(2) 2642. H. Nishikawa, K. Seo, S. Katayama and T. Takemoto. Laser irradiation unit. Molten area, A / mm 2. Laser incident angle. Laser oscillator Sample. −. 1050 5052. 4. Defocus. YAG LASER. + distance. 2024 6063. 3003 7075. 4343. 3 2 1 0 -15. -10. -5. 0. 5. 10. 15. Defocus distance, d / mm. Fig. 1 Schematic diagram of experimental apparatus for laser irradiation method.. Fig. 2 Eﬀect of defocus distance on molten area by laser irradiation. ( ¼ 10 , E ¼ 5 kW 7 ms). 3.. Result and Discussion. Table 1 Experimental parameters for laser irradiation in this work. Defocus distance (mm): d. 15, 10, 5, 0, 5, 10, 15. Input energy (J): E Peak power (kW)Pulse width (ms) Laser incident angle (degree): . 5:0 7:0, 5:0 10:0, 7:0 5:0, 7:5 6:5 10, 20, 30, 40, 50. laser was used as the heat source to melt the surface of the sample. This laser beam is suitable for this experiment because it can partially melt the surface. Table 1 shows the experimental parameters for the laser irradiation. As shown in this table, the input energy, laser incident angle and defocus distance were varied. The eﬀect of these parameters on the surface morphology after irradiation was investigated to establish the appropriate conditions of laser irradiation for sorting aluminum alloys. After the surface of the sample was irradiated, the surface morphology was observed, including the molten area, brightness proﬁle and change in color. Then, the features of the morphology after laser irradiation were extracted for identifying the aluminum alloy numbers. Seven representative aluminum alloy samples were selected from seven wrought aluminum alloy series; 1050, 2024, 3003, 4343, 5052, 6063 and 7075. The basic properties of these aluminum alloys are summarized in Table 2. The size of all samples was 50 mm 50 mm 6 mm.. Table 2. Alloy number. 3.1 Melting of the aluminum alloy To establish the appropriate experimental conditions to identify the aluminum alloy, the eﬀect of laser irradiation conditions, such as defocus distance, input energy and laser irradiation angle on the surface morphology after laser irradiation was investigated. Firstly, the eﬀect of the defocus distance, which is the focus-to-sample distance as shown in Fig. 1, on the morphology of the irradiated area was investigated. The input energy was 5 kW 7 ms and the laser incident angle was 10 . The measuring results of the molten area for seven samples are shown in Fig. 2. For each sample, the molten area is quite diﬀerent according to defocus distance. On the focus point (the defocus distance is 0 mm), there isn’t a signiﬁcant diﬀerence in the molten area among alloys. On the other hand, the defocus distance of 15 mm gave the best results for identifying the diﬀerence in surface morphology after irradiation, because the molten areas signiﬁcantly diﬀers from each other under this distance compared to other defocus distances. Figure 3 shows examples of the irradiated area using the laser beam at the defocus distance of 0 mm [Fig. 3(a)] and 10 mm [Fig. 3(b)]. The aluminum alloy shown is 1050 alloy. It is clear that not only the molten area but also the surface morphology is quite diﬀerent according to the defocus distance. On the focus point, the surface of. Basic properties of test samples for this experiment. Nominal chemical composition (max or range, mass %). Alloy system Si. Cu. Mn. Mg. Zn. Al. Thermal conductivity (W/mK). Liquidus temperature (K). 1050. Al. 0.25. 0.05. 0.05. 0.05. 0.05. Bal.. 231. 930. 2024. Al–Cu. 0.5. 3.8–4.9. 0.3–0.9. 1.2–1.8. 0.25. Bal.. 193. 911. 3003. Al–Mn. 0.6. 0.05–0.2. 1.0–1.5. —. 0.1. Bal.. 193. 928. 4343. Al–Si. 11.0–13.5. 0.5–1.3. —. 0.8–1.3. 0.25. Bal.. 180. 886. 5052 6063. Al–Mg Al–Mg–Si. 0.25 0.2–0.6. 0.1 0.1. 0.1 0.1. 2.2–2.8 0.45–0.9. 0.1 0.1. Bal. Bal.. 138 218. 923 928. 7075. Al–Zn–Mg. 0.4. 1.2–2.0. 0.3. 2.1–2.9. 5.1–6.1. Bal.. 130. 908.
(3) Application of Nd:YAG Laser to Aluminum Alloy Sorting. 2643. (b). (a). Fig. 3 Eﬀect of defocus distance on surface morphology. (a) d ¼ 0 mm, (b) d ¼ 10 mm (Aluminum alloy: 1050, ¼ 10 , E ¼ 5 kW 7 ms). 6 1050 5052. 5. 2024 6063. 3003 7075. 1050 5052. 4343. 4 3 2 1. Molten area, A / mm2. Molten area, A / mm 2. 6. 5. 2024 6063. 3003 7075. 4343. 4 3 2 1 0. 0 5kW 7ms. 7kW 5ms. 5kW 7.5kW 10ms 6.5ms. Input energy, E / J Fig. 4 Eﬀect of input energy on molten area by laser irradiation. (d ¼ 15 mm, ¼ 10 ). irradiated area is extremely rough because of the high-power laser irradiation. The eﬀect of input energy, which is the product of the peak power and pulse width for laser output, was investigated next. The defocus distance was 15 mm and the laser incident angle was 10 . The measuring results of the molten area for the seven samples are shown in Fig. 4. The molten area for 7 kW 5 ms is larger than that for 5 kW 7 ms because of the stronger peak power. On the other hand, the molten area for 5 kW 10 ms is almost similar to that for 5 kW 7 ms, in spite of the longer pulse width. It is clear that peak power rather than pulse width has a larger eﬀect on the molten area. In view of the performance limitation for the laser oscillator, the input energy of 7:5 kW 6:5 ms gave the best results for identifying the diﬀerence of the surface morphology after irradiation. The eﬀect of the laser incident angle on the morphology of the irradiated area was investigated. The defocus distance was 15 mm and the input energy was 7:5 kW 6:5 ms. The measuring results of the molten area for the seven samples are shown in Fig. 5. Except for 1050 alloy, the molten area for each sample does not signiﬁcantly change according to laser incident angle. For the 1050 alloy, the mirror-like surface of the sample seems to reﬂect the laser beam when. 0. 10. 20. 30. 40. 50. Laser incident angle, θ /degree Fig. 5 Eﬀect of laser incident angle on molten area by laser irradiation. (d ¼ 15 mm, E ¼ 7:5 kW 6:5 ms). the laser incident angle is 30 , 40 and 50 . Figure 6 shows examples of the irradiated area for the laser incident angle of 10 [Fig. 6(a)] and 50 [Fig. 6(b)]. Aluminum alloy is 5052 alloy. At 10 , the shape of the irradiated area is almost round. At 50 , the shape becomes elliptical, although the molten area is almost similar according to the incident angle. So, it is clear that the laser incident angle of 10 gave the best results for identifying the diﬀerence of surface morphology after irradiation. Judging from the above results, the appropriate conditions of laser irradiation for sorting aluminum alloys in this study is as follows: defocus distance is 15 mm, input energy is 7:5 kW 6:5 ms and the laser irradiation angle is 10 . Figure 7 shows the surface morphologies after irradiation by the laser beam under these conditions. As shown in this ﬁgure, the size, the color and the shape of the molten area are diﬀerent among the samples. Therefore, depending on these diﬀerences, it is possible to identify the alloy number. These diﬀerences of the molten area seem to be caused mainly by the diﬀerences of the physical properties, such as the thermal conductivity and liquidus temperature, which depend on the chemical composition. Figure 8 shows the eﬀect of thermal conductivity on the molten area. The molten area surely trends to increase with the decrease of thermal conductivity. Figure 9 shows the eﬀect of the liquidus temperature on the.
(4) 2644. H. Nishikawa, K. Seo, S. Katayama and T. Takemoto. (a). (b). Fig. 6 Eﬀect of laser incident angle on surface morphology. (a) ¼ 10 , (b) ¼ 50 (Aluminum alloy: 5052 alloy, d ¼ 15 mm, E ¼ 5 kW 7 ms). 3003. 6. 2024. Molten area, A / mm2. 1050. 4343. 1050 5052. 5. 2024 6063. 3003 7075. 4343. 4 3 2 1 0 100. 150. 200. 250. Thermal conductivity, λ / W/m • K 5052. Fig. 8 Relationship between molten area and thermal conductivity. (d ¼ 15 mm, ¼ 10 , E ¼ 7:5 kW 6:5 ms). 6063. 7075. 1.0mm. Fig. 7 Surface morphology of each aluminum alloy sample after irradiation. (d ¼ 15 mm, ¼ 10 , E ¼ 7:5 kW 6:5 ms). Molten area, A / mm2. 6 1050 5052. 5. 2024 6063. 3003 7075. 4343. 4 3 2 1 0 880. 900. 920. 940. Liquidus temperature, T / K. molten area. The molten area trends to increase with the decrease of liquidus temperature. It is clear from these ﬁgures that there is a close relationship between the molten area and physical properties such as thermal conductivity and liquidus temperature. It was found that characteristic features could be extracted from each aluminum alloy by the laser irradiation method and the features could be used for the identiﬁcation of the aluminum alloy series. Therefore, in fact, it would be possible to sort the aluminum scraps according to the. Fig. 9 Relationship between molten area and liquidus temperature. (d ¼ 15 mm, ¼ 10 , E ¼ 7:5 kW 6:5 ms). aluminum alloy number by using the laser irradiation method. 3.2 Pattern matching method It is necessary to automatically sort the aluminum scraps when the sorting system is utilized commercially. Therefore, the investigation of a pattern-matching method using an.
(5) Application of Nd:YAG Laser to Aluminum Alloy Sorting. Brightness value. 300 200 100 0. Fig. 10 Brightness distribution of 1050 alloy in reference data.. image processing system was performed to establish an automated sorting system of mixed aluminum scraps. In this study, the brightness distribution reﬂected from the aluminum surface was used as comparative data for the patternmatching method. The brightness distribution, which represents the surface morphology, was described with 256 tones. After irradiation by the laser beam, the brightness distribution on the surface of seven samples (1050, 2024, 3003, 4343, 5052, 6063, 7075) was measured to the create referential data, di (d1 ; d2 ; d3 ; . . . ; di ; . . . ; dn ) where di indicated the brightness value of reference aluminum at position i, that was stored in a computer. For example, Fig. 10 shows the brightness distribution of 1050 alloy in the reference data. Seven unknown samples, which were called No. 1–No. 7, were prepared. In fact, No. 1 was 1050 alloy, No. 2 was 2024 alloy, No. 3 was 3003, No. 4 was 4343, No. 5 was 5052, No. 6 was 6063, and No. 7 was 7075. For the identiﬁcation of an unknown aluminum alloy, the surface was irradiated and the brightness distribution on the surface was measured and the unknown aluminum data was obtained, hi (h1 ; h2 ; h3 ; . . . ; hi ; . . . ; hn ) where hi indicated the brightness value of the unknown aluminum at position i. The brightness data of the unknown aluminum alloy was compared with the reference data stored in the computer. The diﬀerence between the reference data and the unknown aluminum data was computed as shown below, n 1X G¼ jdi hi j ð1Þ n i¼1 where G is the diﬀerence value. When the diﬀerence value is smallest, the unknown aluminum is approximately equal to. 2645. the aluminum alloy for the smallest reference data. The alloy number of unknown aluminum is determined. The diﬀerence values computed from eq. (1) are shown in Table 3. The table shows the correlation of the unknown sample data, No. 1–No. 7, with the reference data, 1050– 7075. The smallest value for the unknown sample numbers in a row corresponded to the reference data listed in the same row. In other words, the alloy number of the unknown aluminum alloy was decided. Actually, No. 1 ﬁts with 1050, No. 2 ﬁts with 2024, and so on. Therefore, the identiﬁcation of the unknown aluminum alloys was successfully performed. It was clear that the patter-matching method is useful for the identiﬁcation of aluminum alloys to automatically sort the mixed aluminum alloys. The basic feasibility of applying the laser irradiation method to automatic sorting system for aluminum scraps was investigated and satisfying results was obtained as described above. As the next step for using commercially, further investigation into irradiation-condition tolerance for sorting is required. On the other hand, in this study, new aluminum alloy samples were used for test samples. Actual aluminum scraps are only from used products. Aluminum scraps exist as irregularly shaped particles and the surface is contaminated by dirt, paint and abrasion. Therefore the eﬀect of the scrap shape and surface on the identiﬁcation accuracy is now being addressed. 4.. Conclusion. The investigation into the sorting system using the laser irradiation method was performed to sort aluminum scraps according to the aluminum alloy number. The results obtained in this work are summarized as follows. (1) The appropriate conditions of pulsed Nd:YAG laser for sorting aluminum alloys in this study are obtained aas the following: defocus distance is 15 mm, input energy is 7:5 kW 6:5 ms and laser irradiation angle is 10 . (2) When the surface of the aluminum is irradiated and melted by the laser beam, there is a signiﬁcant diﬀerence in the surface morphology depending on the physical properties. (3) The diﬀerences of the surface morphology after laser irradiation could be used to identify the aluminum alloy number, and it is possible to sort the aluminum alloys according to their alloy number. (4) It is found that the pattern-matching method is useful to automatically sort aluminum alloy scraps.. Table 3 Result of pattern matching for unknown samples. No. 4. No. 5. No. 6. 1050. No. 1 24:65. No. 2 80.86. No. 3 52.24. 52.41. 41.78. 47.03. No. 7 44.90. 2024. 90.24. 18:30. 107.22. 93.07. 65.13. 63.06. 87.02. 3003. 65.06. 101.83. 15:29. 29.47. 56.56. 60.70. 63.35. 4343. 67.22. 89.64. 32.82. 11:46. 40.59. 39.86. 62.21. 5052. 55.72. 57.37. 61.60. 42.48. 19:53. 22.07. 51.29. 6063. 54.04. 56.78. 65.85. 45.36. 22.03. 19:31. 51.27. 7075. 45.72. 64.69. 62.46. 55.51. 37.83. 36.25. 37:28.
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