A Physically Based Constitutive Description for Nonproportional Cyclic Plasticity

1991 ◽  
Vol 113 (2) ◽  
pp. 254-262 ◽  
Author(s):  
Fan Jinghong ◽  
Peng Xianghe
Keyword(s):  
Stress Responses ◽  
Sudden Change ◽  
Dislocation Cell ◽  
Cyclic Plasticity ◽  
Cyclic Process ◽  
Planar Slip ◽  
History Effects ◽  
Physically Based ◽  
Physical Foundation ◽  
Two Parameters

The hardening behavior of materials in nonproportional cyclic process is related to the internal changes of materials, such as dislocation cell for wary slip material and ladder or vein substructures for planar slip material. The multiplicatively separated form of hardening function f, in terms of nonhardening region proposed by Ohno [1], and the measure of nonproportionality A proposed by Banallal and Marquis in 1987 [2], is then explained on this physical foundation. The new contributions of this hardening function are: (a) two parameters (f2 and f3) dependent on A are used to differentiate between the influence of latent hardening realized by a sudden change of loading direction, and hereditary hardening associated with nonproportional loading, (b) a general differential form fi (i = 1,2,3) is proposed, and memorial parameters a1 and a3 are introduced to describe different deformation history effects for wary and planar slip materials, (c) different hardening mechanisms through fi are embedded into thermomechanically constitutive relation. The stress responses of 304 and 316 stainless steels subjected to biaxial nonproportional loadings at room temperature are analyzed and compared with the experimental results obtained by Chaboche [3], Tanaka [4, 5] and Ohno [1].

Physically based modeling of cyclic plasticity for highly oriented nanotwinned metals

2021 ◽  
pp. 1-28
Author(s):  
Wufan Chen ◽  
Haofei Zhou ◽  
Wei Yang
Keyword(s):  
Fatigue Life ◽  
Cyclic Deformation ◽  
Engineering Application ◽  
Back Stress ◽  
Cyclic Plasticity ◽  
Dissipation Energy ◽  
Twin Lamella ◽  
History Independence ◽  
Physically Based ◽  
Precise Prediction

Abstract Fatigue resistance is crucial for the engineering application of metals. Polycrystalline metals with highly oriented nanotwins have been shown to exhibit a history-independent, stable and symmetric cyclic response [Pan et al. Nature 551 (2017) 214-217]. However, a constitutive model that incorporates the cyclic deformation mechanism of highly oriented nanotwinned metals is currently lacking. This study aims to develop a physically based model to describe the plastic deformation of highly oriented nanotwinned metals under cyclic loading parallel to the twin boundaries. The theoretical analysis is conducted based on a non-uniform distribution of twin boundary spacing measured by experiments. During cyclic plasticity, each twin lamella is discretely regarded as a perfect elastoplastic element with a yielding strength depending on its thickness. The interaction between adjacent nanotwins is not taken into consideration according to the cyclic plasticity mechanism of highly oriented nanotwins. The modeling results are well consistent with the experiments, including the loading-history independence, Masing behavior and back stress evolution. Moreover, the dissipation energy during cyclic deformation can be evaluated from a thermodynamics perspective, which offers an approach for the prediction of the fatigue life of the highly oriented nanotwins. The cyclic plasticity modeling and fatigue life prediction are unified without fatigue damage parameters. Overall, our work lays down a physics-informed framework that is critical for the precise prediction of the unique cyclic behaviors of highly oriented nanotwins.

Creep After Cyclic-Plasticity Under Multiaxial Conditions for Type 316 Stainless Steel at Elevated Temperature

1990 ◽  
Vol 112 (3) ◽  
pp. 346-352 ◽  
Author(s):  
S. Murakami ◽  
M. Kawai ◽  
Y. Yamada
Keyword(s):  
Stainless Steel ◽  
Uniaxial Tension ◽  
Flow Direction ◽  
Cyclic Plasticity ◽  
Total Strain Amplitude ◽  
316 Stainless Steel ◽  
Creep Flow ◽  
History Effects ◽  
Simple Tension ◽  
Strain Paths

History effects of cyclic-plasticity on subsequent creep have been elucidated for type 316 stainless steel at 600°C under multiaxial states of stress. Tension-compression and circular strain paths were specified for the prior cyclic plasticity. Constant stress creep experiments under simple tension, simple torsion, and combined tensiontorsion were first performed after uniaxial tension-compression cycles stabilized under a constant total strain amplitude. Then, in order to elucidate the path shape effects of prior strain cycles, the subsequent creep curves under uniaxial tension were compared for the uniaxial tension-compression and the non-proportional circular strain cycles which stabilized at identical stress amplitudes. The experimental results showed that the prior tension-compression cycles induced the anisotropy in creep behavior; creep resistance which was initially isotropic was enhanced in torsional direction, while it was decreased in tensile one. Another significant observation was that the circular strain cycles showed much larger hardening effect on creep than the tension-compression cycle. Regarding the creep flow direction, the effect of the prior cycles was negligible.

Flow recession behavior of dendritic subsurface flow patterns

2020 ◽  
Author(s):  
Jannick Strüven ◽  
Stefan Hergarten
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Conductivity ◽  
Power Law ◽  
Preferential Flow ◽  
Minimum Energy ◽  
Subsurface Flow ◽  
Flow Patterns ◽  
Short Term ◽  
Physically Based ◽  
Two Parameters

<p>Discharge curves of springs are the fingerprint of aquifers. In particular, the recession of flow after strong recharge events has been widely used for aquifer characterization. While an exponential decay is often found at long time scales, the short-term behavior is less unique and widely used in the context of characterizing karst systems. Several empirical and a few physically-based models describing the short-term recession behavior were proposed.</p><p>This study investigates the flow recession behavior of aquifers with preferential flow paths with a structure according to the concept of minimum energy dissipation.<br>Assuming a power-law relationship between hydraulic conductivity and porosity, the subsurface flow patterns used in our model are organized towards an optimal spatial distribution of these two parameters in a way that the total energy dissipation of the flow is minimized. This leads to two-dimensional dendritic network structures similar to river networks. Starting from a steady-state initial condition with a constant recharge rate we model the decrease of discharge over time, under the assumption of a linear storage behavior.<br>As expected the long-term flow recession can be approximated by an exponential function. At short times, however, our model predicts a power-law behavior with exponents ranging from 0.7 to 0.9. For the most realistic scenario, a quadratic relationship between hydraulic conductivity and porosity, the power-law exponent approximates 0.8 which corresponds well to what other studies have found for suitable recession events of karst springs.</p>

scholarly journals Influence of gaseous hydrogen on plastic strain in vicinity of fatigue crack tip in Armco pure iron

2018 ◽  
Vol 165 ◽  
pp. 03006 ◽  
Author(s):  
Tomoki Shinko ◽  
Gilbert Hénaff ◽  
Damien Halm ◽  
Guillaume Benoit
Keyword(s):  
Fatigue Crack ◽  
Plastic Strain ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Pure Iron ◽  
Cell Structure ◽  
Crack Tip ◽  
Dislocation Cell ◽  
Gaseous Hydrogen ◽  
Cyclic Plasticity

A multi-scale characterisation of the crack tip plasticity has been investigated in a fatigue crack propagation under gaseous hydrogen at gas pressure of 35 MPa in a commercially pure iron, Armco iron. The dislocation structure beneath a fracture surface was observed by a Transmission Electron Microscopy(TEM), and the cyclic and monotonic plastic zones were evaluated by an Out-of-Plane Displacement (OPD) measurement. By the TEM observation in a non-accelerated regime (ΔK = 11 MPa×m1/2), a dislocation cell structure was observed even in the brittle intergranular fracture in hydrogen. This result indicates a certain amount of plastic strain is introduced into the grains in front of an intergranular crack in hydrogen, and this may explain the mechanism of hydrogen-induced intergranular fatigue crack propagation. On the other hand, in an accelerated regime (ΔK = 18 and 20 MPa×m1/2), a distribution of scattered dislocation tangles without any cell or vein structure was observed in hydrogen. Besides, the inhibition of the cyclic plasticity near the crack path in hydrogen was confirmed by the OPD measurement. These results are clear evidences of hydrogen-induced localization of cyclic plasticity in the vicinity of a crack tip, which suggests a mechanism model of hydrogen-enhanced fatigue crack growth based on the plasticity localization.

scholarly journals Physically based alternative to the PE criterion for meteoroids

2020 ◽  
Vol 494 (1) ◽  
pp. 316-324
Author(s):  
Manuel Moreno-Ibáñez ◽  
Maria Gritsevich ◽  
Josep M Trigo-Rodríguez ◽  
Elizabeth A Silber
Keyword(s):  
Classification Accuracy ◽  
Input Data ◽  
Scaling Laws ◽  
Ablation Efficiency ◽  
The Earth ◽  
Physically Based ◽  
Dimensionless Variables ◽  
Input Variables ◽  
New Formulation ◽  
Two Parameters

ABSTRACT Meteoroids impacting the Earth atmosphere are commonly classified using the PE criterion. This criterion was introduced to support the identification of the fireball type by empirically linking its orbital origin and composition characteristics. Additionally, it is used as an indicator of the meteoroid tensile strength and its ability to penetrate the atmosphere. However, the level of classification accuracy of the PE criterion depends on the ability to constrain the value of the input data, retrieved from the fireball observation, required to derive the PE value. To overcome these uncertainties and achieve a greater classification detail, we propose a new formulation using scaling laws and dimensionless variables that groups all the input variables into two parameters that are directly obtained from the fireball observations. These two parameters, α and β, represent the drag and the mass-loss rates along the luminous part of the trajectory, respectively, and are linked to the shape, strength, ablation efficiency, mineralogical nature of the projectile, and duration of the fireball. Thus, the new formulation relies on a physical basis. This work shows the mathematical equivalence between the PE criterion and the logarithm of 2αβ under the same PE criterion assumptions. We demonstrate that log(2αβ) offers a more general formulation that does not require any preliminary constraint on the meteor flight scenario and discuss the suitability of the new formulation for expanding the classification beyond fully disintegrating fireballs to larger impactors including meteorite-dropping fireballs. The reliability of the new formulation is validated using the Prairie Network meteor observations.

scholarly journals The role of lateral erosion in the evolution of nondendritic drainage networks to dendricity and the persistence of dynamic networks

2021 ◽  
Vol 118 (16) ◽  
pp. e2015770118
Author(s):  
Jeffrey S. Kwang ◽  
Abigail L. Langston ◽  
Gary Parker
Keyword(s):  
Steady State ◽  
Dynamic Networks ◽  
River Networks ◽  
Stable Configuration ◽  
Lateral Incision ◽  
Drainage Networks ◽  
Physically Based ◽  
Physically Based Models ◽  
Lateral Erosion ◽  
Two Parameters

Dendritic, i.e., tree-like, river networks are ubiquitous features on Earth’s landscapes; however, how and why river networks organize themselves into this form are incompletely understood. A branching pattern has been argued to be an optimal state. Therefore, we should expect models of river evolution to drastically reorganize (suboptimal) purely nondendritic networks into (more optimal) dendritic networks. To date, current physically based models of river basin evolution are incapable of achieving this result without substantial allogenic forcing. Here, we present a model that does indeed accomplish massive drainage reorganization. The key feature in our model is basin-wide lateral incision of bedrock channels. The addition of this submodel allows for channels to laterally migrate, which generates river capture events and drainage migration. An important factor in the model that dictates the rate and frequency of drainage network reorganization is the ratio of two parameters, the lateral and vertical rock erodibility constants. In addition, our model is unique from others because its simulations approach a dynamic steady state. At a dynamic steady state, drainage networks persistently reorganize instead of approaching a stable configuration. Our model results suggest that lateral bedrock incision processes can drive major drainage reorganization and explain apparent long-lived transience in landscapes on Earth.

scholarly journals Snow cover duration trends observed at sites and predicted by multiple models

2020 ◽  
Author(s):  
Richard Essery ◽  
Hyungjun Kim ◽  
Libo Wang ◽  
Paul Bartlett ◽  
Aaron Boone ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Snow Cover ◽  
Strongly Correlated ◽  
Seasonal Snow ◽  
Physically Based ◽  
Physically Based Models ◽  
The Common ◽  
Snow Cover Duration ◽  
Two Parameters ◽  
Seasonal Snow Cover

Abstract. Thirty-year simulations of seasonal snow cover in 22 physically based models driven with bias-corrected meteorological reanalyses are examined at four sites with long records of snow observations. Annual snow cover durations differ widely between models but interannual variations are strongly correlated because of the common driving data. No significant trends are observed in starting dates for seasonal snow cover, but there are significant trends towards snow cover ending earlier at two of the sites in observations and most of the models. A simplified model with just two parameters controlling solar radiation and sensible heat contributions to snowmelt spans the ranges of snow cover durations and trends. This model predicts that sites where snow persists beyond annual peaks in solar radiation and air temperature will experience rapid decreases in snow cover duration with warming as snow begins to melt earlier and at times of year with more energy available for melting.

Use of CDM in Materials Modeling and Component Creep Life Prediction

2000 ◽  
Vol 122 (3) ◽  
pp. 281-296 ◽  
Author(s):  
Brian Dyson
Keyword(s):  
Damage Mechanics ◽  
Creep Damage ◽  
Inelastic Strain ◽  
Constant Load ◽  
Operating Conditions ◽  
Cyclic Plasticity ◽  
Rate Equations ◽  
Materials Modeling ◽  
Creep Life Prediction ◽  
Physically Based

Physically based continuum creep damage mechanics (CDM) has been reviewed and shown to provide a unifying framework for some seemingly diverse methods of predicting design and remanent creep lifetimes. These methods—theta projection, omega parameter, Larson-Miller parameter, and Robinson’s life fraction rule—exhibit certain strengths in common with CDM, but also weaknesses which CDM identifies and avoids. CDM consists of sets of coupled rate equations for inelastic strain, internal stress, and microstructural evolution (damage) which can then be integrated under boundary conditions appropriate to the test or service operating conditions: constant load/temperature for creep; constant total strain for stress-relaxation, variable stress/temperature, etc. Other state-variable approaches to creep and cyclic plasticity (for example, those due to Bodner, Miller, Chaboche, and Robinson), differ from CDM mainly in concentrating on the primary/secondary stages of creep (or cyclic work-hardening) and/or by their introduction of damage in an empirical Kachanov manner. The application of physically based CDM to LCF/thermal fatigue and its potential for predicting lifetimes of welded joints are also discussed. [S0094-9930(00)00903-3]

Statistically stored, geometrically necessary and grain boundary dislocation densities: microstructural representation and modelling

2007 ◽  
Vol 463 (2087) ◽  
pp. 2833-2853 ◽  
Author(s):  
O Rezvanian ◽  
M.A Zikry ◽  
A.M Rajendran
Keyword(s):  
Grain Boundary ◽  
Dislocation Cell ◽  
Misfit Dislocations ◽  
Triple Junctions ◽  
Crystalline Materials ◽  
Failure Initiation ◽  
Dislocation Densities ◽  
Physically Based ◽  
Crystalline Aggregates ◽  
Critical Regions

A unified physically based microstructural representation of f.c.c. crystalline materials has been developed and implemented to investigate the microstructural behaviour of f.c.c. crystalline aggregates under inelastic deformations. The proposed framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations (SSDs), geometrically necessary dislocations (GNDs) and grain boundary dislocations. This interrelated dislocation density formulation is then coupled to a specialized finite element framework to study the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic crystalline deformation. The GND densities are used to understand where crystallographic, non-crystallographic and cellular microstructures form and the nature of their dislocation composition. The SSD densities are formulated to represent dislocation cell microstructures to obtain predictions related to the inhomogeneous distribution of SSDs. The effects of the lattice misorientations at the grain boundaries (GBs) have been included by accounting for the densities of the misfit dislocations at the GBs that accommodate these misorientations. By directly accounting for the misfit dislocations, the strength of the boundary regions can be more accurately represented to account for phenomena associated with the effects of the GB strength on intergranular deformation heterogeneities, stress localization and the nucleation of failure surfaces at critical regions, such as triple junctions.

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