Error estimation and adaptivity for nonlocal damage models

Nonlocal damage models are typically used to model failure of quasi-brittle materials. Due to brittleness, the choice of a particular model or set of parameters can have a crucial influence on the structural response. To asse ss this influence, it is essential to keep finite element discretization er rors under control. If not, the effect of these errors on the result of a c omputation could be erroneously interpreted from a constitutive viewpoint. To ensure the quality of the FE solution, an adaptive strategy based on err or estimation is proposed here. It is based on the combination of a residua l-type error estimator and quadrilateral h-remeshing. Another important con sequence of brittleness is that it leads to structural responses of the sna p-through or snap-back type. This requires the use of are-length control, w ith a definition of the are parameter that accounts for the localized natur e of quasi;brittle failure. All these aspects are discussed for two particu lar nonlocal damage models (Mazars and modified von Mises) and for two test s: the Brazilian tensile splitting test and the single-edge notched beam te st. For the latter test, the capability of the Mazars model to capture the curved crack pattern observed in experiments - a topic of debate in the lit erature - is confirmed. (C) 2000 Elsevier Science Ltd. All rights reserved.