13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- 2. Experimental Procedure The material used in this study was Hastelloy X (see Table 1 for the chemical composition), which was acquired in the annealed condition in the form of a cold finished plate with a thickness of 6.35mm. From this plate a sample was removed in the T-L orientation for the creep-fatigue test. Table 1. Nominal chemical composition of Hastelloy X in weight % Alloy Ni Fe Cr Mo Cu Co W Ti C Mn Si Al Other Hastelloy X Bal. 18 22 9 <0.50 1.5 0.6 <0.15 0.1 <1 <1 <0.5 <0.08 From this plate a sample was removed in the T-L orientation for the creep-fatigue test with the geometry shown in Figure 1. Figure 1. Creep-fatigue specimen geometry (dimensions are in mm) The specimen was then prepared for the noncontact digital image correlation. A high contrast random, speckle pattern was applied in two steps. First a flat white high temperature ceramic based coating (VHT Flame ProofTM) was applied to one surface of the specimen. After the coating had dried, a mist of a flat black high temperature coating was sprayed over the white coating layer to provide the contrasting speckle pattern. The specimen was fatigue pre-cracked for ~2.5mm, ending with ∆K = 27.6 MPam1/2. The fatigue pre-cracking and creep-fatigue test were conducted using a 100kN MTS servo-hydraulic test system. The creep-fatigue test was performed using a trapezoidal waveform with a 1.5 second ramp up, a 120 second dwell at max load, and a 1.5 second ramp down. A loading ratio of R=0.05 was used. The test was conducted in laboratory air at 650ºC ± 3 ºC. The elevated temperature was applied using a 1.2kW Ameritherm induction heater and monitored using a two-color optical infrared thermometer. 31.75 0.25 25.40 5.08 6.35 6.35 7.62 8.26 15.24 30.48 6.35
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