Effect of constraint on fatigue crack propagation near threshold in medium carbon steel

0044935 - ÚFM 2007 RIV NL eng J - Journal Article
Hutař, Pavel - Seitl, Stanislav - Knésl, Zdeněk
Effect of constraint on fatigue crack propagation near threshold in medium carbon steel.
[Vliv constraintu na prahové hodnoty šíření trhliny pro oceli se středním obsahem uhlíku.]
Computational Materials Science. Roč. 37, 1-2 (2006), s. 51-57. ISSN 0927-0256. E-ISSN 1879-0801
R&D Projects: GA ČR GA101/03/0331; GA ČR GP101/04/P001
Institutional research plan: CEZ:AV0Z20410507
Keywords : Fatigue crack propagation rate * Constraint * Two-parameter fracture mechanics
Subject RIV: JL - Materials Fatigue, Friction Mechanics
Impact factor: 1.104, year: 2006

The influence of constraint caused by different specimen geometry on fatigue crack growth in the threshold region is analyzed and a phenomenological model is proposed to correlate the fatigue crack propagation rate under different constraint levels. The approach is based on an application of two-parameter fracture mechanics and the corresponding calculations are performed according to the finite element method. The constraint level is quantified by the value of T-stress. The fatigue crack propagation rate is then expressed in terms of the stress intensity factor K and T-stress. Plastic zone size is considered as a controlling variable for near threshold fatigue crack behavior and a simple procedure making it possible to estimate the changes of the fatigue crack propagation rate in the threshold region due to different constraint level quantitatively is formulated. It is concluded that experimental values correspond well with those numerically predicted.

V práci je analyzován vliv constraintu na šíření únavových trhlin zejména v oblasti blízké prahovým hodnotám. Metodika založená na dvouparametrové lomové mechanice je využita pro zahrnutí vlivu constraintu do popisu rychlosti šíření únavových trhlin. Dále je diskutován vliv plasticity a vliv plasticky indukovaného zavírání trhliny na její další šíření.
Permanent Link: http://hdl.handle.net/11104/0137601