FE analysis of strain constraint around the crack tip under cyclic loading
International Journal of Structural Integrity
ISSN: 1757-9864
Article publication date: 14 October 2019
Issue publication date: 26 August 2020
Abstract
Purpose
The purpose of this paper is to deal with the FE analysis of strain constraint around the crack tip under cyclic loading and its utilization using crack growth prediction strip yield model (SYM). During cycling, the constraint develops based on the load history. The monotonic loading is analyzed mostly, but during cyclic loading the conditions are different. The constraint is analyzed after several loading cycles applied in upwards part of the cycle and the formula for its development is proposed.
Design/methodology/approach
The study is based on the 3D FE analysis of middle-cracked tension specimen M(T). The strain constraint is described by Newman’s factor α. The variability of constraint factor α was analyzed for several load levels and specimen thicknesses. The crack is considered as non-propagating with straight crack front. The material is modelled as elastic-perfectly plastic. The SYM is modified by implementing variable constraint and the experimental results are compared with the simulation.
Findings
In major part of the loading cycle, it was found by FE analysis, that the constraint factor αg is lower after overloads than when creating monotonic plastic deformation on the same load level. The value of αg is governed by the ratio of thickness B over the plastic zone size rp. By implementing the variable constraint factor into the SYM, the improvement of the predicted specimens lives under variable amplitude loading was shown.
Originality/value
The new phenomenon on the variability of strain constraint during cyclic loading is presented. The development of constraint factor αg during cyclic loading is different from the monotonic loading and should be accordingly implemented into prediction models.
Keywords
Citation
Šedek, J., Růžek, R. and Oliva, V. (2020), "FE analysis of strain constraint around the crack tip under cyclic loading", International Journal of Structural Integrity, Vol. 11 No. 5, pp. 698-709. https://doi.org/10.1108/IJSI-10-2018-0065
Publisher
:Emerald Publishing Limited
Copyright © 2019, Emerald Publishing Limited