Model-Based Estimation of Thin Multi-Layered Media Using Ultrasonic Measurements

Abstract

Abstract-In ultrasonic measurement situations, when dealing with media of multi-layered structures consisting of 1 or more thin layers, analysis of the measured ultrasonic waveform can be difficult because of overlapping and reverberant echoes. Information from the individual layers is then difficult to extract because the individual echoes cannot be detected. In this study, we use a parametric layer model to analyze the multi-layered material in a system identification approach. The parameters of the model are connected to physical properties of the investigated material, e.g., the reflection coefficients, the time-of-flight, and the attenuation. The main advantage using this model is that the complexity of the model is connected to the number of layers rather than the number of observable echoes in the received ultrasonic waveform. A system of linear equations is presented, giving the opportunity to find the model for both pulse-echo and through-transmission measurements. A thorough effort is made on the parameter estimation and optimization algorithm. The model is validated with practical measurements on a 3-layered structure using both pulse-echo and through-transmission techniques. The 3-layered material consists of a thin embedded middle layer with the time-of-flight in that layer shorter than the emitted signal's time support, giving rise to overlapping echoes. Finally the relation between the model parameters and physical properties of the material is established.

Sparse signal model for ultrasonic nondestructive evaluation of CFRP composite plates

“…In first place, the through-transmission configuration is considered as a discrete-time linear system. Thus, the material under investigation can be represented by a transfer function, which relates the discrete excitation and response signals [12]. Our proposal extends the intuitive physics-based all-pole signal model proposed by Fuentes et al [10], solely inspired by concepts drawn from signal theory.…”

Ultrasonic classification of thin layers within multi-layered materials

“…The maximum likelihood estimate, θ, of the parameter vector θ is then obtained using the algorithm presented in [11].…”

“…In this study, we use a parametric model of the wave propagation to analyze the multi-layered material. The parameters of the model are directly connected to physical properties of the investigated material [11]. The subsequent analysis and classification are then performed on the model parameters rather than on the entire waveform, which enables cost-effective storage and fast processing, necessary for applications in process control.…”

A Nonlinear Method for Characterizing Discrete Defects in Thick Multilayer Composites

“…In Part II of the study, the advantage of the model-based estimation method in ultrasonic applications has been explored [10]. Using model-based methods, the ultrasonic signal waveform consisting of multiple overlapping echoes from within thin multilayer structures has been successfully reconstructed [11]. However, thick multilayer composites have large number of layers and diverse layering methods, and they are difficult to be described by a generic model.…”