Cracks are the most dangerous defects because of its tendency to increase, followed by an avalanche of destruction. The parameter which characterizes the ability of the structural member to resist the destruction of this kind is a crack. There are a significant number of dependencies crack growth rate on the mechanical properties of the material and loading parameters. However, a universal analytic dependence, reflecting the peculiarities of fatigue failure for a variety of materials and allowing to predict this process has not yet been found.
For further improvement of test methods in the evaluation of the parameters of fracture toughness, it has been tasked to implement them under biaxial loading, as real metal structures operate in complex stress state. Tests were conducted under biaxial loading of samples using the testing machine. As the test material was selected steel St3. To determine the rate of crack growth under cyclic biaxial loading and evaluation of fracture toughness were selected cross-shaped patterns.
Practical use of diagrams of fatigue failure for applied engineering problems is difficult because of their personality. There is an urgent need to develop experimental and analytical tools, allowing to describe the rate of fatigue crack growth of fatigue failure of a single diagram. Carrying dimensionless normalization allows us to reduce to a single line diagram of fatigue failure for a variety of conditions and materials.
The obtained normalized chart represents a single experimental curve, which connects the rate of crack growth and stress intensity factor under various conditions of cyclical testing. The diagram describes the values of fracture toughness both uniaxial and biaxial loading, and has the property of universality. This diagram allows on the basis of individual experimental data on crack growth rate under biaxial loading characteristics to obtain cyclic crack resistance
elements in any combination of external force.


Crack, metal structures, biaxial loading, chart, fatigue failure.

Issue number: 2
Year: 2016
UDK: 621.642
Authors: Samigullin G. Kh., Lyagova A. A.

About authors: Samigullin G.Kh., Candidate of Technical Sciences, Assistant Professor, Head of Chair, e-mail:, Lyagova A.A., Candidate of Technical Sciences, Assistant of Chair , National Mineral Resource University «University of Mines», 199106, Saint-Petersburg, Russia.

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