Search results for "laser"
showing 10 items of 3161 documents
Numerical support for laser welding of zinc-coated sheets process development
2002
Abstract A lap welding process for zinc-coated sheets has been developed with the help of numerical simulations. This process has been improved and is now compatible with industrial requirements. The zinc boiling point (1180 K) is lower than the steel melting point (1800 K). Consequently, a violent boiling of zinc in melted steel produces serious defects in the seam. To get round this difficulty, we choose to consider a two-spots process: the first spot vaporizes the zinc coating at the interface; the second one welds the sheets. Previously, we develop a numerical model that permits a process parameters choice and limits the plan of experimentations. The zinc ablation spotlight shape is cho…
Improvement of flame spraying PEEK coating characteristics using lasers
2011
Flame spraying is frequently used for PEEK coatings elaboration on metallic surfaces. However, this process has a certain number of limitations particularly considering the quality of the coatings like high porosity or low interfacial adherence. For that reason a thermal post-processing is often necessary. From all of the processes which can be used (flame, oven, etc.), laser can be an interesting technology. Then, the aim of this study is to analyse the dependence of the morphological structure (compactness) and the adherence of the flame sprayed PEEK coatings to the stainless steel (304L) and aluminium alloy (AA2017) substrates on laser parameters. Moreover, the influence of the laser bea…
The Effect of Building Direction on Microstructure and Microhardness during Selective Laser Melting of Ti6Al4V Titanium Alloy
2021
AbstractDuring the last few years, additive manufacturing has been more and more extensively used in several industries, especially in the aerospace and medical device fields, to produce Ti6Al4V titanium alloy parts. During the Selective Laser Melting (SLM) process, the heterogeneity of finished product is strictly connected to the scan strategies and the building direction. An optimal managing of the latter parameters allows to better control and defines the final mechanical and metallurgical properties of parts. Acting on the building direction it is also possible to optimize the critical support structure. In particular, more support structures are needed for the sample at 0°, while very…
Optimization of spodumene identification by statistical approach for laser-induced breakdown spectroscopy data of lithium pegmatite ores
2021
Mapping with laser-induced breakdown spectroscopy (LIBS) can offer more than just the spatial distribution of elements: the rich spectral information also enables mineral recognition. In the present study, statistical approaches were used for the recognition of the spodumene from lithium pegmatite ores. A broad spectral range (280–820 nm) with multiple lines was first used to establish the methods based on vertex component analysis (VCA) and K-means and DBSCAN clusterings. However, with a view to potential on-site applications, the dimensions of the datasets must be reduced in order to accomplish fast analysis. Therefore, the capability of the methods in mineral identification was tested wi…
Laser beam scattering effects in non-absorbent inhomogenous polymers
2007
Ilie, Mariana Kneip, Jean-Christophe Mattei, Simone Nichici, Alexandru Roze, Claude Girasole, Thierry; In this paper a numerical model for laser beam scattering in the semi-transparent polymers is presented, using a Monte Carlo algorithm and the Mie theory. The algorithm correctly accounts for the independent multiply-scattered light. We describe the algorithm, present a number of important parameters that account in the welding process, and explicitly show how the algorithm can be used to estimate the laser beam intensity both inside the semi-transparent component and at the welding interface and the beam widening. For the model validation an experimental bench test has been realized and s…
Modelling nanoparticles formation in the plasma plume induced by nanosecond pulsed lasers
2012
International audience; Nanoparticles formation in a laser-induced plasma plume in the ambient air has been investigated by using numerical simulations and physical models. For high irradiances, or for ultrashort laser pulses, nanoparticles are formed by condensation, as fine powders, in the expanding plasma for very high pairs of temperature and pressure. At lower irradiances, or nanosecond laser pulses, another thermodynamic paths are possible, which cross the liquid-gas transition curve while laser is still heating the target and the induced plasma. In this work, we explore the growth of nanoparticles in the plasma plume induced by nanosecond pulsed lasers as a function of the laser irra…
Synthesis and physico-chemical characterization of Au/TiO2 nanostructures formed by novel "cold" and "hot" nanosoldering of Au and TiO2 nanoparticles…
2011
Abstract A novel approach to synthesize Au/TiO2 nanostructures with interesting optical properties is presented and discussed. It is based on the nanoparticle “cold” or “hot” nanosoldering occurring when two water suspensions of Au and TiO2 nanoparticles are merely mixed at room temperature or laser irradiated after mixing. Thanks to the high fraction and mutual reactivity of surface species, immediately after the mixing process, the encounters between Au and TiO2 nanoparticles in liquid phase are enough for “cold” nanosoldering of gold nanoparticles onto TiO2 nanoparticles to occur. The optical characterizations show that this fast process (timescale less than 1 min) is followed by a slowe…
Cell and tissue response to nanotextured Ti6Al4V and Zr implants using high-speed femtosecond laser-induced periodic surface structures
2019
In this paper, the effect of femtosecond laser nanotexturing of surfaces of Ti6Al4V and Zr implants on their biological compatibility is presented and discussed. Highly regular and homogeneous nanostructures with sub-micrometer period were imprinted on implant surfaces. Surfaces were morphologically and chemically investigated by SEM and XPS. HDFa cell lines were used for toxicity and cell viability tests, and subcutaneous implantation was applied to characterize tissue response. HDFa proliferation and in vivo experiments evidenced the strong influence of the surface topography compared to the effect of the surface elemental composition (metal or alloy). The effect of protein adsorption fro…
Infrared pulsed laser deposition of niobium nitride thin films
2011
We have successfully fabricated superconducting niobium nitride thin films on single crystals of magnesium oxide using a pulsed laser deposition technique where 1064 nm (photon energy ~1.16 eV) laser pulses from an Nd:YAG laser were used for ablation. A correlation between the superconducting transition temperature, the nitrogen base pressure during deposition and the lattice parameter of the produced NbN films was observed. Superconductor-insulator-normal metal junctions fabricated using these NbN films as the superconductor revealed nonlinear electrical characteristics at 4.2 K associated with quasiparticle tunneling.
Use of pure vanadium and niobium/copper inserts for laser welding of titanium to stainless steel
2020
Abstract Niobium and vanadium have high metallurgical compatibility with titanium and therefore can be used as inserts to avoid the accumulation of brittle intermetallic phases such as Fe2Ti during the fusion welding of titanium alloys with steels. In the present study, the continuous double pass welding of 1 mm thick Ti-6Al-4V alloy and 316 L stainless steel plates through several mm wide pure vanadium or niobium insert was studied. In case of a vanadium insert, a beam offset on the vanadium was found to produce cold crack formation in vanadium/316 L melted zones containing more than 40 wt.% V despite the absence of σ phase. Whereas a centered beam position and offset on the steel side pro…