In the course of an ARIANE 5 evolution program, the booster cases made of 48 CrMoNiV 4 10 high strength, low alloy steel will be modified such that 6 of the shear bolt connections will be replaced by electron-beam welds. The introduction of welds has been chosen to achieve the following goals: mass reduction, cost reduction, increase of reliability, simplification of thermal insulation application. The presented investigations successfully showed that even highly complex weld configurations can be simulated close to the experimental results: The accurate characterization of microstructural zones from a weld cross section allows the classification of most critical zones for further test planning. Small specimen tensile testing gives the necessary input data (true stress-strain curve) even of small zones for numerical simulations and allows first interpretations in combination with the microstructural classification. The use of BS 7448 Part II for weld fracture toughness characterization is recommended as it takes into account weld typical aspects. The tensile and fracture toughness testing could be simulated with high accuracy, based on ductile (Gurson) or cleavage (RKR) damage models. In the case of fracture analysis even constraint dependent effects can be simulated or eliminated by suitable application of the respective models. The predictions in general showed a maximum deviation of about 5% which is excellent. Based on this laboratory based pre-characterization, any structural geometry can be predicted with high accuracy. In this case even natural defects could be predicted with a (conservative) deviation of about 10 %. This is judged as a good agreement under consideration of simplifications which had to be made at this stage of work, where several characterization data are not yet available. The burst tests on sub-scale pressure vessels all reached the defined minimum burst pressure, although the above mentioned natural defects were present. This demonstrates that the damage tolerance of the structure has successfully been achieved. The here presented methodology is able to identify critical points at the very beginning such that unnecessary effort can be avoided.
Damage tolerance verification concept of the ARIANE 5 booster case welded interface
Schadenstoleranzkonzept für die geschweißten Verbindungen der ARIANE 5 Boostergehäuse
Materialwissenschaft und Werkstofftechnik ; 32 , 4 ; 307-315
2001
9 Seiten, 19 Bilder, 3 Tabellen, 9 Quellen
Aufsatz (Zeitschrift)
Englisch
Damage Tolerance Verification Concept of the Ariane 5 Booster Welding Interface
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