scholarly journals Modeling the Post-Yield Flow Behavior After Neutron and Electron Irradiation of Steels and Iron-Base Alloys

1998 ◽  
Vol 540 ◽  
Author(s):  
R.J. Dimelfi ◽  
D.E. Alexander ◽  
L.E. Rehn
Keyword(s):  
Yield Strength ◽  
Flow Behavior ◽  
True Strain ◽  
Practical Importance ◽  
Tensile Behavior ◽  
True Stress ◽  
Irradiation Hardening ◽  
Strain Behavior ◽  
Pressure Vessel Steels ◽  
Entire Flow

AbstractIrradiation hardening is an issue of practical importance as it relates to the remanent life and the nature of failure of reactor components exposed to displacement-producing radiation. Understanding these phenomena requires studies of fundamental microstructural mechanisms of hardening. In this paper, we analyze the tensile behavior of pressure vessel steels (A212B and A350) irradiated by neutrons and electrons. The results show that the post-yield true stress/true strain behavior can provide fingerprints of the different hardening effects that result from irradiation by the two particles, which suggests correspondingly different hardening microstructures for the two particles. Microstructurally-based models for irradiation-induced yield strength increases, combined with a model for strain hardening, are used to make predictions of the different effects of irradiation by the two particles on the entire flow curve that agree well with data.

Computational Process Simulation and Energy Parameter Analysis From Mechanical Deformation of Aerospace Alunimum Alloys

2002 ◽  
Author(s):  
James M. Fragomeni ◽  
Giridhar Venugopal
Keyword(s):  
Yield Strength ◽  
Experimental Testing ◽  
True Strain ◽  
Energy Parameter ◽  
True Stress ◽  
Parameter Analysis ◽  
Dissipated Energy ◽  
Strain Hardening Exponent ◽  
Element Analysis ◽  
Buckling Strength

Many systems that work on the processing of energy can be modeled in terms of that energy. The energy that is given to the system may be stored or dissipated in the form of heat. It was proposed to extend this concept to attainment of critical level of stored energy and/or dissipated energy for occurrence of buckling of a metal column under compressive loading. The fact that Energy Factor Parameter (E.F.P.) computed from the experimental true stress-true strain values, suddenly decreased and approached value close to zero indicated either buckling and/or softening, but deviated with the E.F.P. computed from the theoretical true stress and true strain values. The 7050-T7451 (Al-Zn-Mg-Cu-Zr) and Al-Li-Cu aluminum alloys in longitudinal and transverse grain orientations were compression tested for mechanical properties of yield strength, buckling strength, strength coefficient, strain hardening exponent. Correlation between ratio of buckling strength and yield strength with aging time for preaged ASTM compression specimens was established. The compression deformation of aluminum alloy 7050 was modeled using finite element analysis, with the experimental testing parameters and the database in the software package.

A Mathematical Description for the Stress-Strain Behavior of Annealed 2 1/4 Cr-1 Mo Steel

1976 ◽  
Vol 98 (2) ◽  
pp. 118-125 ◽  
Author(s):  
R. L. Klueh ◽  
T. L. Hebble
Keyword(s):  
Mathematical Description ◽  
Flow Behavior ◽  
True Strain ◽  
Empirical Relationship ◽  
Tensile Tests ◽  
Strain Rates ◽  
Strain Behavior ◽  
Test Conditions ◽  
Wide Range ◽  
Strain Data

We have conducted a detailed series of tensile tests on one heat of annealed 2 1/4 Cr-1 Mo steel over the range 25 to 593°C (75 to 1100°F) and at nominal strain rates of 0.4, 0.04, 0.004, and 0.0004/min. To determine an empirical relationship to represent the flow behavior, we fitted the true-stress true-strain data from these tests to several proposed models. The models fit were those proposed by Hollomon, Ludwik, Ludwigson, and Voce. From a comparison of the standard error of estimate, the Voce equation was concluded to be the best mathematical description of the data under most test conditions and the best single representation over the wide range of test conditions.

scholarly journals Stress-Strain Behavior of Perfluorosulfonic Acid Membranes at Various Temperatures and Humidities: Experiments and Phenomenological Modeling

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Ahmet Kusoglu ◽  
Yaliang Tang ◽  
Michael H. Santare ◽  
Anette M. Karlsson ◽  
Simon Cleghorn ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Flow Behavior ◽  
True Strain ◽  
Plastic Behavior ◽  
Stress Strain ◽  
True Strain Rate ◽  
Material Constants ◽  
Strain Behavior ◽  
Constitutive Response ◽  
Perfluorinated Sulfonic Acid

The constitutive response of perfluorinated sulfonic acid (PFSA) membranes based on tensile testing is investigated, and a phenomenological constitutive model for the elastoplastic flow behavior as a function of temperature and humidity is proposed. To this end, the G’Sell–Jonas (1979, “Determination of the Plastic Behavior of Solid Polymers at Constant True Strain Rate,” J. Mater. Sci., 14, pp. 583–591) constitutive model for semicrystalline polymers is extended by incorporating, in addition to temperature, relationships between the material constants of this model and the measured relative humidity. By matching the proposed constitutive model to the experimental stress-strain data, useful material constants are found. Furthermore, correlations between these material constants and Young’s modulus and proportional limit stress are investigated. The influence of material orientation, inherited from processing conditions, on the stress-strain behavior is also studied. The proposed model can be used to approximate the mechanical behavior of PFSA membranes in numerical simulations of a fuel cell operation.

Expression of a Generic Full-Range True Stress-True Strain Model for Pipeline Steels Using the Product-Log (Omega) Function

2017 ◽  
Author(s):  
Onyekachi Ndubuaku ◽  
Michael Martens ◽  
J. J. Roger Cheng ◽  
Samer Adeeb
Keyword(s):  
True Strain ◽  
Full Range ◽  
True Stress ◽  
Stress Strain ◽  
Pipeline Steels ◽  
Strain Behavior ◽  
Proposed Model ◽  
Strain Relationship ◽  
Strain Model

Steel pipelines are subjected to a variety of complex, and sometimes difficult to predict, loading schemes during the fabrication, installation and operation phases of their lifecycles. Consequently, the mechanical behavior of steel pipelines is not only influenced by the steel grade but also by the loading history of the pipe segments. Due to the resultant intricacies of the nonlinear load-deformation behavior of pipelines, adequate numerical analysis techniques are usually required for simulation of pipelines under different loading schemes. The validity of such numerical simulations is largely influenced by the accuracy of the true stress-true strain characterization of the pipeline steels. However, existing stress-strain mathematical expressions, developed for the characterization of metallic materials over the full-range of the stress-strain relationship, have been observed to either loose predictive accuracy beyond a limited strain range or, for the more accurate full-range models, are cumbersome due to their requirement of a large number of constituent parameters. This paper presents a relatively accurate and simple true stress-true strain model which is capable of accurately predicting the stress-strain behavior of pipeline steels over the full range of strains. The proposed stress-strain model is characteristically unlike existing stress-strain models as it is essentially defined by a Product-Log function using two proposed parameters, and is capable of capturing a reasonable approximation of the yield plateau in the stress-strain curve. To validate the proposed model, curve-fitting techniques are employed for comparison to experimental data of the stress-strain behavior of different pipeline steel grades (X52 – X100). Excellent agreements are observed between the proposed model and the different pipeline steels over the full-range of the true stress-true strain relationship. Furthermore, the applicability of the proposed model is validated by means of a proposed parametric procedure for predicting the ultimate compressive strength of shell elements.

scholarly journals Twinning and texture development in an extruded AM30 magnesium alloy during compressive deformation

2021 ◽  
Author(s):  
Dyuti Sarker
Keyword(s):  
Magnesium Alloy ◽  
Volume Fraction ◽  
Texture Evolution ◽  
Flow Behavior ◽  
True Strain ◽  
Compressive Strain ◽  
Extrusion Direction ◽  
Compressive Deformation ◽  
Strain Behavior ◽  
Loading Direction

This study was aimed at evaluating the microstructure, mechanical behavior and texture response of extruded AM30 magnesium alloy in uniaxial compression with special attention to the effect of compressive strain amount, sample orientation, loading direction, compressive prestrain, and annealing. Compressive deformation along the extrusion direction (ED) resulted in sigmoidal true stress-true strain behavior together with three distinct stages of strain hardening, due to the presence of two sets of basal textures {0001}<2110> and {0001}<1010>, with caxes aligned nearly parallel to the normal direction (ND) of the extruded plate which facilitated the occurrence of {1012} extension twinning. The effect of in-plane loading direction, i.e., 0°,15°, 30°, 45° from the ED on the compressive flow behavior was investigated, which revealed nearly constant yield and ultimate compressive strengths but with a remarkable increase of fracture strain compared to the ED sample. The effect of pre-strain along the ED on the formation of twinning and texture was investigated during re-compression along the ED, transverse direction (TD) and ND. In the two-step ED-ED compression, the disappearance of twin boundaries or the coalescence of twins via twin growth was observed. After pre-strain along the ED, re-compression along the TD showed two seemingly opposite phenomena, i.e., the formation of new twins and de-twinning to be coexistent due to the presence of multiple sets of textures after the first-step pre-straining. The de-twinning activity decreased and the texture weakening was achieved with increasing pre-strain in the ED while doing recompression along the ND at a constant strain amount. Texture measurements revealed that the c-axes of hcp unit cells were always rotated towards the compression direction, regardless of compression in the ED, TD or ND. The annealing temperature and time also had a pronounced effect on microstructure and texture evolution. With increasing annealing time, the twins in the pre-compressed samples were observed to disappear gradually, as demonstrated by a decreased volume fraction of twins and weakened texture which became more randomly distributed. As a result, during re-compression along the ED, fewer twin formation and less intense texture were observed, resulting in a significant increase of ductility.

Flow Behavior of “EPDM” Rubber during Dry Compression

2014 ◽  
Vol 14 (2) ◽  
pp. 115-123
Author(s):  
Abhijit Mukhopadhyay
Keyword(s):  
Flow Behavior ◽  
True Strain ◽  
Practical Importance ◽  
Compressive Load ◽  
Flow Characteristics ◽  
Compressive Force ◽  
Recent Time ◽  
Compression Tests ◽  
Epdm Rubber ◽  
Suitable Material

AbstractIn the recent time rubber has emerged as a very useful and suitable material for wider varieties of engineering and other applications which includes but not limited to domestic, sports and many more. It possesses large elasticity compared to metals, has greater damping capability, high internal friction and can accumulate energy to a greater extent compared to steel or other metals. During the deformation of rubber material, particularly by compressive force, internal damping of the material leads to energy dissipation. This is the cause of hysteretic friction of rubber. Friction of rubber has practical importance. At the same time it has many disadvantages tooUse of rubber as engineering material is not new. However, in the recent time its application is gaining renewed importance as well as interest due to several engineering researches and property enhancement too. It is, however, needless to be mentioned that prediction of exact behavior of any viscoelastic material like rubber is very difficult.In the present work compression tests have been carried out to determine the flow characteristics of EPDM rubber of different hardness. Flat mild steel platens have been used to apply axysymetric compressive load on the specimen under dry working condition. The flow behavior like load – elongation curves, true stress – true strain curves and specific energy requirements have been computed from the experimental data. Statical hysteresis and the loss factors have also been obtained.Experimental results reveal that the hardness of EPDM rubber has significant effect on the flow behavior. Thus, it can be stated that the flow behavior can be governed by controlling the carbon black (CB) concentration in EPDM rubber as the hardness depends on it. It is proposed to extend the experiments with the application of different kind of lubricants.

scholarly journals Twinning and texture development in an extruded AM30 magnesium alloy during compressive deformation

2021 ◽  
Author(s):  
Dyuti Sarker
Keyword(s):  
Magnesium Alloy ◽  
Volume Fraction ◽  
Texture Evolution ◽  
Flow Behavior ◽  
True Strain ◽  
Compressive Strain ◽  
Extrusion Direction ◽  
Compressive Deformation ◽  
Strain Behavior ◽  
Loading Direction

This study was aimed at evaluating the microstructure, mechanical behavior and texture response of extruded AM30 magnesium alloy in uniaxial compression with special attention to the effect of compressive strain amount, sample orientation, loading direction, compressive prestrain, and annealing. Compressive deformation along the extrusion direction (ED) resulted in sigmoidal true stress-true strain behavior together with three distinct stages of strain hardening, due to the presence of two sets of basal textures {0001}<2110> and {0001}<1010>, with caxes aligned nearly parallel to the normal direction (ND) of the extruded plate which facilitated the occurrence of {1012} extension twinning. The effect of in-plane loading direction, i.e., 0°,15°, 30°, 45° from the ED on the compressive flow behavior was investigated, which revealed nearly constant yield and ultimate compressive strengths but with a remarkable increase of fracture strain compared to the ED sample. The effect of pre-strain along the ED on the formation of twinning and texture was investigated during re-compression along the ED, transverse direction (TD) and ND. In the two-step ED-ED compression, the disappearance of twin boundaries or the coalescence of twins via twin growth was observed. After pre-strain along the ED, re-compression along the TD showed two seemingly opposite phenomena, i.e., the formation of new twins and de-twinning to be coexistent due to the presence of multiple sets of textures after the first-step pre-straining. The de-twinning activity decreased and the texture weakening was achieved with increasing pre-strain in the ED while doing recompression along the ND at a constant strain amount. Texture measurements revealed that the c-axes of hcp unit cells were always rotated towards the compression direction, regardless of compression in the ED, TD or ND. The annealing temperature and time also had a pronounced effect on microstructure and texture evolution. With increasing annealing time, the twins in the pre-compressed samples were observed to disappear gradually, as demonstrated by a decreased volume fraction of twins and weakened texture which became more randomly distributed. As a result, during re-compression along the ED, fewer twin formation and less intense texture were observed, resulting in a significant increase of ductility.

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