Nondestructive evaluation of cooling passages and their blockage using vapor excited active thermography

Non-destructive testing of cooling passages has attracted a considerable interest due to the critical rule of these segments in the performance and endurance of different parts. In this research, the performance of active infrared thermography in the non-destructive inspection of cooling passages located inside the metallic bases has been investigated. Water vapour was selected as an excitation fluid so as to create the thermal contrast. Specimen material, hole depth, hole diameter and injection pressure were selected as the input parameters effecting on the thermal contrast. The results obtained via statistical analysis revealed that the hole depth and injection pressure have the noticeable influence on the dimensionless output temperature recorded with thermal camera. A 50% decrease in dimensionless temperature contrast has been revealed when the hole depth has become four times. Besides, a similar increase in injection pressure, elevated the above-mentioned parameter almost 20%. In contrast, the parameters of specimen material and hole diameter specified no perceptible effects. Moreover, infrared thermography with water-vapour excitation proved proper capability in detection of 60% and 80% blockage located inside the holes.