Studying the Possibility of the Destruction Control of Machine Parts by Applying Directed Sharp Concentrators

Abstract

The problem of preventing fatigue failure is highly relevant in all branches of engineering, especially for such structures, the failure of parts in which can lead to accidental effects. But this problem is becoming incredibly important recently due to the need of intensively increasing of the service life and reliability of machines during operation. As a rule, particular attention is paid to the study of the areas in the details with the sharp change in share and size, in which local zones with stress changes exist, leading to the appearance of cracks and, ultimately, to the destruction of these parts. The most extensive research in this area has been performed on various samples. However, the obtained results do not allow to describe the stress state and the stress concentrators with the help of analytical dependencies, especially in the case of sharp cuts and when superposition of stress concentrations, because they do not take into account the scale factor, state of material, etc. In particular, sharp depressions and small cuts (scratches), which do not reduce the strength of the material according to their concentration coefficients, are of special scientific interest, as well as the development of methods for controlling the destruction process. The usage of numerical methods (in particular, the finite element method) significantly expands the possibilities of analysis of stresses in the concentrators of samples and parts. However despite the results achieved, it is considered that it is still difficult to obtain a satisfactory solution for the stress field in the part’s concentrator, taking into account local design features. The article examines the stress state and fatigue resistance under bending loading of the on specially developed physical models of a crankshaft produced with different technologies, having a sharp decrease in the radii of fillets. Models with applied sharp concentrators of various geometries were tested. The performed studies allow to conclude that research in this direction is promising, since new knowledge about stress concentrators and their effect on the fatigue strength of full-scale parts can open up new reserves for increasing the fatigue strength of full-scale structures.