Evaluation Method of Pipe Corrosion Based on the Natural Frequency II: Corrosion of internal surface of pipe

Corrosion of internal surface of pipe is serious because it is difficult to observe. So it is very important to put forward a new method to evaluate the average corrosion rate of pipe which corrosion occurred in internal surface of pipe. Based on the damage of corrosion to the mechanical properties of materials, the mass loss factor of corroded pipe is defined, and the elastic modulus of pipe materials is equivalent. According to the modal analysis theory of elastic materials, a modal analysis model of corroded pipe was established, and the relationship between the modal of the corroded pipe and the mass loss factor was analyzed. The results indicate that it is effective and feasible to equivalence the elastic modulus of corroded pipe, and external surface corrosion is more destructive to the pipe than internal surface in the case of the same corrosion rate. At the same time, the model can be used to evaluate the corrosion rate of corroded pipe by monitoring and analyzing the modal..