Author Affiliations
1School of Mechanical Engineering, Shenyang University of Technology, Shenyang 110870, Liaoning, China2Key Laboratory of Numerical Control Manufacturing Technology for Complex Surfaces of Liaoning Province, Shenyang 110870, Liaoning, Chinashow less
Fig. 1. Laser cleaning platform. (a) Principle diagram of laser cleaning; (b) experimental equipment for laser cleaning; (c) scanning electron microscope; (d) confocal laser microscope; (e) ultra-depth-of-field microscope; (f) laser cleaning test bench for pipe thread
Fig. 2. Surface morphologies of rust layer. (a) Macro-morphology of petroleum pipe thread; (b) micro-morphology of peeling layer easy to fall off in rust layer; (c) micro-morphology of dense layer; (d) element content distribution of rust layer
Fig. 3. Thread surface after laser cleaning. (a) Overall morphology; (b) local amplification at A′
Fig. 4. Sample after wire cutting
Fig. 5. Micro-morphologies under different laser powers. (a) 600 W; (b) 550 W; (c) 500 W; (d) 450 W; (e) 400 W
Fig. 6. Surface roughnesses under different laser powers
Fig. 7. Contents of oxygen elements under different laser powers
Fig. 8. Micro-morphologies under different defocusing amounts. (a) +4 mm; (b) +3 mm; (c) +2 mm; (d) +1 mm; (e) 0 mm
Fig. 9. Surface roughnesses under different defocusing amounts
Fig. 10. Contents of oxygen elements under different defocusing amounts
Fig. 11. Micro-morphologies under different scanning speeds. (a) 3000 mm/s; (b) 2500 mm/s; (c) 2000 mm/s; (d) 1500 mm/s; (e) 1000 mm/s
Fig. 12. Surface roughnesses under different scanning speeds
Fig. 13. Contents of oxygen elements under different scanning speeds
Fig. 14. Residual plot of mathematical model
Fig. 15. Flow chart of improved particle swarm algorithm
Fig. 16. Convergence curves of two algorithms
Fig. 17. Contents of elements after cleaning under optimized process parameters
Fig. 18. Molten pool morphology after cleaning under optimized process parameters
Parameter | Value |
---|
Wavelength /nm | 1064 | Laser power /W | ≤1000 | Pulse width /ns | 100 | Frequency /kHz | ≤100 | Scanning speed /(mm·s-1) | ≤3000 | Spot diameter /mm | 0.05 |
|
Table 1. Main parameters of pulsed lasers
Level | Laser power /W | Scanning speed /(mm·s-1) | Defocusing amount /mm |
---|
Level 1 | 400 | 3000 | +4 | Level 2 | 450 | 2500 | +3 | Level 3 | 500 | 2000 | +2 | Level 4 | 550 | 1500 | +1 | Level 5 | 600 | 1000 | 0 |
|
Table 2. Orthogonal test level and parameters
Experiment No. | Laser power /W | Scanning speed /(mm·s-1) | Defocusing amount /mm | Surface roughness /μm |
---|
1 | 600 | 3000 | +4 | 9.13 | 2 | 600 | 2500 | +3 | 8.84 | 3 | 600 | 2000 | +2 | 8.23 | 4 | 600 | 1500 | +1 | 9.27 | 5 | 600 | 1000 | 0 | 11.82 | 6 | 550 | 3000 | +3 | 8.21 | 7 | 550 | 2500 | +2 | 7.62 | 8 | 550 | 2000 | +1 | 8.13 | 9 | 550 | 1500 | 0 | 8.44 | 10 | 550 | 1000 | +4 | 7.42 | 11 | 500 | 3000 | +2 | 6.53 | 12 | 500 | 2500 | +1 | 7.14 | 13 | 500 | 2000 | 0 | 7.37 | 14 | 500 | 1500 | +4 | 8.83 | 15 | 500 | 1000 | +3 | 5.44 | 16 | 450 | 3000 | +1 | 8.25 | 17 | 450 | 2500 | 0 | 7.67 | 18 | 450 | 2000 | +4 | 7.39 | 19 | 450 | 1500 | +3 | 6.64 | 20 | 450 | 1000 | +2 | 6.92 | 21 | 400 | 3000 | +1 | 7.81 | 22 | 400 | 2500 | +4 | 8.27 | 23 | 400 | 2000 | +3 | 7.23 | 24 | 400 | 1500 | +2 | 6.44 | 25 | 400 | 1000 | 0 | 10.41 |
|
Table 3. Experimental data
Level | Laser power | Scanning speed | Defocusing amount |
---|
Level 1 | 9.458 | 7.986 | 8.208 | Level 2 | 7.964 | 7.908 | 7.388 | Level 3 | 7.062 | 7.670 | 7.148 | Level 4 | 7.374 | 7.924 | 8.120 | Level 5 | 8.032 | 8.402 | 9.142 | Range | 2.396 | 0.732 | 1.994 |
|
Table 4. Range analysis table
Experiment No. | Laser parameter | Surface roughness /μm |
---|
Laser power /W | Defocusing amount /mm | Scanning speed /(mm·s-1) |
---|
1 | 500 | 2 | 2000 | 5.77 | 2 | 450 | 2 | 1500 | 6.26 | 3 | 500 | 2 | 2000 | 6.36 | 4 | 450 | 3 | 2000 | 5.14 | 5 | 500 | 2 | 2000 | 5.82 | 6 | 500 | 2 | 2000 | 5.44 | 7 | 450 | 2 | 2500 | 5.61 | 8 | 500 | 1 | 1500 | 6.14 | 9 | 550 | 2 | 1500 | 6.38 | 10 | 500 | 1 | 2500 | 7.14 | 11 | 500 | 3 | 2500 | 5.25 | 12 | 550 | 2 | 2500 | 7.62 | 13 | 500 | 3 | 1500 | 4.85 | 14 | 450 | 1 | 2000 | 6.75 | 15 | 550 | 1 | 2000 | 8.13 | 16 | 500 | 2 | 2000 | 5.74 | 17 | 550 | 3 | 2000 | 6.65 |
|
Table 5. Experimental design matrix
Source | Sum of squares | Degree of freedom | Mean square | F value | P value | Reliability |
---|
Model | 11.90 | 9 | 1.32 | 15.43 | 0.0008 | Significant | A | 3.15 | 1 | 3.15 | 36.75 | 0.0005 | | B | 4.91 | 1 | 4.91 | 27.34 | 0.0001 | | C | 0.50 | 1 | 0.50 | 5.78 | 0.0472 | | AB | 4.225×10-3 | 1 | 4.225×10-3 | 0.049 | 0.8306 | | AC | 0.89 | 1 | 0.89 | 10.42 | 0.0145 | | BC | 0.09 | 1 | 0.09 | 1.05 | 0.3396 | | A2 | 2.26 | 1 | 2.26 | 26.32 | 0.0014 | | B2 | 0.05 | 1 | 0.05 | 0.59 | 0.4679 | | C2 | 0.034 | 1 | 0.034 | 0.40 | 0.5460 | | Residual | 0.60 | 7 | 0.086 | | | | Lack of fit value | 0.16 | 3 | 0.052 | 0.47 | 0.7347 | Not significant | Pure error | 0.44 | 4 | 0.11 | | | | Total | 12.50 | 16 | | | | | =0.7458 | =0.8903 | | | | R=13.734 | | | |
|
Table 6. Analysis of model variance