Application of the acoustic emission method for ranking by fatigue damage of the material of trunnions of drying cylinders of cardboard and paper-making machines

Abstract

Using the example of assessing the technical condition of the trunnions of drying cylinders of cardboard-making machines (CDM), the question of the possibility of ranking cyclically loaded elements of dynamic equipment according to the degree of damage to their material by fatigue cracks using acoustic emission (AE) measurements is discussed. As a result of special laboratory studies with varying loads in the cycle of loading and lubrication of the crack banks, the features of AE from the friction of the crack banks and plastic deformation at the crack tip during its growth in a viscous material have been established. It is shown that during cyclic loading of the material, AE signals from the friction of its shores are detected more steadily than AE signals from a crack jump with an increase in its length, and that tracking the former ensures the detection of fatigue damage of the material even under loading conditions insufficient for crack growth. Based on the data obtained, three AE signs of the presence of fatigue damage of the material of the elements of dynamic equipment were developed under the condition of cyclic activation of the movement of the crack banks. As a result of industrial testing of the developed AE features, their operability was confirmed and their boundary values on the operating trunnions of CDM drying cylinders were clarified, and a method for ranking trunnions by the level of damage by fatigue cracks was proposed. By comparing the results of AE measurements with ultrasound control, the reliability of the proposed approach was evaluated, which showed the probability of detecting a fatigue crack in the trunnions of CDM drying cylinders at the level of 71 %, with the probability of their skipping and false rejection of the product 12 and 17 %, respectively. The developed technique is also transferable to other massive dynamic equipment after clarifying the boundary values of AE signs of fatigue damage of the material on this type of object.