Fatigue Life Estimation of 6061 Aluminium Alloy Based on Modal Damping Measurements

Abstract

The damping property of 6061 aluminium alloys, fabricated by hot isostatic pressing (HIP), has been studied for different ratios of fatigue on the base of modal damping analysis. The effects of age hardening on hardness, fatigue strength and damping loss factor of the material are discussed. On the other hand, the interrelations of fatigue life ratios and the damping loss factor are examined using modal analysis of free-free standard fatigue specimens within a wide range of resonance frequencies (2000 Hz-25 kHz). Methodologies used to generate data and extract the characteristics of damping phenomenon have been illustrated. Numerical analysis of values of damping loss factor has been evaluated and compared with experimental measurements. A rotating bending fatigue test is performed to correlate the modal damping to fatigue damage. The results show that, age hardening process increases the fatigue strength by 15% and the damping loss factor by 160 %. The underlying mechanisms are analyzed and discussed. The results seem to be a useful guide that may help in estimating the lifetime or at least the remaining life of a member loaded under fatigue through measuring damping loss factor. &LJj,yl &I + + 4;ii-ilJ 7. 7 \ ?+&I &&dl A &. ? ! +k L i j~ + I \.4h JJ&-1 JJUJ.(modal damping analysis)+&dl &+?I1

Fatigue fracture cross-sections after cyclic tests with a combination of cyclic bending and torsion of samples made of aluminum alloy 6060

“…For extruded profiles, alloys from the 6XXX group are mainly used [2]. During the alloy selection, the heat treatment process is also determined, which affects the requirements for the material from which a given element or structure is made.…”

“…The comparison of fatigue characteristics shows that they are practically parallel. In the case of aluminum after T64 treatment, the slope of the characteristics reaches a value in the range of 0.096-0.110 according to formulas (1), (3), and (4), and for torsion it is a smaller value equal to 0.078 -Eg (2)…”