ISSN:
1460-2695
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The presence of hard alpha (HA) anomalies in titanium alloys represents a significant potential degradation to gas turbine component performance. Although HA defects in titanium alloys are rare, when they are present, they can crack and ultimately result in failure. In static fracture and fatigue test specimens, embedded HA defects had significantly higher fracture strengths than anticipated. The objective of this work was to determine if residual stresses caused by thermal expansion mismatch during material fabrication were the cause of the observed behaviour. The residual stress fields in and around surface and embedded HA particles in Ti–6Al–4V (Ti–6–4) were determined using an elasticity solution and measured coefficient of thermal expansion (CTE) data. The calculated stress distributions serve as the foundation for comparisons of the local stress and the fracture strength, the stress intensity factor K and the crack growth threshold ΔKth, with the experimentally determined fatigue lives. The analytical results indicated that CTE-induced residual stress around HA particles can contribute to the fatigue strength of Ti–6–4 by delaying microcracking of HA anomalies and reducing the driving force (effective ΔK) of the fatigue crack. Based on the analysis results, the differences between the surface and subsurface results as well as the difference between predicted and measured fatigue lives could be largely attributed to the residual stress effects caused by the mismatch of the particle and matrix properties.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1460-2695.2003.00714.x
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