Thinning identification technique using stainless steel film heater and response surface method

摘要

The infrared thermography has not been widely applied to nondestructive inspection for metals. It is because the metal emissivity is too low to be measured the temperature. To make up for this disadvantage, a new heating technique using a stainless steel film was proposed and a nondestructive inspection system with the response surface method was developed. The stainless film has a high electric resistance and generates large Joule heat. Its response is quick and the quantity of heat is easily controlled. Moreover, the film has a high enough thermal conductivity, therefore a black painted film can be a blackbody surface of metal structures. Consequently IR camera can easily measure the metal temperature accurately. The nondestructive inspection system that can quantitatively identify geometrical parameters of a local thinning was developed. The system consists of a forward analysis and an inverse analysis. In the forward analysis, the response surface that shows a relationship between geometrical parameters and characteristic values is built by experimental design method. In the inverse analysis, substituting the characteristic values into the response surface, the geometrical parameters are finally identified. The inspection system can identify the local thinning shape robustly by selecting the attribute for the shape parameters.