Modeling and Identification of Elastic-Plastic Systems Using the Distributed-Element Model

1997 ◽  
Vol 119 (4) ◽  
pp. 332-336 ◽  
Author(s):  
Dar-Yun Chiang
Keyword(s):  
Distribution Function ◽  
Bauschinger Effect ◽  
Biaxial Tension ◽  
Kinematic Hardening ◽  
Element Model ◽  
Strength Distribution ◽  
Experimental Results ◽  
Modeling Technique ◽  
Elastic Plastic ◽  
Hardening Rules

A modeling technique is proposed for a class of distributed-element models, which is able to account for the multi-axial Bauschinger effect without any additional kinematic hardening rules. The parameters associated with each of the elements in the model are specified by introducing an appropriate strength distribution function so as to make the model parsimonious in parameters regardless of the number of elements introduced in the model. Validity of the proposed modeling technique, in both modeling and identification of elastic-plastic systems, is demonstrated by biaxial tension-torsion applications using experimental results from the literature.

Predictions of microtorsional experiments by micropolar plasticity

2005 ◽  
Vol 461 (2053) ◽  
pp. 189-205 ◽  
Author(s):  
Paschalis Grammenoudis ◽  
Charalampos Tsakmakis
Keyword(s):  
Size Effects ◽  
Bauschinger Effect ◽  
Kinematic Hardening ◽  
Circular Cylinders ◽  
Isotropic Hardening ◽  
Gradient Plasticity ◽  
Material Response ◽  
Micropolar Plasticity ◽  
Classical Plasticity ◽  
Hardening Rules

Kinematic hardening rules are employed in classical plasticity to capture the so–called Bauschinger effect. They are important when describing the material response during reloading. In the framework of thermodynamically consistent gradient plasticity theories, kinematic hardening effects were first incorporated into a micropolar plasticity model by Grammenoudis and Tsakmakis. The aim of the present paper is to investigate this model by predicting size effects in torsional loading of circular cylinders. It is shown that kinematic hardening rules compared with isotropic hardening rules, as adopted in the paper, provide more possibilities for modelling size effects in the material response, even if only monotonous loading conditions are considered.

A Practical Two Surface Plasticity Theory

1975 ◽  
Vol 42 (3) ◽  
pp. 641-646 ◽  
Author(s):  
R. D. Krieg
Keyword(s):  
Bauschinger Effect ◽  
Kinematic Hardening ◽  
Uniaxial Stress ◽  
Plasticity Theory ◽  
Experimental Results ◽  
Limit Surface ◽  
Hardening Model ◽  
Loading Surface ◽  
Surface Plasticity ◽  
Usual Concept

A plasticity theory is presented using the usual concept of a loading surface which moves and isotropically grows, but in addition uses a “limit surface” which grows and moves independently and encloses the loading surface. The plastic stiffness is a function of the distance between the surfaces at the loading point. Characteristics of the theory are a smoother transition between elastic and plastic regions on loading, an inherent Bauschinger effect, and more latitude on the description of hardening characteristics than the traditional methods used in structural codes. The full capability of the theory requires a memory of three vectors and three scalars, while some of the foregoing characteristics can be retained with only two vectors, the same as a traditional kinematic hardening model. The multiaxial theory is presented, particularized, specialized to uniaxial stress and the equations solved. The theory is compared to uniaxial stress experimental results.

Modeling and Identification of Inelastic Systems Using the Endochronic Model

1998 ◽  
Vol 65 (2) ◽  
pp. 513-518 ◽  
Author(s):  
Dar-Yun Chiang
Keyword(s):  
Parameter Estimation ◽  
Biaxial Tension ◽  
Equilibrium Points ◽  
Estimation Procedure ◽  
Experimental Results ◽  
Modeling Technique ◽  
Practical Applications ◽  
Modeling Process ◽  
Parameter Estimation Procedure ◽  
Systematic Optimization

An effective modeling method is proposed for the endochronic model based on the concept of plastic equilibrium points, which reduces the number of parameters involved and greatly simplifies the modeling process for practical applications. A systematic, optimization-based parameter estimation procedure for the proposed class of endochronic models is also presented for identification studies. Validity of the proposed modeling technique in both modeling and identification of inelastic systems is demonstrated by biaxial tension-torsion applications using experimental results available in the literature.

A method for the simultaneous derivation of tensile and compressive behaviour of materials under Bauschinger effect using bend tests

2006 ◽  
Vol 220 (10) ◽  
pp. 1509-1518 ◽  
Author(s):  
G Urriolagoitia-Sosa ◽  
J F Durodola ◽  
A Lopez-Castro ◽  
N A Fellows
Keyword(s):  
Compressive Stress ◽  
Bauschinger Effect ◽  
Experimental Testing ◽  
Kinematic Hardening ◽  
Theoretical Data ◽  
Test Results ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behaviour ◽  
Hardening Rules

Some materials exhibit Bauschinger effect as a consequence of strain hardening. The effect leads to asymmetric tensile and compressive stress-strain behaviour. If the hardening behaviour in either tension or compression is known, combined isotropic/kinematic hardening rules can be used to estimate the hardening behaviour in the other. These rules are, however, only approximate empirical relationships that are derived from the analysis of separate tensile and compressive test results. This article presents a method for the simultaneous derivation of tensile and compressive stress-strain behaviour from bending tests only. The information required is strains at the top and bottom surfaces of beams and moment as load is incrementally applied. The derivation of the method is based on the application of tensile and moment equilibrium conditions. The proposed method is tested on theoretical data obtained from finite-element analysis and as well as on data from actual experimental testing. The agreement between the results obtained is very good.

On the Macroscopic Response and Field Statistics in Particulate Composites With Elasto-Plastic Phases and Random Microstructures

2021 ◽  
Vol 88 (3) ◽  
Author(s):  
Michalis Agoras ◽  
Konstantinos Garyfallogiannis ◽  
Nikolaos Aravas
Keyword(s):  
Bauschinger Effect ◽  
Kinematic Hardening ◽  
Local Strain ◽  
Spherical Particles ◽  
Particulate Composites ◽  
Variational Procedure ◽  
Two Phase ◽  
Effective Response ◽  
Elastic Plastic ◽  
Macroscopic Response

Abstract In this article, we carry out a theoretical investigation of the macroscopic response and field statistics in two-phase particulate composites with elasto-plastic constituents and random microstructures under cyclic loading conditions. To this end, we make use of the “incremental variational homogenization” (IVH) procedure of Agoras et al. (2016, “Incremental Variational Procedure for Elasto-Viscoplastic Composites and Application to Polymer- and Metal-Matrix Composites Reinforced by Spheroidal Elastic Particles,” Int. J. Solid Struct., 97–98, pp. 668–686) and corresponding unit cell finite element simulations. Results are obtained for statistically isotropic distributions of spherical particles and for “spheroidal distributions” of spheroidal particles. It is shown analytically that the IVH estimate of Agoras et al. and that of Lahellec and Suquet (2013, “Effective Response and Field Statistics in Elasto-Plastic and Elasto-Visco-Plastic Composites Under Radial and Non-Radial Loadings,” Int. J. Plasticity, 42, pp. 1–30) are equivalent. In addition, it is illustrated by means of specific numeral comparisons that the IVH estimate is also equivalent (to within numerical accuracy) to the corresponding estimates of Idiart and Lahellec (2016, “Estimates for the Overall Linear Properties of Pointwise Heterogeneous Solids With Application to Elasto-Viscoplasticity,” J. Mech. Phys. Solids, 97, pp. 317–332) and Lucchetta et al. (2019, “A Double Incremental Variational Procedure for Elastoplastic Composites With Combined Isotropic and Linear Kinematic Hardening,” Int. J. Solid Struct., 158, pp. 243–267). Furthermore, it is shown in the context of specific exact results for composite materials with lamellar microstructures that the elastic–plastic coupling and the Bauschinger effect are the macroscopic manifestations of the incompatibility of the local elastic strains. Local strain hardening is incorporate in the IVH model. The predictions of the IVH model for the macroscopic response of particulate composites are found to be in good agreement with the corresponding numerical results, in general. For the extreme cases of rigidly reinforced composites and porous materials, however, the IVH model fails to capture the elastic–plastic coupling and the Bauschinger effect. The underlying reasons for this shortcoming are discussed and a strategy toward the improvement of the IVH model is proposed.

Improved Finite Element Model to Predict the Reverse Loading Behavior of Autofrettaged A723 and HB7 Cylinders

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
E. Troiano ◽  
J. H. Underwood ◽  
A. M. Venter ◽  
J. H. Izzo ◽  
J. M. Norray
Keyword(s):  
Finite Element ◽  
Bauschinger Effect ◽  
Kinematic Hardening ◽  
Element Model ◽  
Significant Error ◽  
Strain Hardening Exponent ◽  
Element Analysis ◽  
Strong Function ◽  
Reverse Loading ◽  
Loss Of Strength

Ideal isotropic or kinematic hardening is often utilized in order to simplify the modeling of the loading and reverse loading behavior of materials when using finite element analysis. Unfortunately, this simplification can result in significant error if the material exhibits the Bauschinger effect (BE), which is the loss of strength of the material upon reverse loading. The error associated with this simplification is further compounded in heavily autofrettaged, Cr-Mo-V, thick walled cylinders due to the fact that the Bauschinger effect and the reverse loading strain hardening exponent are a strong function of the initial applied plastic strains, which can vary significantly throughout the wall of the cylinder.

Plasticity Analysis of Fibrous Composites

1982 ◽  
Vol 49 (2) ◽  
pp. 327-335 ◽  
Author(s):  
G. J. Dvorak ◽  
Y. A. Bahei-El-Din
Keyword(s):  
Volume Fraction ◽  
Mechanical Load ◽  
Kinematic Hardening ◽  
Small Diameter ◽  
Local Stress ◽  
Plastic Behavior ◽  
Elastic Plastic ◽  
Elastic Filaments ◽  
Stress Concentration Factors ◽  
Hardening Rules

The elastic-plastic behavior of composites consisting of aligned, continuous elastic filaments and an elastic-plastic matrix is described in terms of constituent properties, their volume fractions, and mutual constraints between the phases indicated by the geometry of the microstructure. The composite is modeled as a continuum reinforced by cylindrical fibers of vanishingly small diameter which occupy a finite volume fraction of the aggregate. In this way, the essential axial constraint of the phases is retained. Furthermore, the local stress and strain fields are uniform. Elastic moduli, yield conditions, hardening rules, and overall instantaneous compliances, as well as instantaneous stress concentration factors are derived. Specific results are obtained for the case of a Mises-type matrix which obeys the Prager-Ziegler kinematic hardening rule. Any multiaxial mechanical load may be applied. Comparisons are made between the present results and certain other theories.

Reverse Modeling and Topological Optimization for Lightweight Design of Automobile Wheel Hubs with Hollow Ribs

2019 ◽  
Vol 17 (09) ◽  
pp. 1950064
Author(s):  
P. F. Xu ◽  
S. Y. Duan ◽  
F. Wang
Keyword(s):  
Finite Element ◽  
Lightweight Design ◽  
Element Model ◽  
Optimization Method ◽  
Modeling Technique ◽  
Topological Optimization ◽  
Time Interval ◽  
Braking Performance ◽  
Existing Structures ◽  
Physical Conditions

Lightweight of wheel hubs is the linchpin for reducing the unsprung mass and improving the vehicle dynamic and braking performance of vehicles, thus, sustaining stability and comfortability. Current experience-based lightweight designs of wheel hubs have been argued to render uneven distribution of materials. This work develops a novel method to combine the reverse modeling technique with the topological optimization method to derive lightweight wheel hubs based on the principles of mechanics. A reverse modeling technique is first adopted to scan and reproduce the prototype 3D geometry of the wheel hub with solid ribs. The finite element method (FEM) is then applied to perform stress analysis to identify the maximum stress and its location of wheel hub under variable potential physical conditions. The finite element model is then divided into optimization region and nonoptimized region: the former is the interior portion of spoke and the latter is the outer surface of the spoke. A topology optimization is then conducted to remove the optimization region which is interior material of the spokes. The hollow wheel hub is then reconstructed with constant wall thickness about 5[Formula: see text]mm via a reverse modeling technique. The results show that the reconstructed model can reduce the mass of 12.7% compared to the pre-optimized model. The present method of this paper can guarantee the optimal distribution of wheel hub material based on mechanics principle. It can be implemented automatically to shorten the time interval for optimal lightweight designs. It is especially preferable for many existing structures and components as it maintains the structural appearance of optimization object.

ISOVECTOR PYGMY DIPOLE EXCITATION IN NEUTRON-RICH NUCLEI

2010 ◽  
Vol 25 (34) ◽  
pp. 2905-2913 ◽  
Author(s):  
KUTSAL BOZKURT
Keyword(s):  
Random Phase ◽  
Nucleon Nucleon ◽  
Strength Distribution ◽  
Experimental Results ◽  
Heavy Nuclei ◽  
Quasiparticle Random Phase Approximation ◽  
Dipole Excitation ◽  
Dipole Resonance ◽  
Pygmy Dipole Resonance ◽  
Full Interaction

We investigate isovector pygmy dipole resonance (IVPDR) for the case of neutron-rich nuclei 68 Ni , 130 Sn and 134 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the (quasiparticle) random phase approximation (Q)RPA. We calculate and compare the PDR strength in the PDR energy region for the case of density dependent central and full interaction modes for RPA and QRPA calculations. We observe that the results for the pygmy dipole resonance for neutron-rich soft nuclei 68 Ni that we consider are in reasonable agreement with their experimental results in both interactions and calculations. We also study the PDR for highly neutron-rich heavy nuclei, such as 130 Sn and 134 Sn . We see that only the QRPA calculation with full interaction is in good agreement with the experimental results for these nuclei and with a recent study in the literature. We find that the PDR strength distribution sensitively depends on the chosen interaction modes, especially for the neutron-rich heavy nuclei 134 Sn .

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