Finite Element Analysis of guided waves for NDT

Testing of pipes under a road surface using Teletest ® guided wave technology system. Picture courtesy of Plant Integrity Ltd ( www.plantintegrity.com)

The inspection of engineering structures using long-range guided waves is attractive because it is possible to investigate complete material volumes in regions over 100m away from the point of measurement. Because effective inspections require a good understanding of the different vibration modes, finite element modelling is a powerful tool in assessing feasibility of guided wave inspections.

Generation of dispersion curves

• Identification of non-dispersive wave modes
• Elimination of unwanted modes
• Accurate location of defects

Wave propagation analysis

• Assessment of modes sensitive to defects
• Investigation of branch connections (pipe)
• Investigation of constrained structures (pipe, rail)
• Evaluation of most geometric configurations

Benefits of using guided waves for inspection No need to remove coatings - time/cost saving Ability to access 'difficult' areas, e.g. underground pipes, rail level crossings, etc Full volume evaluation Large coverage from a single position Benefits of guided wave modelling Plan inspection procedures Optimise location of probes for defect detection Evaluate difficult situations, e.g. branches, joints Potential applications include: railway rails, storage tanks, bridge suspension cables, bridge pre-stressing tendons

Dispersion curves for a typical rail section with pictures of some wave modes

Results of analysis - contour plot of axial displacement after interaction of longitudinal pulse with flaw in pipe

To find out more about how TWI could benefit your company, please contact us at nmo@twi.co.uk