Fatigue Damage and Life Assessment of Al6061/Al2O3 and Al6061/SiC PMM Composites under various Loading Conditions

Fatigue damage and life prediction of three metal matrix composites (PMMCs) of Al6061/Al2O3/20p-T6, Al6061/Al2O3/22p-T6 and Al6061/SiC/17w-T6 tested under tensile, torsion, and combined tension-torsion fatigue cycling were evaluated with various fatigue damage models. The fatigue damage models of Smith-Watson-Topper (SWT), Ellyin (E), Brown-Miller (BM), Fatemi-Socie (FS) and Varvani (V) were compared for their capability to assess the fatigue damage of materials undergoing various loading conditions. Both critical plane models of BM and FS on the other hand collapsed the fatigue damage data in a reasonably narrower band under uniaxial and multiaxial loading conditions. Over both the low-cycle and high-cycle fatigue regimes, SWT approach and E energy model resulted in a wide scatter range of correlated damage data. Material dependent parameters in Varvani damage approach, enabled an accurate damage assessment of PMMCs as the effect of the shear and normal fatigue properties was accounted in the damage model by means of α and β terms to estimate fatigue damage of PMMCs in the presence of metal-matrix strain-life data. The critical plane-energy approach successfully predicted fatigue lives of PMMCs within a factor of ±3 under various loading conditions. This approach successfully evaluated fatigue damage values versus fatigue lives within a narrower band for both uniaxial and multiaxial loading conditions as compared with other damage approaches studied in this paper.

Keywords:

Metal-matrix composite , fatigue damage , uniaxial and multiaxial loading , criticalplane-energy approach