Experimental investigation on the influence of small defects on fatigue life of 7075-T6511 aluminum alloy and of 1020 steelTuesday (26.05.2020) 11:10 - 11:30
This work addresses the influence of small surface defects on the fatigue life of two materials, 7075-T6511 aluminum alloy and 1020 steel, under fully reversed tension-compression. Artificial defects with different shapes (cylindrical, oblong and spherical cap) and dimensions produced by milling or indentation were investigated. Defect sizes ranged from 360 to 750 micrometers, and depths varied from 9 to 750 micrometers. The study focused on fatigue lives from 10^4 to 10^7 cycles. The milled defects decreased the fatigue lives by a factor of up to two hundred for the 7075 alloy and up to nine for low carbon steel. For defects produced by indentation, fatigue life reduced up to thirty times relative to those observed in smooth specimens. In all cases, the lower the stress amplitude, the higher was the fatigue life reduction. The characteristics of the small defects (square root of area, length, depth) were observed to have different influences on fatigue life. Defects with the same square root of area but distinct aspect ratios resulted in different life reductions.