Health Monitoring of Welded Steel Pipes by Vibration Analysis

Abstract

In the present work, structure health monitoring (SHM) of welded steel pipes was used to diagnosis their state via vibration based damage detection techniques. The dynamic quantities such as Frequency Response Functions (FRFs), mode shapes and modal parameters from structural vibration to detect damage were measured, set on linear averaging mode, with a maximum frequency of analysis of 3.2 kHz. Two most commonly used welding techniques were used, namely: shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW). Static tests were performed to assure the quality of welded steel pipes such as three point bending test (3PB), face bending, and tensile testing. In addition, X- ray, liquid penetration inspection methods were utilized as a NDT. The results show for non-cracked pipes, the first three modes, the higher the damping frequency and lower the damping ratio. This reflects the difficulty of dissipating energy at higher frequency. Also, it was found that SMAW to give higher damping ratio (7.418%) as compared with GTAW joints (7.220). So, the latter joints have higher stiffness than the former ones. However, cracked pipes welded lay 85 A seem to are highest damping for all the tested pipes (8.110%). The results demonstrated that the FRFs technique is a potentially powerful tool for damage detection, health monitoring of welded steel structural pipes