Effect of High Temperature Exposure on the Mechanical Properties of Cold Expanded Open Holes in 7050-T7451 Aluminium Alloy
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AIR VEHICLES DIV
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Cold expansion of fastener holes has been widely used in the manufacture, maintenance and repair of airframe components to provide beneficial compressive residual stresses around fastener holes and to extend their fatigue life. However, some components may experience exposure to high temperatures due to operational, maintenance or accidental factors. The high temperature exposure could lead to relaxation of compressive residual stresses and potentially affect the components properties such as fatigue life and static strength properties. This report summaries the investigation on the effect of exposure time at a temperature on the mechanical properties of cold expanded open holes in 7050-T7451 aluminium alloy. The experimental results show that for a given exposure temperature of 350 deg F 177 deg C, the fatigue life of the specimens decreased with increasing exposure time. When the exposure time exceeds 3 hours, the fatigue life remained relatively unchanged. The yield strength at the same exposure temperature fell below the minimum allowable value after 1 hour exposure.
- Metallurgy and Metallography