INFLUENCE OF SURFACE CONDITION ON THE FATIGUE OF AN ALUMINUM-LITHIUM ALLOY (2090-T3)

This report examines the axial fatigue life data of the shot peened an d unpeened 2090-T3 aluminum-lithium alloy. The effect of shot peening on life was detrimental and insignificant at higher and lower stresses respectively. This life variation is discussed in terms of crack init iation and, subsequently, such shot peened induced surface characteris tics as the surface roughness and the surface compressive residual str ess. The former eases cracking at all stresses; the latter, on the oth er hand, offers an opposing effect which was noted to be most signific ant at low stresses and minimal at high stresses. The life was conceiv ed to depend on the way these factors respond to applied stress.