Rotating Bending Fatigue Microscopic Fracture Characteristics and Life Prediction of 7075-T7351 Al Alloy

Abstract

Rotating bending fatigue tests were carried out by using the 7075-T7351 Al alloy with a microarc oxidation (MAO) coating (h = 10 µm) and with no coating. Tests were conducted in air and 5.0% NaCl aqueous solution conditions. The fatigue microscopic fracture behavior of the metals was investigated by using scanning electron microscope and three-dimensional digital microscope technologies. The empirical formulas between the stress intensity factor ∆K and the fatigue life N f in the different conditions were obtained. In addition, the reason for data scattering in the fatigue lives of uncoated 7075-T7351 samples under the same stress amplitude in air was analyzed. Furthermore, the fatigue characteristic life of 7075-T7351 alloy was predicted by the three-parameter Weibull distribution model.

A review on isothermal rotating bending fatigue failure: Microstructural and lifetime modeling of wrought and additive manufactured alloys

“…In Figure 19, a portion of the phase diagram for aluminum as well as other materials that are primary solutions has been displayed. Let us look at the 7075‐T7351 aluminum alloy that Yang et al 100 researched and found to have a chemical composition (in wt.%) of 5.89 zinc, 2.48 magnesium, 1.59 copper, 0.22 chromium, 0.06 iron, 0.02 titanium, and the remaining weight in Al. Concerning Figure 19, the representation of our material in each diagram is represented by a green line.…”

The Role of Mg Content and Aging Treatment on the Tensile and Fatigue Properties of Die-Cast 380 Alloy

“…However, this type of fracture normally occurs under mechanical fatigue testing caused by alternate compression-tension, an example of which is shown in Figure 18b. Yang et al [44] studied the effect of rotating-bending fatigue on the lifetime of a 7075 alloy in the T6 condition. Their observations show that the fatigue crack initiation takes place at the sample outer surface (marked 1) and propagation (a smooth rubbed surface-marked 2), followed by a rough area in relief indicating final break (marked 3), as illustrated schematically in Figure 18a.…”

“…Figure19demonstrates the fracture mechanism of the present fatigue-tested bars. The crack commenced from the outer surface due to certain defects and propagates radially toward the center of the samples (black arrows); this leads to an increase in the applied stress, ultimately reaching the fracture point-see the white arrow which is in contrast to the model proposed in[44].…”

Notch fatigue life prediction considering nonproportionality of local loading path under multiaxial cyclic loading

“…Multiaxial loading paths can produce complex stress-strain responses at the notch area and cause a fatigue failure problem at or near the notch root. [1][2][3][4][5][6][7] In order to satisfy the increasing design requirement for notched components in accordance with lifetime expectancy, light weight, and cost reduction, an efficient and reliable numerical methodology to the fatigue life predictions of practical notched components is urgently needed. [8][9][10] Most service load histories for notched components and structures are multiaxial nonproportional.…”

“…Moreover, practical notched components are subjected to multiaxial cyclic loadings at service conditions. Multiaxial loading paths can produce complex stress‐strain responses at the notch area and cause a fatigue failure problem at or near the notch root . In order to satisfy the increasing design requirement for notched components in accordance with lifetime expectancy, light weight, and cost reduction, an efficient and reliable numerical methodology to the fatigue life predictions of practical notched components is urgently needed …”