SENSORS OF FATIGUE DATA ANALYSIS AND AUTOMATED EVALUATION OF DAMAGE FOR STRUCTURAL HEALTH MONITORING

The need in ensuring the reliable diagnostics of the technical condition and predicting the residual life of the high-tech equipment is preconditioned by the use of fatigue sensors and development of new algorithms for the analysis of the condition of the surface with fatigue damage. Flat specimens of size 70 × 10 × 1 mm were cut using the electrical discharge method. A central opening of diameter 2.4 mm was cut in specimens before the fatigue tests. Cyclic tension tests were performed servo-hydraulic test machine. During the fatigue tests, the surface damage was evaluated using the optical-digital method based on the deformation relief parameters. During the tests, the surface condition was photographed using the Canon EOS 550D camera. The processes of deformation behavior of polycrystal (17Mn1Si steel, aluminium alloys) under conditions of cyclic loading are investigated. The influence of loading conditions on the local parameters of damage is investigated at the mesolevel, the formation of plastic shears during cyclic plastic deformation is analyzed. The methods of optical-digital control of the condition of 17Mn1Si steel and aluminium alloys are proposed, which allow calculating several damage parameters. The algorithm of damage identification on the surface of the material with a stress concentrator, which is based on the generalized hierarchical approach, is proposed, the universal mechanism for calculation of the in-service characteristics of the damaged surface is offered. Based on the calculation of the specific variation of the marker orientation, the method for the evaluation of damageability variation in polycrystalline materials is proposed, which is based on determining the degree of the marker distortion in case of interaction with fatigue cracks. The mathematical methods for calculation of the surface deformation, integral evaluation of its condition are developed, which include a description of defects in the form of the formalized hierarchical structure, and allow calculating the values of the detected characteristics. The software, which is a structural model of damage accumulation, was created and implemented, which links the optical-digital properties of the material to the appearance, growth and interaction between multiple deformation defects.