Mode I and mixed I/III crack initiation and propagation behavior of V-4Cr-4Ti alloy at 25{degrees}C
- Pacific Northwest National Lab., Richland, WA (United States)
The mode I and mixed-mode I/III fracture behavior of the production-scale heat (No. 832665) of V-4Cr-4Ti has been investigated at 25{degrees}C using compact tension (CT) specimens for a mode I crack and modified CT specimens for a mixed-mode I/III crack. The mode III to mode I load ratio was 0.47. Test specimens were vacuum annealed at 1000{degrees}C for 1 h after final machining. Both mode I and mixed-mode I/III specimens were fatigue cracked prior to J-integral testing. It was noticed that the mixed-mode I/III crack angle decreased from an initial 25 degrees to approximately 23 degrees due to crack plane rotation during fatigue cracking. No crack plane rotation occurred in the mode I specimen. The crack initiation and propagation behavior was evaluated by generating J-R curves. Due to the high ductility of this alloy and the limited specimen thickness (6.35 mm), plane strain requirements were not met so valid critical J-integral values were not obtained. However, it was found that the crack initiation and propagation behavior was significantly different between the mode I and the mixed-mode I/III specimens. In the mode I specimen crack initiation did not occur, only extensive crack tip blunting due to plastic deformation. During J-integral testing the mixed-mode crack rotated to an increased crack angle (in contrast to fatigue precracking) by crack blunting. When the crack initiated, the crack angle was about 30 degrees. After crack initiation the crack plane remained at 30 degrees until the test was completed. Mixed-mode crack initiation was difficult, but propagation was easy. The fracture surface of the mixed-mode specimen was characterized by microvoid coalescence.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 543268
- Report Number(s):
- DOE/ER-0313/21; ON: DE97008798; TRN: 97:020309
- Resource Relation:
- Other Information: PBD: Apr 1997; Related Information: Is Part Of Fusion materials semiannual progress report for the period ending December 31, 1996; PB: 296 p.
- Country of Publication:
- United States
- Language:
- English
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