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An elastic-plastic finite element analysis is used to simulate the cyclic tipdeformation of a mode I long central crack in a plate subjected to a remote in-phasebiaxial cyclic stress field with the three biaxial ratios of 1, 0 and -1. One-stress amplitudeat a zero stress ratio is considered. The loading and unloading modes of a cycle aresimulated. Results are presented in the form of the development of both monotonic andcyclic crack tip plastically deformed zones and opening displacements as the crack tipartificially advances.After five increments of crack tip advance within the equi-biaxial base loading cycles, thebiaxial ratio is allowed to be either 0 or -1 for a single cycle. With further crack tipadvance at the original base load for both types of transient cycles, the corresponding tipdeformation shows behaviour similar to the effect of a single overload injected withinuniaxial loading cycles. Generally, crack tip deformation starts with a relatively high valueto decrease and then increases after reaching a minimum value beyond which an increasefollows until matching with the behaviour due to the original base load takes place.