Propagation of Guided Acoustic Waves in the Shafts of Centrifugal Pumps With Longitudinal Cracks of Axial Holes

Abstract

During the production and operation of centrifugal pump shafts, defects may appear in their inner diameter, which in the vast majority of cases are longitudinal cracks. Such defects entail the complete destruction of the centrifugal pump power unit, production delay and high economic costs, while their detection by magnetic, eddy current, capillary types of testing is often excluded or limited due to the small internal diameter of the shaft. The work is devoted to the development of a new technique designed to detect defects in the axial holes of the shafts of centrifugal pumps by the combined use of two types of guided acoustic waves – torsional and longitudinal (rod). The technique is based on the use of echopulse and time-shadow methods of acoustic non-destructive testing. Within the work, studies were carried out on guided wave testing of three groups of shafts, divided according to the criteria of the methods used in the work, as well as computer modeling confirming the reliability of the testing result presented in the work. It is proposed to use a new informative parameter – the torsional wave velocity in the defective part of the tested sample. The results of experiments and computer modeling by the finite element method have shown the high efficiency of the studied method and the nonlinear nature of the dependence of the propagation of guided waves in the shafts relative to the number and size of cracks in axial holes.