PROGRAM TO IMPROVE THE FRACTURE TOUGHNESS AND FATIGUE RESISTANCE OF ALUMINUM SHEET AND PLATE FOR AIRFRAME APPLICATIONS

摘要

The fatigue crack growth rate (FCGR) characteristics of a 7000 series and a 2000 series alloy were evaluated. The bulk of the work was carried out on thermomechanically aged (TMA) RX725 (Al-6Zn-2.5Mg-1.5Cu-.1 Zr) and 2048 in the TMA and -T3E9 tempers respectively. Crack growth rate was reduced by either crack branching or deviation of the crack from the plane normal to the applied stress. Both experimental materials were found to be sensitive to environment (high or low humidity) even though they were resistant to exfoliation corrosion.. An inverse hyperbolic tangent model fitted the data well, but the parameters in the model did not lend themselves to characterizing FCGR material performance. It was concluded that significant benefits could be achieved by TMA processing.