Model-Based Flaw Reconstruction and Flaw Parameter Estimation Using a Limited Set of Radiographic Projections [chapter]

Richard M. Wallingford, John P. Basart
1990 Review of Progress in Quantitative Nondestructive Evaluation  
INTRODUCfiON This paper presents an approach to the reconstruction and parameter estimation of flaw models in NDE radiography. The reconstruction of flaw models rather than the flaw distribution itself reduces the required number of projections as well as the complexity of the measurement system [1, 2] . In this approach, crack-like flaws are modeled as piecewise linear curves, and volumetric flaws are modeled as ellipsoids. Our emphasis here is on a method for estimating the model parameters
more » ... r crack-like flaws using a linear model with more than the minimal number of required projections. Extra projections reduce the effects of measurement errors and film noise. We also present the development of the volumetric flaw model and outline a method for its inversion. PARAMETER ESTIMATION FOR CRACK-LIKE FLAWS We have shown previously [1] that two projections using a linear sample shift is the minimum number required for a unique solution of the model parameters. With two projections, there are 10 governing equations, 6 unknown desired parameters, and two unknown nuisance parameters. We therefore have an overdetermined linear system of equations with many possible solutions due to random fluctuations in the measurement variables. The linear model describing the crack-like flaw is given by Equation (1 ).
doi:10.1007/978-1-4684-5772-8_93 fatcat:zspq4ojynjcj3lt6qkv4zya3oq