报告题目：Influence of Foreign Object Damage on High Cycle Fatigue of Ti–6Al–4V Alloy
报告人：Prof. S.L Mannan, FNAE, FIIM, FIIW
报告时间：2016年10月28日（周五）13:30-15:00
报告地点：实验17楼308室

Abstract: The influence of foreign object damage (FOD)  on high cycle fatigue (HCF) of Ti–6Al–4V alloy has been investigated.  FOD was induced by shooting 3.2 mm diameter steel spheres at a velocity  of 300 m/s on the centre of flat plate specimens using a compressed air  gun facility. Both normal and 60 angular impacts were carried out. In  order to assess debit in the fatigue strength due to notch effect,  machined notches of the same notch profile (radii and depth dimensions)  as those observed in high velocity impact were also tested. The tests  were conducted at room temperature and at two R ratios of 0.1 and 0.5.  Fatigue life was found to be reduced in FOD impacted samples and the  debit in fatigue life was much larger than that for machined notch  specimens. This might be attributed to the effect of residual stresses.  Further, the role of residual stresses were also brought out by  comparing results of HCF tests at R = 0.1 and R = 0.5. As expected, a  larger debit in fatigue life was found to occur at low R values where  residual stresses were not expected to be relaxed. No significant  differences in fatigue life between the normal and angular impacted  samples were noticed. Optical and SEM investigations were carried out to  examine the shape of the indents and micro-structural features.