FREQUENCY PARAMETERS OF NATURAL OSCILLATIONS IN PLATE STRUCTURES TO DETECT PRESET INADMISSIBLE CRACK SIZES

The method for determining the parameters of natural oscillations of an object under test is offered, which allows detecting crack sizes in structures made of plates. The use of this method is particularly relevant for monitoring large structures that takes much time if other NDT types are used. The relation between the natural oscillations parameters and crack sizes is built on the use of the mathematical model of the energy carrier of free oscillations, and on dynamic crack theory. Resultant diagrams are made for various deformation types on crack edges, to be used to determine wave length and frequency of natural oscillations in a plate against a preset inadmissible crack length, thus enabling crack detection. To ensure efficient non-destructive testing, an example of essential set of forms of natural oscillations for a plate structure is given.