Evaluation of the StressWave Cold Working (SWCW) Process on High- Strength Aluminum Alloys for Aerospace

摘要

This report was developed under a SBIR contract. A new and innovative cold working process called StressWave Cold Working (SWCW) was investigated and compared to the conventional split sleeve cold working method that is used to enhance the fatigue life of fastener holes in high strength aluminum alloys used on USAF aircraft structures. StressWave cold working was found to be superior in enhancing fatigue lives compared to split sleeve cold working in both constant amplitude and spectrum fatigue loading environments, when used in its preferred embodiment, upstream cold working. The investigation also included extensive finite element analysis, in the post-yield regime which revealed the presence of deep compressive stresses throughout the thickness of specimens examined. This study also evaluated the fatigue and crack growth performance of over 300 specimens, which demonstrated the superior performance of Upstream StressWave cold working as compared to the split sleeve method. The new method was also shown to be significantly less expensive than the split sleeve method for a USAF fighter aircraft program currently under development. Various production implementation methods were investigated and proof-of- concept physical and hardware models were produced.