The ASCOR Test: A Simple Automated Method for Stress Corrosion Testing of Aluminum Alloys

Abstract

Abstract Alternate immersion stress corrosion testing according to ASTM G 44, Practice for Alternate Immersion Stress Corrosion Testing in 3.5% Sodium Chloride Solution, has proves to be representative for alumimum alloys in natural environments resembling the actual eavironmental conditions for aircraft. A simple automated stress corrosion testing method called the ASCOR (automated stress corrosion ring) test was developed to test aluminum alloys according to ASTM G 44 and using direct stressing as in ASTM G 49. Recommended Practice for Preparation and Use of Direct Tension Stress Corrosion Test Specimens. The method involves testing cylindrical or pin-loaded flat tension test specimens in a loading sing provided with strain gages to measure the load. Initiation of a stress corrosion crack (SCC) results in a small load decrease. During the test the load is measured periodically and stored in a data acquisition system controlled by a personal computer. A specific load decrease is used as the criterion for SCC initiation. The main advantages of the method are that a large number of specimens can be tested simultaneously in a climate chamber and that SCC initiation lives can be determined according to a clearly defined criterion without time consuming and subjective inspections, and without disturbing the test procedure.