Author(s)

E.W. O'Brien

Abstract

Four dimensional strain analysis in some thick aircraft alloys with large holes cold expanded for fatigue enhancement E.W. O'Brien Experimental Stress Analysis Group, British Aerospace - Airbus, Bristol, UK ABSTRACT Three methods of hole cold expansion are reviewed within the context of surface treatments. It is clear from the results of strains for thick aircraft light alloy plate with large holes that the expansion is no longer a surface phenomenon but must be considered in four dimensions. Most published closed form solutions for the stress-strain state around a cold expanded hole assume infinitely thin material and instantaneous application of the process. Experimental work clearly demonstrates that the thicker material is in fact a 3-dimensional continuum with different levels of expansion being produced through the thickness. Split sleeve expansion has been shown to cause strain rates of the order of 1.0 sec-*, therefore strains must be considered in th

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