Abstract:The paper presents a study on the surface modifications of nickel based superalloy Nimonic 263 induced by laser shock peening (LSP) process. The process was performed by Nd 3+ :Yttrium Aluminium Garnet (YAG) picosecond laser using the following parameters: pulse duration 170 ps; repetition rate 10 Hz; pulse numbers of 50, 100 and 200; and wavelength of 1064 nm (with pulse energy of 2 mJ, 10 mJ and 15 mJ) and 532 nm (with pulse energy of 25 mJ, 30 mJ and 35 mJ). The following response characteristics were analyzed: modified surface areas obtained by the laser/material interaction were observed by scanning electron microscopy; elemental composition of the modified surface was evaluated by energy-dispersive spectroscopy (EDS); and Vickers microhardness tests were performed. LSP processing at both 1064 nm and 532 nm wavelengths improved the surface structure and microhardness of a material. Surface morphology changes of the irradiated samples were determined and surface roughness was calculated. These investigations are intended to contribute to the study on the level of microstructure and mechanical properties improvements due to LSP process that operate in a picosecond regime. In particular, the effects of laser wavelength on the microstructural and mechanical changes of a material are studied in detail.

This paper presents the effects of laser light irradiation on the surface of ceramics dating from archaeological site Stubline (Obrenovac, Belgrade), Serbia. Two different pulsed lasers: TEA CO2 (10.6 ?m wavelength, pulse duration tp = 100 ns) and Nd:YAG (wavelengths 1064 nm and 532 nm, tp = 150 ps) have been used for surfaces treatment. Laser irradiation fluence was in the range of 1-20 J/cm2. Ceramics surface modifications induced by pulsed laser treatment were examined by scanning electron microscope, SEM, and the composition with energy dispersive X-ray, EDX, analysis. The tests were performed in order to obtain as much as possible information about the appropriate choice of materials and techniques for the further conservation and restoration of these items. The second objective was to determine the surface modifications induced by pulsed laser treatment above damage threshold (a safe cleaning laser fluence), as an important parameter in the use of lasers for the cleaning of cultural ceramic items. [Projekat Ministarstva nauke Republike Srbije, br. TR 34028 i br. TR 34022]

No abstract

No abstract

Textile samples with metallic threads from the collection of the Ethnographic Museum Belgrade were subjected to Nd:YAG laser irradiation in order to determinate certain parameters for successfully and safely clean corrosion products without degrading the surrounding material. Application of conventional cleaning methods did not give the expected results, and the implementation of laser technology was the next step. The Nd:YAG laser energy 150 mJ (1064 nm) and 50 mJ (532 nm) and pulse width 150 ps was used. The commercial, Thunder Art Laser was also used. Effects of the irradiated areas was investigated by optical and SEM microscopy and EDX analysis.

Primena lasera u čišćenju korozije na starim tekstilnim predmetima sa metalnim vezama Klаsične metode čišćenjа starih tekstilnih predmeta sа metаlnim nitimа često puta ne dаje očekivаne rezultаte. Primenа lаserа u zaštiti i konzervaciji predmetа kulturne bаštine poslednjih godinа ima veliku ulogu. Nаjkomplikovаnijа je primenа lаserа u čišćenju eksponаtа koji imаju višekomponentni sаstаv, kаo što su, kombinаcije metаl-tekstil. U rаdu se razmatra problem koji se pojavio u fundusu tekstila Etnografskog muzeja u Beogradu. Prikаzаni su rezultаti ispitivаnjа efekаtа lаserskog čišćenjа na eksperimentalnim uzorcima etnografskog tekstila sа metаlnim nitimа. korišćenjem Nd:Yag lаsera. Ispitivаnje efekаtа čišćenja je vršeno optičkom i skenirаjućom elektonskom mikroskopijom i EDX аnаlizom. Određeni su pаrаmetri zа uspešno i bezbedno čišćenje korozionih produkаtа nа metаlnim nitimа, nа izabranim eksponatima.

Nimonic 263 is an alloy with superior mechanical strength and creep resistance at high temperatures and pressure, good formability, and corrosion and oxidation resistance. Due to their high beam density and very short pulses which reduces the heat affected zone (HAZ) Nd:YAG lasers are very suitable for materials drilling. In this paper, the Nimonic 263 sheets, thickness of 2 mm, are laser drilled with various parameters. The influence of laser drilling process on microstructural changes along with the geometrical characteristics are analysed and discussed.

A multidisciplinary research method was employed with the intention to create a series of bio-inspired flattened airfoils, observe their aerodynamic characteristics, and analyse their applicability to small devices or to designs of high-speed trains, within the shortest period in the conceptual stage. A research specimen of a kingfisher, selected for biomimicry, was examined with the following methods: visual inspection, analysis of photographs, manufacturing quality control measurement with a 3D laser scanner, and microscopy. A basic multi-arc-line profile, re-engineered from the overlapped specimen shape data and based on the observations, was used for designing a series of seven derived airfoils. The aerodynamic characteristics of the bio-inspired airfoils were obtained with the panel methods at low and moderate subsonic speeds, while the small transonic difference method was used in the high-subsonic speed range. Basic and ellipse-like airfoils produce higher total drag at low and moderate velocities and higher forebody drag in the high-subsonic range when compared to derived and parabola-like airfoils. The obtained critical Mach numbers are in the range from 0.76 to 0.78, where three bionic airfoils show values equal to or smaller than the values of ellipse-and parabola-like airfoils. The profile with the shortest bio-inspired relative chord has a higher critical Mach number value than the parabola-like profile. The sonic lines above these profiles appear at close positions. The applied set of examination methods of the bio-inspired design is not time consuming and produces sufficiently good results in the conceptual stage. Therefore, a further development of unique and adjusted numerical methods and codes at pre-computational fluid dynamics run is encouraged, together with shape parameterization.