Ultrasonic testing remains the most common Non-Destructive Evaluation (NDE) technique for inspecting adhesive joints at the bond line as it can be targeted at small volume elements of interest. Whilst it can detect finite thickness disbonds, there is still no known NDE technique to detect kissing bonds (KB) and therefore assess the integrity of the bond. The literature describes the potential of non linear ultrasonic techniques, but previous work has failed to fully quantify nonlinearities generated by the experimental system. In this thesis, a new prediction tool that provides realistic simulations of nonlinear ultrasonic wave propagation is introduced to assess the detectability of KB in multi-layered structures. A series of experiments that quantify nonlinearities generated by the different sources are described, and a finite-element (FE) model in which the experimental data is incorporated is developed. This new prediction tool is expected to enable NDE engineers to know whether KB are at all detectable in a given adhesive joint, and if so, what experimental set-up, driving frequency and post-processing method to use in order to optimise KB detection capability.
|Date of Award||2012|