Fatigue crack propagation in UFG Ti grade 4 processed by severe plastic deformation

0471662 - ÚFM 2018 RIV GB eng J - Článek v odborném periodiku
Fintová, Stanislava - Arzaghi, M. - Kuběna, Ivo - Kunz, Ludvík - Sarrazin-Baudoux, C.
Fatigue crack propagation in UFG Ti grade 4 processed by severe plastic deformation.
International Journal of Fatigue. Roč. 98, MAY (2017), s. 187-194. ISSN 0142-1123. E-ISSN 1879-3452
Grant CEP: GA MŠMT(CZ) LQ1601; GA MŠMT LM2015069
Institucionální podpora: RVO:68081723
Klíčová slova: Titanium * Fatigue * Crack growth * Crack closure * Equal channel angular processing
Obor OECD: Audio engineering, reliability analysis
Impakt faktor: 3.132, rok: 2017
http://www.sciencedirect.com/science/article/pii/S014211231730035X

Fatigue crack growth was investigated in commercially pure Ti grade 4 processed by severe plastic deformation. The ultrafine-grained structure was prepared by means of equal channel angular pressing technique followed by cold drawing. The growth of fatigue cracks was investigated also in the as-received coarse-grained state of material for comparison.
The fatigue crack growth rate in the ultrafine-grained material was found to be higher and the threshold stress intensity range delta Kth for crack growth lower than in the coarse-grained Ti, 2.5 and 4.7 MPa m1/2, respectively. A combination of transcrystaline and intercrystaline crack growth was typical for all crack growth rates in the coarse-grained material. Contrary to the combined fracture mechanism in coarse-grained Ti only transcrystalline crack growth was a characteristic feature of crack propagation in the ultrafine-grained material.
It has been found that the experimentally and theoretically determined values of closure are in reasonable agreement. Crack closure calculated according to the Newman model taking into account only plasticity induced closure was in the range from 67% to 69% of Kmax for as-received and 70% for UFG state of material. Crack closure determined experimentally was 67% of Kmax for as-received and 67% for UFG CP Ti grade 4.
Investigation of fracture surfaces did not bring any evident signs of the effects of fracture surface morphology resulting in roughness induced closure or oxide induced closure under testing conditions used. This indicates that plasticity induced closure seems to be a dominant closure mechanism in both states of the investigated Ti grade 4.
Trvalý link: http://hdl.handle.net/11104/0271226