IDENTIFICATION METHOD FOR MARKS ON FRACTURE SURFACES AND CASE STUDY (FAILURE OF PROPELLER BLADE OF EXHAUST GAS VENTILATOR)

摘要

There is possible to find some marks on the fracture surfaces. That marks are following the crack tiprnpositions during the crack propagation. We can assume that these marks are connected with changes inrncharacteristics of loading or in chemical regimes.rnWe can measure positions of marks on the crack surface. We can try to estimate kinetics of crackrnpropagation as dependence on load and position of crack. Mainly in the case, in which we can assumernfatigue crack propagation, we can propose a model of kinetics. But it is very difficult or even impossible torndetermine exactly the real load.rnIf we know data about the character of failed part operation, if we can design a kinetic model of crackrnpropagation and if we have determined positions of marks on the fracture surface, we can compare thatrndata. This comparison can be done by computer program by help of calculation of overlap integrals. Therndata about operation and positions of marks on crack surface can be presented as sum Gauss curves.rnComputed overlap integral will depend on the coefficient in kinetic model. The maximum values of thernintegral will be points in which coefficients in kinetic model mean the most probable values. We canrnassume by this way a real crack propagation rates and lifetime.rnThe presented method was applied on the case of fatigue fracture of exhaust gas propeller blade on thernclassic coal power plant. The application of this method contributed to the explanation of real crackrnpropagation rate and lifetime.