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Aviation History
1964
1964 - 1158.PDF
'LIGHT International, 23 April 1964 651 fig 4 Two structure-test speci- mens: a machined fuselage-skin panel, with window cut-outs (upper) and a machined wing-skin panel, with tank-inspection cut-out Test Programme and Production These few indications give an idea of the extent of the test pro- gramme undertaken for checking the suitability of the selected alloy in all its aspects. One cannot fail to be struck by the excep- tional length of individual creep tests which have to cover the entire service life of the aircraft, by the length of fatigue tests at low frequency of load modulation, and again by preliminary heating times to which the metal had to be subjected prior to test measure- ment in order to take soaking into account. To give a fuller idea of the effort accomplished in the last five years in the laboratories of metal producers Pechiney and CEGEDUR, at ONERA and at Sud Aviation, it should be added that it is always necessary to carry out at least five tests for each measurement in order to eliminate the scatter factor. This effort has, however, borne fruit, since it enables us to claim that in A-U2GN we have a light alloy, which, in contrast to con- ventional alloys, can fully meet requirements of flight at Mach 2.2. This is due to:— Its cold mechanical properties are unchanged after soaking at 130°Cfor30,000hr. At that temperature these properties are only slightly reduced, sothat no additional restriction is introduced in the design stresses. Creep is practically nil after 30,0O0hr at 130°C at flight stresses.Fatigue resistance, which is comparable with that of the best current alloys at normal temperature, is not affected by temperature up to150°C. A-U2GN also has the advantage of being a well-known and proved material, in industrial production in Britain and France for some ten years in the form of forgings or stampings [e.g., for the Caravelle undercarriage ribs]. Facilities for conversion in existence or being installed by the Compagnie Generate du Duralumin et du Cuivre—CEGEDUR—for making available rolled products for the Concord are considerable, and in keeping with requirements. In the foundry, casting of very large slabs of A-U2GN weighing 2,500 and 4,000kg (5,512 and 8,8201b) has been developed, and an excellent metallurgical quality has been obtained. These slabs are capable of providing very large forgings or very thick sheet, ade- quately hot-worked, with uniform fine grain, free from internal defects and with uniform mechanical properties which are satis- factory in all three planes. A four-high reversible rolling mill 3.400m (133.9in) wide has been installed in France for rolling the thick sheet required in the construction of the Concord wing. This mill now permits the production of sheet up to 3.200m (126in)w 'de, with a thickness of from 6mm (0.236in) up to 180mm (7.1in) and more. Continuous rolling mills 2.850m (112in) wide, which have been available in France for many years, are adequate to meet we requirements for production of any width of thin sheet in A-U2GN for the Concord. Existing heat-treatment installations were already capable of dealing with sheet up to 2.5 x 10m (98.4 x 394in). An additional furnace, specially adapted for thick sheet, has been brought into ^ice in order to gain greater flexibility and increased capacity in sneet production. Thick sheet up to 15m x 3.2m (590 x 126in) can be heat-treated in this furnace.3 >900-ton stretching machine, which has been in operation for several months, enables thick sheet to be levelled by stretching, and at the same time gives a controlled elongation of the order of 2 % in order to eliminate internal quenching stresses and consequently prevent distortion during machining. This machine is capable of taking sheet 15m x 3.2m, up to 180mm thick. Finally, equipment for ultrasonic immersion inspection of thick sheet has been installed, also capable of handling sheet 15m x 3.2m. This equipment permits automatic inspection at high speed. All this equipment is in addition to existing facilities in France and Britain to ensure regular and quality production of the various types of sheet in A-U2GN. Where extrusion is concerned, existing presses in both countries, with capacities of up to 6,000 tons, are amply sufficient to ensure production of all required sections and tubes in A-U2GN. This also applies to forging equipment, with presses of up to 20,000 tons. Finally, the laboratories have been equipped with additional means for controlling the uniformity of hot properties of materials produced for this aircraft, in particular by creep measurements. These checks will be carried out systematically for each batch of products destined for the Concord, in accordance with a control schedule laid down by Sud Aviation and BAC to cover the most severe operational conditions of the material in service with a com- fortable safety margin. Considerable capital investment by French producers of light alloys therefore makes A-U2GN already available in the forms required for the Concord. In addition to forgings, there are sections and thin sheet with or without cladding; but the main effort has concerned the supply of stretched thick sheet or plate of the large dimensions already quoted, which will be used for producing integrally stiffened components for the fuselage and wings. As a result of this effort, powerful automatic machines in the works of Sud Aviation and BAC have already been able to start machining these components. Parts intended for Concord structure tests are beginning to take shape (Figs 4 and 5), and soon components for the prototype airframes will have been produced. Fig S BAC Operating (Preston Division) is responsible for the rear fuselage and fin; in this picture a fin attachment member is being machined in A-U2GN alloy
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