| 1. |
- Koh, Yang Sook, et al.
(författare)
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Surface cleaning of iron artefacts by lasers
- 2005
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Ingår i: Lasers in the Conservation of Artworks. - Berlin : Encyclopedia of Global Archaeology/Springer Verlag. - 9783540229964 ; , s. 95-100
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Konferensbidrag (refereegranskat)abstract
- In this paper the general method and ethics of the laser cleaning technique for conservation are presented. The results of two experiments are also presented; experiment 1 compares cleaning of rust by an Nd:YAG laser and micro-blasting whilst experiment 2 deals with removing the wax coating from iron samples by a TEA CO2 laser. The first experiment showed that cleaning with a pulsed laser and higher photon energy obtained a better surface structure than micro blasting. The second experiment showed how differences in energy density affect the same surface.
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| 2. |
- Miroshnikova, Natalia, et al.
(författare)
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Percussion hole drilling of metals with a fourth-harmonic Nd:YAG laser studied by defocused laser speckle correlation
- 2005
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165. ; 44:17, s. 3403-3408
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Tidskriftsartikel (refereegranskat)abstract
- Defocused speckle correlation is introduced as a tool for measuring the response in metal sheets during percussion laser drilling. For this procedure the fourth-harmonic Nd:YAG wavelength (266 nm) was used in pulsed mode. The method provides a cost-efficient and robust alternative to speckle interferometry for the study of the small deformations that appear during laser processing. The accuracy was shown to be of the order of a few tens of microradians for the tilt component that is measured, which translates to a few nanometers in deflection when the component is spatially integrated. In the measurements, deflections in the form of craters as large as 50 nm were detected on the back sides of silver and copper sheets. The diameters of the craters were 300 μm in the silver and 150 μm in the copper sheet; the output diameter of the hole was ~5 μm.
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| 3. |
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| 4. |
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| 5. |
- Sjödahl, Mikael, et al.
(författare)
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Laser hole drilling process studied using laser speckle correlation
- 2006
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Ingår i: Speckle06. - Bellingham, Wash. : SPIE - International Society for Optical Engineering. - 9780819464262 ; , s. 63412M-
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Konferensbidrag (refereegranskat)abstract
- This paper revisits defocused speckle correlation as a tool for measuring the response in metal sheets during percussion laser drilling processing. For the processing the 4th harmonic Nd:YAG wavelength (266 nm) was used in pulsed mode. It is shown that the method provides a cost efficient and robust alternative to speckle interferometry for the study of the small deformations that appear during laser processing. The accuracy was shown to be in the order of a few tens of μrads for the tilt component being measured which translates to a few nm in deflection when being spatially integrated. In the measurements deflections up to 50 nm was detected on the backside of silver and a copper sheet, respectively.
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| 6. |
- Yalukova, O., et al.
(författare)
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Investigation of interaction mechanisms in laser drilling of thermoplastic and thermoset polymers using different wavelengths
- 2006
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 66:10, s. 1289-1296
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a comparison of the percussion drilled holes in fiber reinforced polymer and non-reinforced thermoplastic sheets using three wavelengths, 1064, 532 and 266 nm is presented. At near infrared and visible wavelengths, 1064 and 532 nm, most of the bulk thermoplastic and thermoset polymers are partially transparent. The degree of transparency is dependent upon the degree of crystallinity. The most amorphous thermoplastics, such as PMMA have the highest transparency. In comparison, the fibre reinforced thermosets - graphite fibre reinforced epoxy - have low transparency. If the IR or visible laser beam is strongly focused, it can cause thermally induced degradation and sometimes burning and other damages (cracking, boiling, etc.) around the focused laser spot and the interaction zone. By using the fourth harmonics ultraviolet light (266 nm) of a diode-pumped and AOQ-switched Nd:YAG-laser with pulse duration of about 100 ns, the hole drilling process was significantly improved and the risk for thermal damage has been significantly reduced for both materials. Around the irradiated spot or drilled holes the material is influenced. This was investigated by both scanning electron microscopy and optical microscopy. There was clear evidence of a change in the interaction mechanism if UV light with high enough photon energy was used. By using UV light, bond breaking rather than thermal material removal occurred, i.e., a change from thermal to photo-chemical dissociation or photo-ablation becomes the dominant interaction mechanism.
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| 7. |
- Yalukova, O., et al.
(författare)
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Investigation of laser percussion hole drilling by use of speckle correlation
- 2005
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 44:30, s. 6338-44
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Tidskriftsartikel (refereegranskat)abstract
- In this paper speckle correlation is introduced as a tool to investigate the heat-influenced area during material processing with laser light. Two materials were investigated, a pure silver sheet and a sheet of SiC-diamond composite. The processing laser used in the experiments was a diode-pumped acousto-optical Q-switched Nd:YAG laser that allowed percussion hole drilling to be performed using green light through a second-harmonic crystal. The measurements were performed using a continuous-wave He-Ne laser and a digital camera. The experimental results show that the heat-influenced area is ~5000 times larger than the actual hole being drilled and that it reaches a steady-state condition toward the end of the processing cycle
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