Author Contributions
Data curation, M.G.; Formal analysis, G.R.P.; Investigation, M.G.; Methodology, M.G. and G.R.P.; Project administration, I.C.P.M.-M. and G.R.P.; Resources, I.C.P.M.-M.; Supervision, G.R.P.; Validation, M.G.; Visualization, I.C.P.M.-M.; Writing—original draft, M.G.; Writing—review & editing, I.C.P.M.-M. All authors have read and agree to the published version of the manuscript.
Figure 1.
Visual aspect of the defects before the coating application for sample: (a) S1, (b) S2 and (c) S3 and visual aspect after the coating application of the samples (d) S1, (e) S2 and (f) S3.
Figure 1.
Visual aspect of the defects before the coating application for sample: (a) S1, (b) S2 and (c) S3 and visual aspect after the coating application of the samples (d) S1, (e) S2 and (f) S3.
Figure 2.
Photography illustrating the positioning of the equipment during the performance of the experimental tests: 1—sample, 2—halogen lamps and 3—infrared camera.
Figure 2.
Photography illustrating the positioning of the equipment during the performance of the experimental tests: 1—sample, 2—halogen lamps and 3—infrared camera.
Figure 3.
Heat flux incident function on the sample surface over time obtained.
Figure 3.
Heat flux incident function on the sample surface over time obtained.
Figure 4.
Virtual solid of the samples evaluated in this study, with the same geometric parameters of the samples used in the experimental tests: (a) sample S1, (b) sample S2 and (c) sample S3.
Figure 4.
Virtual solid of the samples evaluated in this study, with the same geometric parameters of the samples used in the experimental tests: (a) sample S1, (b) sample S2 and (c) sample S3.
Figure 5.
The highest thermal contrast thermogram obtained for: (a) S1, (b) S2 and (c) S3 samples.
Figure 5.
The highest thermal contrast thermogram obtained for: (a) S1, (b) S2 and (c) S3 samples.
Figure 6.
Images illustrating the temperature distribution on sample S1 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 6.
Images illustrating the temperature distribution on sample S1 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 7.
Images illustrating the temperature distribution on sample S2 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 7.
Images illustrating the temperature distribution on sample S2 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 8.
Images illustrating the temperature distribution on sample S3 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 8.
Images illustrating the temperature distribution on sample S3 obtained by the simulation model developed: (a) 0 s (at the moment that the lamps are turned on), (b) 10 s, (c) 20 s and (d) 30 s.
Figure 9.
Comparison between temperature evolution obtained by simulation and experimentally for sample: (a) S1, (b) S2 and (c) S3.
Figure 9.
Comparison between temperature evolution obtained by simulation and experimentally for sample: (a) S1, (b) S2 and (c) S3.
Figure 10.
Cross section of the virtual solid illustrating defects of the same diameter with different depths (0.94, 1.88, 2.82 and 3.76 mm).
Figure 10.
Cross section of the virtual solid illustrating defects of the same diameter with different depths (0.94, 1.88, 2.82 and 3.76 mm).
Figure 11.
Image illustrating the thermal distribution on the sample obtained by the simulation at the time of the greatest thermal contrast.
Figure 11.
Image illustrating the thermal distribution on the sample obtained by the simulation at the time of the greatest thermal contrast.
Figure 12.
Analysis of the maximum thermal contrast behavior in relation to the depth of defects, with defects of 5, 10 and 15 mm diameter being evaluated.
Figure 12.
Analysis of the maximum thermal contrast behavior in relation to the depth of defects, with defects of 5, 10 and 15 mm diameter being evaluated.
Figure 13.
Inspection from the side opposite the defects: (a) top view of the virtual solid, (b) cut line for defects of 5 mm in diameter, (c) cut line for defects of 10 mm in diameter and (d) cut line for defects of 15 mm in diameter.
Figure 13.
Inspection from the side opposite the defects: (a) top view of the virtual solid, (b) cut line for defects of 5 mm in diameter, (c) cut line for defects of 10 mm in diameter and (d) cut line for defects of 15 mm in diameter.
Figure 14.
Image illustrating the thermal distribution of in the time of highest contrast, with inspection being performed on the opposite side of the defects.
Figure 14.
Image illustrating the thermal distribution of in the time of highest contrast, with inspection being performed on the opposite side of the defects.
Figure 15.
Evolution of absolute thermal contrast over time obtained by computational simulation for all defects contained in the sample (inspection performed on the opposite surface of the defects).
Figure 15.
Evolution of absolute thermal contrast over time obtained by computational simulation for all defects contained in the sample (inspection performed on the opposite surface of the defects).
Figure 16.
Absolute thermal contrast behavior for defects of: (a) 5 mm in diameter, (b) 10 mm in diameter and (c) 15 mm in diameter.
Figure 16.
Absolute thermal contrast behavior for defects of: (a) 5 mm in diameter, (b) 10 mm in diameter and (c) 15 mm in diameter.
Table 1.
Defects in samples S1, S2 and S3.
Table 1.
Defects in samples S1, S2 and S3.
Defects | S1 * | S2 * | Defects | S3 |
---|
Diam. (mm) | Depth (mm) | Diam. (mm) | Depth (mm) | Width (mm) | Length (mm) | Depth (mm) |
---|
hole 1 | 5.65 | 3.43 | 4.89 | 3.51 | notch 1 | 5.99 | 25.02 | 3.26 |
hole 2 | 5.56 | 2.46 | 4.98 | 2.46 | notch 2 | 5.96 | 24.99 | 3.15 |
hole 3 | 5.53 | 1.47 | 4.64 | 1.37 | notch 3 (star) | 51.25 | 52.22 | 0.05 |
Table 2.
Specifications of the coatings.
Table 2.
Specifications of the coatings.
Sample | Coating | Dry Coating Thickness (µm) |
---|
S1 | epoxy phenolic reinforced with glass flake | 582 ± 125 |
S2 | 670 ± 140 |
S3 | epoxy reinforced with ceramic flakes | 719 ± 33 |
Table 3.
Materials chosen to represent each sample component.
Table 3.
Materials chosen to represent each sample component.
Component | S1 | S2 | S3 |
---|
Substrate | Steel AISI 4340 |
Coating | Filled Epoxy Resin |
Defects | Fe3O4 | Fe3O4 | Air |
Table 4.
Remaining thickness values of the defects inserted in the virtual solid for inspection on the opposite surface.
Table 4.
Remaining thickness values of the defects inserted in the virtual solid for inspection on the opposite surface.
Defects |
---|
Diameter (mm) | Depth (mm) | Remaining Thickness (mm) |
---|
5 | 3.76 | 0.14 |
2.82 | 1.08 |
1.88 | 2.02 |
0.94 | 2.96 |
10 | 3.76 | 0.14 |
2.82 | 1.08 |
1.88 | 2.02 |
0.94 | 2.96 |
15 | 3.76 | 0.14 |
2.82 | 1.08 |
1.88 | 2.02 |
0.94 | 2.96 |
Table 5.
Maximum values of absolute thermal contrast of the defects present in the virtual solid, with inspection being carried out on the opposite side to the defects.
Table 5.
Maximum values of absolute thermal contrast of the defects present in the virtual solid, with inspection being carried out on the opposite side to the defects.
Defects | Maximum Absolute Thermal Contrast (°C) |
---|
Diameter (mm) | Remaining Thickness (mm) |
---|
5 | 0.14 | 0.97 |
1.08 | 0.16 |
2.02 | 0.05 |
2.96 | 0.03 |
10 | 0.14 | 3.09 |
1.08 | 0.52 |
2.02 | 0.20 |
2.96 | 0.06 |
15 | 0.14 | 5.56 |
1.08 | 1.02 |
2.02 | 0.38 |
2.96 | 0.11 |
Table 6.
Limit values for the remaining thickness of the defects for their detection, with inspection being carried out on the side opposite to the defects.
Table 6.
Limit values for the remaining thickness of the defects for their detection, with inspection being carried out on the side opposite to the defects.
Diameter of Defects (mm) | R2 | Equation | Minimum Thermal Contrast (y) | Remaining Thickness Required for Detection (x) |
---|
5 | 0.9461 | y = 0.836 × 10 −1.235x | 2 °C | Not detectable |
10 | 0.9832 | y = 3.0775 × 10 −1.364x | 2 °C | 0.32 mm |
15 | 0.9878 | y = 5.7002 × 10 −1.353x | 2 °C | 0.77 mm |