scholarly journals Modification induced by laser irradiation on physical features of plastics materials filled with nanoparticles

2018 ◽  
Vol 167 ◽  
pp. 05008 ◽  
Author(s):  
Cristina Scolaro ◽  
Annamaria Visco ◽  
Lorenzo Torrisi ◽  
Nancy Restuccia ◽  
Eugenio Pedullà
Keyword(s):  
Laser Welding ◽  
Laser Irradiation ◽  
Welding Process ◽  
Polymeric Materials ◽  
Maximum Energy ◽  
Laser Wavelength ◽  
Wetting Ability ◽  
Thin Foils ◽  
Before And After ◽  
Physical Features

The Thermal Laser Welding (TLW) process involves localized heating at the interface of two pieces of plastic that will be joined. Polymeric materials of Ultra High Molecular Weight Polyethylene (UHMWPE), both pure and containing nanostructures at different concentrations (titanium and silver nanoparticles), were prepared as thin foils in order to produce an interface between a substrate transparent to the infrared laser wavelength and an highly absorbent substrate, in order to be welded by the laser irradiation. The used diode laser operates at 970 nm wavelength, in continuum, with a maximum energy of 100 mJ, for times of the order of 1 -60 s, with a spot of 300 μm of diameter. The properties of the polymers and of nanocomposite sheets, before and after the laser welding process, were measured in terms of optical characteristics, wetting ability, surface roughness and surface morphology.

Laser alloying of Cu and Cr

1986 ◽  
Vol 1 (5) ◽  
pp. 652-660 ◽  
Author(s):  
J.F.M. Westendorp ◽  
W. Koelewijn ◽  
W.G.J.H.M. van Sark ◽  
F.W. Saris ◽  
N.M. van der Pers ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Threshold Energy ◽  
Peak Shift ◽  
Laser Wavelength ◽  
Laser Alloying ◽  
X Ray Diffraction ◽  
X Ray ◽  
Before And After ◽  
Cu Substrates ◽  
The Individual

CuCr multilayers, 0.5−1 /um total thickness, on Cu substrates have been laser irradiated. Threshold energy densities for complete alloying with different laser wavelengths and different multilayer structures were determined using Rutherford backscattering. Results are discussed in terms of absorbance of Cu and Cr as a function of laser wavelength, overall chemical composition, and thicknesses of the individual Cu and Cr layers. Also, x-ray diffraction was used to study the microstructure of the CuCr before and after laser irradiation. A method is outlined for unraveling the contributions to peak shift of stacking faults, stresses, and change in'chemical composition. The CuCr alloy produced by the laser irradiation consisted of small, very defective Cu-rich and Cr-rich crystallites. The CuCr layer was subjected to a high tensile stress. The distinct change in preferred orientation of crystallites on laser irradiation indicated a complete melting of the CuCr multilayer. A high tensile strength (> 935 MPa) of the CuCr before and after laser alloying is suggested by the microstructure as observed by x-ray diffraction and sustained by hardness measurements. In the Cu-rich crystals 4.0 at. % Cr was in solid solution, i.e., five times the maximum equilibrium solid solubility.

scholarly journals CHARACTERIZATION OF PHOTODIODES FOR DETECTION OF VARIATIONS IN PART-TO-PART GAP AND WELD PENETRATION DEPTH DURING REMOTE LASER WELDING OF COPPER-TO-STEEL BATTERY TAB CONNECTORS

2021 ◽  
pp. 1-34
Author(s):  
Giovanni Chianese ◽  
Pasquale Franciosa ◽  
Jonas Nolte ◽  
Dariusz Ceglarek ◽  
Stanislao Patalano
Keyword(s):  
Laser Welding ◽  
Penetration Depth ◽  
Energy Intensity ◽  
Low Cost ◽  
Welding Process ◽  
Thin Foil ◽  
Supervised Machine Learning ◽  
Weld Penetration ◽  
Thin Foils ◽  
Remote Laser Welding

Abstract This paper addresses sensor characterization to detect variations in part-to-part gap and weld penetration depth using photodiode-based signals during Remote Laser Welding (RLW) of battery tab connectors. Photodiode-based monitoring has been implemented largely for structural welds due to its relatively low cost and ease of automation. However, research in sensor characterization, monitoring and diagnosis of weld defects during joining of battery tab connectors is at an infancy and results are inconclusive. Motivated by the high variability during the welding process of dissimilar metallic thin foils, this paper aims to characterize the signals generated by a photodiode-based sensor to determine whether variations in weld quality can be isolated and diagnosed. Photodiode-based signals were collected during RLW of copper-to-steel thin-foil lap joint (Ni-plated copper 300 μm to Ni-plated steel 300 μm). The presented methodology is based on the evaluation of the energy intensity and scatter level of the signals. The energy intensity gives information about the amount of radiation emitted during the welding process, and the scatter level is associated with the accumulated and un-controlled variations. Findings indicated that part-to-part gap variations can be diagnosed by observing the step-change in the plasma signal, with no significant contribution given by the back-reflection. Results further suggested that over-penetration corresponds to significant increment of the scatter level in the sensor signals. Opportunities for automatic isolation and diagnosis of defective welds based on supervised machine learning are discussed.

scholarly journals Visualization of laser back-reflection distribution during laser welding

2021 ◽  
Vol 1135 (1) ◽  
pp. 012015
Author(s):  
Petr Horník ◽  
Hana Šebestová ◽  
Jan Novotný ◽  
Libor Mrňa
Keyword(s):  
Laser Radiation ◽  
Laser Welding ◽  
High Speed ◽  
Partial Information ◽  
Welding Process ◽  
Laser Wavelength ◽  
Laser Source ◽  
High Speed Imaging ◽  
Additional Illumination ◽  
Welding Head

Abstract There are several approaches to weld quality monitoring during laser welding. Reflected laser radiation carries partial information about the welding process. Fibre lasers has usually a built-in diode to detect excessive back-reflected laser radiation to protect the laser source from damage. Reflected laser radiation measured in the laser source is compared with reflected laser radiation measured in the welding head. Moreover, coaxial high-speed imaging with a narrow bandpass filter on laser wavelength is used to visualize the reflected laser radiation. The advantage of this solution is that no additional illumination is needed and the reflected laser intensity and spatial distribution can be obtained from the image. Keyhole inlet dimensions are measured and related to the laser power. The transition between laser welding modes is studied.

Precise Absorbent ink Deposition and Optical Inspection System

2011 ◽  
Vol 1285 ◽  
Author(s):  
Andreas Willert ◽  
Joerg Lucas ◽  
Enrico Sowade ◽  
Christian Rahnfeld ◽  
Andreas Heilmann ◽  
...  
Keyword(s):  
Laser Welding ◽  
Laser Irradiation ◽  
Inkjet Printing ◽  
Continuous Wave ◽  
Welding Process ◽  
Inspection System ◽  
Dye Molecules ◽  
Optical Inspection ◽  
Thermal Welding ◽  
Optical Inspection System

ABSTRACTFoils from the ethylene-tetrafluoroethylene (ETFE) copolymer are used as transparent, humidity resistant and UV-stabile facade and roof coverings, e.g. for stadia, indoor swimming pools or greenhouses [1]. With pneumatically supported cushions, large translucent structures can be realized. Until now, they are assembled through a thermal welding process [2]. The development of welding techniques using laser irradiation is under way.Laser welding of transparent polymer foils requires an optical absorber placed in the interface between the two welding pairs. Usually, dye molecules with absorption properties adapted to the laser wavelength are used as absorbers. At a well-defined temperature, the dye molecules will be chemically modified, and transparent laser welding seams can be achieved. To get reproducible laser welding results, a homogenous layer of absorbent molecules or materials at the welding interface have to be realized, which is often very hard to achieve by wet deposition of dye molecules dispersed in a solution.In our contribution, we report on an inkjet printing system that can be mounted on a R2R manufacturing setup. The main challenge to this approach is to find the right ink that is compatible with this highly hydrophobic ETFE foil. Therefore, both the pretreatment of the substrate as well as the utilization of different inkjet technologies are dealt with in this contribution. It is demonstrated that the inkjet printing of a laser absorbent ink in a defined way onto the substrate is possible.For quality assurance, an optical inspection system has been developed to ensure a proper deposition of material. This ensures the quality control for the inkjet printing process of the special functional material. In that part the results of the comparison of the use of a dedicated 14‑bit grey level CCD line camera is compared to a high quality webcam.Laser irradiation of the foil with printed laser absorbent lines together with the untreated joining partner was performed by a continuous wave diode laser at a wavelength of 808 nm using a defocused laser spot. A nearly transparent welding seam was achieved. Mechanical tensile tests of the laser welding seams have demonstrated that their tensile strength is comparable to conventional thermal welding seams.

Photodiode-Based In-Process Monitoring of Part-to-Part Gap and Weld Penetration Depth in Remote Laser Welding of Copper-to-Steel Battery Tab Connectors

2021 ◽  
Author(s):  
Giovanni Chianese ◽  
Pasquale Franciosa ◽  
Jonas Nolte ◽  
Darek Ceglarek ◽  
Stanislao Patalano
Keyword(s):  
Laser Welding ◽  
Penetration Depth ◽  
Process Monitoring ◽  
Energy Intensity ◽  
Welding Process ◽  
Supervised Machine Learning ◽  
Dissimilar Metals ◽  
Weld Penetration ◽  
Thin Foils ◽  
Remote Laser Welding

Abstract This paper addresses in-process monitoring of part-to-part gap and weld penetration depth using photodiode-based signals during Remote Laser Welding (RLW) of battery tab connectors. Photodiode-based monitoring has been largely implemented for structural welds due to its relatively low cost and ease of automation. However, the application of photodiode-based monitoring to RLW of thin foils of dissimilar metals for battery tab connectors remains an unexplored area of research and will be addressed in this paper. Motivated by the high variability during the welding process of thin foils of dissimilar metals, this paper aims to evaluate the photodiode-based signals to determine if variations in weld quality can be isolated and diagnosed. The main focus is in diagnosing defective weld conditions caused by part-to-part gap variations and/or excessive weld penetration depth. Photodiode-based signals have been collected during RLW of copper-to-steel thin foils lap joint (Ni-plated copper 300 μm to Ni-plated steel 300 μm). The methodology is based on the evaluation of the energy intensity and scatter level of the signals. The energy intensity gives information about the amount of radiation emitted during the welding process, and the scatter level is associated to the accumulated and un-controlled variations. Findings indicated that part-to-part gap variations can be diagnosed by observing the step-change in the plasma signal, with no significant contribution given by the back-reflection. Results further suggested that over-penetration corresponds to significant increment of the scatter level in the sensor signals. Opportunities for automatic isolation and diagnosis of defective welds based on supervised machine learning will be discussed throughout the paper.

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