CAE-Companion-2018-2019

Modeling of Materials & Connections WISSEN CAE

Figure 7: Industrial application: Pedestrian Head impact

Figure 4: Schematic visualization of different cracks in different layer of a shell meshed part Due to different stress states, different crack shapes are expected (figure 5). The validation model shows exactly the expected behaviour of the layers through their thickness, where the dominant shape on the upper layer is circular and on the lower layer the star-shape becomes dominant. Figure 6 shows the simulation results with RADIOSS. It can be seen, that the cracks propagate nearly mesh independent.

Figure 8: Industrial application: Roof crush

Conclusion X-FEM is more physical in terms of crack simulation, due to the split of elements than the classical, unphysical, deletion of elements. Besides, X-FEM aims at avoiding extremely small and CPU expensive meshes. It is successfully implemented in RADIOSS, where it is able to realistically reproduce crack patterns in laminated glass, like in windshields. There is also the possibility of crack initiation which is important for design improvement and stochastic analysis. X-FEM is easy to use in RADIOSS: Only one Flag has to be set. References [1] HyperWorks RADIOSS TheorieManual: 13.0 version – Nov 2014 [2] T. Belytschko, T. Black, “Elastic crack growth in finite elements with minimal remeshing”, Int. J. Numer. Methods Engrg., 45:601–620, 1999. [3] J.M. Melenk, I. Babuska, “The Partition of Unity Finite Element Method: Basic Theory and Applications”, Comput. Meths. Appl. Mech. Engrg., 139:289-314, 1996. [4] N. Moës, J. Dolbow, T. Belytschko, “A finite element method for crack growth without remeshing”, Int. J. Numer. Methods Engrg., 46:131–150,1999. CAEWissen by courtesy of: Marian Bulla - ALTAIR Product Specialist Crash&Safety Jean-Pierre Bobineau - ALTAIR Senior Technical Specialist MaciekWronski - ALTAIR Software Development Manager Mircea Istrate - ALTAIR Senior Software Developer

Figure 5: Different crack shapes due to different stress conditions, over the thickness

Figure 6: Finite element simulation (RADIOSS) results on a validation structure – safety glass After final validation material-, failure criteria and the X-FEM approach can be applied to industrial cases, especially well-suited for modelling fracture in brittle materials as well as in multi-layered shells with different materials (figure 7 and 8).

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