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Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:05:13Z Item is restricted indefinitely. Stubbins, James F. Hour, Kai-Youarn 2011-05-07T14:18:14Z 2011-05-07T14:18:14Z 10000-01-01 1989 Crack growth behavior for three heat resistant materials, namely, Alloy 800H, type 310 Stainless Steel, and Hastelloy X has been investigated under creep, fatigue, and fatigue with hold test conditions at the temperature range from 650 to 900$\sp\circ$C. The loading-unloading (fatigue) and hold (creep) in a hold time test represent a possible interaction between creep and fatigue. Frequency, R-ratio, environment, and hold-period and their synergistic effects on crack growth at elevated temperature were studied. All alloys show a predominantly transgranular crack advance mode when cycled at frequencies above 0.5 Hz. At lower frequencies, the failure in 310 SS transitions to a predominantly intergranular mode while Hastelloy X remains transgranular. Alloy 800H shows a mixed failure mode at intermediate and low frequencies. High R-ratio, temperature, and low frequency can combine to enhance the time-dependent crack growth at elevated temperature and creep damage are predominant in these cases. Creep crack growth rate correlates well with C* for all alloys, and can be extended to correlate fatigue with hold time loading conditions for Alloy 800H and 310 SS, but not for Hastelloy X under the conditions studied here. It was found that hold time crack growth were creep-controlled in Alloy 800H and 310 SS while fatigue-controlled in Hastelloy X. These crack growth observations were supplemented by microhardness, microstructural, and load response measurements. Creep crack growth rate predictions based on a local critical strain criterion were also examined and found to agree with experimental results in this study. Made available in DSpace on 2011-05-07T14:18:14Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9010892.pdf: 4204610 bytes, checksum: 12d7eb4381019b864ed84d9e6f31e78b (MD5) Previous issue date: 1989 Restriction data tranferred 2014-07-01T11:31:13-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9010892 (UMI)AAI9010892 http://hdl.handle.net/2142/23547 eng Copyright 1989 Hour, Kai-Youarn Engineering, Nuclear Crack growth behavior and failure micromechanisms in three heat-resistant materials at elevated temperature text Engineering, Nuclear Engineering, Nuclear University of Illinois at Urbana-Champaign Dissertation Ph.D.