A constitutive model of cyclic plasticity in non-proportional loading conditions. 2nd report Identification of material constants and material functions, and experimental evaluation of the model.

Accurate estimation of material stress–strain response is essential to many fatigue life analyses. In cases where variable amplitude loading conditions exist, the ability to account for transient material deformation behavior can be particularly important due to the potential for periodic overloads and/or changes in the degree of nonproportional stressing. However, cyclic plasticity models capable of accounting for these complex effects often require the determination of a large number of material constants. Therefore, an Armstrong–Frederick–Chaboche style plasticity model, which was simplified in a previous study, was extended in the current study to account for the effects of both general cyclic and nonproportional hardening using a minimal number of material constants. The model was then evaluated for its ability to predict stress–strain response under complex multiaxial loading conditions by using experimental data generated for 2024-T3 aluminum alloy, including a number of cyclic incremental step tests. The model was found to predict transient material response within a fairly high overall level of accuracy for each loading history investigated.

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The Further Exploration of Applying Small-Strain and Large-Strain Formulations to SMA

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.529.228 ◽

2012 ◽

Vol 529 ◽

pp. 228-235

Author(s):

Jie Yao ◽

Yong Hong Zhu

Keyword(s):

Phase Transformation ◽

Constitutive Model ◽

Uniaxial Tension ◽

Driving Force ◽

Research Team ◽

Large Strain ◽

Small Deformation ◽

Small Strain ◽

Proportional Loading ◽

The Difference

Recently, our research team has been considering to applying shape memory alloys (SMA) constitutive model to analyze the large and small deformation about the SMA materials because of the thermo-dynamics and phase transformation driving force. Accordingly, our team use simulations method to illustrate the characteristics of the model in large strain deformation and small strain deformation when different loading, uniaxial tension, and shear conditions involve in the situations. Furthermore, the simulation result unveils that the difference is nuance concerning the two method based on the uniaxial tension case, while the large deformation and the small deformation results have huge difference based on shear deformation case. This research gives the way to the further research about the constitutive model of SMA, especially in the multitiaxial non-proportional loading aspects.

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Study on Multi-Axial Mechanical Properties of a Polyurethane Foam and Experimental Verification

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.311-313.301 ◽

2011 ◽

Vol 311-313 ◽

pp. 301-308

Author(s):

Shou Hong Han ◽

Zhen Hua Lu ◽

Yong Jin Liu

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Polyurethane Foam ◽

Axial Compression ◽

Axial Loading ◽

Hydrostatic Compression ◽

Model Parameters ◽

Loading Conditions ◽

Three Point Bending ◽

Pu Foam

In order to investigate the multi-axial mechanical properties of a kind of PU (polyurethane) foam, some experiments in different loading conditions including uni-axial tension, uni-axial compression, hydrostatic compression and three-point bending were conducted. It is shown that the hydrostatic component influences yield behavior of PU foam, the yield strength and degree of strain hardening in hydrostatic compression exceed those for uni-axial compression. In terms of the differential hardening constitutive model, the evolution of PU foam yield surface and plastic hardening laws were fitted from experimental data. A finite element method was applied to analyze the quasi-static responses of the PU foam sandwich beam subjected to three-point bending, and good agreement was observed between experimental load-displacement responses and computational predictions, which validated the multi-axial loading methods and stress-strain constitutive model parameters. Moreover, effects of two foam models applied to uni-axial loading and multi-axial loading conditions were analyzed and compared with three-point bending tests and simulations. It is found that the multi-axial constitutive model can bring more accurate prediction whose parameters are obtained from the tests above mentioned.

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A Cyclic Plasticity Modeling for Uniaxial and Multiaxial Ratcheting Simulation of Austenitic Steel

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2012-78803 ◽

2012 ◽

Author(s):

Salim Meziani ◽

Lynda Djimli

Keyword(s):

Experimental Data ◽

Stainless Steel ◽

Constitutive Model ◽

Data Base ◽

Good Choice ◽

Cyclic Plasticity ◽

Strain History ◽

Material Parameters ◽

Plastic Shakedown

The first objective of this paper investigates the influence of the previous strain history on ratcheting of the 304 L stainless steel on ambient temperature. The identification is done using the Chaboche constitutive model. New tests were performed where different strain-controlled histories have been applied prior to ratcheting tests. It is demonstrated that under the same conditions, one can observe ratcheting, plastic shakedown or elasticity according to the prior strain-controlled history. The second objective points out the correlation between the experimental data base devoted to the identification of the material parameters and the quality of the predictions in cyclic plasticity. The results suggest that the choice of the tests should be closely linked to the capabilities of the model. In particular, the presence of non proportional strain-controlled tests in the data base may be not a good choice if the model itself is not able to represent explicitly such a character.

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