Laser-Ultrasonic Study of Residual Stresses in Pipes Made of Austenitic Steel

The paper discusses an acoustoelastic study of residual stresses and related structural changes in thin-walled austenitic steel pipes. A probing ultrasonic (US) beam is formed owing to the thermoelastic effect by absorption of a laser pulse in an optoacoustic transducer. Normal and oblique incidence (at an angle close to critical) of the US beam was used on the studied. Distribution maps of US velocity variations over the object’s surface and the volume structural inhomogeneities inside the metal were plotted. Estimates are presented for the residual stresses in the sample under nonstationary thermal loading. The coincidence between the residual stress distribution, structural inhomogeneities of the metal, and distribution of thermal loading sources is established. The possibility of estimating the residual life and finding of macrocrack nucleation centers is discussed.