The dependence of cyclic nonlinear energy toughness on the fatigue lives of precracked specimens was studied using two aluminium alloys, 2024-T3 and 7075-T6. An exponentially increasing load program was used for determining the fatigue lives. The cyclic toughness values for both alloys decreased as a logarithmic function of the fatigue lives. For a given life the toughness value for 2024-T3 was higher than that for 7075-T6, but the difference decrease with increasing cyclic life. An accelerated test program for prediction of constant amplitude fatigue lives of precracked specimens was undertaken. An analytical basis for this method was developed using an exponentially increasing load sequence. Accelerated tests were carried out on 2024-T3 and 7075-T6 using linearly and exponentially in creasing loads and appropriate curves of the form of higher-order hyperbolas were fitted to the data using the method of least squares. The constant amplitude curve predicted from these results will be compared with the constant amplitude test results in the second stage of this program. (Kursetz)
Development of fracture mechanics concepts applicable to aircraft structures
Entwicklung von Konzepten anwendbar auf den Bruchmechanismus von Flugzeugbauteilen
US Government Reports ; May ; 1-27
1979
27 Seiten
Report
English
Fracture mechanics of aircraft structures
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