Regularization of softening plasticity models for explicit dynamics using a gradient-enhanced modified Johnson-Holmquist model
- The behavior of concrete under high strain rates is often described by plasticity models with softening, which is modeled by a reduction of the yield surface as a function of the local equivalent plastic strain. Among these are the RHT model, the K\&C model and the Johnson-Holmquist concrete model. These models are however local and therefore produce mesh-dependent results.
In this contribution, the gradient-enhancement of such models is investigated. First, the mesh-dependency of these local formulations based on the analysis with a modified JH2 model as a representative for these constitutive formulations is demonstrated using a one-dimensional benchmark example. The central difference method is used as solver with a diagonal mass matrix obtained from a Gauß-Lobatto integration.
In the benchmark, the width of the damaged zone decreases upon mesh-refinement and the dissipated plastic energy tends to zero. It is further shown that a significantly small safety factor for theThe behavior of concrete under high strain rates is often described by plasticity models with softening, which is modeled by a reduction of the yield surface as a function of the local equivalent plastic strain. Among these are the RHT model, the K\&C model and the Johnson-Holmquist concrete model. These models are however local and therefore produce mesh-dependent results.
In this contribution, the gradient-enhancement of such models is investigated. First, the mesh-dependency of these local formulations based on the analysis with a modified JH2 model as a representative for these constitutive formulations is demonstrated using a one-dimensional benchmark example. The central difference method is used as solver with a diagonal mass matrix obtained from a Gauß-Lobatto integration.
In the benchmark, the width of the damaged zone decreases upon mesh-refinement and the dissipated plastic energy tends to zero. It is further shown that a significantly small safety factor for the critical time step is needed in order to achieve accurate results for the benchmark example.
Next, two gradient-enhancement approaches are investigated. The enhancement is based on the inclusion of inertia and damping to the additional Helmholtz equation which enables the use of the central difference method as an explicit solver. In the first formulation, the yield surface and therefore the softening is formulated in terms of a nonlocal equivalent plastic strain. In the second approach, a hardening term which depends on the local equivalent plastic strain is introduced to the modified JH2 model in addition to the nonlocal softening. This approach is inspired by results from gradient plasticity in quasi-static loading scenarios. It is shown that the approach without hardening can still lead to mesh-dependent results while the model that includes hardening successfully inhibits strain localization and leads to a converging dissipated plastic energy. This is further confirmed in a two-dimensional wedge-splitting experiment where the damage pattern produced by the local model is mesh-dependent as well and the dissipated plastic energy tends to zero with mesh-refinement. The proposed nonlocal model with hardening results in a consistent damage pattern and the dissipated plastic energy converges. Furthermore, the nonlocal model with hardening is less sensitive to time step refinement, such that computational efficiency can be improved compared to the local model.
The numerical experiments are implemented using the free and open-source tool FEniCSx.…


| Autor*innen: | Sjard Mathis RosenbuschORCiD, Daniel BalzaniORCiD, Jörg F. UngerORCiD |
|---|---|
| Dokumenttyp: | Forschungsdatensatz |
| Veröffentlichungsform: | Graue Literatur |
| Sprache: | Englisch |
| Jahr der Erstveröffentlichung: | 2024 |
| Organisationseinheit der BAM: | 7 Bauwerkssicherheit |
| 7 Bauwerkssicherheit / 7.7 Modellierung und Simulation | |
| Herausgeber (Institution): | Bundesanstalt für Materialforschung und -prüfung (BAM) |
| Verlag: | Zenodo |
| Verlagsort: | Geneva |
| DDC-Klassifikation: | Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik |
| Freie Schlagwörter: | Concrete modeling; Explicit Dynamics; FEniCS; Gradient plasticity; JH2 model; Mesh convergence |
| Themenfelder/Aktivitätsfelder der BAM: | Infrastruktur |
| Infrastruktur / Green Intelligent Building | |
| Art der Ressource: | Software |
| Beginndatum der Datenerstellung: | 23.10.2024 |
| DOI: | 10.5281/zenodo.13983859 |
| Zugehöriger Identifikator: | https://doi.org/10.1016/j.ijimpeng.2024.105209 |
| Verfügbarkeit des Dokuments: | Datei für die Öffentlichkeit verfügbar ("Open Access") |
| Lizenz (Deutsch): | Creative Commons - CC BY - Namensnennung 4.0 International |
| Datum der Freischaltung: | 10.12.2025 |
| Referierte Publikation: | Nein |
| Schriftenreihen ohne Nummerierung: | Forschungsdatensätze der BAM |


