Strain sequence effect on fatigue life and fracture surface topography of 7075-T651 aluminium alloy

The paper studies the effect of strain-loading sequence on fatigue lifetime and fracture surface topographies in 7075-T651 aluminum alloy specimens. Fatigue tests were performed two ways: (i) constant-amplitude loading (ii) series variable amplitude with non-zero mean strain values. topography fractures was measured over their entire surfaces help an optical confocal measurement system. results form equivalent strains, ?aeq, such as weighted components, ?a1, ?a2, life, Nf, used sum partial number cycles N1, N2. This study indicates, inter alia, that values parameter core height Sk, found two-step program, are linearly dependent strain, logarithmically life.