Experimental Analysis and Crystallographic Model of Plastic Deformation after a Change of Loading Path in Mild Steel Polycrystals

1999 ◽  
Vol 578 ◽  
Author(s):  
T. Hoc ◽  
C. Rey
Keyword(s):  
Plastic Deformation ◽  
Mild Steel ◽  
Strain Localization ◽  
Loading Path ◽  
Slip Systems ◽  
Finite Element Code ◽  
Dislocation Densities ◽  
Dislocation Interactions ◽  
Sequential Tests ◽  
Microstructural Anisotropy

AbstractStrain localization in mild steel submitted to a sequential loading paths is investigated at macroscopic, mesoscopic and microscopic scales. The experimental results demonstrate that the morphology of the localization and the nominal load-displacement curves depend on the microstructural anisotropy. A crystalline model using a finite element code is proposed. The anisotropy is described by a hardening matrix whose terms correspond to dislocation-dislocation interactions and depend on the evolution of the dislocation densities on the activated slip systems during the sequential tests. The strain localization predicted by this model fits with the experimental observation and allows us to assume that localization is correlated to the saturation on the activated slip systems.

scholarly journals Dislocation interactions in olivine control postseismic creep of the upper mantle

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David Wallis ◽  
Lars N. Hansen ◽  
Angus J. Wilkinson ◽  
Ricardo A. Lebensohn
Keyword(s):  
Upper Mantle ◽  
Stress Transfer ◽  
Transient Creep ◽  
Slip Systems ◽  
Stress Distributions ◽  
Correlation Lengths ◽  
Mantle Viscosity ◽  
Dislocation Interactions ◽  
Different Temperatures ◽  
New Generation

AbstractChanges in stress applied to mantle rocks, such as those imposed by earthquakes, commonly induce a period of transient creep, which is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the accumulation of stresses among dislocations is the dominant cause of strain hardening in olivine at temperatures ≤600 °C, raising the question of whether the same process contributes to transient creep at higher temperatures. Here, we demonstrate that olivine samples deformed at 25 °C or 1150–1250 °C both preserve stress heterogeneities of ~1 GPa that are imparted by dislocations and have correlation lengths of ~1 μm. The similar stress distributions formed at these different temperatures indicate that accumulation of stresses among dislocations also provides a contribution to transient creep at high temperatures. The results motivate a new generation of models that capture these intragranular processes and may refine predictions of evolving mantle viscosity over the earthquake cycle.

Disorientations in dislocation structures: Formation and spatial correlation

2002 ◽  
Vol 17 (9) ◽  
pp. 2433-2441 ◽  
Author(s):  
Wolfgang Pantleon
Keyword(s):  
Plastic Deformation ◽  
Spatial Correlation ◽  
Distribution Functions ◽  
Scaling Behavior ◽  
Dislocation Dynamics ◽  
Slip Systems ◽  
Experimental Findings ◽  
Good Agreement

During plastic deformation, dislocation boundaries are formed and orientation differences across them arise. Two different causes lead to the formation of two kinds of deformation-induced boundaries: a statistical trapping of dislocations in incidental dislocation boundaries and a difference in the activation of slip systems on both sides of geometrically necessary boundaries. On the basis of these mechanisms, the occurrence of disorientations across both types of dislocation boundaries is modeled by dislocation dynamics. The resulting evolution of the disorientation angles with strain is in good agreement with experimental observations. The theoretically obtained distribution functions for the disorientation angles describe the experimental findings well and explain their scaling behavior. The model also predicts correlations between disorientations in neighboring boundaries, and evidence for their existence is presented.

Plastic Deformation and Pitting Corrosion of Mild Steel in Neutral Media

1978 ◽  
Vol 13 (3) ◽  
pp. 112-117 ◽  
Author(s):  
J. Jelinek ◽  
P. Neufeld ◽  
G. A. Pickup
Keyword(s):  
Plastic Deformation ◽  
Mild Steel ◽  
Pitting Corrosion ◽  
Neutral Media

scholarly journals Studying Deformation Behaviors in Austenitic Stainless Steels within a Temperature Range of 143 K < T < 420 K

2021 ◽  
pp. 22-30
Author(s):  
S. A Barannikova ◽  
A. M Nikonova ◽  
S. V Kolosov
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Strain Localization ◽  
Work Hardening ◽  
Deformation Localization ◽  
Linear Hardening ◽  
Jerky Flow ◽  
Temperature Range ◽  
Α Phase ◽  
Flow Stage

This work deals with studying staging and macroscopic strain localization in austenitic stainless steel 12Kh18N9T within a temperature range of 143 K < T < 420 K. The visualization and evolution of macroscopic localized plastic deformation bands at different stages of work hardening were carried out by the method of the double-exposure speckle photography (DESP), which allows registering displacement fields with a high accuracy by tracing changes on the surface of the material under study and then comparing the specklograms recorded during uniaxial tension. The shape of the tensile curves σ(ε) undergoes a significant change with a decreasing temperature due to the γ-α'-phase transformation induced by plastic deformation. The processing of the deformation curves of the steel samples made it possible to distinguish the following stages of strain hardening, i.e. the stage of linear hardening and jerky flow stage. A comparative analysis of the design diagrams (with the introduction of additional parameters of the Ludwigson equation) and experimental diagrams of tension of steel 12Kh18N9T for different temperatures is carried out. The analysis of local strains distributions showed that at the stage of linear work hardening, a mobile system of plastic strain localization centers is observed. The temperature dependence of the parameters of plastic deformation localization at the stages of linear work hardening has been established. Unlike the linear hardening, the jerky flow possesses the propagation of single plastic strain fronts that occur one after another through the sample due to the γ-α' phase transition and the Portevin-Le Chatelier effect. It was found that at the jerky flow stage, which is the final stage before the destruction of the sample, the centers of deformation localization do not merge, leading to the neck formation.

A New Model of Local Elastic Deflections in Grinding

1984 ◽  
Vol 106 (1) ◽  
pp. 154-163 ◽  
Author(s):  
D. P. Saini
Keyword(s):  
Plastic Deformation ◽  
Mild Steel ◽  
Mathematical Models ◽  
Normal Force ◽  
Tangential Force ◽  
Force Component ◽  
Workpiece Material ◽  
Direct Function ◽  
New Model ◽  
Single Grain

Mathematical models describing the deflection behavior of the wheel-work contact presented so far are based on the assumption that contact deflections are a direct function of the normal force on the wheel or the grains during grinding. This paper presents experimental results showing the evidence of a new mechanism of contact deflections due to the rotation of grain as a result of the tangential force component. In this perspective, a new model which considers the deflections due to both the normal and the tangential force is proposed and developed with the assumption of elasto-plastic deformation of the workpiece material around the grain during cutting. The model is shown to be consistent with experimental deflections obtained from single grain cutting on mild steel and EN25 steel specimens.

Mapping dislocation densities resulting from severe plastic deformation using large strain machining

2018 ◽  
Vol 33 (22) ◽  
pp. 3762-3773
Author(s):  
Sepideh Abolghasem ◽  
Saurabh Basu ◽  
Shashank Shekhar ◽  
M. Ravi Shankar
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Large Strain ◽  
Dislocation Densities ◽  
Image Position

Abstract

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