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Schra, L. (author), Wanhill, R.J.H. (author)In 1991 a simple automated stress corrosion testing method called the ASCOR (Automated Stress corrosion Ring) test was developed to test aluminium alloys according to ASTM specification G49. The present investigation concentrated on evaluating two aspects of the test method: The SCC initiation criterion (2 % load decrease). The possibility of...report 1997
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Schra, L. (author), Wanhill, R.J.H. (author)Flight simulation fatigue growth tests were done on 1.6 mm thick sheets of the damage tolerant aluminium-lithium (Al-Li) alloys 2091-T84 and 8090-T81 in comparison with the industry standard conventional damage tolerant alloy 2024-T3. The flight simulation load spectrum, the gust spectrum MINITWIST, was used in four versions: untruncated,...report 1991
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Schra, L. (author), Wanhill, R.J.H. (author)An extensive programme of notched fatigue testing of aluminium forging alloys has shown that the data result in two basic forms of S-N curve. Analytical approaches to constructing the S-N curves were less satisfactory than fitting the curves freehand. Since freehand curve fitting m\ist involve an element of subjectivity, guidelines for...report 1980
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Wanhill, R.J.H. (author), Schra, L. (author)An investigation was made of the effect of starter notch geometry on flight simulation fatigue crack growth in three damage tolerant aluminium sheet alloys, 2024-T3, 2091-T84 and 8090-T81. Changing the starter notch geometry resulted in significant differences in initial nonstabilized fatigue crack growth behaviour. However, there was only a...report 1995
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Schra, L. (author), van Leeuwen, H.P. (author)The effect of variety of heat treatments on various engineering properties was studied with the aim to derive an optimum heat treatment. The engineering properties comprised Vickers hardness, short-time tensile strength, fatigue crack propagation resistance, fracture toughness and stress corrosion resistance. The test results were compared with...report 1976
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Schra, L. (author)The engineering properties of the aluminium alloys AAT075-TT3, AAT175-TT36, AA705O-T736 and the German alloy AZ74.6l were compared. The properties involved were: strength, fracture toughness, fatigue crack propagation under different load spectra, and resistance to stress corrosion cracking both with respect to initiation and propagation. The...report 1979
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- Bartelds, G. (author), Schra, L. (author) report 1978
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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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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), 't Hart, W.G.J. (author), Schra, L. (author)The fatigue crack propagation resistances of 7010-T7651, 7010-T73651 and 7075-T7351 thick plate were compared for flight simulation (gust spectrum) loading conditions. 7075-T7351 was slightly superior, and it was shown that this superiority was not essentially due to the higher fracture toughness of this alloy. The influence of specimen...report 1979
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Schra, L. (author), van Leeuwen, H.P. (author)The influence of previous corrosion on the fatigue life was investigated. It was foimd that a slight corrosive attack could drastically reduce the fatigue life. The damaging effect of corrosion was greater for the alloy AA 7050 than for AZ 74.61. It could be established that fatigue cracks initiated from various corrosion pits. A second series...report 1977
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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), Schra, L. (author)The SCC resistances of three damage tolerant aluminium sheet materials were determined by means of the ASCOR (Automated Stress Corrosion Ring) test. The conventional damage tolerant sheet material 2024-T3 was used as reference. The sec resistance of 8090-T81 turned out to be only slightly lower than the sec resistance of 2024-T3. In contrast,...report 1991
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van Leeuwen, H.P. (author), Schra, L. (author)Material from forgings rejected after cracking in service was given a variety of heat treatments. Material aged to peak hardness was susceptible to SCC at all ageing temperatures. Overageing at temperatures around 160° C imparted a significant increase in SCC resistance while useful strength was retained. An additional one week ageing at 160° C...report 1973
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't Hart, W.G.J. (author), Schra, L. (author)In the framework of the CEC Brite Euram programme on "Investigations on aluminium-lithium alloys for damage tolerant application", the NLR work in Task 3 concentrated on Fracture Toughness. In part I of the investigation residual strength tests were performed on 500 mm wide CCT panels of the Al-Li sheet alloys 2091-T84 and 8090-T81 and on 2024...report 1992
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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), van der Vet, W.J. (author), van Leeuwen, H.P. (author)Porgings were given a variety of heat treatments after which hardness, static tensile properties, fatigue properties, fracture toughness and stress corrosion resistance were determined. Microstructures were studied in the electron mcroscope using the thinfoil technique. The effect of heat treatment on the microstructure could be explained on the...report 1972
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Wanhill, R.J.H. (author), Schra, L. (author)The effects of flat to slant fracture transitions on flight simulation fatigue crack propagation in specimens of 7O5O aluminium alloy forgings are discussed. For specimens containing flat, shearlipped, or full slant fractures at similar crack lengths the crack resistance (R curve) approach appears to provide an explanation for differences in the...report 1976
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Schra, L. (author), van der Hoeven, W. (author)In the aerospace industry there are continuing demands for weight reductions. These demands translate into the need to develop new materials with greater strength and stiffness and/or improved damage tolerance properties. The NLR has followed these developments by conducting experimental programmes to evaluate engineering properties like static...report 1997
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Wanhill, R.J.H. (author), Schra, L. (author), 't Hart, W.J.G. (author)The fatigue crack growth properties of several aluminium-lithium (Al-Li) sheet alloys were compared with those of the widely used conventional 2024-T3 alloy. The data, which are relevant to the in-service inspectable damage tolerance regime, were obtained using constant amplitude and flight simulation (gust spectrum) loading. The Al-Li alloys...report 1991