Abstract
The fatigue nucleation and crack growth rate (FCGR) characteristics of Laser Shocked Peened (LSP) titanium 6Al–4V were examined and compared with unprocessed material. While crack initiation behavior of smooth ( K t=1.0) LSP processed samples is similar to baseline material, a marked improvement is observed in the notched ( K t>1) fatigue strength of LSP processed samples over unprocessed samples. Similar trends were noted for specimens that had been subjected to simulated foreign object damage (FOD) and subsequently fatigue tested. The FCGR resistance of LSP processed samples tested at low stress ratios ( R) is likewise shown to be significantly greater than for unprocessed, baseline material and is due to the large residual compressive stresses, which reduce the locally applied stress. Advantages in FCGR resistance diminish at higher R. Differences in growth rate behavior are accounted for by using the effective stress intensity range, Δ K eff. The rationale of using Δ K eff is further demonstrated through fractographic investigations.
Published Version
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