Development of an Acoustic Model for Multilayered NDE

A computer based acoustic model has been developed for the NDE of multilayered structures [1]. The model is applicable for normal or off-normal incident excitation, with receiver in pulse-echo, pitch-catch or in array mode. The model can simulate the observed signal for arbitrary frequency response of the transmitting and receiving transducer. In addition, the model considers attenuation and mode conversion effects in each layer in predicting the ultrasonic response.While earlier works [2,3,4] considered normal incidence and non attenuative media, the current model’s capabilities have been expanded to include off-normal incident angles and the attendant mode conversions created with this inspection configuration. Another feature included in this model is provision for attenuation within each layer. It can be modeled as constant over all frequencies or as a frequency dependent quantity, such as a constant “0” model. Common materials such as aluminum, stainless steel, rubber and biological tissues exhibit this property.The paper will focus on model development and discuss results obtained for a bronze-rubber multilayer structure.