Effects of load ratio and temperature on the near-threshold fatigue crack propagation behavior in a CrMoV steel |
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Authors: | P K Liaw A Saxena V P Swaminathan T T Shih |
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Affiliation: | (1) Metallurgy Department, Westinghouse Research and Development Center, 15235 Pittsburgh, PA;(2) Steam Turbine-Generator Division, USA |
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Abstract: | The influence of temperature in the range of 24 to 260 °C and load ratio on the near-threshold fatigue crack growth rate behavior
of a CrMoV steel was characterized. At all temperatures investigated, the threshold stress intensity range, ΔK
th, for fatigue crack growth decreased with increasing load ratio. The near-threshold crack growth rates increased significantly
at 149 °C when compared with the rates at room temperature. However, the crack growth rates at 260 °C were comparable to those
at 149 °C. These observations are rationalized in terms of the concepts of roughness and oxide-induced crack closure. Extensive
fracture surface characterization using SEM, oxide thickness measurements by Auger spectroscopy, and roughness measurements
by light-section-microscopy were conducted to substantiate the explanations. |
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