Abstract
To investigate fatigue fracture behavior of small titanium single crystals, plain bending fatigue test method for thin sheet specimens was developed. One end of the sheet specimen was fixed at a voice coil of a loudspeaker and the other end was set free. A bending mode resonance occurs in the specimen due to forced vibration at the fixed end. In A-specimen whose surface plane and loading direction were (0001) and [1120], the fatigue crack propagated parallel to {1100} plane and striation-like markings were observed on the fatigue fracture surfaces. In B-specimen with (0001) surface and [1100] loading direction, the fatigue crack also propagated parallel to {1100} plane as similar to A-specimen. These fatigue cracks are deduced to extend by alternating shear on two intersecting prismatic slip systems at the crack tip. In D-specimen with (1100) surface and [1120] loading direction, the fatigue crack propagated along [0001] with prismatic slip. In E- and F-specimen with [0001] loading direction, these fatigue cracks propagated parallel to (0001) with {1012} twinning. As a result, S-N plots of each specimen showed strong orientation dependence.
