This is the repository for an updated Voce-Chaboche (UVC) material model to model structural steel materials.
The UVC material model combines the nonlinear kinematic hardening rule of Chaboche with an refined formulation of the nonlinear isotropic hardening law of Voce. This constitutive model is intended to be used for structural steels subjected to cyclic loading. Notably, accounting for the discontinuous yielding phenomenon is shown to influence the buckling modes of steel wide-flange columns subjected to multi-axis cyclic loading. Material models are provided for a variety of stress states, the implementations are shown to have similar, if not better, efficiency in terms of model convergence than the built-in nonlinear isotropic/kinematic model in Abaqus.
The theory and implementations of the material model are described in detail in the references below.
- 02-Jun-2024:
- Fix updating of sigma for UVCuniaxial_IS regression from PR#14
- Make backstress arrays Real(8)
- 15-Sep-2022:
- Add to the README.md regarding using the UMATS with Intel oneAPI and more recent version of Abaqus.
- 06-Jul-2022:
- Improve local convergence of UVCuniaxial (see PR#14)
- Add additional Abaqus files for testing
Instructions for installation are specific to the choice of simulation platform. Detailed instructions are provided in each of the Abaqus and OpenSees directories.
Specific instructions for use are provided in each of the Abaqus and OpenSees directories.
The examples used to validate the implementations are provided in both the Abaqus/testing and OpenSees/testing directories.
Material paramters can be found on the OpenSees wiki at https://opensees.berkeley.edu/wiki/index.php/UVCuniaxial_(Updated_Voce-Chaboche)
(Noted 15 September 2022) Note that the Abaqus UVC UMATs are not compatible in their current form with the Intel Fortran Compiler in oneAPI and recent versions of Abaqus. The problem is that "allocatable arrays" used to hold a variable number of backstresses no longer appear to be supported. This issue can be overcome by modifying the use of the allocatable arrays to be of a constant size. For example, assuming two (2) backstresses, by changing the lines 27-28 in UVCuniaxial.for:
27 REAL, DIMENSION(2, 2) :: chab_coef
28 REAL, DIMENSION(2) :: alpha_k, alpha_k_init
and deleting lines 47-49. UVCplanestress.for and UVCmultiaxial.for can be similarly modified.
Bug fixes can be raised by opening a new issue in the UVC_MatMod repository.
Code written and maintained by Alex Hartloper (alexander.hartloper@epfl.ch).
This project is licensed under the MIT License - see the LICENSE file for details.
- Dimitrios Lignos and Albano de Castro e Sousa for their guidance and assistance in the formulation of the model theory and return mapping algorithms.
[1] Hartloper, de Castro e Sousa, and Lignos (2021). "Constitutive Modeling of Structural Steels: Nonlinear Isotropic/Kinematic Hardening Material Model and Its Calibration", Journal of Structural Engineering, https://doi.org/10.1061/(ASCE)ST.1943-541X.0002964.
[2] Hartloper, de Castro e Sousa, and Lignos (2019). "A Nonlinear Isotropic/Kinematic Hardening Model for Materials with Discontinuous Yielding". Technical Report.
[3] Hartloper, de Castro e Sousa, and Lignos (2019). "Sensitivity of Simulated Steel Column Instabilities to Plasticity Model Assumptions", Proceedings of the 12th Canadian Conference on Earthquake Engineering, Quebec City, QC, Canada