Modern industries increasingly use automatic spraying of heat-resistant Nickel coating with a thickness of T = 1-3 mm for large-size parts made of cast iron with nodular graphite. The process of coating application is characterized by time-dependent behavior of its relative magnetic permeability, μс , that is a function of relaxation time, which can be as long as 24 hours, and by μс deviation from point to point on the surface. Aspects of eddy-current phase method for measuring the T value are considered. The structure of four- winding eddy current transformer transducers is described and results of calculation and optimization of their parameters are presented. The influence of controlled and interfering parameters is considered. Based on the above results, a two-channel combined transducer is developed providing measurement error of ΔТ ≤ ±(0.03T + 0.02) mm in the shop environment in the process of coating application and in the final product check. Results of tests on reference specimens and of application in production processes are presented.
Specific features of technological processes of manufacturing carbon-fiber-reinforced constructions can cause non-observance of proportions of a reinforcing material and binding, a de-viation of wall thickness, porosity and rupture of threads. Difficult service conditions can lead to internal volume stratifications and formation of cracks. Above told defines necessity of carrying out of complex control of carbon-fiber-reinforced constructions at all stages of their life cycle. It is expediently to use the Eddy Current NDT for that purposes. The device with set of Eddy Current Phase and Eddy Current Frequency transducers have been developed for measurement electro-conductivity and wall thickness of constructions, detection of cracks and internal volume stratifications, and also their depth and the area. Principles of calculation and optimization of parameters of transducers, influence suppression of stirring parameters are considered.
