Effect of Coverage in Ball-Burnishing on Fatigue Performance of Al2024-T4

Author:  Mhaede, Wagner
Source:  Conf Proc 2011: ICSP-11 South Bend, IN USA (pgs. 291-296)
Doc ID:  2011048
Year of Publication:  2011
Abstract:  
Abstract The effects of coverage in ball-burnishing (BB) on the surface and sub-surface layer properties such as roughness and residual stress profile as well as on HCF strength were evaluated in Al2024-T4. Results are compared with previous observations on coverage effects in shot peening (SP). While SP at low coverage was seen to drastically deteriorate high-cycle fatigue (HCF) performance relative to an electropolished reference (EP), no such detrimental effect of low coverage was observed in BB. These results are explained mainly by differences in the resistance to fatigue crack nucleation between these two conditions. SP is beneficial only when the early fatigue crack nucleations caused by the high local stress concentrations at indentations are overcompensated by the well developed residual compressive stresses (at higher coverage) and their beneficial effects on micro-crack retardation. However, the absence of these stress concentrations in BB reduces their detrimental effects on the fatigue performance at low coverage. Keywords: Ball-burnishing, coverage, surface layer properties, fatigue performance