###### Abstract  
Guided wave tomography is an effective non-destructive method for mapping corrosion damage in thin-walled metal structures. Its efficiency and accuracy depend on the choice of a suitable forward model and inversion method. Current techniques mainly use acoustic forward models that, while computationally efficient, are approximate and fail to accurately represent wave propagation in physical experiments, making them less suitable for inversion. This study investigates the performance of Mindlin plate theory, which accounts for through-thickness shear deformations, enabling the modeling of flexural modes in a two-dimensional (2-D) plane. The scattering of \(A_{0}\) mode Lamb waves from defects of varying depth, width, and shape is analyzed using finite difference and pseudospectral simulations for 2-D and three-dimensional (3-D) defects, respectively. Results from the Mindlin model are compared to finite element model simulations. It is found that Mindlin plate theory accurately represents smooth defect scattering, but is less accurate for sharp-edged defects. ultrasonic guided wave tomography; corrosion; Mindlin plate theory 2024 14 9351 10.3390/app14209351 10.  
ultrasonic wavenumber imaging with laser interferometers [13; 14]. Nonetheless, this technique is more expensive and requires direct access to the damaged surface, making it less suitable for coated or insulated pipe sections. Alternatively, precise defect mapping can be achieved by integrating transducer arrays typically used in pitch-catch methods with tomographic techniques. This approach involves attaching two transducer rings to the pipe, allowing for measurements to be taken from multiple angles. Guided Wave Tomography (GWT) operates by analyzing waveforms to generate a wall thickness map for a specific pipe section. Variations in these waveforms are interpreted by tomographic algorithms as reductions in thickness at specific locations [15]. In GWT, defect reconstruction is accomplished by solving an inverse problem, where a forward model is used to predict a synthetic dataset based on the structure and defect shape. The defect shape is then iteratively refined by minimizing the difference between the actual and synthetic measurements until a convergence criterion is met, resulting in an accurate reconstruction of wall thickness. The appropriate forward model of GWT needs to be of low computational cost and complexity of combining it with the inversion procedure of the tomography algorithm. Consequently, many tomography applications make use of the simple acoustic model for plates [16; 17], pipes [18; 19], and pipe bends [20; 21] as they are able to map the thickness of the waveguide from the velocity of the propagating wave. However, the accuracy of the acoustic model decreases if the size of the defect is around a few wavelengths of the probing wave, due to inability to describe the scattering [22; 23] including reflections, which are important to achieve higher resolution imaging [24]. This research aims to use Mindlin plate theory [25], to develop an efficient numerical forward model for GWT. Using higher-order plate theories would lead to a better agreement over a wider frequency range, while still retaining analytical simplicity [26; 27]. Mindlin plate theory incorporates shear deformation and rotary inertia in the equations of motion to predict the propagation of low-frequency fundamental Lamb modes, while reducing the 3-D plate motion to a 2-D plane on the mid-thickness plane to simplify computations. Its feasibility to solve different scattering problems has been demonstrated in numerous studies. [PERSON] et. al used Mindlin plate theory to analyze the scattering behavior of GW modes at a cylindrical hole and part-through delamination in beams and plates [28; 29]. Other studies on the scattering of flexural waves from a through-hole [30] and non-symmetrical blind holes [31] have demonstrated good agreement between analytical solutions and experimental results.