of 2¼ Cr-1 Mo Steel Components in Electricity Generating Plant

Abstract: The θ projection method for extrapolating high temperature data has been shown to provide good estimates of the uniaxial and multiaxial creep behaviour of a 2–1/4 Cr-1 Mo steel. Correlations between unaxial and multiaxial minimum creep rates can be achieved using a reference stress approach based on von Mises yielding. Long term component performance may be assessed directly by applying the θ component to the appropriate multiaxial data.

Comparative Analysis BEM-FEM for Stress Concentration Around the Holes in Elasto-Plastic Infinite Medium

Abstract: The paper analyses the stress state around two elliptical holes that form a head water channel.The stress state is analized in the reinforced concrete consolidation layer around the elliptical holes(the gallerys)as well as in the adjacent rock to the gallerys.The methods used in this analysis are the Finite Element Method and the Boundary Element Method. A statical and a dynamical analysis of the holes is done by means of the two methods.The analysis in the elasto-plastic domain of the material is done by means of the Finite Element Method.The elastic and the mechanical characteristics of the material will be taken into account as well as Von Mises criterion for the elasto-plastic domain.there will be done a comparative analysis in the conditions when for the reinforced concrete layer we admit Von Mises criterion and for rock Drucker-Prager criterion.In the pa per will be presented the diagrams with stress concentrations near the holes too.

Three-dimensional elastic-plastic finite-element analysis of fatigue crack propagation

Abstract: Fatigue cracks are a major problem in designing structures subjected to cyclic loading. Cracks frequently occur in structures such as aircraft and spacecraft. The inspection intervals of many aircraft structures are based on crack-propagation lives. Therefore, improved prediction of propagation lives under flight-load conditions (variable-amplitude loading) are needed to provide more realistic design criteria for these structures. The main thrust was to develop a three-dimensional, nonlinear, elastic-plastic, finite element program capable of extending a crack and changing boundary conditions for the model under consideration. The finite-element model is composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material is assumed to be elastic-perfectly plastic. The cycle stress-strain curve for the material is shown Zienkiewicz's initial-stress method, von Mises's yield criterion, and Drucker's normality condition under small-strain assumptions are used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary conditions under cyclic loading.

On the large plastic deformation on clamped annular diaphragms under impulsive loading

Abstract: A simple theoretical study, together with experimental vindication, is presented for the inertial forming of annular diaphragms, clamped at their outer edges and subjected to impulsive loading. Starting from the von Mises yield condition and the associated flow rule, a governing equation is deduced for the title problem which can be reduced to a single second order partial differential equation which is solved numerically. Theoretical values of the major parameters over the entire deformation history are compared with corresponding experimental results obtained from tests on such diaphragms using an inertial forming machine. Results of high-speed photographic recordings are presented showing instantaneous profiles, velocities and hoop strain distributions.