Determination of the Characteristics of Cyclic Crack Resistance of Steels Under Transverse Shear (A Survey)
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DETERMINATION OF THE CHARACTERISTICS OF CYCLIC CRACK RESISTANCE OF STEELS UNDER TRANSVERSE SHEAR (A SURVEY) Т. M. Lenkovs’kyi
UDC 620.178.3:539.421.2
We present a survey of works devoted to the investigation of the fatigue fracture of steels under the conditions of transverse shear. Numerous methods aimed at the determination of the characteristics of cyclic crack resistance of structural steels of different strength classes are analyzed. The analysis of the results of investigations enables us to make a conclusion about the necessity of improvement of the available methods and development of new methods for the construction of the kinetic diagrams of fatigue fracture with regard for the influence of friction of the lips of fatigue cracks on the stress intensity factor KII and the elimination of stresses in the vicinity of the crack tip. Keywords: transverse shear, fatigue fracture, kinetic diagram of fatigue fracture, characteristics of cyclic crack resistance.
Under the actual conditions, the components of machines and mechanisms, as a rule, operate under cyclic loading. In the course of long-term operation, defects (such as cracks) are initiated and propagate in the material of structural elements, thus leading to the premature failures of elements and structures as a whole. To predict and guarantee their service life, it is necessary to know the fatigue fracture resistance of materials. This is why, in the scientific and engineering practice, it is customary to use the methods of fracture mechanics based on the determination of the characteristics of cyclic crack resistance (CCR) from the kinetic diagrams of fatigue fracture (KDFF) [1–3]. For mode I cracks, the KDFF were plotted and the CCR characteristics were established for numerous materials [2, 3]. At the same time, the fatigue fracture of bearings, rolls of forge-rolling mills, and railroad wheels and rails [4, 5] in their contact zone also occurs according to the (mode II) mechanism of transverse shear and, therefore, for the evaluation of the durability of these elements, it is necessary to know the CCR characteristics determined under the conditions of transverse shear [6].
In this connection, it is necessary to solve the problem of creation and application of new methods aimed at modeling the processes of initiation and growth of mode II cracks, construction of the corresponding KDFF, and evaluation of the CCR characteristics. It is known from the previous investigations that the construction of the KDFF of steels under transverse shear is connected, for various reasons, with serious difficulties [7–9] and the obtained results are not always correct [9–14]. This requires a more detailed analysis of the proposed procedures [7–16] with an aim to improve the existing methods or to develop new methods suitable for the determination of the CCR characteristics of steels of different strength classes under transverse shear.
In [10], the fatigue tests under transverse shear were carried out with the use of beam specimens with central notches by the scheme
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