Standard or reference data on environmental properties, including corrosion and stress corrosion, are mandatory for the qualification and certification of materials for aerospace vehicles and the design of actual structures and components. This review discusses the determination and classification of the ambient temperature corrosion and stress corrosion properties of aerospace structural alloys and some of the issues involved. Recommendations for further testing and evaluation are given also.

Inhalt: Reibrührschweißen wird zunehmend im Flugzeugbau und der Raumfahrt als Fügemethode für hochfeste Aluminiumlegierungen genutzt. Die dabei entstehenden Eigenspannungen können sich ungünstig auf das Betriebsverhalten auswirken und müssen in der Auslegung der Bauteile berücksichtigt werden. Für Eigenspannungsanalysen werden verständlicherweise keine kompletten Bauteile herangezogen, sondern bevorzugt Probekörper aus größeren, bauteilnahen Komponenten. Die Frage ist, ob der Eigenspannungszustand in diesen Komponenten und Probekörpern demjenigen im tatsächlichen Bauteil nahe kommt oder zumindest eine konservative Bewertung des Eigenspannungseinflusses ermöglicht.

Purpose – The purpose of this paper is to validate the strain-based failure assessment diagram (SB-FAD) approach for surface cracks in components subjected to displacement controlled boundary conditions. Design/methodology/approach – Numerical analyses are performed for several crack geometries and materials representative for aerospace applications. The performance of the SB-FAD is judged by comparing numerically calculated J-integrals to respective analytical estimates, using both Options 1 and 2 approximations. Findings – In the most cases, both Options 1 and 2 SB-FAD method results in reasonably conservative J-estimates. Exceptions are for surface cracks in a pressurized vessel made of a material with low-strain hardening, for which Option 2 assessment produces non-conservative results. In contrast, Option 1 assessment is conservative for all geometries considered. In general, Option 1 results in a considerable overestimation of the crack driving force, whereas Option 2 produces rather accurate results in many cases. Originality/value – The results demonstrate both the potential of the SB-FAD method and needs for its further improvements.

Friction stir welding (FSW) is a well-known technique which allows joining of metal parts without severe distortion. Because FSW involves less heat input relative to conventional welding, it may be assumed that cutting specimens from larger friction stir welded components results in a negligible redistribution of residual stresses. The aim of the investigations was to verify these assumptions for a welded aluminum plate and a circumferentially-welded aluminum cylinder. Strain gage measurements, X-ray diffraction and the incremental hole drilling method were used.

Aluminium-lithium (Al-Li) alloys offer attractive properties for lightweight aerospace structures, due to their low density, high strength and fatigue crack growth resistance. Although there are many advantages with Al-Li alloys. limitations remain while using conventional joining techniques.Friction stir welding is a well-established solid-state joining process that is expected to reduce many of the concerns about Al-Li welding.The work presented in this paper involves the characterisation of the fatigue performance of the AA2195-T8X at room temperature. SN and crack growth tests of base material and friction stir welded 5 mm thick specimens were performed. During crack growth tests, three different R ratios (minimum remote stress/maximum remote stress), 0.1, 0.5 and 0.8, were used per each three different material conditions: base material, heat affected zone (HAZ), and weldment. M(T) specimens containing notches at the centre of the weld, at the HAZ and at the base material, were tested. The fatigue crack growth specimens were left with an un-cracked ligament for final evaluation of fracture toughness.Novel results are presented for fatigue crack growth and toughness on T-L orientation. The results for SN fatigue behaviour, fatigue crack growth and toughness of the studied alloy and its friction stir weldments present high values when compared with data found in the literature. (C) 2012 Elsevier Ltd. All rights reserved.

The study shows the main properties of AA2195 in relation to the microstructure developing in the friction stir weld process, which were comprehensively investigated in the ESA Technology and Research Programme Damage Tolerance of Cryogenic Pressure Vessels (TRP T401-02 MC). Friction Stir Welding (FSW) on 5 mm sheets of AA2195 in T8 condition was performed and process parameters were optimized. Non-destructive Inspection (NDI) methods were used to detect potential defects and metallographic investigations were applied in order to detect their origin. The properties on the friction stir joints were determined and the influence of temperature down to 20 K is shown. Particular attention is given to the microstructure and the fracture characteristics of the friction stir welds and base material. Optical and scanning electron microscopy investigations are used to determine the failure mode. Additionally, the influence of temperature is discussed on the basis of samples fractured at RT, 77 K, 20 K and 4 K. The metallographic analysis of NDI results of friction stir welds indicates that a thorough process control can avoid the main large defects in FS welds. High strength FSW joints of AA2195 can be achieved with promising toughness down to cryogenic temperatures. The potential for the application in future launcher systems is discussed with respect to potential future serial production.

Damage mechanics based material models have been applied to establish fracture control procedures for the failure prediction of ARIANE 5 main structural components as the booster cases including welds, the main stage, and the upper stage cryogenic tank. The main goals of the damage mechanics based investigations were the accurate failure prediction, the clarification of dependency of fracture toughness on geometry, the calibration of analytical methods and the interpretation and optimisation of small scale fracture tests for material characterization and quality assurance.The results of these investigations allowed a failure prediction accuracy with analytical tools which is close to 3D numerical simulations. This could be demonstrated both with ductile (Gurson) and brittle (RKR) damage mechanics models. (c) 2008 Elsevier Ltd. All rights reserved.