Method for determining the thickness of a material by means of a radiant energy probe

摘要

A nondestructive method for determining the thickness of a non-electrically conductive material is provided that comprises the steps of uniformly dispersing a quantity of a ferromagnetic particulate tagging substance in the material whose presence and distribution is detectable by a form of radiant energy, such as the high-frequency electromagnetic field emanated from an eddy current probe, and then calibrating the output of the eddy current probe with a sample material having a known thickness that has been tagged with the same tagging substance at the same density. The thickness of the material is then determined by comparing the amplitude of electromagnetic coupling with the material with that obtained with the sample. The method may advantageously be applied to determine the thickness of a granular material such as asphalt concrete over a roadbed, as well as the strain and wear patterns in gaskets formed from elastic materials.