7075-T651 Fatigue Failures
7075-T651 Fatigue Failures
(OP)
We have a part fabricted from 7075-T652 aluminum and subjected to axial compression loading and bending in two orthogonal planes. We have problems with fatigue failures and have performed an FEA to address high-stress areas and reduce stress concntrations. Currently, the maximum applied stresses are ar or below 20 kpsi in most areas. The part has passed a 3 million cycle fatigue test in the unanodized condition. After a hard-coat anodize layer (0.0004" thick) is applied, the part fails at about 380,000 cycles. The failure is at the tangent point of a radius between section changes. The FEA shows the Max Principal Tensile Stress magnitude is approximately 20 - 26 kpsi in the area of the failure. (A fatigue limit of about 36 kpsi was assumed for the material). Any ideas concerning a possible reason for the huge change in performance is welcome.





RE: 7075-T651 Fatigue Failures
RE: 7075-T651 Fatigue Failures
For example, according to MIL-A-8625F ANODIC COATINGS FOR ALUMINUM AND ALUMINUM ALLOYS,
6.10.7 Effect on fatigue. The fatigue properties of aluminum alloys can be severly reduced by anodic coatings.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: 7075-T651 Fatigue Failures
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RE: 7075-T651 Fatigue Failures
What kt are you getting from the fem?