Calibration of Elastoplastic Constitutive Model Parameters from Full‐field Data with Automatic Differentiation‐based Sensitivities

An elastoplastic constitutive model that takes into account the stress–strain relationship and creep-induced hardening behavior of rockfill materials is proposed in light of previous experimental observations. It is assumed that the mechanical response during loading and the final amounts of creep strains under a constant stress state are independent of the strain rate. The focus of the proposed model is the coupling effect between loading and creep, including the influence of loading history on subsequent creep strains and the influence of creep history on subsequent loading behavior. An extended yield function, which allows flexible control over the shape of yield surfaces, is used not only to distinguish among loading, unloading, and neutral loading, but also to manipulate the creep-induced hardening using a plastic strains–based hardening parameter. A stress-dependent dilatancy equation is used, instead of a plastic potential function, to define the directions of plastic strains during loading. The hardening law is established based on three different types of experimental results. Only routine experiments are required for calibration of model parameters, and the model can be used in a reduced form according to the available test results. The model is verified using typical experimental data and is found to be capable of capturing important behavior of rockfill materials, such as pressure-dependent strength, shear contraction and dilation, and creep-induced stiffening.

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Elastoplastic Model and Three-Dimensional Method for Unsaturated Soils

Shock and Vibration ◽

10.1155/2020/8592628 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Jinjin Fang ◽

Yixin Feng

Keyword(s):

Constitutive Model ◽

Unsaturated Soils ◽

Three Dimensional ◽

Three Dimensions ◽

Degree Of Saturation ◽

Triaxial Tests ◽

Model Parameters ◽

Elastoplastic Model ◽

True Triaxial ◽

Elastoplastic Constitutive Model

This paper proposed a new elastoplastic constitutive model to predict the deformation and strength behaviour of unsaturated soils. Applying the modified Cambridge model as a generalization, the degree of saturation is introduced into the elastoplastic model of unsaturated soil. Under the condition of ensuring that the model parameters are unchanged, the model is transformed into three dimensions based on the SMP criterion transformation stress method. Enhanced modified van Genuchten model under true triaxial conditions is also proposed in this paper to describe hydromechanical behaviours of unsaturated soils. The proposed constitutive model can capture the observed mechanical and hydraulic behaviours. Then, the model is validated via equal p and equal b value true triaxial tests, and the results show that a reasonable agreement can be obtained.

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On the optimisation efficiency for the inverse identification of constitutive model parameters

10.25518/esaform21.1486 ◽

2021 ◽

Author(s):

Miguel Guimarães Oliveira ◽

João Miguel Peixoto Martins ◽

Bernardete Coelho ◽

Sandrine Thuillier ◽

António Andrade-Campos

Keyword(s):

Constitutive Model ◽

Mechanical Tests ◽

Model Parameters ◽

Inverse Identification ◽

Full Field ◽

Material Parameters ◽

Gradient Based ◽

Identification Techniques ◽

Optimisation Algorithms ◽

Optimisation Technique

The development of full-field measurement techniques paved the way for the design of new mechanical tests. However, because these mechanical tests provide heterogeneous strain fields, no closed-form solution exists between the measured deformation fields and the constitutive parameters. Therefore, inverse identification techniques should be used to calibrate constitutive models, such as the widely known finite element model updating (FEMU) and the virtual fields method (VFM). Although these inverse identification techniques follow distinct approaches to explore full-field measurements, they all require using an optimisation technique to find the optimum set of material parameters. Nonetheless, the choice of a suitable optimisation technique lacks attention and proper research. Most studies tend to use a least-squares gradient-based optimisation technique, such as the Levenberg-Marquardt algorithm. This work analyses optimisation algorithms, gradient-based and -free algorithms, for the inverse identification of constitutive model parameters. To avoid needless implementation and take advantage of highly developed programming languages, the optimisation algorithms available in optimisation libraries are used. A FEMU based approach is considered in the calibration of a thermoelastoviscoplastic model. The material parameters governing strain hardening, temperature and strain rate are identified. Results are discussed in terms of efficiency and the robustness of the optimisation processes.

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Parameter identification of a non-associative elastoplastic constitutive model using ANN and multi-objective optimization

International Journal of Material Forming ◽

10.1007/s12289-009-0392-1 ◽

2009 ◽

Vol 2 (2) ◽

pp. 75-82 ◽

Cited By ~ 4

Author(s):

H. Aguir ◽

A. Chamekh ◽

H. BelHadjSalah ◽

A. Dogui ◽

R. Hambli

Keyword(s):

Constitutive Model ◽

Parameter Identification ◽

Multi Objective Optimization ◽

Multi Objective ◽

Elastoplastic Constitutive Model

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A General Temperature-Dependent Stress–Strain Constitutive Model for Polymer-Bonded Composite Materials

Polymers ◽

10.3390/polym13091393 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1393

Author(s):

Xiaochang Duan ◽

Hongwei Yuan ◽

Wei Tang ◽

Jingjing He ◽

Xuefei Guan

Keyword(s):

Composite Materials ◽

Constitutive Model ◽

Model Parameters ◽

Temperature Dependent ◽

Stress Strain ◽

Proposed Model ◽

Single Temperature ◽

Testing Data ◽

Bonded Composite ◽

Tension And Compression

This study develops a general temperature-dependent stress–strain constitutive model for polymer-bonded composite materials, allowing for the prediction of deformation behaviors under tension and compression in the testing temperature range. Laboratory testing of the material specimens in uniaxial tension and compression at multiple temperatures ranging from −40 ∘C to 75 ∘C is performed. The testing data reveal that the stress–strain response can be divided into two general regimes, namely, a short elastic part followed by the plastic part; therefore, the Ramberg–Osgood relationship is proposed to build the stress–strain constitutive model at a single temperature. By correlating the model parameters with the corresponding temperature using a response surface, a general temperature-dependent stress–strain constitutive model is established. The effectiveness and accuracy of the proposed model are validated using several independent sets of testing data and third-party data. The performance of the proposed model is compared with an existing reference model. The validation and comparison results show that the proposed model has a lower number of parameters and yields smaller relative errors. The proposed constitutive model is further implemented as a user material routine in a finite element package. A simple structural example using the developed user material is presented and its accuracy is verified.

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