Evaluation of the Crack Development at a Cyclic Loading of Plate Elements Using the Parameters of Scattered Damages of the Material

Abstract

The purpose of these studies was to work out the methods for the computation of crack development in the plate and axisymmetric elements of structures at cyclic loading for the plasto-elastic arrangement using the conception of the accumulation of scattered damages in the material. The processes of sign-changing plasto-elastic deformation and crack resistance of the material were simulated at the crack tip using the smooth specimen fatigue test data. Thermal and stress-strain behaviors of the construction were determined in different loading modes using the method of final elements for several fixed crack depths. The material damage was estimated using the curves of low-cycle fatigue and those of the range of plasto-elastic deformations on the would-be way of the crack development resorting to the hypothesis of linear summation. When the damageability reaches a critical value at the crack tip its depth is increased nonuniformly by a value of the specified step. This scientific paper gives consideration to the kinetics of the surface crack in the region exposed to the action of zero-repetition cyclic loading. The results were compared with the data obtained using the Paris equations. A satisfactory agreement of the data is observed. This technique can be used for the evaluation of the service life of the elements of steam turbines.