MATEC Web Conf.
Volume 165, 201812th International Fatigue Congress (FATIGUE 2018)
|Number of page(s)||6|
|Section||Growth of Short and Long Cracks - Crack Growth Thresholds|
|Published online||25 May 2018|
The coupled criterion for description of fatigue fracture. Material embrittlement in pre-fracture zone
Lavrentyev Insti subareas tute of Hydrodynamics SB RAS, Novosibirsk, 630090, Russia
* Corresponding author: email@example.com
Step-wise extension of a crack in quasi-brittle materials under low-cycle loading conditions is considered. Both steady and unsteady loadings in pulsating loading mode are studied. It is proposed to use quasi-brittle fracture diagrams for bodies under cyclic loading conditions. When diagrams are plotted, both necessary and sufficient fracture criteria by Neuber-Novozhilov are used. A specific implementation is made on the base of the Leonov-Panasyuk-Dugdale model for the mode I cracks when the pre-fracture zone width coincides with the plasticity zone width near the crack tip. The condition of a step-wise crack tip extension has been derived. A crack extends only in the embrittled material of the pre-fracture zone. The number of cycles between jumps of the crack tip is calculated by the Coffin equation, when damage accumulation in material in the pre-fracture zone is taken into account. Critical fracture parameters under low-cyclic loading conditions have been obtained in a closed form. Estimates of the average rate of crack tip advance for a loading cycle at step-wise crack extension and S − N curves have been obtained.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
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