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The purpose of this study was to determine the acceptability of nonpenetrating, key-locked inserts in 2099 aluminum-lithium. The tests conducted to make this assessment were: (1) microscopic examination for thread damage and delaminations after key installation, (2) pull-out load at 21°C (70°F) and )179°C ()290°F), and (3) mechanical cycling tests at room temperature and )179°C ()290°F). The test results indicated that for the three sizes evaluated, key-locked inserts in 2099-T6 and 2099-T8 were acceptable and although delaminations did occur on some T6 temper specimens, it was only as a failure mode at ultimate load and such behavior was judged to be acceptable.

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The purpose of this investigation was to develop an understanding of the biaxial behavior of titanium sheet. An experimental test method was developed and found to provide homogeneous stress fields for obtaining biaxial data in a variety of stress states. Data were obtained using the same specimen geometry for 1-to-2 and 1-to-1 axial-to-hoop stress states. Significant increases in the biaxial yield strength were obtained over those predicted by von Mises’ yield criterion for isotropic materials. Very high biaxial burst strengths were also obtained; the maximum was 246 ksi for annealed Ti-5Al-2.5 Sn alloy in a 1-to-1 stress state. The data followed the general form predicted by Hill’s model for anisotropic materials.