@misc{ElKhatibHuetterPhametal., author = {El Khatib, Omar and H{\"u}tter, Geralf and Pham, Rinh-Dinh and Seupel, Andreas and Kuna, Meinhard and Kiefer, Bjoern}, title = {A non-iterative parameter identification procedure for the non-local Gurson-Tvergaard-Needleman model based on standardized experiments}, series = {International Journal of Fracture}, volume = {241}, journal = {International Journal of Fracture}, number = {1}, issn = {0376-9429}, doi = {10.1007/s10704-023-00689-9}, pages = {73 -- 94}, abstract = {Damage mechanics models exhibit favorable properties such as the intrinsic influence of stress triaxiality on damage evolution and the prediction of crack initiation as well as propagation leading to structural failure. However, their application requires advanced expertise hindering the transfer of these models into industrial practice, especially since the parameter calibration is a key obstacle. In this paper, a simplified procedure is proposed for a non-local extension of the Gurson-Tvergaard-Needleman model (GTN), which is a highly accepted model for ductile failure of metals. The procedure is iteration free and requires experimental input data from only two standardized tests. The parameters are determined using look-up diagrams created on the basis of systematic simulations and made available for different material behavior covering the majority of ductile metals. Benchmark tests for three different steels are conducted to evaluate the robustness of the proposed procedure. The reliability of the GTN model is validated for all investigated materials.}, language = {en} } @misc{ElKhatibPhamHuetteretal., author = {El Khatib, Omar and Pham, Rinh-Dinh and H{\"u}tter, Geralf and Seupel, Andreas and Kiefer, Bjoern}, title = {On the predictive capabilities of non-local models for ductilecrack propagation under different levels of stress triaxiality}, series = {Proceedings in applied mathematics and mechanics : PAMM}, volume = {23}, journal = {Proceedings in applied mathematics and mechanics : PAMM}, number = {4}, issn = {1617-7061}, doi = {10.1002/pamm.202300274}, abstract = {Ductile materials are used in many applications such as hydrogen storage andtransport, energy plants and additively manufactured components. High safetystandards are vital for such applications, which underline the necessity of thor-oughly investigating ductile failure to ensure safety and increase componentsefficiency. Ductile failure is mainly prompted by the evolution of the so-calledductile damage, characterized by the nucleation, growth and coalescence ofmicrovoids due to plastic deformation. Moreover, the plastic zones formed at thecrack tip of ductile materials exhibit high sensitivity to the stress triaxiality level,which in turn distinctly depends on the geometry of the considered component.The quantification of the stress triaxiality at the crack tip is therefore essential tobetter understand and predict ductile crack propagation and failure. For that rea-son, a non-local ductile damage model is employed in this work to simulate theductile crack propagation under different stress triaxiality conditions. Differentgeometries are considered, such as constrained geometries of notched bendingspecimens and unconstrained geometries of center cracked tension specimens,which characterize the different triaxiality levels. To address the effects of thick-nessandinitialcracklength,three-dimensionalgeometriesaresimulated,whichaccount for the out-of-plane crack-tip constraints. Finally, to evaluate the predic-tion quality of the simulations, corresponding experiments have been carried outand direct comparisons are conducted, with respect to the crack length, ductilecrack propagation and resistance curves.}, language = {en} }