Structural Integrity Assessment of Engineering Components Under Cyclic Contact by Oleksandra Datsyshyn & Volodymyr Panasyuk

Author:Oleksandra Datsyshyn & Volodymyr Panasyuk
Language: eng
Format: epub
ISBN: 9783030230692
Publisher: Springer International Publishing

Comparing the results obtained for various types of contact of the crack faces, we conclude that the difference between the results obtained for the cases of partial and full contact of the faces (the case of full contact of the crack faces is illustrated by the dashed lines in Figs. 4.9 and 4.10) is insignificant in all analyzed cases and can be observed mainly for large values of the friction coefficient fc when the counterbody is located to the right of the crack mouth. In this case, the extreme values of the SIF FII are not affected.

It is worth noting that, in analyzing the kinetics of contact of the faces of shear edge macrocracks presented in Figs. 4.9 and 4.10, we can conclude that, for the indicated direction of motion of the counterbody, the crack always starts to close from the mouth (the only exception is the case of smooth contact (fc = 0) in which the crack is simultaneously closes in the mouth and also, for a while, at the tip). Moreover, the higher the friction coefficient fc between the crack faces, the faster the process of closing. However, the behavior of the friction coefficient f exerts almost no influence on the rate of the crack closure. After the full passage of the counterbody over the crack mouth (i.e., for  < −1), the crack immediately begins to open from the mouth.

Finally, it is now reasonable to recall that the maps of contact of the crack faces in Figs. 4.9 and 4.10 are plotted not for the same angle β but for different angles β =  (Table 4.2). Hence, these maps illustrate the kinetics of opening displacements of the crack faces just in these cases depending on the friction coefficients f and fc.

We now consider a more general case of the behavior of shear edge cracks where the following contact conditions on the crack faces are realized: normal opening displacement of the faces, slipping with friction, and sticking. For this purpose, we plot the corresponding contact maps. The obtained dependences give more possibilities to analyze the behavior of shear edge cracks in a single cycle of contact of the bodies and enable us to estimate the relationship between FII() and the conditions of opening displacement, contact, and sticking of the faces.

The plots of the functions FII() for various values of the friction coefficients f and fc and the corresponding contact maps for the inclination angle β ≈ β* = 5π/6 are presented in Fig. 4.11. As follows from the results presented in Fig. 4.11a, c that, for fc = 0.1, the threefold increase in the friction coefficient f causes a significant reduction of the sections sticking in the crack mouth and has almost no influence on the same sections at the crack tip. For the friction coefficient fc = 0.3, no phenomena of this kind are observed: a similar increase in the coefficient of friction between the contacting bodies almost does not affect the sections of sticking (Fig. 4.11b, d). It is also worth noting that, in the case of

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