Nondestructive density measurements of cylindrical specimens by gamma-ray attenuation

Abstract

This paper describes a nondestructive laboratory technique for density measurement that can achieve a 95% confidence limit on the order of ±0.01 g/cm3 for a useful range of density from 0.8 to 2.7 g/cm3, relevant to the above materials. The technique uses a 5 milliCurie (mCi) Cesium 137 source with a scintillation detector and counter assembly to recorde the radiation transmitted through the specimen. This is converted to a density value by calibration to an empirical radiation attenuation law. The principles of the method are described with consideration to the variables of the measuring system and the specimen geometry. It is shown that for solid cylindrical specimen of the materials tested, the radiation attentuation law is satisfied to a very high degree. From the law, a diameter ratio to count ratio relationship is established. Thus detailed calibration is only necessary for specimens of one diameter to determine the density of specimens of other diameters.