THE USE OF LAMB WAVES FOR THE LONG-RANGE INSPECTION OF LARGE STRUCTURES

Lamb waves are very attractive for the quick inspection of large struc tures because they can propagate long distances along plates and shell s. The chief drawback of Lamb wave inspection is that at least two mod es exist at all frequencies and the modes are generally dispersive, wh ich means that the received signals can be very complicated. As a resu lt, the potential advantages of Lamb wave inspection have seldom been realized in practice. The key to the successful application of Lamb wa ves is the excitation of a single mode in a non-dipersive region. This paper discusses the selection of an appropriate mode and its excitati on and reception. Examples of the use of Lamb waves for the detection of delaminations in composite materials and corrosion in pipes are the n given.