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Schra, L. (author), 't Hart, W.G.J. (author)Long-term outdoor exposure tests were done to investigate the effect of cooling rate on corrosion and stress corrosion properties of extruded rods of the high strength aluminium alloys 2024-T4, 2023-T6, 7075-T6 and 7075-T73. The 2024 alloy exhibited a high susceptibility to SCC irrespective of best treatment and cooling rate, whereas 7075-T6 was...report 1990
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Wanhill, R.J.H. (author), Schra, L. (author), 't Hart, W.G.J. (author)Qualification of Al-Li alloys for damage tolerant aerospace structures requires extensive testing and evaluation. In this paper the emphasis is on fracture and fatigue crack growth properties of two candidate sheet alloys, 2091 and 8090, compared with the conventional and widely used 2024 alloy. The relative merits of these materials are...report 1990
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- Wanhill, R.J.H. (author), Schra, L. (author) report 1989
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Wanhill, R.J.H. (author), Schra, L. (author), 't Hart, W.G.J. (author)New impetus to continued use of alximinium alloys in major structural areas of aircraft has been given by the development of aluminium-lithium alloys. However, qualification of these new materials for service requires extensive testing and evaluation, preferably in international cooperative programmes. The evaluation of aluminium-lithium alloys...report 1989
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Wanhill, R.J.H. (author), Schra, L. (author)The economic life of airframes is largely determined by widespread initiation and growth of fatigue cracks at low stress intensities. Any factor reducing the low stress intensity fatigue damage rate could, if controllable, increase the structural durability. One such factor is corrosion fatigue crack arrest. Corrosion product build-up within a...report 1988
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Schra, L. (author), 't Hart, W.G.J. (author)Long-term outdoor stress corrosion tests were executed on overaged 7000 series aluminium alloy plate and forgings. Plate material of the alloys 7010-T7651, 7010-T7451 and 7075-T7351 exhibited an excellent resistance to SCC. PM alloy X7091-T7E69 forgings combined a higher strength with superior SCC resistance as compared to IM alloy forgings. The...report 1988
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Kolkman, H.J. (author), 't Hart, W.G.J. (author), Schra, L. (author)One of the first commercially available Al-Li plate alloys, DTD XXXA-T651, produced by ALCAN International Ltd., was tested in the framework of a European cooperative programme (GARTEUR). The engineering properties were determined in a previous investigation. The present report describes the results of an additional investigation with respect to...report 1987
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van Leeuwen, H.P. (author), Groep, F.F. (author), Schra, L. (author), Dam, N. (author)Test results reported in the literature show that in creep cracking tests at elevated temperature under steady load, the crack growth rate correlates best with the contour integral C*, also called J*, in comparison to other possible parameters. In the case of fatigue at elevated temperature, the crack growth rate correlates best with C* if...report 1987
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Wanhill, R.J.H. (author), Schra, L. (author)Constant amplitude low stress Intensity fatigue crack growth for 2024-T3 and 7475-T761 aluminium alloys In laboratory air, sump tank water and synthetic seawater was Investigated. Corrosion fatigue crack grouwt retardation and arrest occurred In both sump tank water and synthetic seawater, resulting In higher AKth values than In air. Crack...report 1987
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Schra, L. (author), Han, M.O.T.H. (author)The influence of different variables in the chromic acid anodizing process on the surface attack and the thickness of the anodizing layer was investigated for aluminium alloy 7050-T7451 (formerly T73651) plate, 7075-T7351 plate, 7075-T6 forgings and 7075-T73 forgings. A preliminary investigation was carried out to enable the selection of a...report 1986
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de Koning, A.U. (author), Schra, L. (author)Crack growth prediction methods were evaluated and a preliminary selection was made of models that appear to be applicable to ESA space structures. In this report predictions based on the candidate models are verified by comparison with experimental results. Test configurations, materials and initial defects are specified as well as the load...report 1986
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't Hart, W.G.J. (author), Kolkman, H.J. (author), Schra, L. (author), Wanhill, R.J.H. (author)Engineering properties of the recently developed plate alloy 2324-T39 and the conventional alloy 2024-T351 are compared. Some results for the aluminium-lithium alloy DTD XXXA-T651 (Aluminium Association designation 8090) are also included. The strengths of 2324-T39 and DTD XXXA-T651 were comparable and significantly higher than that of 2024-T351...report 1985
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Schra, L. (author), 't Hart, W.G.J. (author)Engineering property comparisons have been made for plate material of the newly developed aluminium alloy 2324-T39 and the widely used alloy 2024-T351. The properties considered were: tensile strength, fracture toughness, notched fatigue strength, and the resistance to fatigue crack propagation under both constant amplitude and flight simulation...report 1984
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Schra, L. (author)In this addendum to report NLR TR 82054 U the results of additional fracture toughness tests and of prolonged stress corosion tests are given. A considerably better resistance to crack extension of the IM alloys 7075-T73 and 7050-T736 as compared to the PM alloy X7091-T7E69 was found in the fracture toughness tests for the same test orientation...report 1983
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Wanhill, R.J.H. (author), Schra, L. (author)Engineering properties of the PM alloy 7091-T7E69 and the IM alloys 7075-T73, 7175-T736, 7010-T736 and 7050-T736 were compared. The properties considered were strength, fracture toughness, fatigue strength, fatigue crack propagation resistance under constant amplitude and spectrum loading, stress corrosion crack initiation and propagation...report 1983
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't Hart, W.G.J. (author), Schra, L. (author)A comparative experimental investigation was done on the advanced plate alloys 7010-T651 from ALCAN and 7150-T6E189 from ALCOA. The mechanical properties, fracture toughness and corrosion properties were determined. The most notable finding was the excellent fracture toughness of alloy 7150-T6E189 combined with a high tensile strength. The...report 1982
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't Hart, W.G.J. (author), Kolkman, H.J. (author), Schra, L. (author)The Jominy end-quench test was applied to rods of the alximinium alloys T010 and X TO9I to obtain a decreasing cooling rate over the length of the rods. After heat treating to a high strength T6 and an overaged TT condition the corrosion properties and the microstructure were determined related to the cooling rate. No influence of cooling rate...report 1982
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't Hart, W.G.J. (author), Schra, L. (author)The engineering properties of PM alloy X7091-T7E69 forgings were compared with those of forgings of the IM alloys 7075-T73, 7175-T736, 7050-T736 and 7010-T736. The properties considered were: strength, fracture toughness, fatigue crack propagation under constant amplitude and flight simulation loading, stress corrosion crack initiation and...report 1982
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Schra, L. (author), Faber, J. (author)An experimental investigation was carried out into the applicability of various corrosive environments for stress corrosion crack propagation testing of high strength aluminium alloys using double cantilever beam specimens. Testing under atmospheric conditions was used as a reference. It was found that stress corrosion crack growth under...report 1981
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Schra, L. (author), Huisman, H.N. (author)An experimental investigation was carried out into the applicability of various corrosive environments for stress corrosion crack initiation testing of high strength aluminium alloys using constant strain loaded tuning fork type specimens. The effect of surface preparation was also involved. The most important findings were that salt-chromate...report 1981