Defects Detection on the Welded Thin Steel Plates Using Vibroacustic Method

Abstract

The aim of this paper is the development and validation of a vibroacustic technique to welding defects detection, especially for welded thin plate structures. In welded structures subjected to dynamic cyclic loads may appear and propagate fatigue cracks due to local structural damage. These cracks may initiate due to the technological parameters used in welding process, or due to environmental operating conditions. By the means of Finite Element Method (FEM), the natural frequencies and shape modes of welded stainless steel specimens are determined. The analysis is carried out in undamaged condition as well as damaged one, after artificially induced damages. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone, which is suitable for high-fidelity acoustic measurements in the frequency range of 40 – 18.000 Hz. The vibration responses of the welded specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform and Prony’s series. The results are compared to modal parameters estimated using FE Analysis and with natural frequencies computed by Euler-Bernoulli theory.