عنوان مقاله [English]
نویسندگان [English]چکیده [English]
This paper tries to find a suitable probability distribution function for the optical density of weld lines in the radiographic films. For this purpose, real gamma ray radiography films of oil and gas pipelines in the operational areas of national oil company were used. The number of radiographic films was 4 and due to the unpredictability of radiographic conditions and the existence of different regions on the surface of the films, histogram curves of scattered data were selected to do this study. More than 36 probability distribution functions were fitted on the histograms. 11 fitted probability functions with R-sq.≥0.95 were selected among the total functions. In addition, the final selected functions fitted to 4 internal concavity (Suk Back) defects. The best function was Pearson IV based on the obtained results. Although the Gaussian function also behaved well but it was not perfect. In addition, Rational and Cauchy functions were simple and very good fitable probability distribution functions.