Rapid assessment of fracture toughness of steel

The presence in industry of a huge Park of equipment with expired passport life constantly poses the question of the justification of the lifetime extension. This is a complex task that requires reliable methods for assessing the state of metal in the product. Large objects, which are in operation, cannot be delivered to the laboratory for testing. Many objects are so long that the methods of calculation of products of this type, as well as criteria for evaluating the suitability for further work changed long ago. This, in particular, is experiencing the effects of variable loads. The latter lead to growth of cracks and pose a risk of brittle fracture or pseudographs. The modern method for assessing the propensity of a material to brittle fracture is to determine the fracture toughness. The method is proposed for predicting the fracture toughness according to the results of the tensile tests. The proposed model shows the validity of using methods of continuum mechanics in analysis of the processes taking place in the area bounded plasticity in front of the crack. The regularities of the relationships of fracture toughness and specific energy of plastic deformation of layers of metal adjacent to the fracture surface, for steels of different strength levels.