Modeling and measurement of the notched strength of gamma titanium aluminides under monotonic loading
- Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Mechanical Engineering
A substantial concern with gamma titanium aluminides is their limited ductility and, in particular, the consequences of limited ductility at stress concentrators. In this study, the notched strength of a cast Ti-47.9Al-2.0Cr-2.0Nb alloy is considered under monotonic tensile loading at room temperature. Efforts are further focused on the alloy`s behavior under conditions of plane stress and on cases where notch radii are large relative to grain size. Finite element predictions for notched tensile specimens and the Neuber design criterion are used to quantify relationships between tensile ductility, the ability to reduce local stress concentrations through plastic flow, and ultimate failure loads in notched components. Results from the testing of two modeled configurations are presented, and the numerical models are used to interpret the test results. Two major issues are addressed in this work. The first is how much plastic deformation is needed to blunt stress concentrations in gamma TiAl components under monotonic loading. For values of elastic stress concentrations commonly encountered in components, it is demonstrated that a total strain at failure as low as 1 pct (corresponding to a plastic strain at failure of 0.8 pct) is sufficient to essentially achieve the maximum reduction in stress concentration due to plastic flow. Second, the relationship between continuum-theory predictions of notched component failure (made using uniaxial tensile test strains at failure) and failure loads observed in notched specimens is explored. It is shown that, on average, continuum-theory predictions of notched strength based on unnotched specimen strains at failure act as conservative lower bounds on actual results. It is suspected that the notch strengthening observed in gamma TiAl is due to smaller volumes of highly strained material (a size effect) in the notched specimens.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 347478
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 4 Vol. 30; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
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