scholarly journals Overview of an Experimental Program for Development of Yield Surfaces Tracing Method

2021 ◽  
Vol 11 (16) ◽  
pp. 7606
Author(s):  
Jan Štefan ◽  
Slavomír Parma ◽  
René Marek ◽  
Jiří Plešek ◽  
Constantin Ciocanel ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Plastic Flow ◽  
Experimental Technique ◽  
Yield Surface ◽  
Equivalent Plastic Strain ◽  
Experimental Program ◽  
Metallic Materials ◽  
Initial Yield ◽  
Yield Surfaces ◽  
Loading Modes

This paper develops an experimental technique to evaluate the initial yield surfaces of metallic materials, as well as to study their evolution during plastic flow. The experimental tracing of yield surfaces is necessary for deriving and calibrating more robust phenomenological models of directional distortional hardening. Such models can be used to characterize the behavior of structures experiencing complicated and demanding loading modes, such as multiaxial ratcheting. The experimental technique developed in this work uses thin-walled tubular specimens, along with a servo-hydraulic machine, under various modes of tension/compression and torque. Identification of the onset of plastic flow is based on a small proof equivalent plastic strain evaluated from the outputs of a contact biaxial extensometer firmly attached to a specimen surface. This allows for evaluation of both the initial yield surface, as well as theevolved yield surface after a plastic prestrain. Throughout a test, continuous and fully automatized evaluation of elastic moduli and proof plastic strain is assured through algorithms written in C# language. The current technique is shown to provide promising results to effectively capture the yield surfaces of conventional metallic materials.

Neutron Irradiation and the Yield Surfaces of Copper

1967 ◽  
Vol 34 (1) ◽  
pp. 200-206 ◽  
Author(s):  
T. D. Dudderar ◽  
J. Duffy
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Yield Surface ◽  
Large Change ◽  
The Other ◽  
Polycrystalline Copper ◽  
Initial Yield ◽  
Principal Effect ◽  
Yield Surfaces ◽  
Extensive Plastic Deformation

Tests were conducted to determine the effects of irradiation and plastic deformation on the yield surfaces of polycrystalline copper. It was found that the principal effect of plastic deformation on unirradiated copper was to translate the yield surface without appreciably changing its size or shape. Irradiation, on the other hand, produced a very large change in the overall size of the initial yield surface; in other words, it produced an effect phenomenologically similar to extensive isotropic strain-hardening. In addition, the shape of the initial yield surface after irradiation was dependent on the plastic strain offset chosen to define yield. This effect was not observed for the unirradiated metal. Extensive plastic deformation after irradiation caused the yield surface to translate and grow smaller without significantly changing shape.

Effect of Cyclic Loading on the Yield Surface

1979 ◽  
Vol 101 (1) ◽  
pp. 59-63 ◽  
Author(s):  
F. Ellyin ◽  
K. W. Neale
Keyword(s):  
Aluminum Alloy ◽  
Steady State ◽  
Cyclic Loading ◽  
Yield Surface ◽  
Stress Ratio ◽  
Axial Stress ◽  
Repeated Loading ◽  
Plastic Response ◽  
Initial Yield ◽  
Yield Surfaces

The effect of repeated loading on the yield surface is investigated experimentally for an aluminum alloy. Initial yield surfaces under combined axial stress and torsion are first obtained, and yield surfaces subsequent to steady-state plastic response are then determined for various cyclic loading programs. The results suggest that the initial yield surface expands and translates under cyclic loading and that the form of the steady-state yield surface is independent of the stress ratio.

The Yield, Flow and Creep Behaviour of Annealed En24 Steel under Combined Stress

1975 ◽  
Vol 17 (2) ◽  
pp. 82-92 ◽  
Author(s):  
S. N. Shahabi ◽  
A. Shelton
Keyword(s):  
Plastic Strain ◽  
Internal Pressure ◽  
Equivalent Stress ◽  
Equivalent Plastic Strain ◽  
Yield Locus ◽  
Combined Stress ◽  
Initial Yield ◽  
Strain And Strain Rate ◽  
Initial Anisotropy ◽  
Strain Components

Constant stress-ratio tests under combinations of tension, torsion and internal pressure have been performed on annealed En24 steel. The initial yield locus conformed to the Maxwell Mises criterion under tension-internal pressure but lay between the Maxwell-Mises and Tresca criteria under tension-torsion. This implies a small degree of initial anisotropy. Post-yield behaviour showed the plastic strain and strain-rate vectors to be normal to the initial yield locus and to remain so with respect to both time and increasing stress. The work-hardening hypotheses of plasticity theory were unsatisfactory in correlating any of the combined-stress results but equivalence of the strains was established from a consideration of the strain components and the angle between the stress and plastic-strain vectors. This resulted in the graphs of equivalent stress versus equivalent plastic strain in different stress fields being superposable. Room-temperature creep of the logarithmic form ε a In t + c was exhibited by all strain components and correlation of the creep coefficients was established by a method similar to that introduced for plastic strains. This finally led to a complete correlation of the stress-strain-time behaviour of this material under complex stress.

One-dimensional plasticity

2020 ◽  
pp. 369-405
Author(s):  
Lallit Anand ◽  
Sanjay Govindjee
Keyword(s):  
Numerical Methods ◽  
Plastic Strain ◽  
Plastic Flow ◽  
Kinematic Hardening ◽  
Equivalent Plastic Strain ◽  
Additive Decomposition ◽  
One Dimensional ◽  
Rate Dependent ◽  
Viscoplastic Models ◽  
The One

This chapter provides an introduction to plasticity models in the one-dimensional setting. The phenomenology of plasticity is discussed together with concepts of isotropic and kinematic hardening. The additive decomposition of the strain is introduced along with the concepts of plastic strain and equivalent plastic strain. Plastic flow is discussed and defined, and complete models of plasticity are formulated with loading/unloading conditions. Both rate independent and rate dependent (viscoplastic) models are discussed. In addition, basic numerical methods for evaluating plasticity models are presented.

Generalized Initial Yield Surfaces for Unidirectional Composites

1974 ◽  
Vol 41 (1) ◽  
pp. 249-253 ◽  
Author(s):  
G. J. Dvorak ◽  
M. S. M. Rao ◽  
J. Q. Tarn
Keyword(s):  
Yield Surface ◽  
Hydrostatic Stress ◽  
Stress Axis ◽  
Fiber Direction ◽  
Dimensional System ◽  
Uniform Temperature ◽  
Temperature Changes ◽  
Initial Yield ◽  
Yield Surfaces ◽  
External Loads

A numerical method is described for determination of generalized initial yield surfaces of unidirectional metal matrix composites under arbitrary external loads and uniform temperature changes. The method leads to the representation of the surface in a three-dimensional system of generalized stress coordinates which, respectively, coincide with the direction of the normal composite stress in the fiber direction, and with the two principal directions of the composite stresses acting in the transverse plane. The initial yield surface of the composite is an irregular ellipsoid with its longest axis inclined toward the hydrostatic stress axis. A thermomechanical analogy is used to show that as a result of a uniform temperature change, the yield surface experiences a rigid-body translation in the direction of the hydrostatic axis in the stress space. The initial yield behavior of a B-Al composite is described in detail. It is shown that microplastic yielding can take place in the composite under relatively small magnitudes of external loads, and hydrostatic stress, or as a result of moderate temperature changes.

scholarly journals Closed system of coupling effects in generalized thermo-elastoplasticity

2016 ◽  
Vol 21 (2) ◽  
pp. 461-483 ◽  
Author(s):  
Z. Śloderbach
Keyword(s):  
Plastic Strain ◽  
Strain Rate ◽  
Plastic Flow ◽  
Yield Surface ◽  
Plastic Strain Rate ◽  
Generalized Function ◽  
Strain Rate Tensor ◽  
Field Equations ◽  
Coupling Effects ◽  
Thermodynamic Forces

Abstract In this paper, the field equations of the generalized coupled thermoplasticity theory are derived using the postulates of classical thermodynamics of irreversible processses. Using the Legendre transformations two new thermodynamics potentials P and S depending upon internal thermodynamic forces Π are introduced. The most general form for all the thermodynamics potentials are assumed instead of the usually used additive form. Due to this assumption, it is possible to describe all the effects of thermomechanical couples and also the elastic-plastic coupling effects observed in such materials as rocks, soils, concretes and in some metalic materials. In this paper not only the usual postulate of existence of a dissipation qupotential (the Gyarmati postulate) is used to derive the velocity equation. The plastic flow constitutive equations have the character of non-associated flow laws even when the Gyarmati postulate is assumed. In general formulation, the plastic strain rate tensor is normal to the surface of the generalized function of plastic flow defined in the the space of internal thermodynamic forces Π but is not normal to the yield surface. However, in general formulation and after the use the Gyarmati postulate, the direction of the sum of the plastic strain rate tensor and the coupled elastic strain rate tensor is normal to the yield surface.

scholarly journals Investigation of the Thickness Differential on the Formability of Aluminum Tailor Welded Blanks

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 875
Author(s):  
Jie Wu ◽  
Yuri Hovanski ◽  
Michael Miles
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Dome Height ◽  
Tailor Welded Blanks ◽  
Simulation Results

A finite element model is proposed to investigate the effect of thickness differential on Limiting Dome Height (LDH) testing of aluminum tailor-welded blanks. The numerical model is validated via comparison of the equivalent plastic strain and displacement distribution between the simulation results and the experimental data. The normalized equivalent plastic strain and normalized LDH values are proposed as a means of quantifying the influence of thickness differential for a variety of different ratios. Increasing thickness differential was found to decrease the normalized equivalent plastic strain and normalized LDH values, this providing an evaluation of blank formability.

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2019 ◽  
Vol 287 ◽  
pp. 3-7
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

Yield surfaces and plastic flow of 45 steel under tension-torsion loading paths

2012 ◽  
Vol 25 (4) ◽  
pp. 348-360 ◽  
Author(s):  
Guijuan Hu ◽  
Keshi Zhang ◽  
Shihong Huang ◽  
Jiann-Wen Woody Ju
Keyword(s):  
Plastic Flow ◽  
Loading Paths ◽  
Yield Surfaces
Sign in / Sign up

Export Citation Format

Share Document