Issue 48

O. Plekhov et alii, Frattura ed Integrità Strutturale, 48 (2019) 50-57; DOI: 10.3221/IGF-ESIS.48.07

min

     

max K K K K

(4)

K  

min

where Q 1 are the heat flux and the crack length in the second stage. The superscripts “max” and “min” denote maximum and minimum values during the fatigue test. and a 1 are the heat flux and the crack length in the first stage, Q 2 and a 2

C ONCLUSION

A

series of experiments was carried out to study the energy dissipation at the fatigue crack tip under biaxial loading. The experimental technique for measuring the energy dissipation during fatigue test under biaxial loading was developed based on the contact heat flux sensor and the method of infrared thermography. The results of this study confirm the hypothesis for the existence of two modes of energy dissipation during the fatigue cracks propagation. The first mode corresponds to slowly propagating cracks (10e-7 – 10e-5 m/cycle) and is described by the relation 1 1 ~ da Q a dN       .The point corresponding to a change in the character of energy dissipation lies on the linear section of the Paris curve. The obtained experimental results allows us to generalize the hypothesis about the linear relationship between the energy dissipation at the fatigue crack tip and its growth rate to the case of biaxial loading. The study revealed qualitative agreement between the energy approach to the description of the fatigue crack propagation and the classical approach, which is based on the use of the stress intensity factor.

A CKNOWLEDGMENTS

T

his work was supported by the grant of the President of Russian Federation for support of young Russian scientists and leading scientific schools [MK-1236.2017.1] and the Russian Foundation for Basic research [grant number 16-48-590148].

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