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.

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.

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.

Production of Ultra-Fine-Grained Aluminum Plates by Constrained Groove Pressing Technique

2013 ◽  
Author(s):  
Hadi Miyanaji ◽  
Ali Keshavarz Panahi ◽  
Ramin Hajavifard
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Yield Strength ◽  
The Other ◽  
Fine Grained ◽  
New Methods ◽  
Pressing Operation ◽  
Resistance To Wear ◽  
Aluminum Plates

One of the new methods of producing materials that have ultra-fine grains or grains of nanometer size is the method of severe plastic deformation (SPD). In this technique, by applying severe strains to the samples, the size of the grains is reduced to the nano scale, and as a result, the mechanical properties of the metal (including the yield strength and resistance to wear and abrasion) improve considerably. In this research, the effect of the constrained groove pressing process (as one of the SPD methods) on aluminum plates was studied. In this method, two dies (one with asymmetrical grooves, and the other, flat) were used for pressing the aluminum samples. With respect to the die’s geometry, at each pressing run, a shear strain equal to 0.58 is applied to some parts of the sample. By repeating the pressing operation, a large and significant amount of plastic strain is applied throughout the sample. In the present investigation, tensile and microhardness tests were employed to determine the effect of this process on the mechanical properties of the samples,. The results showed that, by increasing the number of pressing steps, hardness and strength of the samples increase, and the elongation ability diminishes. Of course, at higher numbers of pressing steps, a little decrease in strength was observed in the samples. Complete explanations regarding this decrease have been given in the text of the article.

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.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

Electron microscope studies of the plastic deformation of ternary alloys based on GaAs

1990 ◽  
Vol 48 (4) ◽  
pp. 1120-1120
Author(s):  
R. Haswell ◽  
U. Bangert ◽  
P. Charsley
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Room Temperature ◽  
Stacking Faults ◽  
The Other ◽  
Ternary Alloys ◽  
Dislocation Mobility ◽  
Semiconducting Materials ◽  
Micro Indentation

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.

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.

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