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- Miroshnikova, N., et al.
(author)
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Study of the interaction mechanisms between different materials and pulses from CO2- and Nd:YAG-lasers using digital speckle photography
- 2004
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In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5506, s. 42-50
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Journal article (peer-reviewed)abstract
- Pulsed irradiation from CO2- and Nd:YAG lasers focused on the front side of different plates produces nearly instantaneous surface changes on the rear side of the plate. The responses of the materials depend on physical parameters such as pulse energy and duration, photon energy, the absorption and mechanical characteristics of the target material. The equipment built up for visualization of these phenomena consists of a cw. He-Ne laser, a digital CCD camera and a fast computer. The analysis is done using Digital Speckle Photography (DSP). Using focused and defocused laser speckle patterns, DSP enables measurement of in-plane strain fields, Brownian motion and residual micro-structural changes in the material caused by a laser pulse. Results are obtained at the frame rate of the digital camera and allow the creation of animated real-time or "movie" sequences. Results from CO2- and Nd:YAG pulse interaction on Al2O3 ceramics and steel plates will be presented. The Brownian motion during the relaxation phase is more or less localized to the impacted area for both materials and both wavelengths but the relaxation times differ significantly. Steel also exhibits some residual material changes and doesn't recover completely while Al2O3 returns to its initial state some time after the impact
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- Yalukova, O., et al.
(author)
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Investigation of laser percussion hole drilling by use of speckle correlation
- 2005
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In: Applied Optics. - 1559-128X .- 2155-3165. ; 44:30, s. 6338-44
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Journal article (peer-reviewed)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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