Defect detection in pipes by torsional guided-waves: a tool of recognition and decision-making for the inspection of pipelines

Damage detection by guided waves is an effective technique in the structural health monitoring domain of pipelines as opposed to conventional methods. The guided waves propagation in long tubes allows the rapid inspection and identification of defects (cracks, corrosion, notches...) and singularities (elbows, welds, flanges...). The torsional waves T(0,1) has attractive advantages in defect detection. In this paper, the development of an inspection tool for pipelines was described. It is based on the generation of torsional mode by piezoelectric transducers. In addition, a numerical tool for the recognition of defects and singularities has been developed. It enables the user to acquire the measurement signals on the industrial installation and provide guidance on the location and dimensions of defects. The guided-waves generator allows the emission of T-waves and the reception of reflected echoes. Subsequently, an expert system will use some tools of signal processing for filtering and analyzing of recorded responses in order to extract relevant information. It will also appeal to a database of numerical simulations carried out with the Wave Finite Element Method (WFEM) for the defect sizing. Several experimental tests have been performed on real installations. The T-waves are well excited and its velocity was verified. From the recorded responses, the identification of echoes allows the recognition of defects and singularities in the pipelines.