Study On Infrared Testing With Internal Heat Generation For Smart Concrete

The research theme of this thesis stems from the key project of national nature and science fund: SMART CONCRETE AND IT'S STRUCTURE (serial number 50238040).Infrared thermographic Non Destructive Testing (NDT) technique as a new NDT technology has been widely and successfully used in a variety of fields for it's unique advantages: non-contact, fast, accurate, reliable, real-time and intuitional. It adopted two kinds of methods: internal heating methods and external heating methods, which have their defects in their application. On the research of CFRC, Infrared thermograph detection under Joule heat by adding voltage to the CFRC specimens is found to be a feasible and effective method of inspection, which can avoid the defects. Because of its good electrical conductivity, CFRC specimens will engender Joule effect when a relatively low voltage was added to them. If there are flaws inside, the surface temperature distribution of the specimens should be uneven. Therefore, Infrared thermograph NDT can be conducted.Combined with experimental data, this paper conducted the theoretical analysis and computer simulation of the Infrared thermograph NDT. The main work lists as following:1 On the condition that CFRC is an macroscopically isotropic material, the governing equations of electric and thermal conduction for the inspection were established; The current density and Joule heat distribution around several kinds of flaws were investigated2 By FEM , the process of inspection was simulated; The current density, Joule heat and temperature distribution were also investigated, and the simulation results were contrasted with experimental data.3 The analytical solution of steady-state temperature field with internal Joule heat generation for sound structure is firstly investigated. By adopting appropriate transformation, this paper transform the heat conduction equation with internal heat source into a non-source heat conduction equation, and then solve the problem successfully by the method of separation of variables.4 Due to the irregular geometric boundary and the complicated internal heat source distribution, the theoretical solution of transient temperature field for specimens with flaws is very difficult. Numerical solution is mainly applied for this problem. Adopting certain assumptions, this paper presents an approximate method of obtaining the temperature field by Green's function, and gives the solution of a two-dimensional field involving a circular vacant flaw.