The strong wrought aluminium alloys, SDH, SDR, ESDW and ESDT, and clad sheets, SDCH, SDCR and ESDC have been fatiguetested by the method of 3% salt water spray, with Schenck's vibratory endurance testing machine. The S-N diagram thus obtained indicates the scattering of results for the test particulary in the corroded condition. No difinite conclusion was obtained from this test, but the results are as follows: (1) The fatigue strength and orrosionfatigue resistance of ESD has the highest value in these specimens. (2) The ratio of fatigue strength of the simple sheet to the clad sheet are in the range of 47% to 28% in air, the decreasing percentage of fatigue strength in the salt water spray to that in air changes from 88% to 39% in the sheet, and from 71%,to 51% in the clad sheet. (3) From the microscopic study, many hair cracks are seen to be produced in the surface layer of a clad material, and this phenomenon indicates the decrease of its 6,tigue resistance.
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