Small fatigue crack growth behavior of TB6 titanium alloy
Liang XU1,2, Shuang-jun HUANG1, Li HUI1,2,*(), Lei WANG1,2, Song ZHOU1,2, Qing ZHAO1
1 School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China 2 Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136, China
The growth behavior of naturally-initiated small cracks in single edge notched tensile (SENT) specimen of TB6 titanium alloy was studied. Fatigue experiments were conducted under constant amplitude loading with the stress ratios R of 0.1 and 0.5 at room temperature. Small cracks were allowed to be monitored by replica method during fatigue testing. Results show that at the same stress ratio, the initiation life of crack increases from 60% to 80% of the total fatigue life with the decrease of stress level. However, the stress level has no significant effect on the crack growth rate of TB6 titanium alloy. The crack growth rate at the early stage is greatly affected by the microstructure. Once the crack length reaches 200μm, the crack growth rate will increase rapidly regardless of grain boundary or grain orientation. Small cracks of TB6 titanium alloy are originated from the sample notch root in the form of corner crack, and the major part of total fatigue life is consumed in small fatigue crack initiation phase.
MILLER K J . The behaviour of short fatigue cracks and their initiation Part Ⅱ-a general summary[J]. Fatigue and Fracture of Engineering Materials and Structures, 1987, 10, 93- 113.
doi: 10.1111/j.1460-2695.1987.tb01153.x
2
NEWMAN J J , PHILIPS E P , SWAIN M H . Fatigue-life prediction methodology using small-crack theory[J]. International Journal of Fatigue, 1999, 21, 109- 119.
3
LI W F , ZHANG X P . Investigation of initiation and growth behavior of short fatigue cracks emanating from a single edge notch specimen using in-situ SEM[J]. Materials Science and Engineering:A, 2001, 318, 129- 136.
doi: 10.1016/S0921-5093(01)01325-9
CHEN B , GAO Y K , WU X R , et al. Small crack behavior and fatigue life prediction for shot peening aluminum alloy 7475-T7351[J]. Acta Aeronautica et Astronautica Sinica, 2010, 31 (3): 519- 525.
CHEN B , WU X R , LIU J Z . Durability analysis and economic life prediction using small crack theory[J]. Journal of Mechanical Strength, 2004, (Suppl 1): 246- 249.
WU X R , LIU J Z . Total fatigue life prediction for aeronautical materials by using small crack theory[J]. Acta Aeronautica et Astronautica Sinica, 2006, 27 (2): 219- 226.
doi: 10.3321/j.issn:1000-6893.2006.02.010
TONG D H , WU X R , LIU J Z , et al. Fatigue life prediction of cast titanium alloy ZTC4 based on the small crack theory[J]. Journal of Materials Engineering, 2015, 43 (6): 60- 65.
8
KUJAWSKI D . A new driving force parameter for crack growth in aluminum alloys[J]. International Journal of Fatigue, 2001, 23 (8): 733- 740.
9
KUJAWSKI D . A fatigue crack driving force parameter with load ratio effects[J]. International Journal of Fatigue, 2001, 23 (1): 239- 246.
10
DINDA S , KUJAWSKI D . Correlation and prediction of fatigue crack growth for different R-ratios using and parameters[J]. Engineering Fracture Mechanics, 2004, 71 (12): 1779- 1790.
doi: 10.1016/j.engfracmech.2003.06.001
DING C F , LIU J Z , WU X R . An investigation of small crack and long crack propagation behavior in titanium alloy TC4 and aluminum alloy 7475[J]. Journal of Aeronautical Materials, 2005, 25 (6): 11- 17.
12
CONNOLLEY T , REED P , STARINK M J . Short crack initiation and growth at 600℃ in notched specimens of Inconel 718[J]. Materials Science and Engineering:A, 2003, 340 (1/2): 139- 154.
ZHANG L , WU X R , HUANG X Y . Experimental investigation on the growth behavior of naturally initiated small cracks in superalloy GH4169[J]. Acta Aeronautica et Astronautica Sinica, 2015, 36 (3): 840- 847.
14
NISITANI H , GOTO M , KAWAGOISHI N . A small-crack growth law and its related phenomena[J]. Engineering Fracture Mechanics, 1992, 41 (4): 499- 513.
15
BLANKENSHIP C P , STARKE E A . The fatigue crack growth behavior of the Al-Cu-Li alloy weldalite 049[J]. Fatigue and Fracture of Engineering Materials and Structures, 1991, 14 (1): 103- 114.
16
DEMULSANT X , MENDES J . Microstructure effects on small fatigue crack initiation and growth in Ti6Al4V alloys[J]. Fatigue and Fracture of Engineering Materials and Structures, 1995, 18 (12): 1483- 1497.