The paper deals with the finite element analysis of airframes crash situations. Different recent crash tests highlighted the influence of local rupture mechanisms on global ruin modes of aeronautical structures, and more particularly, ruptures in joint areas. Investigations always show two possible failure modes of riveted assemblies. In the one hand the rivets could shear, in the other hand cracks could propagate along rivets lines. The F.E. computing costs are linked to the shell element size (for explicit algorithms) which still do not enable today to mesh these local failure behaviours.

The main topic of this work is to set up a methodology which enables to introduce embrittlement in riveted plates, through the use of specific equivalent finite elements. According to previous experimental and modelling works on riveted joints, the ruin of an academic case of punched plates is leaded using the Gürson material model in the FE code Pam-solid^TM. Relations between local and global behaviours of the tested specimen are numerically established and basic validations are undertaken.

A general description of the plate failure is proposed as being the summation of local contributions, of failed finite elements only, to the global strength of the thinly meshed plate specimen. A first equivalent approach is then attempted where the strain gradient and history observed in the failed finite elements are redistributed in parallel elements the size of which is the one of the total plate (to avoid small size elements). Finally, once these basics have proved their potentialities, a modified explicit algorithm is derived to be implemented in commercial FE crash codes.

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