1,721,059 research outputs found
Laser micro-welding of high carbon steels [Microsaldatura laser di acciai ad elevato tenore di carbonio]
No full textHigh carbon steels are commonly used in modern mechanical industry due to their good mechanical properties and to their relatively low cost. Unfortunately, when dealing with welding processes, these materials must be set aside because of their very high crack susceptibility and more refined and expensive steels must be taken into consideration, such as HSLA, DP and TRIP ones, thanks to their lower carbon equivalent and similar, or even better, mechanical properties. In micro-scale components industry the use of high carbon steels is also very common, in particular in precision mechanics, watch and MEMS industry. Considering the very low thicknesses typical of these components and the intrinsic welding difficulty related to the material, several studies stressed on the possibility to exploit nanosecond pulsed lasers in welding this kind of steels. These sources, taking advantage from the short duration of the pulse and from a repetition rate as high as I MHz, allow a very accurate control of the heat input delivered to the material and pave new ways in micro-welding of medium and high carbon steels. The present paper deals with the exploitation of a 20 W nanosecond pulsed laser source in welding low thickness C70 (AISI1070) plain carbon steel. The process is studied by evaluating the influence of the main parameters on its feasibility. The activity pointed out that, by properly selecting the main parameters, it is possible to achieve sound and crack-free weld beads with a maximum penetration as high as 200 μm and a very small heat affected zone. The main interesting point concerning this specific welding process is related to the fact that, by simply selecting the proper process parameters, it is possible to achieve high productivity working cycles involving laser cutting, welding and marking on the same machine and exploiting the same workpiece positioning
Long Pulse Laser Wire Deposition of Hard Steels
No full textAbstractLaser deposition of hard steel wires on martensitic stainless steel substrates has been investigated in order to evaluate the possibility of performing localized mold repairs. An experimental campaign has been carried out to assess the role of the deposition strategy and process parameters such as pulse duration, peak power and frequency on process outcome. The extent of the dilution layer between the substrate and deposited track, as well as tempering effects due to the mutual interaction between tracks and layers, are studied as functions of process parameters in order to assess the characteristics of the deposited tracks. In particular, it is observed that under suitable conditions hard (HV>550) deposits can be achieved with minimal tempering effects even in the case of multiple tracks and layers
Environmental Impact, Mechanical Properties, and Productivity: Considerations on Filler Wire and Scanning Strategy in Laser Welding
Full text linkSustainability, as well as high-quality outcomes, pose significant challenges within the context of current manufacturing cycles, in alignment with European strategies aimed at decarbonization. This framework encourages a systematic evaluation of manufacturing processes in terms of their performance and carbon footprint. One sector where this is particularly relevant is the production of batteries for electric mobility, thanks to its exponential growth. Out of all the processes involved, laser welding stands out as being a critical step since it offers potential energy savings through optimization. With the dual goals of achieving mechanical strength and environmental sustainability, this study investigates alternative solutions for laser welding of aluminium sheets.
Different laser welding configurations are tested to evaluate the effect of process setups on weld quality and carbon emissions across different productivity scenarios.
The key findings can be summarized as follows: (1) the selection of welding setup significantly influences both quality and sustainability requirements; (2) the optimal conditions for meeting strength requirements may diverge from those aimed at minimizing environmental impact; (3) the choice of the final solution is influenced by the specific industrial scenario. The study specifically demonstrated that aluminium alloys can be welded with higher quality (porosity below 1% and Equivalent Ultimate Strength up to 204 MPa) when filler wire is introduced alongside an active wobbling scanning strategy. Conversely, filler wire can be omitted in scenarios prioritizing high-productivity and low-carbon emissions, such as when employing a linear scanning strategy, resulting in a reduction of equivalent carbon emissions by up to 140%.Sustainability, as well as high-quality outcomes, pose significant challenges within the context of current manufacturing cycles, in alignment with European strategies aimed at decarbonization. This framework encourages a systematic evaluation of manufacturing processes in terms of their performance and carbon footprint. One sector where this is particularly relevant is the production of batteries for electric mobility, thanks to its exponential growth. Out of all the processes involved, laser welding stands out as being a critical step since it offers potential energy savings through optimization. With the dual goals of achieving mechanical strength and environmental sustainability, this study investigates alternative solutions for laser welding of aluminum sheets. Different laser welding configurations are tested to evaluate the effect of process setups on weld quality and carbon emissions across different productivity scenarios. The key findings can be summarized as follows: (1) the selection of welding setup significantly influences both quality and sustainability requirements; (2) the optimal conditions for meeting strength requirements may diverge from those aimed at minimizing environmental impact; (3) the choice of the final solution is influenced by the specific industrial scenario. The study specifically demonstrated that aluminum alloys can be welded with higher quality (porosity below 1% and equivalent ultimate strength up to 204 MPa) when filler wire is introduced alongside an active wobbling scanning strategy. Conversely, filler wire can be omitted in scenarios prioritizing high-productivity and low-carbon emissions, such as when employing a linear scanning strategy, resulting in a reduction of equivalent carbon emissions by up to 140%
Characterization and process optimization of remote laser cutting of current collectors for battery electrode production
Full text linkAluminum (Al) and copper (Cu) metal foils of thickness 6-20 mu m are employed as current collectors for the production of Li-ion battery cathodes and anodes. Greater demand for this product is driving up production rate requirements, especially in the field of car manufacturing. Laser-based cutting processes for trimming and cutting electrodes are considered suitable for meeting this demand as they can achieve very high throughput while maintaining process quality. In order to meet market requirements, laser manufacturers are developing new laser sources, optics, and scanning heads that will improve process productivity and quality. Establishing the relationship between the laser system and cut quality will lead to competitiveness, increased productivity, and sustainability production. This paper presents a thorough analysis of the cutting performance of pulsed and continuous-wave lasers with scanning speeds of up to 28 m/s for processing thin Al and Cu current collectors. Comparisons between process outcomes are made in terms of maximum and minimum cutting speed and power, kerf geometry, cut quality, and presence of defects. Identification of configurations leading to high and low cut quality enables detailed process parameter windows to be defined for both laser system systems employing continuous-wave and pulsed sources. By analyzing correlations between the materials, laser source, and process variables, the main outcome is that continuous-wave single-mode fiber lasers enable highest cut quality in the high-productivity regime, surpassing the current state-of-the-art in laser cutting of metal foils
Analysis of process parameters, deposition strategies and build orientations in wire-arc additive manufacturing (WAAM)
No full textAdditive manufacturing (AM) has transitioned from prototyping to commercialization in many industrial sectors. In addition,
direct energy deposition (DED) processes are enabling the AM for large-scale depositions. One such DED process is wire-arc
additive manufacturing (WAAM), popular for its high deposition rates. The influence of process parameters and deposition
strategies play a vital role in the WAAM process. Therefore, in the first part of this study, a response surface methodology
(RSM) was employed based on a central composite design (CCD) for bead-on-plate analysis to understand the effects of
process parameters on bead morphologies and material hardness. Similarly, for the second part of the study, different deposition
strategies were employed for test wall depositions to analyse their effects on built structures. Particularly, the effects of
layer-stacking on 10-layer and 20-layer walls were analysed in detail. Finally, employing an optimised deposition strategy,
cubic samples were deposited with various deposition parameters based on a 2
K factorial design. Hardness, microstructural
and SEM analysis were performed for in-depth analysis of the samples. Results revealed a strong relationship between
process parameters (current and travel speed) versus bead characteristics and material hardness. The deposition strategies
significantly influenced the built structure and wall formation. Similarly, layer-stacking played a critical role for mechanical
properties of deposited samples. Cubic structures demonstrated small anisotropy for microstructural results based on various
parameter settings. Similarly, small discrepancies were observed in the hardness results
Rotations from a New Perspective: Experiments, Modelling and Analogies Based on Angular Momentum as an Extensive Quantity
No full textConcepts and mathematical instruments used in elementary mechanics are often perceived as abstract entities by students. We propose therefore an approach to the description of rotational mechanical processes based on a conceptualization of angular momentum grounded on image schemes and analogies from common everyday experience (Fuchs, 2007). In our approach angular momentum is described as a conserved extensive quantity, whose balance equation is either an instrument to foster clear mental images of rotational processes, or a solid base for algebraic development. Exploiting analogies, in this work we show how this way angular momentum can be stored in rotating bodies, how their moment of inertia represents their angular momentum capacities, and finally how a torque applied to a rotating body can be imagined as an angular momentum flow.
We analyse from this point of view three experiments, using on-line data acquisition and dynamical modelling. The use of analogies allows indeed to develop dynamical models in a wide range of contexts, able to strengthen basic concepts and discuss phenomena in relation with the initial conditions and the parameter values
High speed laser cutting of ultrathin metal foils for battery cell production
No full textLaser-based manufacturing has become a key enabling technology in the production of batteries and battery cells for the e-mobility field. Several applications, in fact, have already been industrialized, such as laser-based welding, cutting, stripping, and cleaning. Among all those technologies, laser cutting, in particular, has to deal with several very stringent constraints: the presence of highly reflective materials (aluminum and copper), very low thicknesses (6-12 mu m), on-the-fly processing, and high quality of the cutting surface. According to those considerations, the present paper deals with the application of remote cutting of 12 mu m thick aluminum and 6 mu m thick copper foils by means of a galvo scanner and two different fiber laser sources: single mode constant wave and nanosecond pulsed wave ones. The experimental activity is devoted to understanding the feasibility of the process and to point out the pros and cons of the two different lasers involved. The cutting edges are analyzed by means of optical and SEM microscopy, in order to characterize cutting quality. The process is also characterized in terms of maximum achievable speed in order to understand the limits of both lasers and galvo scanning systems
Dissimilar laser welding of high-thickness Cu/Al plates for high-current density electrical batteries
Full text linkElectrical batteries connecting is a crucial phase in the fabrication of electrical vehicles. It is usually performed using high-quality lasers focused
on narrow spot, to overcome the low optical absorptivity of copper and/or aluminum and displaced with high-speed scanner to accomplish the
production rate. In applications where the current density is high (naval, heavy transport, etc) the busbars used for the electrical connections are
thick (0.8-1 mm) increasing the difficulties of having joints with no defects. In this paper, an in-depth analysis of the impact of laser power,
welding speed, and innovative scanning strategy on joint quality is presented for lap welding of nickel-plated copper (0.8 mm) to AA1050 alloy
(3 mm). Process optimization involves achieving the desired weld area while controlling metal-mixing indices to limit the formation of brittle
intermetallic compounds, cracks and voids. Weld joint quality assessment, including metallographic examination, microhardness tests and SEM-
EDX analysis is presented and discusse
Experimental investigation on the effect of spot diameter on continuous-wave laser welding of copper and aluminum thin sheets for battery manufacturing
Full text linkWelding of dissimilar materials, particularly copper and aluminum alloys, has gained considerable industrial interest in many different electric and electronic fields, such as the production of lithium-ion batteries for automotive applications. The differences in physical and chemical properties of these materials make fusion welding processes difficult to apply due to the formation of hard and brittle intermetallic compounds that impair both mechanical and electrical performance. In this paper, the effect of spot diameter on dissimilar laser autogenous lap-welding of copper and aluminum was studied. Experiments were conducted using a mid-power fiber laser source equipped with a galvo scanner and two different focal lengths to obtain two different spot diameters. The results showed that a smaller spot diameter promoted the formation of sound weld beads with better control of penetration depth, reduced mixing of the base metals and lower laser power requirements. By selecting the correct process parameters, good mechanical properties and low contact resistance could be obtained with both focal lengths. SEM-EDX analysis confirmed that a smaller spot diameter minimized the formation of copper rich phases in the weld bead
The effect of process parameters on the morphology, mechanical strength and electrical resistance of CW laser-welded pure copper hairpins
No full textManufacturing of high-performance electric motors has become a key industrial goal over recent years due to increasing demand for electrification, in particular in the automotive field. The use of windings comprising pure copper conductors with a rectangular cross section allows the overall performance of electric motors to be increased. In the present work, the influence of processing parameters on weld quality for joining of copper hairpins with near-infrared laser irradiation performed with a specific welding path. After determining a feasible operating window, the effect of process parameters on fusion zone morphology, presence of pores and mechanical and electrical properties was investigated. The results showed that high power and high welding speed lead to joints characterized by less than 1 % pores. A maximum tensile load of 490 N was achieved during tensile tests performed on specimens obtained with optimized welding parameters, with fracture taking place in the heat affected zone (HAZ). Micro-hardness profiles confirmed slight softening near the HAZ, corresponding to a reduction in mechanical strength in this region. Electrical tests highlighted a correlation between mechanical properties and the electrical resistance of the connection
- …
