Polyaxial Stress-Strain Relations of a Strain-Hardening Metal

1954 ◽  
Vol 21 (4) ◽  
pp. 323-326
Author(s):  
S. B. Batdorf ◽  
Bernard Budiansky
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Stress Strain ◽  
Anisotropic Strain ◽  
Explicit Consideration ◽  
Plastic Stress

Abstract The authors assess a plastic stress-strain law of anisotropic strain-hardening type which they previously developed on the basis of explicit consideration of the polycrystalline nature of metals and the mechanism of plastic deformation. The assumptions made are reviewed, together with the successes and limitations of the theory. The authors indicate the lines along which they feel that improvement of the theory is to be sought.

A Theory of Elastic, Plastic, and Creep Deformations of an Initially Isotropic Material Showing Anisotropic Strain-Hardening, Creep Recovery, and Secondary Creep

1958 ◽  
Vol 25 (4) ◽  
pp. 529-536
Author(s):  
J. F. Besseling
Keyword(s):  
Plastic Deformation ◽  
Energy Dissipation ◽  
Strain Hardening ◽  
Isotropic Material ◽  
Creep Recovery ◽  
Secondary Creep ◽  
Stress Strain ◽  
Microscopic Scale ◽  
Anisotropic Strain ◽  
Creep Deformations

Abstract Stress-strain relations are given for an initially isotropic material, which is macroscopically homogeneous, but inhomogeneous on a microscopic scale. An element of volume is considered to be composed of various portions, which can be represented by subelements showing secondary creep and isotropic work-hardening in plastic deformation. If the condition is imposed that all subelements of an element of volume are subjected to the same total strain, it is demonstrated that the inelastic stress-strain relations of the material show anisotropic strain-hardening, creep recovery, and primary and secondary creep due to the nonuniform energy dissipation in deformation of the sub-elements. Only quasi-static deformations under isothermal conditions are considered. The theory is restricted to small total strains.

Analysis of Plastic Properties of Fe-Based Coatings at Different Annealing Temperatures by Nanoindentation

2019 ◽  
Vol 807 ◽  
pp. 121-127
Author(s):  
Zhe Yu ◽  
Hao Yue Yang ◽  
Zi Kun Song ◽  
Sui Xuan Lin ◽  
Hua Yi Li
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Penetration Depth ◽  
Elastic Recovery ◽  
Strain Hardening Exponent ◽  
Stress Strain ◽  
Plastic Properties ◽  
Different Temperatures ◽  
Critical Yield ◽  
1045 Steel

Fe-based alloys were deposited on 1045 steel by plasma cladding technique and the specimens were annealed at different temperatures. Instrumented indentation technique was adopted to investigate the plastic properties of the coatings, especially the stress-strain relations, critical yield stress and the strain hardening exponent. The results show that the elastic recovery in nanoindentation is less than 20% for all coatings and proves an obvious existence of plastic deformation in the coatings. It is found in the stress-strain curves that the annealing process makes the distribution of elastic modulus among the whole coating more uniformly. With the penetration depth increasing, the initial plastic deformation value gradually decreased which is more obvious for coatings annealing at high temperatures. In addition, the strain hardening exponent of the as-cladding coating and coatings annealed at 500°C keeps steady around 0.15 while the corresponding values of coatings annealed at 600°C and 700°C increased sharply with the penetration depth increasing and the maximum value is up to 0.32.

Influence of Assumed Strain Hardening Relation on Plastic Stress-Strain Response Identification From Conical Indentation

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Yupeng Zhang ◽  
Alan Needleman
Keyword(s):  
Strain Hardening ◽  
Power Law ◽  
Indentation Depth ◽  
Uniaxial Stress ◽  
Strain Response ◽  
Stress Strain ◽  
Indentation Force ◽  
Engineering Materials ◽  
Plastic Stress ◽  
Conical Indentation

Abstract Instrumented indentation tests provide an attractive means for obtaining data to characterize the plastic response of engineering materials. One difficulty in doing this is that the relation between the measured indentation force versus indentation depth response and the plastic stress-strain response is not unique. Materials with very different uniaxial stress-strain curves can give essentially identical curves of indentation force versus indentation depth. Zhang et al. (2019, “Identification of Plastic Properties From Conical Indentation Using a Bayesian-Type Statistical Approach,” ASME J. Appl. Mech., 86, p. 011002) numerically generated “experimental” conical indentation data and showed that using surface profile data and indentation force versus indentation depth data together with a Bayesian-type statistical analysis permitted the uniaxial plastic stress-strain response to be identified even for materials with indistinguishable indentation force versus indentation depth curves. The same form of hardening relation was used in the identification process as was used to generate the “experimental” data. Generally, a variety of power law expressions have been used to characterize the uniaxial plastic stress-strain response of engineering materials, and, of course, the form that gives the best fit for a material is not known a priori. Here, we use the same Bayesian statistics-based analysis but consider four characterizations of the plastic uniaxial stress-strain response and show that the identification of the hardening relation parameters and the associated uniaxial stress-strain response is not very sensitive to the form of the power law strain hardening relation chosen even with data that have significant noise.

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

The Effect of Plastic Deformation on the Thermoelastic Constant and the Potential to Evaluate Residual Stress

2011 ◽  
Vol 70 ◽  
pp. 458-463 ◽  
Author(s):  
A. F. Robinson ◽  
Janice M. Dulieu-Barton ◽  
S. Quinn ◽  
R. L. Burguete
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Thermoelastic Stress ◽  
Paint Coating ◽  
Full Field ◽  
Thermoelastic Constant ◽  
Thermoelastic Response ◽  
Measured Change

In some metals it has been shown that the introduction of plastic deformation or strain modifies the thermoelastic constant, K. If it was possible to define the magnitude of the change in thermoelastic constant over a range of plastic strain, then the plastic strain that a material has experienced could be established based on a measured change in the thermoelastic constant. This variation of the thermoelastic constant and the ability to estimate the plastic strain that has been experienced, has potential to form the basis of a novel non-destructive, non-contact, full-field technique for residual stress assessment using thermoelastic stress analysis (TSA). Recent research has suggested that the change in thermoelastic constant is related to the material dislocation that occurs during strain hardening, and thus the change in K for a material that does not strain harden would be significantly less than for a material that does. In the work described in this paper, the change in thermoelastic constant for three materials (316L stainless steel, AA2024 and AA7085) with different strain hardening characteristics is investigated. As the change in thermoelastic response due to plastic strain is small, and metallic specimens require a paint coating for TSA, the effects of the paint coating and other test factors on the thermoelastic response have been considered.

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