Simulations for problems of estimating structural residual life

This paper presents an overview of the accumulated experience in the development and implementation of simulation principles in predicting the residual fatigue life of structural elements during their design and operation in accordance with the concept of tolerance damage. The formulated principles assume the preservation of the accumulated damage under the completed operation of structural elements as heredity of the history of their loading. The proposed sequence of the developed approach implementation includes the analysis of the stress-strain state of the damaged structural element, the development and justification of the geometry and loading conditions in operation, as well as experimental verification and validation by testing simulation models. We analyzed blades and rotating disks of steam turbines and aircraft engines. Configurations and loading conditions of the proposed simulation models reproducing the state of the critical zones of the structural elements are presented. Combinations of conditions of a multi-axial stress state, defect shape, operating temperature and profile of the in-service deformation cycle are considered. Numerical solutions are obtained for the most complex situations of modeling the behavior of surface part-through defects with a combination of mixed modes by separation, longitudinal and transverse shear. The achieved results of residual life estimations are attributed to the composition of original testing devices and methods.