Low cycle crack propagation and loosening in the critcal joints

Abstract

The aim of this work is to establish a tightness change of the threaded joints depending on cyclic loading, magnitude tightening and crack propagation. The tested threaded joints M16...M52 made of various steel. Experimental examinations have shown that in some cases total of tension and bending stress reach a plastic range and penetrate to a certain depth. In the case of strong prestress up to 0.8 ay, the working conditions can occur, that plastic strains take place on the boundary layers at bolt in the process of using fluctuation load. An analysis of crack formation and propagation showed that a crack could be either one-sided or double-sided. In tightened threaded joints that are subjected to cyclic bending there is a link established between loosening and the fracturing process parameters (such as the configuration and depth of crack).