Methods for evaluation of mechanical stress condition of materials

¹ Institute of Mechanics of Bulgarian Academy of Science, 1113 Sofia, Bulgaria
² Multitest Ltd., 9000 Varna, Bulgaria

^* Corresponding author: mirchev@imbm.bas.bg

Abstract

Primary attention is given to the following methods: method by drilling cylindrical holes (drill method) and integrated ultrasonic method using volume (longitudinal and transverse), surface, and sub-surface waves. Drill method allows determination of residual mechanical stress in small depth of material surfaces, assessing type, size, and orientation of principal stresses. For the first time, parallel studies are carried out of mechanical stress in materials using the electroacoustic effect of volume, surface and sub-surface waves on the one hand, and effective mechanical stresses on the other. The experimental results present electroacoustic coefficients for different types of waves in the material of gas pipeline tube of 243 mm diameter and 14 mm thickness. These are used to evaluate mechanical stresses in pipelines, according to active GOST standards.