TY - JOUR A1 - Titscher, Thomas A1 - Unger, Jörg F. A1 - Oliver, J. T1 - Implicit explicit integration of gradient enhanced damage models JF - JOURNAL OF ENGINEERING MECHANICS N2 - Quasi-brittle materials exhibit strain softening. Their modeling requires regularized constitutive formulations to avoid instabilities on the material level. A commonly used model is the implicit gradient-enhanced damage model. For complex geometries, it still Shows structural instabilities when integrated with classical backward Euler schemes. An alternative is the implicit–explicit (IMPL-EX) Integration scheme. It consists of the extrapolation of internal variables followed by an implicit calculation of the solution fields. The solution procedure for the nonlinear gradient-enhanced damage model is thus transformed into a sequence of problems that are algorithmically linear in every time step. Therefore, they require one single Newton–Raphson iteration per time step to converge. This provides both additional robustness and computational acceleration. The introduced extrapolation error is controlled by adaptive time-stepping schemes. This paper introduced and assessed two novel classes of error control schemes that provide further Performance improvements. In a three-dimensional compression test for a mesoscale model of concrete, the presented scheme was about 40 times faster than an adaptive backward Euler time integration. KW - Implicit explicit schemes KW - Gradient-enhanced damage model KW - Adaptive time stepping KW - Continuum damage KW - Robustness PY - 2019 DO - https://doi.org/10.1061/(ASCE)EM.1943-7889.0001608 SN - 0733-9399 SN - 1943-7889 VL - 145 IS - 7 SP - 04019040-1 EP - 04019040-13 PB - ASCE - American Society of Civil Engineers AN - OPUS4-48361 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Titscher, Thomas A1 - Unger, Jörg F. A1 - Oliver, J. ED - von Scheven, M. ED - Keip, M.-A. ED - Karajan, N. T1 - Cycle-by-cycle fatigue damage model for concrete T2 - 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry N2 - Damage caused by stress concentrations in the complex mesoscopic geometry of concrete leads to continuous stress redistribution over the material’s life time. The presented fatigue damage model captures this by resolving each load cycle in a cycle-by-cycle time integration. The model extends a static damage model to failure caused by the (time dependent) strain amplitudes and, thus, allows calibrating the majority of the material’s parameters in static experiments. T2 - 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry CY - Stuttgart, Germany DA - 11.10.2017 KW - Cycle-by-cycle KW - Fatigue damage KW - Mesoscopic PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-436681 DO - https://doi.org/10.18419/opus-9334 VL - 7 SP - MS13, 440 EP - 443 PB - Institute for Structural Mechanics, University of Stuttgart CY - Stuttgart AN - OPUS4-43668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -