scholarly journals A Phenomenological Model for Transient Deformation Based on State Variables

1981 ◽  
Vol 103 (4) ◽  
pp. 314-325 ◽  
Author(s):  
M. S. Jackson ◽  
C. W. Cho ◽  
P. Alexopoulos ◽  
Che-Yu Li
Keyword(s):  
Phenomenological Model ◽  
General Structure ◽  
Complex Loading ◽  
Dislocation Motion ◽  
Deformation Model ◽  
State Variables ◽  
Transient Effects ◽  
Variable Theory ◽  
Transient Deformation ◽  
Deformation Properties

The state variable theory of Hart, while providing a unified description of plasticity-dominated deformation, exhibits deficiencies when it is applied to transient deformation phenomena at stresses below macroplastic yielding. It appears that the description of stored anelastic strain is oversimplified. Consideration of a simple physical picture based on continuum dislocation pileups suggests that the neglect of weak barriers to dislocation motion is the source of these inadequacies. An appropriately modified description incorporating such barriers allows the construction of a modified phenomenological model including transient effects. The applicability of the modified model to aluminum has been investigated at room temperature. A consistent set of parameters describing the mechanical properties of the material has been determined experimentally. Agreement between experiment and model predictions for fairly complex loading histories is good. Although the constitutive equations for microplastic flow could not be established unambiguously, the results indicate that the general structure of the transient deformation model represents the deformation properties well.

scholarly journals Phenomenological model for transient deformation based on state variables

1980 ◽  
Author(s):  
M S Jackson ◽  
C W Cho ◽  
P Alexopoulos ◽  
H Mughrabi ◽  
C Y Li
Keyword(s):  
Phenomenological Model ◽  
State Variables ◽  
Transient Deformation

Internal Variable Theory Formulated by One Extended Potential Function

2020 ◽  
Vol 45 (3) ◽  
pp. 311-318
Author(s):  
Qiang Yang ◽  
Zhuofu Tao ◽  
Yaoru Liu
Keyword(s):  
Potential Function ◽  
Internal Variable ◽  
The State ◽  
Internal Variables ◽  
State Variables ◽  
Kinetic Rate ◽  
Variable Theory ◽  
Rate Laws ◽  
Flow Potential ◽  
Internal Variable Theory

AbstractIn the kinetic rate laws of internal variables, it is usually assumed that the rates of internal variables depend on the conjugate forces of the internal variables and the state variables. The dependence on the conjugate force has been fully addressed around flow potential functions. The kinetic rate laws can be formulated with two potential functions, the free energy function and the flow potential function. The dependence on the state variables has not been well addressed. Motivated by the previous study on the asymptotic stability of the internal variable theory by J. R. Rice, the thermodynamic significance of the dependence on the state variables is addressed in this paper. It is shown in this paper that the kinetic rate laws can be formulated by one extended potential function defined in an extended state space if the rates of internal variables do not depend explicitly on the internal variables. The extended state space is spanned by the state variables and the rate of internal variables. Furthermore, if the rates of internal variables do not depend explicitly on state variables, an extended Gibbs equation can be established based on the extended potential function, from which all constitutive equations can be recovered. This work may be considered as a certain Lagrangian formulation of the internal variable theory.

scholarly journals Deformation of rockfill in bodies of rockfill dams

2019 ◽  
pp. 5-5
Author(s):  
Mikhail Sainov
Keyword(s):  
Reinforced Concrete ◽  
Deformation Modulus ◽  
Deformation Model ◽  
Observation Data ◽  
Linear Deformation ◽  
Laboratory Test Results ◽  
Wide Range ◽  
Deformation Properties ◽  
Non Linear ◽  
The Impact

Introduction. The main factor determining the stress-strain state (SSS) of rockfill dam with reinforced concrete faces is deformability of the dam body material, mostly rockfill. However, the deformation properties of rockfill have not been sufficiently studied yet for the time being due to technical complexity of the matter, Materials and methods. To determine the deformation parameters of rockfill, scientific and technical information on the results of rockfill laboratory tests in stabilometers were collected and analyzed, as well as field data on deformations in the existing rockfill dams. After that, the values of rockfill linear deformation modulus obtained in the laboratory and in the field were compared. The laboratory test results were processed and analyzed to determine the parameters of the non-linear rockfill deformation model. Results. Analyses of the field observation data demonstrates that the deformation of the rockfill in the existing dams varies in a wide range: its linear deformation modulus may vary from 30 to 500 МPа. It was found out that the results of the most rockfill tests conducted in the laboratory, as a rule, approximately correspond to the lower limit of the rockfill deformation modulus variation range in the bodies of the existing dams. This can be explained by the discrepancy in density and particle sizes of model and natural soils. Only recently, results of rockfill experimental tests were obtained which were comparable with the results of the field measurements. They demonstrate that depending on the stress state the rockfill linear deformation modulus may reach 700 МPа. The processing of the results of those experiments made it possible to determine the parameters on the non-linear model describing the deformation of rockfill in the dam body. Conclusions. The obtained data allows for enhancement of the validity of rockfill dams SSS analyses, as well as for studying of the impact of the non-linear character of the rockfill deformation on the SSS of reinforced concrete faces of rockfill dams.

scholarly journals Transient deformation properties of Zircaloy for LOCA simulation. Final report

1980 ◽  
Author(s):  
C. R. Hann ◽  
C. L. Mohr ◽  
K. M. Busness ◽  
N. J. Olson ◽  
F. R. Reich ◽  
...  
Keyword(s):  
Final Report ◽  
Transient Deformation ◽  
Deformation Properties

A Phenomenological Model for Shape Memory Alloys With Uniformly Distributed Porosity

2020 ◽  
Author(s):  
Wael Zaki ◽  
N. V. Viet
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Phenomenological Model ◽  
Free Energy Density ◽  
State Variables ◽  
Mapping Algorithm ◽  
Return Mapping ◽  
Return Mapping Algorithm ◽  
Generalized Standard Materials ◽  
Inelastic Strains

Abstract A phenomenological model is proposed for shape memory alloys considering the presence of uniformly distributed voids. The model is developed within a modified generalized standard materials framework, which considers the presence of constraints on the state variables and ensures thermodynamic consistency. Within this framework, a free energy density is first proposed for the porous material, wherein the influence of porosity is accounted for by means of scalar state variables accounting for damage and inelastic dilatation. By choosing key thermodynamic forces, derived from the expression of the energy, as sub-gradients of a pseud-potential of dissipation, loading functions are derived that govern phase transformation and martensite detwinning. Flow rules are also proposed for damage and inelastic dilatation in a way that ensures positive dissipation. The model is discretized and the integration of the time-discrete formulation is carried out using an implicit formulation, whereby a return mapping algorithm is implemented to calculate increments of dissipative variables including inelastic strains. Comparison with data from the literature is finally presented.

Inelastic Deformation of Copper Nanoparticle Based Joints and Bonds

2021 ◽  
Author(s):  
Sanoop Thekkut ◽  
Maan Z. Kokash ◽  
Rajesh Sharma Sivasubramony ◽  
Yuki Kawana ◽  
Kabir Mirpuri ◽  
...  
Keyword(s):  
Inelastic Deformation ◽  
Practical Interest ◽  
Dislocation Motion ◽  
Metal Nanoparticle ◽  
Subsequent Work ◽  
Sintered Metal ◽  
Deformation Properties ◽  
Rapid Sintering ◽  
Stable Structures ◽  
Nanoporous Structures

Abstract The inelastic deformation properties of sintered metal nanoparticle joints are complicated by the inherent nanocrystalline and nanoporous structures as well as by dislocation networks formed in sintering or under cyclic loading. Creep rates of sintered nanocopper structures were found to be dominated by the diffusion of individual atoms or vacancies, while dislocation motion remained negligible up to stresses far above those of practical interest. Rapid sintering of one material led to unstable structures the creep of which could be strongly reduced by subsequent annealing or aging. Longer sintering of another material led to more stable structures, but creep rates could still be strongly enhanced by subsequent work hardening in mild cycling.

scholarly journals Linear models of two-component structure

2019 ◽  
Vol 135 ◽  
pp. 03058 ◽  
Author(s):  
Svetlana Nekrasov ◽  
Andrew Varlamov ◽  
Daliia Khamidulina ◽  
Vladimir Rimshin
Keyword(s):  
Linear Models ◽  
Concrete Specimen ◽  
The Body ◽  
Deformation Model ◽  
Component Structure ◽  
Concrete Prism ◽  
Deformation Properties ◽  
Two Component ◽  
Model Matrix ◽  
Strength And Deformation

Two-component model of the concrete composite was considered. The model is considered in two ways. Model “matrix - defects” and model of “matrix-filler”. In the model of “matrix - defects” we made the analysis of the behavior of the model depending on the number and distribution of defects in the body of the concrete prism. It is Described how to change in the number of defects in the process of loading a prismatic concrete specimen and their influence on strength and deformation properties of concrete. We obtained mathematical model of a two-component structure of concrete. We considered the changing deformation model of “matrix-filler” depending on the number and distribution of filler in the body of the concrete prism. Further models have been tested by comparison with computer models and experiments on standard prismatic specimens. It is revealed that the vertical cracks do not affect the vertical deformation of a prism.

Modeling of High Homologous Temperature Deformation Behavior Using the Viscoplasticity Theory Based on Overstress (VBO): Part I— Creep and Tensile Behavior

1995 ◽  
Vol 117 (4) ◽  
pp. 456-461 ◽  
Author(s):  
Yukio Tachibana ◽  
Erhard Krempl
Keyword(s):  
Cyclic Hardening ◽  
Back Stress ◽  
Tensile Tests ◽  
Tensile Behavior ◽  
Temperature Deformation ◽  
State Variables ◽  
Homologous Temperature ◽  
Variable Theory ◽  
Alloy 800 ◽  
High Homologous Temperature

The viscoplasticity theory based on overstress (VBO) is a state variable theory without a yield surface and without loading/unloading conditions. It contains two tensor valued state variables, the equilibrium (back) stress and the kinematic stress that is a repository for work hardening (softening). The scalar valued isotropic or time (rate)-independent stress models cyclic hardening (softening). For application to high homologous temperature, the effects of diffusion which counteracts the hardening of inelastic deformation has to be accounted for. Recovery of state terms are introduced in the growth laws for the state variables. A high homologous temperature VBO model is introduced and applied to the creep and tensile tests of Alloy 800 H between 750°C and 1050°C. Primary, secondary and tertiary creep as well as tensile behavior were well reproduced. It is shown that the transition to fluid state can be modeled with VBO.

scholarly journals Strength evaluation of concrete elements with non-metallic reinforcement under short-term dynamic compression

2019 ◽  
Vol 221 ◽  
pp. 01035
Author(s):  
Vasilii Plevkov ◽  
Igor Baldin ◽  
Andrei Nevskii
Keyword(s):  
Nonlinear Deformation ◽  
Dynamic Compression ◽  
Deformation Model ◽  
Short Term ◽  
External Reinforcement ◽  
Deformation Properties ◽  
Metallic Reinforcement ◽  
Properties Of Materials ◽  
Concrete Elements ◽  
Nonlinear Deformation Model

The article presents a method for calculating the strength of concrete elements with non-metallic fiber, rod and external reinforcement. The algorithm and the calculation program are shown, which are based on the use of a nonlinear deformation model of the normal section of such elements, taking into account the real deformation properties of materials under static and short-term dynamic loading.

scholarly journals Some aspects of forecasting the post-mining substratum deformation for evaluation of its influence on constructions

2018 ◽  
Vol 36 ◽  
pp. 01008
Author(s):  
Piotr Strzałkowski ◽  
Roman Ścigała ◽  
Katarzyna Szafulera
Keyword(s):  
Empirical Formula ◽  
Time Factor ◽  
Extraction Rate ◽  
Deformation Model ◽  
Building Structure ◽  
Time Intervals ◽  
Transient Deformation ◽  
Extraction Field ◽  
Long Time ◽  
Horizontal Strain

Some problems have been discussed, connected with performing predictions of post-mining terrain deformations. Especially problems occur with the summation of horizontal strain over long time intervals as well as predictions of linear discontinuous deformations. Of great importance in recent years is the problem of taking into account transient values of deformations associated with the development of extraction field. The exemplary analysis has been presented of planned extraction influences on two characteristic locations of building structure. The proposal has been shown of calculations with using transient deformation model allowing to describe the influence of extraction advance influence on the value of coefficient of extraction rate c (time factor), according to own original empirical formula.

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