E-Thesis 545 views 53 downloads
Neural Network Based Constitutive Modelling of Inelastic Materials / REEM ALHAYKI
Swansea University Author: REEM ALHAYKI
DOI (Published version): 10.23889/SUThesis.66509
Abstract
New materials that are associated with novel micro-structures are becoming available at a rapid speed. The mechanical characteristics of solid materials are studied using constitutive models. The formulation of constitutive relations is challenging and may be related with the limiting hypothesis. Ma...
| Published: |
Swansea University, Wales, UK
2024
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Dettmer, W., and Peric, D. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa66509 |
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| Abstract: |
New materials that are associated with novel micro-structures are becoming available at a rapid speed. The mechanical characteristics of solid materials are studied using constitutive models. The formulation of constitutive relations is challenging and may be related with the limiting hypothesis. Machine learning approaches have been widely used to simulate material behaviour in recent years. This study presents a neural network-based approach to reproduce the complex constitutive relations of solid materials including the modelling of rate-independent, elastic or inelastic, isotropic or anisotropic material behaviours. The approach can follow a history-based or an internal variables-based strategy. The network is developed using a generic internal variable formalism, with the number of internal variables determined by the nature of the problem and the degree of accuracy desired. It is demonstrated that the history-based and internal variable based techniques accurately describe the von Mises elastoplastic material model in uniaxial stress condition.However, a thorough examination indicates that the internal variable-based strategy is most suited.In this work, the network is trained on data sequences of strains and corresponding stresses that can be generated with physical experiments or numerical simulations based on Representative Volume Element (RVE). The used training strategy is based on gradient-free optimisation. The model performance is evaluated on different numerical examples including uniaxial damage mechanics and multiaxial elastoplasticity under plane strain conditions. The trained model is compared against the corresponding constitutive model to evaluate the accuracy. An efficient criterion for the verification of thermodynamic consistency is proposed and applied to the trained stress update models.The proposed strategy is tested with numerical examples that represent relations of porous solid materials. The training data are generated with numerical multi-scale homogenisation based on an RVE composed of the von Mises elastoplastic matrix with an arbitrary void volume fraction. The RVE simulation was performed by enforcing appropriate RVE boundary conditions, and the stress responses are computed for various macro strain data sequences to generate different loading paths. The neural network based stress update algorithm is trained and validated. The obtained results show the ability of the proposed procedure in describing the material stress/strain relationship with high accuracy. In addition, plots of stress paths in the hydrostaticdeviatoric space show accurate results when compared against the corresponding Gurson model for porous elastoplastic material. |
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| Keywords: |
Data driven computational mechanics, Neural network, Constitutive modelling, Elasto-plasticity, Damage mechanics. |
| College: |
Faculty of Science and Engineering |