scholarly journals An Isotropic Model for Cyclic Plasticity Calibrated on the Whole Shape of Hardening/Softening Evolution Curve

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 950 ◽  
Author(s):  
Jelena Srnec Novak ◽  
Francesco De Bona ◽  
Denis Benasciutti
Keyword(s):  
Finite Element ◽  
Copper Alloy ◽  
Cyclic Hardening ◽  
Uniaxial Stress ◽  
Cyclic Plasticity ◽  
Stress And Strain ◽  
Isotropic Model ◽  
Physical Behavior ◽  
Proposed Model ◽  
Kinematic Models

This work presents a new isotropic model to describe the cyclic hardening/softening plasticity behavior of metals. The model requires three parameters to be evaluated experimentally. The physical behavior of each parameter is explained by sensitivity analysis. Compared to the Voce model, the proposed isotropic model has one more parameter, which may provide a better fit to the experimental data. For the new model, the incremental plasticity equation is also derived; this allows the model to be implemented in finite element codes, and in combination with kinematic models (Armstrong and Frederick, Chaboche), if the material cyclic hardening/softening evolution needs to be described numerically. As an example, the proposed model is applied to the case of a cyclically loaded copper alloy. An error analysis confirms a significant improvement with respect to the usual Voce formulation. Finally, a numerical algorithm is developed to implement the proposed isotropic model, currently not available in finite element codes, and to make a comparison with other cyclic plasticity models in the case of uniaxial stress and strain-controlled loading.

A Constitutive Model of Cyclic Plasticity for Nonlinear Hardening Materials

1986 ◽  
Vol 53 (2) ◽  
pp. 395-403 ◽  
Author(s):  
N. Ohno ◽  
Y. Kachi
Keyword(s):  
Constitutive Model ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Cyclic Plasticity ◽  
Elastoplastic Behavior ◽  
Surface Plasticity ◽  
Proposed Model ◽  
Cyclic Straining ◽  
Nonlinear Hardening ◽  
Mean Strain

A constitutive model is proposed for cyclic plasticity of nonlinear hardening materials. The concept of a cyclic nonhardening range, which enables us to describe the dependence of cyclic hardening on the amplitude of cyclic straining or stressing, is employed together with the idea of a two-surface plasticity model. Results of the proposed model are compared with experiments of 304 and 316 stainless steels in several cases of cyclic loading in which mean strain is zero or nonzero and strain limits are fixed or variable. Thus, it is shown that the model successfully describes both the cyclic hardening phenomenon and the transient elastoplastic behavior after initial and reverse yields of these materials. The capability of the model to provide nonlinear cyclic stress-strain curves is also discussed.

Modeling of Fatigue Crack Closure by Finite Element Method

2012 ◽  
Vol 544 ◽  
pp. 145-150
Author(s):  
Zhen Yu Ding ◽  
Xiao Gui Wang ◽  
Zeng Liang Gao
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Closure ◽  
Fe Simulation ◽  
Crack Tip ◽  
Cyclic Plasticity ◽  
Stress And Strain

Crack closure concept is often used to explain the crack propagation behavior in cracked components. The effective stress intensity factor range is considered as a driving force of fatigue crack growth based on the traditional crack closure concept. The crack closure process and the plastic deformation near the crack tip were discussed in this paper. The standard compact tension specimen with the plane-stress condition was used to study the crack closure. A dynamic crack propagation method was proposed to simulate the effect of previous fatigue crack growth on the successive crack growth behavior. To obtain the accurately numerical results of stress and strain components, the Jiang and Sehitoglu cyclic plasticity model was implemented into ABAQUS as UMAT. With the detailed stress and strain response taken from the finite element (FE) simulation, the whole process of crack closure was described by the load curve. The load corresponding to maximum crack closure length is firstly proposed to describe the effect of fatigue damage. According to the results of FE simulation, the cyclic plasticity of the material near the crack tip persists during the crack closure period and should not be ignored.

scholarly journals A Cyclic Plasticity Model with Martensite Transformation for S30408 and Its Finite Element Implementation

2020 ◽  
Vol 10 (17) ◽  
pp. 6002
Author(s):  
Yanan Chen ◽  
Xiaohui Chen ◽  
Bingjun Gao ◽  
Xu Chen ◽  
Kai Zhang ◽  
...  
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Constitutive Model ◽  
Numerical Algorithm ◽  
Kinematic Hardening ◽  
Cyclic Plasticity ◽  
Flow Rule ◽  
Proposed Model ◽  
Metastable Austenitic Stainless Steel

The ability of the constitutive model to simulate the ratcheting behavior of metastable austenitic stainless steel S30408 is significant to ensure the safety of the liquefied natural gas (LNG) semi-trailer tanks in the lightweight process of the inner containers. This is because the lightweight inner vessels often encounter cyclic stresses due to the road inertia loads together with high mean stresses due to internal pressures. In this study, we performed cryogenic uniaxial tension experiments and a series of ratcheting experiments to investigate the cyclic plasticity behavior of the metastable austenitic stainless steel S30408. Based on the Ohno-Wang II model, we proposed a new cyclic plasticity constitutive model with martensitic transformation, which relates the content of deformation-induced martensite with isotropic hardening and kinematic hardening. The ratcheting behaviors of S30408 were first simulated by the proposed model with the incremental loading method using MATLAB. The results showed that the model could reasonably predict the ratcheting behavior of S30408, and the evolution law of martensite content could well predict the content of deformation-induced martensite. Under the assumption of the von Mises yield criterion and normal plasticity flow rule, we developed a numerical algorithm of plastic strain with the proposed model to implement the finite element calculation of the model. Internal iteration in the numerical algorithm was implemented with the Euler backward method, which calculated the trial strain for each equilibrium iteration using the consistent tangent matrix. With a user subroutine, the proposed model was programmed into ANSYS for a user - executable version. By simulating the uniaxial ratcheting of a S30408 round bar, we found that the calculated results were in good agreement with the experimental results, which promises further applications in the design of structures, such as LNG semi-trailer tanks.

Detailed and Simplified Elastoplastic Analyses of a Cyclically Loaded Notched Bar

1987 ◽  
Vol 109 (3) ◽  
pp. 194-202 ◽  
Author(s):  
N. Ohno ◽  
M. Sˇatra
Keyword(s):  
Detailed Analysis ◽  
Cyclic Load ◽  
Strain Curve ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Cyclic Plasticity ◽  
Stress And Strain ◽  
Plastic Behavior ◽  
Mean Values ◽  
Axial Cyclic Loading

To find some features in the development of cyclic hardening in structural components with areas of strain concentration, detailed and simplified elastoplastic analyses are performed on an axisymmetric notched bar subjected to axial cyclic loading. For the detailed analysis, the constitutive model based on the cyclic nonhardening region is implemented in an incremental FEM. The model can describe an important feature in cyclic plasticity, i.e., the dependence of cyclic plastic behavior on cyclic stress and strain ranges. The simplified method which utilizes the cylic stress-strain curve as the constitutive relation is applied to the case of nonzero as well as zero mean values of the cyclic load, and its validity is discussed on the basis of the results of the detailed analysis. The detailed analysis with accelerated cyclic hardening and the methods of Neuber and Stowell-Hardrath-Ohman are examined, too.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

scholarly journals Evaluation of Bone–Implant Interface Stress and Strain Using Heterogeneous Mandibular Bone Properties Based on Different Empirical Correlations

2021 ◽  
Author(s):  
Mostafa Omran Hussein ◽  
Mohammed Suliman Alruthea
Keyword(s):  
Finite Element ◽  
Group Iv ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Dental Arch ◽  
Stress And Strain ◽  
Bone Implant ◽  
Bone Properties ◽  
Group I ◽  
Von Mises

Abstract Objective The purpose of this study was to compare methods used for calculating heterogeneous patient-specific bone properties used in finite element analysis (FEA), in the field of implant dentistry, with the method based on homogenous bone properties. Materials and Methods In this study, three-dimensional (3D) computed tomography data of an edentulous patient were processed to create a finite element model, and five identical 3D implant models were created and distributed throughout the dental arch. Based on the calculation methods used for bone material assignment, four groups—groups I to IV—were defined. Groups I to III relied on heterogeneous bone property assignment based on different equations, whereas group IV relied on homogenous bone properties. Finally, 150 N vertical and 60-degree-inclined forces were applied at the top of the implant abutments to calculate the von Mises stress and strain. Results Groups I and II presented the highest stress and strain values, respectively. Based on the implant location, differences were observed between the stress values of group I, II, and III compared with group IV; however, no clear order was noted. Accordingly, variable von Mises stress and strain reactions at the bone–implant interface were observed among the heterogeneous bone property groups when compared with the homogenous property group results at the same implant positions. Conclusion Although the use of heterogeneous bone properties as material assignments in FEA studies seem promising for patient-specific analysis, the variations between their results raise doubts about their reliability. The results were influenced by implants’ locations leading to misleading clinical simulations.

scholarly journals Modeling the cyclic plasticity behavior of 42CrMo4 steel with an isotropic model calibrated on the whole shape of the evolution curve

2020 ◽  
Vol 28 ◽  
pp. 53-60
Author(s):  
Jelena Srnec Novak ◽  
Marina Franulović ◽  
Denis Benasciutti ◽  
Francesco De Bona
Keyword(s):  
Cyclic Plasticity ◽  
Isotropic Model ◽  
42Crmo4 Steel ◽  
Evolution Curve
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