The effect of peening on the fatigue life of 7050 aluminium alloy
Scientific Publication
- Report Number:
- DSTO-RR-0208
- Authors:
- Sharp, P.K.; Clark, G.
- Issue Date:
- 2001-03
- AR Number:
- AR-011-795
- Classification:
- UNCLASSIFIED
- Report Type:
- Research Report
- Division:
- Airframes and Engines Division (AED)
- Release Authority:
- Chief, Airframes and Engines Division
- Task Sponsor:
- DGTA ASI Section
- Task Number:
- AIR 98/217
- File Number:
- M1/9/328
- Pages:
- 53
- References:
- 51
- Terms:
- Crack propagation; Aluminium alloy 7050; Crack growth; Finishing; Peening; Metal finishing
- URI:
- http://hdl.handle.net/1947/3292
Abstract
Many changes in the design and manufacture of high-performance military aircraft -- for example, the use of highly optimised design and the use of higher-strength material -- have led to an increased sensitivity of airframe fatigue life to surface features such as corrosion or mechanical damage. The peening applied to the F/A-18 represents a significant departure from traditional manaufacture, and it is therefore important that the RAAF and AMRL have a through understanding of the peening process, the surface conditions produced, and their effect on structural integrity. This discusses discusses the fatigue crack growth research at AMRL, and elsewhere, relating to peening of aluminium alloys, and summarises the improvements in peening which have arisen from this research. The overall aim of the peening research and development discussed was to establish a Life-Improvement-Factor (LIF) for the peening used on the F/A-18, as well as any future peening required by modifications.
Executive Summary
Many changes in the design and manufacture of high-performance military aircraft - for example, the use of highly optimised design and the use of higher-strength materials  have led to an increased sensitivity of airframe fatigue life to surface features such as corrosion or mechanical damage. The peening applied to the F/A-18 represents a significant departure from traditional manufacture, and it is therefore important that the RAAF and AMRL have a thorough understanding of the peening process, the surface conditions produced, and their effect on structural integrity. To build the required level of understanding, AMRL has undertaken a number of research programs, over nearly ten years, investigating the effects of glass bead peening on the aluminium alloy 7050 used in RAAF F/A-18 aircraft. The overall aim of the peening research and development discussed was to establish a Life-Improvement-Factor (LIF) for the peening used on the F/A-18, as well as any future peening required by modifications. It also attempted to provide a means of measuring peening quality, to allow the full exploitation of peening to improve fatigue life. From this research came methods of surface peening and methods of surface removal, which allowed development of localised life extension methods for the airframe. These life extension methods are now being applied in full-scale fatigue tests (to keep tests going after initial failures) and are likely to be applied to both RAAF and CF fleet aircraft. This report discusses the fatigue crack growth research at AMRL, and elsewhere, relating to peening of aluminium alloys, and summarises the improvements in peening which have arisen from this research. It also highlights areas where further research could be beneficial in relation to peening and the structural integrity of the F/A-18 aircraft. It highlights the practical problems of introducing changes to fatigue critical surfaces, with particular reference to the RAAF and CF fleets.