Effects of temperature and frequency on fatigue crack growth in Ti-β21S monolithic laminate

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This paper describes the high temperature fatigue crack growth behavior in the titanium β21S monolithic laminates. Effects of laminate consolidation procedure as well as the test specimen geometry on the reliability of the experimental crack growth data were first investigated. The influence of temperature and both high and low frequency loadings on the crack growth rate in this laminate material were then determined. In addition to room temperature three other temperature levels were used in this study: 482°C, 650° and 760°C. The test frequencies encompassed the range (10-8) × 10-3 Hz. Results of this study demonstrate that temperature effects could be interpreted in terms of the yield strength and elastic modulus variations as a function of the testing temperature. Furthermore, it was determined that crack growth rate in these laminates is influenced by viscoplastic related effects at frequencies as low as 1 Hz. This was supported by an analytical solution determining the transition time required for the crack tip to experience extensive creep behavior. Fractographic analysis carried out on fracture surfaces showed that the dominant fracture mechanism is transgranular cleavage with the appearance of intergranular facets in tests corresponding to 760°C at 10 Hz and 650°C at 5 × 10-2 Hz. © 1993.

Publication Title

Materials Science and Engineering A