Krasnopolskii V. Boundary state prediction of aviation structures riveted joints in case of multiple site damage

The thesis is devoted to solution of the problem of determination the reliability and service life of aircraft structures riveted joints in case of multiple site damage. This problem is solved by scientific substantiation and development of new mathematical method for modeling the processes of fatigue cracks formation and growth in structures with holes made of aluminum alloy D16AT, taking into account experimentally established regularities. The paper proposes a new method for life prediction and reliability determination of riveted joints based on the probabilistic model of multiple site damage. It includes the function of time distribution before the occurrence of a crack with initial length, the stochastic model of the crack length distribution at a fixed time, and calculation of coalescence probability for counter cracks at a specific time. To test the efficiency of the developed method, it was carried out fatigue tests of model specimens with many stress concentrators to simulate multiple site damage. During the test special techniques to get experimental data on the initiation and propagation of fatigue cracks without stopping the test were used to increase the reliability of the obtain data and to achieve better repeatability of the results.