Numerical Simulation And Experiment Of Constant Heat Flux Infrared Thermography

Infrared thermograpgy is a valid mathod for defect inspecting and diagnosing in the field of engineering structure. As the infrared thermography inspecting is developing from nature determining to quantity determining, some basic study is done in this paper for this development in the area of building inspection.First, the 1D temperature distribution of multilayer material heated under constant heat flux is resolved by the method of laplacian transform, which can be used to simulate the tempreture distribution of the defective area in the model. Then the temperature distribution in concrete component with shallow voids heated by constant heat flux is simulated by means of 1D finity deference method and 3D finity element method. By analysing the temperature contrast curve vs time of the model with different defects, it is obviously that the peak value of the contrast and the peak-time is related to the depth of the defect as the same in the pulse thermography. For the sake of validating the result, the experiment is planed. The concrete plank with different shallow voids is heated continously under constant heat flux, and the temperatrue is recordered by the infrared camara. The relationship between the contrast and the defect depth is gained. The comparison between the experimental result and the simulation indicated that the 3D FEM method is more effective than the 1D difference method. After all the parameters relating to the peak value contrast is analysed, the inverse problem of the depth is resolved by means of neural network with a satisfied result.At last, the thermal and radiometric model of wall for inspection is proposed after the heat exchang between the wall and the envoriment is studied in the building inspection project. The idea of inspecting wall with different orientation at the best time is proposed after simulating the effect of the the radiation on the building by means of 3D FEM method.