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.

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.

Cyclic behaviour of materials

1970 ◽  
Vol 5 (3) ◽  
pp. 185-192 ◽  
Author(s):  
K J Miller
Keyword(s):  
Strain Rate ◽  
Strain Curve ◽  
Cyclic Hardening ◽  
Fatigue Behaviour ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Static Tests ◽  
Static Test ◽  
Cyclic Behaviour ◽  
Incremental Step

The effect of strain rate on the cyclic behaviour of two materials is presented. For the material that cyclically hardens (En 32B) a decrease in strain rate decreases the maximum cyclic hardening of the material, whilst for a material that cyclically softens (En 25) a decrease in the rate of deformation increases the maximum cyclic softening. It is concluded that the effect of strain rate on the cyclic stress-strain curve should be more closely studied than the effect of frequency since the frequency may be constant whilst the straining rate may vary considerably in plastically deformed zones. For those zones that suffer low strain rates the inclusion of time-dependent deformation processes can maximize the degree of softening or minimize the degree of hardening, thereby creating a greater localization of the plastic strain which should increase strain-concentration factors. Finally it is argued that it is better to predict fatigue behaviour from an incremental-step high-strain fatigue test on a single specimen than from static-test data. For the same reasons correlations between static tests and fatigue tests should be discouraged, especially for those materials that exhibit marked cyclic softening.

On the Cyclc Behavior of 304L and 316L Stainless Steels

2013 ◽  
Vol 535-536 ◽  
pp. 201-204 ◽  
Author(s):  
Lakhdar Taleb
Keyword(s):  
Steady State ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Stress And Strain ◽  
Strain Control ◽  
Stress Control ◽  
Elastic Shakedown

This work is devoted to a survey of the ratcheting phenomenon and follows the study presented in [1]. Two current austenitic stainless steels 304L and 316L are considered and tested under cyclic stress and strain control at 350°C. Under stress control ratcheting seems very small under proportional as well as non-proportional stress control. The elastic shakedown steady state exhibited by both materials may be explained by their capabilities to develop very significant cyclic hardening (especially isotropic) at 350°C.

scholarly journals Acceleration techniques for the numerical simulation of the cyclic plasticity behaviour of mechanical components under thermal loads

2018 ◽  
Vol 165 ◽  
pp. 19010 ◽  
Author(s):  
Jelena Srnec Novak ◽  
Francesco De Bona ◽  
Denis Benasciutti ◽  
Luciano Moro
Keyword(s):  
Strain Curve ◽  
Cyclic Hardening ◽  
Cyclic Plasticity ◽  
Design Rule ◽  
Plastic Strains ◽  
Thermal Loads ◽  
Small Plastic ◽  
Acceleration Techniques ◽  
Cyclic Behaviour ◽  
Number Of Cycles

Numerical simulations of components subjected to cyclic thermo-mechanical loads require an accurate modelling of their cyclic plasticity behaviour. Combined models permit to capture monotonic hardening as well as cyclic hardening/softening phenomena, that occur in reality. In principle the durability assessment of a component under thermal loads can be performed only if the cyclic behaviour is simulated until complete material stabilization. As materials stabilize approximately at half the number of cycles to failure, it follows that in case of small plastic strains a huge number of cycles must be considered and an unfeasible simulation time would be required. Accelerated models have thus been proposed in literature. The aim of this work is that of comparing the different acceleration techniques in the case a round mould for continuous casting loaded thermo-mechanically. It can be observed that the usual approach of using the stabilized stress-strain curve already from the first cycle could lead to relevant errors. An alternative method is that of increasing the value of the parameter that controls the speed of stabilization in the combined model. This approach permits the number of cycles to reach stabilization to be drastically reduced, without affecting the overall mechanical behaviour. Based on this approach, a simple design rule, that can be adopted, particularly when relatively small plastic strains occur, is finally proposed.

Low Cycle Fatigue Behavior and Microcracks Nucleation on Duplex Stainless Steels

2008 ◽  
Vol 378-379 ◽  
pp. 17-28 ◽  
Author(s):  
I. Alvarez-Armas ◽  
Suzanne Degallaix
Keyword(s):  
Stainless Steels ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Curve ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Duplex Stainless Steels ◽  
Stress Strain Curve ◽  
Beneficial Effects ◽  
Stress Components

The cyclic hardening–softening response, the cyclic stress–strain curve and the substructure evolution of a high nitrogen duplex stainless steel S32750 have been evaluated and the results compared with reference to low and medium nitrogen duplex stainless steels, S32205 and S32900 grades, respectively. The beneficial effects of nitrogen on the cyclic properties of most modern alloys have been analyzed in terms of the flow stress components, i.e. the internal and the effective stress.

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.

Cyclic Softening of Cu-Ni-Si Alloy Single Crystals under Low-Cycle Fatigue

2010 ◽  
Vol 654-656 ◽  
pp. 1287-1290 ◽  
Author(s):  
Toshiyuki Fujii ◽  
Hiroshi Kamio ◽  
Yoshifumi Sugisawa ◽  
Susumu Onaka ◽  
Masaharu Kato
Keyword(s):  
Plastic Strain ◽  
Single Crystals ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Electron Microscopic Observation ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Electron Microscopic

Cu-2.2wt%Ni-0.5wt%Si alloy single crystals were grown by the Bridgman method and aged at 723 K for 10 h to form Ni2Si precipitates. Fully reversed tension-compression fatigue tests were conducted on the aged single crystals with a single slip orientation under constant plastic-strain amplitudes at room temperature. Cyclic softening occurred at plastic-strain amplitudes between 2.5x10-4 and 2.5x10-2. Using the maximum stress amplitude in each cyclic hardening/softening curve, a pseudo cyclic stress-strain curve (CSSC) was obtained. The CSSC was found to exhibit a plateau region with a stress level of about 167 MPa. Transmission electron microscopic observation revealed the formation of persistent slip bands (PSBs) in the plateau regime. It was found that the Ni2Si precipitate particles were intensively sheared by glide dislocations within the PSBs and were eventually re-dissolved into the Cu matrix. The macroscopic cyclic softening can be attributed to the local softening induced by the re-dissolution of the Ni2Si particles in the PSBs.

Effect of Temperature on the Cyclic Stress Components of Gamma - TiAl Based Alloy with Niobium Alloying

2011 ◽  
Vol 465 ◽  
pp. 447-450 ◽  
Author(s):  
Martin Petrenec ◽  
Petr Buček ◽  
Tomáš Kruml ◽  
Jaroslav Polák
Keyword(s):  
Hysteresis Loops ◽  
Lamellar Microstructure ◽  
Strain Curve ◽  
Cyclic Strain ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Effect Of Temperature ◽  
Stress Strain ◽  
Stress Components ◽  
Increasing Temperature

Cyclic strain controlled multiple step tests have been performed on cylindrical specimens of cast -TiAl based alloy with 2 at.% of Nb with nearly lamellar microstructure at 23 and 750 °C in laboratory atmosphere with the aim to study the effect of temperature on the internal and effective cyclic stress components. At these temperatures, the evolution of the effective and internal stress components and the effective elastic moduli were derived from the hysteresis loops analyzed according to the statistical theory of hysteresis loop. Cyclic hardening/softening curves and cyclic stress-strain curves were obtained at both temperatures. Cyclic stress–strain curves measured using short-cut procedure coincide with the basic cyclic stress-strain curve. They are shifted to lower stresses with increasing temperature. Cyclic stress-strain response at both temperatures was compared and discussed in relation to changes of internal and effective stress components and dislocation modes referred in literature concerning this class of the material.

Cyclic Plasticity and Fatigue Crack Growth

2006 ◽  
Vol 324-325 ◽  
pp. 603-606
Author(s):  
Rui Zhang ◽  
Sun Yi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Cyclic Hardening ◽  
Cyclic Plasticity ◽  
Plastic Behavior ◽  
Free Zone ◽  
Growth Criterion ◽  
Calculated Curve ◽  
Propagation Pattern

The relation between material’s cyclic plastic behavior and fatigue crack growth is investigated. The present model is proposed on the dislocation-free zone (DFZ) theory. A cohesive zone theory is developed to determine the stress field of the DFZ and the value of J-integer under cyclic loading. The crack growth criterion is proposed based on J-integral. The calculated curve of fatigue crack growth rate da/dN is agreement with the general propagation pattern and the predicted threshold accords with the experiment threshold well. It is found that the near threshold characteristics are most determined by the cyclic deformation behavior of the material. The relation between fatigue crack growth threshold and material’s cyclic hardening behavior is discussed.

Description of Planer Anisotropy and Cyclic Plasticity Behavior of Aluminum Sheet Based on Crystal Plasticity Theory

2011 ◽  
Vol 117-119 ◽  
pp. 1397-1401
Author(s):  
Takumi Kobayashi ◽  
Kohshiroh Kitayama ◽  
Takeshi Uemori ◽  
Fusahito Yoshida
Keyword(s):  
Crystal Plasticity ◽  
Metal Forming ◽  
Bauschinger Effect ◽  
Cyclic Stress ◽  
Plasticity Theory ◽  
Cyclic Plasticity ◽  
Plastic Behavior ◽  
Planar Anisotropy ◽  
Crystal Plasticity Theory ◽  
Strain Responses

In sheet metal forming, the anisotropy and the Bauschinger effect of sheets affect greatly their formability. This paper discusses how the planar anisotropy and cyclic plastic behavior (the Bauschnger effect and cyclic workhardening characteristics) correlate with the crystallographic texture based on the crystal plasticity analysis on A5052-O sheet. The analytical predictions of r-values and the cyclic stress-strain responses are compared with the experimental observations (S. Tamura et al., Materials Trans, 52-5 (2011), pp.868-875).

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