I’m working on HCF analysis of an aluminum alloy component but material data is not available.
In order to estimate the endurance limit of material at N=5*10^8, could be correctly compute it with UML algorithm in VLAB?
I’ve tried to change the number of cycles in “Static Endurance Data” panel (default is 1.1312*10^6) but the stress amplitude is less than 30% of Tensile Strength so I’ve thought the endurance limit might be underestimated.
In alternative, I could build a bilinear SN curve where N1, S1 are estimated with the UML, and NE=10^8, SE=(0.3 or 0.4)*Tensile Strength.
Firstly the estimation tools lik UML had been developed with test data in the area up to 1e6.
That is the reason that the UML estimate puts the Se there, even knowing that there is no endurance limit for aluminum.
But looking at experiments there is a flatening of the curve in the VHCF area, that is not in the curves of UML.
Therefore if you extrapolate the UML estimate you will be too conservative for the small cycles. But I would expect the effect of the overestimation of the damage as small if there are any larger load cycles.
If your cycles are only in the VHCF area your approach with the adapted SN curve will be ok, at least for low to mid strength Al alloys 0,4 Su seems a goos estimate . For high strength (>300MPa) the ratio gets smaller
again even below the 0,3 Su
Hope this helps
Dr.Michael Hack Business Product Line Manager Durability Simulation and Testing Solutions