Comparative Study of Coupling Techniques in Lamb Wave Testing of Metallic and Cementitious Plates

Abstract

Lamb waves have emerged as a valuable tool to examine long plate-like structures in a faster way compared to conventional bulk wave techniques, which make them attractive in non-destructive testing. However, they present a multimodal and dispersive nature, which hinders signal identification. Oblique incidence is one of the most known methods to generate and receive Lamb waves and it is applied in different experimental arrangements with different types of sensors. In this work, several setups were conducted and compared to determine the optimal ones to launch and detect ultrasonic Lamb waves, especially in non-homogeneous specimens. The chosen arrangements were contact with angle beam transducers, immersion in a water tank, localised water coupling using conical containers and air coupling. Plates of two different materials were used, stainless steel and Portland cement mortar. Theoretical and experimental dispersion curves were compared to verify the existence of Lamb modes and good correspondence was achieved.

Assessment of cure cycle shortening for advanced composites via ultrasonics and dynamic mechanical analysis

“…The layed up composite goes into the oven according to the curing cycle set by the manufacturer and shown in Figure 3 (4hr-soak). The temperature ramps up from room temperature to 70°C in 50 min then soaks at this temperature for 4 h before ramping up again to 120°C within 25 min, 37 soaking for 1 h and then cooling naturally. The cool down shown in the figure is in just 1 h, whereas there is no cooling system inside the oven.…”

“…Displacement of particles in an (a) antisymmetric and (b) symmetric Lamb wave modes. The median dotted line of the plate is shown 37.…”