This page provides information for the implementation of CDPM2 in LS-DYNA. This information is provided as is, without warranty of any kind. If you find any mistakes or have any useful information about this material model and are willing to share it with others, please get in touch with Peter Grassl so that we can add it to this page. Most of the examples provided here were performed with the double precision version of Release 9.3.1 or higher.
On this page information about the concrete damage plasticity constitutive model MAT_CDPM (MAT_273) in LS-DYNA is provided. This model is based on work published in Grassl and Jirásek (2006) (DOI), Grassl et al. (2011) (Preprint) and Grassl et al. (2013) (DOI, Preprint).
In Grassl and Jirásek (2006), the main framework of the present damage plasticity model was developed, which was called CDPM. In this work an effective stress based plasticity model was combined with a scalar damage approach with one damage variable for both tension and compression. The effective plasticity part was designed to describe the pressure sensitive hardening response. For the post-peak regime a perfect plastic response was chosen and softening was described by the damage part.
Peter Grassl from the University of Glasgow proposed in collaboration with Kent Gylltoft, Rasmus Rempling and Ulrika Nyström from Chalmers University in Sweden, an extension of the CDPM, which was called CDPM2. A short description of the new model was published first in a conference paper in Grassl et al. (2011). Three main changes in CDPM2 (compared to CDPM) were introduced:
Firstly, hardening was introduced in the plasticity part in the post-peak regime, so that the contribution of damage and plasticity in the post-peak regime could be controlled.
Secondly, two damage variables, one for tension and one for compression, were introduced, with the aim to improve the description from tension to compression.
Thirdly, strain rate dependence was introduced in the damage function which among others describes the onset of the damage evolution.
Subsequently, the first two modifications of CDPM2 described in the conference paper (hardening in the post-peak regime and introduction of two damage variables) were refined and described in more detail in the journal article Grassl et al. (2013) together with Dimitrios Xenos. The approach to model strain rate dependence was not changed and was not included again in Grassl et al. (2013). For obtaining a detailed description of CDPM2, it is recommended to study Grassl et al. (2013). For the way how strain rate dependence is considered, it is referred to Grassl et al. (2011).
CDPM2 was implemented in LS-DYNA for the first time around 2013/14. In LS-DYNA it is called simply MAT_CDPM (or MAT_273). In 2015, Dimitrios Xenos and Peter Grassl reimplemented MAT_CDPM to increase its robustness. This improved version is available in Release 9.1 onwards. Here, we describe the user material implementation of CDPM2 in LSDYNA.
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User material subroutine
Fortran file for user material version of MAT_CDPM for UMAT50V and UTAN50V (only elastic stiffness for now) are available on github:
Example material card for the user material:
materialUser.k (Last update 16 May 2021)
Explanation of the input parameters:
MAT_CDPM_Grassl.docx (Last update 16 May 2021)
If you find any bugs in this user material version of MAT_CDPM or are able to provide improvements, please let us know by contacting Peter Grassl so that we can fix it and update it on this page.
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Key references for the theory of MAT_CDPM (MAT_273) in LS-DYNA
P. Grassl, D. Xenos, U. Nyström, R. Rempling, K. Gylltoft. "CDPM2: A damage-plasticity approach to modelling the failure of concrete". International Journal of Solids and Structures. Volume 50, Issue 24, pp. 3805-3816, 2013
DOI || Preprint
P. Grassl, U. Nyström, R. Rempling and K. Gylltoft, "A damage-plasticity model for the dynamic failure of concrete", 8th International Conference on Structural Dynamics, Leuven, Belgium, 2011.
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