Software analyses bird strikes on aircraft

Paul Boughton

Samtech, a European technology leader in the development of integrated computer aided engineering software, is launching the commercial release 2006 of the general-purpose explicit and fast dynamic analysis software Europlexus.

Since 2000, Europlexus has been jointly developed by the French Atomic Energy Commission (CEA Saclay), the Joint Research Centre (European Commission), EDF and Samtech.

Europlexus is a conveniently integrated simulation package that has been widely demonstrated to adequately and effectively address the field of fast transient dynamics involving fluid-structure interaction phenomena.

It is used by academic institutions, research centres, energy agencies and aerospace manufacturers (Snecma and Sonaca, for example) to perform advanced 1D, 2D and 3D non-linear explicit dynamic analyses of complex fluid-structure interaction systems subjected to fast transient dynamic loading (for instance, explosions in enclosures, shocks and impacts, pipelines dynamics under transient internal flows, propagation of subsonic, and transonic and supersonic flow variations associated with obstacles).

Europlexus has also been adapted to bird strikes simulation using SPH (smooth particle hydrodynamics) models of the bird with tuned material properties (porous gelatine). Equivalent models of riveted structures are also available, enabling progressive damage and ultimate failure analysis of rivets and shells.

The newest version of Europlexus 2006 features enhanced modelling and analysis tools that allow accurate dynamic progressive damage simulation of composite structures.

Major enhancements to Europlexus include: implementation of multi-material and multi-layered shell elements (quadrilateral and triangular); implementation of a new elasto-plastic law with orthotropic Hook's matrix and based on Hill's criteria; and noticeable performance improvements in terms of contact computation.

Europlexus 2006 runs on Linux, Unix and Windows platforms. The Linux versions are now available for x86, Itanium2, AMD64 and EM64T processors. The IBM version is parallelised based on Open-MP approach.

“With Airbus, Embraer, Dassault and Bombardier as main customers, Sonaca's core business is the development, testing, manufacturing and assembly of aerospace structures and their associated subsystems, in particular wing leading edges, the fuselage sections and wing panels” says Claude Nyssen, technical director of Sonaca.

“In accordance with certification requirements, we have to demonstrate, in particular, that wing leading edge components can absorb the major part of a 4 lb [1.8kg] bird impact energy at a speed of 650km/h. In order to reduce development costs, time-to-market and to optimise structural concepts, appropriate bird strike numerical modelling and simulation techniques appear clearly as a vital alternative to expensive and time-consuming destructive testing.

“A collaboration was thus established with Samtech and specifications were defined to tailor the Europlexus package to our specific requirements. Using the SPH bird model and including in our models largely deformable shell elements, non-linear spring elements representing the riveted joints, and failure modes capabilities (skin tearing or rivet failure), we have been able to finalise and integrate a methodology for the modelling and simulation of bird impacts against metallic components.

“This methodology has been validated through extensive testing, providing numerical predictions in very close agreement with experimental data. Needless to say that we are very excited about the new features in Europlexus 2006, as we intend now to extend this approach to the simulation of bird impacts against composite components and associated specific damage mechanisms.”

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