Stress Corrosion

Stress Corrosion Facility

The Department of materials technology has experience in analysing the results of the ESA PSS-01-737 test and classifying the metal alloys into the class I, II, III tables, that are defined by ESA and NASA. Stress corrosion tests have been performed for ESA e.g. for Al-MMC's or AlBe alloys. Stress corrosion tests can be carried out in accordance to ESA PSS-01-737: issue 1 at a stress level of 75 % of the Rp0.2 proof stress over a period of 30 days. The tensile tests are described above. Three parallel specimens of the material are subjected to 75 % of the proof stress and immersed in 3.5 % NaCl solution for ten minutes and dried for 50 minutes which is repeated over a period of 30 days; the sodium chloride solution is renewed after 7, 15 and 21 days. The stress is maintained by connecting the 3 testing rigs to a hydraulic pressure regulator. The hydraulic system operates with special testing cylinders. High accuracy secures a constant load up to 15 kN. The testing system is superior to the proposed method as described in 3.3.1 of ESA PSS-01-737, which utilises the compression of a pre- calibrated spring to apply the axial tensile stress to the specimen under test, as yielding, creep or slide of the specimen during the test will have no influence on the applied load. Three parallel specimens of the same material are used as unstressed control specimens. Metallographic inspection is made for the tensile specimen, the SCC-specimen and the unstressed control specimen. The available testing devices allow to test up to 12 specimens simultaneously.