Three-dimensional mapping of non-complex specimens by image processing and optical density evaluation of digitised radiographs

摘要

Digital radiography has been studied extensively for thickness measurement in recent years. This has resulted in enhanced image quality and improved overall evaluation. In this research, an innovative numerical method was used for image enhancement and radiographic interpretation through the use of MATLAB software. Film digitising was carried out by a scanner. Thickness profiles of specimens were extracted from the optical density of radiographs by a numerical method. Therefore, digital imaging and optical density measurements were combined to evaluate the thickness profile of samples. Results were used to create a three-dimensional mapping of the non-complex specimens for further investigation. Then the volumetric information could be used for the evaluation of various defects, such as corrosion, erosion and pitting. The most important challenge in the calculations was measuring the exact effective atomic attenuation coefficient for the samples. For this purpose, some reference blocks were designed, fabricated and used. In addition to practical experiments, Monte Carlo simulation was carried out for accurate assessment of the developed method. Although results show a high correlation between real and calculated values for plates, insulated and non-insulated pipes, this method cannot be used for thernvolumetric rendering of samples with a complex geometry. Ordinary computerised tomography has to be used for complex specimens.