Accession Number : ADA568044


Title :   Incorporating Small Fatigue Crack Growth in Probabilistic Life Prediction: Effect of Stress Ratio in Ti-6Al-2Sn-4Zr-6-Mo (Preprint)


Descriptive Note : Journal article preprint


Corporate Author : AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH STRUCTURAL MATERIALS DIV


Personal Author(s) : Larsen, James M ; John, Reji ; Jha, Sushant K


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a568044.pdf


Report Date : Aug 2012


Pagination or Media Count : 54


Abstract : The effect of stress ratio on the statistical aspects of small fatigue crack growth behavior was studied in a duplex microstructure of Ti-6Al-2Sn-4Zr-6Mo (Ti-6-2-4-6) at 260 degrees C with particular emphasis on incorporating small-crack data into probabilistic life prediction and the influence of stress ratio on probabilistic lifetime limits. A Focused Ion Beam (FIB) was used to machine micro-notches in test specimens, which served as crack-initiation sites and enabled the acquisition of multiple small-crack growth data sets from single experiment. Stress ratios of -0.5, 0.05, and 0.5 were employed, and small-crack growth was monitored by the acetate replication method. Qualitatively, change in the stress ratio produced almost negligible influence on the small-crack growth behavior when plotted as crack growth rate (da/dN) versus applied stress intensity factor range (delta K). A probabilistic method was employed to represent the variability in the small-crack growth behavior and the statistical differences with respect to stress ratio.


Descriptors :   *FATIGUE LIFE , *MICROCRACKING , CRACK PROPAGATION , STATISTICAL ANALYSIS , STRESSES , TITANIUM ALLOYS


Subject Categories : Metallurgy and Metallography
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE