Experimental Study of Internal Variable Evolution in SS304L, at Multiple Rates and Temperatures

1999 ◽  
Vol 121 (2) ◽  
pp. 162-171 ◽  
Author(s):  
E. J. Harley ◽  
M. P. Miller ◽  
D. J. Bammann
Keyword(s):  
Yield Strength ◽  
Kinematic Hardening ◽  
Internal Variable ◽  
Isotropic Hardening ◽  
304L Stainless Steel ◽  
Strain Rates ◽  
Inelastic Behavior ◽  
Model Framework ◽  
Wide Range ◽  
Strength Asymmetry

Most metals exhibit a deformation-induced uniaxial yield strength asymmetry. Interpreted within the context of macroscale viscoplastic models, it is conventional to describe this yield strength asymmetry with an isotropic hardening variable, κ, and a kinematic hardening variable, α. The focus of this work was to conduct a series of reverse yield experiments to directly measure the evolution of α and κ in 304L stainless steel (SS304L) over large ranges of temperatures and strain rates. We found that the material exhibited inelastic behavior immediately on changing the straining direction. We discussed the ramifications of this behavior on our goal to directly measure α and κ within the context of an isotropic/kinematic hardening model framework. We also explored the capability of the model to simulate the behavior of SS304L under different loading conditions across a wide range of temperatures and strain rates.

Analytical Solutions for Circular Bars Subjected to Large Strain Plastic Torsion

1990 ◽  
Vol 57 (2) ◽  
pp. 298-306 ◽  
Author(s):  
K. W. Neale ◽  
S. C. Shrivastava
Keyword(s):  
Closed Form ◽  
Analytical Solutions ◽  
Large Strain ◽  
Kinematic Hardening ◽  
Flow Theory ◽  
Constitutive Laws ◽  
Isotropic Hardening ◽  
Large Strains ◽  
Inelastic Behavior ◽  
Rate Dependent

The inelastic behavior of solid circular bars twisted to arbitrarily large strains is considered. Various phenomenological constitutive laws currently employed to model finite strain inelastic behavior are shown to lead to closed-form analytical solutions for torsion. These include rate-independent elastic-plastic isotropic hardening J2 flow theory of plasticity, various kinematic hardening models of flow theory, and both hypoelastic and hyperelastic formulations of J2 deformation theory. Certain rate-dependent inelastic laws, including creep and strain-rate sensitivity models, also permit the development of closed-form solutions. The derivation of these solutions is presented as well as numerous applications to a wide variety of time-independent and rate-dependent plastic constitutive laws.

Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams

2006 ◽  
Vol 306-308 ◽  
pp. 905-910 ◽  
Author(s):  
Zhi Hua Wang ◽  
Hong Wei Ma ◽  
Long Mao Zhao ◽  
Gui Tong Yang
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Aluminum Foams ◽  
Wide Range ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.

scholarly journals Прогнозирование динамического предела текучести металлов с помощью двух структурно-временных параметров

2018 ◽  
Vol 60 (2) ◽  
pp. 240
Author(s):  
Н.С. Селютина ◽  
Ю.В. Петров
Keyword(s):  
Yield Strength ◽  
Incubation Time ◽  
Deformation Process ◽  
Empirical Models ◽  
Strain Rates ◽  
Loading History ◽  
Time Criterion ◽  
Temporal Features ◽  
Plastic Deformation Process ◽  
Wide Range

AbstractThe behavior of the yield strength of steel and a number of aluminum alloys is investigated in a wide range of strain rates, based on the incubation time criterion of yield and the empirical models of Johnson-Cook and Cowper-Symonds. In this paper, expressions for the parameters of the empirical models are derived through the characteristics of the incubation time criterion; a satisfactory agreement of these data and experimental results is obtained. The parameters of the empirical models can depend on some strain rate. The independence of the characteristics of the incubation time criterion of yield from the loading history and their connection with the structural and temporal features of the plastic deformation process give advantage of the approach based on the concept of incubation time with respect to empirical models and an effective and convenient equation for determining the yield strength in a wider range of strain rates.

A Dislocation Density-Based Viscoplasticity Model for Cyclic Deformation: Application to P91 Steel

2018 ◽  
Vol 10 (05) ◽  
pp. 1850055 ◽  
Author(s):  
Xu He ◽  
Yao Yao
Keyword(s):  
Cyclic Loading ◽  
Dislocation Density ◽  
Yield Strength ◽  
Cyclic Deformation ◽  
Kinematic Hardening ◽  
Strain Tensor ◽  
Isotropic Hardening ◽  
P91 Steel ◽  
Numerical Predictions ◽  
Proposed Model

To describe the viscoplastic behavior of materials under cyclic loading, a dislocation density-based constitutive model is developed based on the unified constitutive theory in which both the creep and plastic strain are integrated into an inelastic strain tensor. The stress evolution during cyclic deformation is caused by the mutual competition and interaction between hardening and recovery. To incorporate the physical mechanisms of cyclic deformation, the change of mobile dislocation density is associated with inelastic stain in the proposed model. The evolution of immobile dislocation density induced by strain hardening, dynamic recovery, static recovery and strain-induced recovery are simulated separately. The deterioration of yield strength following the hardening in tension (or compression) and subsequently in compression (or tension) is described by the Bauschinger effect and reduction of immobile dislocation density, the latter is induced by static- and strain-induced recovery. A kinematic hardening law based on dislocation density is proposed, both isotropic hardening and softening are described by determining the evolution of hardening parameters. The experimental data of P91 steel under different strain rates and temperatures are adopted to verify the proposed model. In general, the numerical predictions agree well with the experimental results. It is demonstrated that the developed model can accurately describe the hardening rate change, the yield strength deterioration and the softening under cyclic loading.

scholarly journals Моделирование временных эффектов необратимого деформирования на основе релаксационной модели пластичности

2019 ◽  
Vol 61 (6) ◽  
pp. 1015
Author(s):  
Н.С. Селютина ◽  
Ю.В. Петров
Keyword(s):  
Plastic Deformation ◽  
Yield Strength ◽  
High Strength ◽  
High Rate ◽  
Smooth Transition ◽  
Strain History ◽  
Strain Rates ◽  
Relaxation Model ◽  
Yield Drop ◽  
Wide Range

The analysis of plastic deformation of metals and polymethylmethacrylate under dynamic loading is carried out using a relaxation model of plastic deformation. The invariance of the parameters of the relaxation model of plasticity to the strain history allows us to obtain any set of deformation curves from a united viewpoint, both monotonic, with varying yield strength, and non-monotonic, with emerging and varying yield drop, as it is observed in experiments. The increase of the yield strength of high-strength 2.3Ni-1.3Cr steel together with the hardening effect both under high-rate and slow deformation is also modeled on the basis of the relaxation model. Using DP600 steel and nanocrystalline nickel as an example it is shown that the relaxation model of plasticity allows one to predict a smooth transition to the plastic deformation stage at slow quasi-static effects of ~ 10–3 s – 1, and also the appearance of a yield drop effect at strain rates of 500–6000 s –1. It is also shown that the developed approach allows one to simulate similar effects under high-rate deformation of polymethylmethacrylate. Thus, it was demonstrated using specific materials as an example that it is possible to effectively predict the deformation dependencies of the materials studied in a wide range of strain rates of 10-4-104 s-1 based on the parameters of the relaxation model of irreversible deformations.

scholarly journals Finite Plane Strain Bending under Tension of Isotropic and Kinematic Hardening Sheets

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1166
Author(s):  
Stanislav Strashnov ◽  
Sergei Alexandrov ◽  
Lihui Lang
Keyword(s):  
Plane Strain ◽  
Kinematic Hardening ◽  
Tensile Force ◽  
Plastic Region ◽  
Equivalent Plastic Strain ◽  
Isotropic Hardening ◽  
Finite Plane ◽  
Present Solution ◽  
Bending Under Tension ◽  
Elastic Unloading

The present paper provides a semianalytic solution for finite plane strain bending under tension of an incompressible elastic/plastic sheet using a material model that combines isotropic and kinematic hardening. A numerical treatment is only necessary to solve transcendental equations and evaluate ordinary integrals. An arbitrary function of the equivalent plastic strain controls isotropic hardening, and Prager’s law describes kinematic hardening. In general, the sheet consists of one elastic and two plastic regions. The solution is valid if the size of each plastic region increases. Parameters involved in the constitutive equations determine which of the plastic regions reaches its maximum size. The thickness of the elastic region is quite narrow when the present solution breaks down. Elastic unloading is also considered. A numerical example illustrates the general solution assuming that the tensile force is given, including pure bending as a particular case. This numerical solution demonstrates a significant effect of the parameter involved in Prager’s law on the bending moment and the distribution of stresses at loading, but a small effect on the distribution of residual stresses after unloading. This parameter also affects the range of validity of the solution that predicts purely elastic unloading.

Free volume based nonlinear viscoelastic model for polyurea over a wide range of strain rates and temperatures

2021 ◽  
Vol 152 ◽  
pp. 103650
Author(s):  
Chencheng Gong ◽  
Yan Chen ◽  
Ting Li ◽  
Zhanli Liu ◽  
Zhuo Zhuang ◽  
...  
Keyword(s):  
Free Volume ◽  
Viscoelastic Model ◽  
Strain Rates ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Nonlinear Viscoelastic Model

Pertinence of the Grain Size on the Mechanical Strength of Polycrystalline Metals

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
N. A. Zontsika ◽  
A. Abdul-Latif ◽  
S. Ramtani
Keyword(s):  
Grain Size ◽  
Mechanical Strength ◽  
Kinematic Hardening ◽  
Uniaxial Stress ◽  
Isotropic Hardening ◽  
Ultrafine Grained ◽  
Consistent Model ◽  
Micromechanical Approach ◽  
Interaction Law ◽  
Small Deformations

Motivated by the already developed micromechanical approach (Abdul-Latif et al., 2002, “Elasto-Inelastic Self-Consistent Model for Polycrystals,” ASME J. Appl. Mech., 69(3), pp. 309–316.), a new extension is proposed for describing the mechanical strength of ultrafine-grained (ufg) materials whose grain sizes, d, lie in the approximate range of 100 nm < d < 1000 nm as well as for the nanocrystalline (nc) materials characterized by d≤100 nm. In fact, the dislocation kinematics approach is considered for characterizing these materials where grain boundary is taken into account by a thermal diffusion concept. The used model deals with a soft nonincremental inclusion/matrix interaction law. The overall kinematic hardening effect is described naturally by the interaction law. Within the framework of small deformations hypothesis, the elastic part, assumed to be uniform and isotropic, is evaluated at the granular level. The heterogeneous inelastic part of deformation is locally determined. In addition, the intragranular isotropic hardening is modeled based on the interaction between the activated slip systems within the same grain. Affected by the grain size, the mechanical behavior of the ufg as well as the nc materials is fairly well described. This development is validated through several uniaxial stress–strain experimental results of copper and nickel.

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