Ultrasonic monitoring of plastic deformation

Abstract

Accident impact assessment, safety analysis, and risk reduction are among the core research topics in the field of shipping. Analysis of emergency situations shows that all of them in most cases are characterized by a combination of some causes, one of which is the occurrence of inadmissible stress-strain state in ship elements. Determining the nature of fracture is one of the ship’s reliability improving measures. The presence of plastic deformation is a sign of the limiting condition when monitoring the structure. This leads to a visible change in the geometry of the structural components, but not to a violation of continuity, which, according to the rules of the Register, is controlled during the technical inspection of the ship. Having only regulated standard controls at its disposal, it is not possible to identify plastic deformation. The article discusses the issues of plastic deformations’ control in 10ХСНД shipbuilding steel by a method that is based on the analysis of the ultrasonic wave propagation characteristics in a controlled product. The complex of mechanical tensile tests and metallographic studies is described. The uniaxial stress-strain state of the material was created by tensile testing of a flat proportional sample. Changes in the metal structure were investigated when the required level of deformation was reached. The analysis of ultrasonic data with pulsed ultrasonic sensing and the level of second harmonic generation with continuous monochromatic ultrasonic emission is presented. Experimental data demonstrate the ability of the ultrasonic method to detect the pre-existing defects in metal under static loading, and allow for a more accurate assessment of the stress and strain state of ship's components, which can fundamentally change the picture of destruction. The use of ultrasonic plastic deformation monitoring in the framework of ship maintenance will help reduce accidents in the fleet.