For a class of systems of nonlinear and nonlocal balance laws in several space dimensions, we prove the local in time existence of solutions and their continuous dependence on the initial datum. The ...choice of this class is motivated by a new model devoted to the description of a metal plate being cut by a laser beam. Using realistic parameters, solutions to this model obtained through numerical integrations meet qualitative properties of real cuts. Moreover, the class of equations considered comprises a model describing the dynamics of solid particles along a conveyor belt.
The study on the roughness of Hardox cut laser parts is exploited in this article ranging from input parameters (laser power, pressure, cutting speed) to a Taguchi reduced to 9 references and then ...replicated under the same conditions 4 times. For the experiment, a fractional factorial plan L339 was chosen for three experimental parameters (P, v, p), each varied at 3 distinct levels. The blank used was HARDOX400 steel sheet with a thickness of 10 mm. This thickness is suitable for the study of several parameters that characterize the quality of laser cut parts: slot width, taperedness, flange roughness, dimensional precision. With the help of Statistica 7, the prediction and correlation formula of the influence factors were highlighted. DOE and SSM were used to obtain roughness while maintaining a constant parameter - laser power and simultaneously varying the pressure and cutting speed. It is found that pressure is a dominant influence factor.
•Laser cutting studies with a short focus head were performed on stainless steel plates.•The cutting experiments were performed at both constant speed and two-step speed cutting.•Cuts up to a ...thickness of 60 mm were achieved with a cutting capability of ∼10 mm/kW.•The kerf widths for all conditions were narrow within 2 mm.
The cutting studies conducted on stainless steel plates with thicknesses of 10–60 mm using a short focus head and a high power fiber laser to evaluate application to nuclear decommissioning. The cutting performance was evaluated by determining the maximum cutting speed for each plate thickness and laser power. Both constant speed cutting and two-step speed cutting were experimentally performed. For a thickness of 10 mm, constant speed cutting had the better performance. On the other hand, two-step speed cutting achieved faster cutting for thicknesses greater than 10 mm. Even with a short focus head, cuts up to a thickness of 60 mm were achieved with a laser power of 6 kW, which corresponds to a cutting capability of ∼10 mm/kW. Kerf widths, which indicate the amount of secondary waste, were also measured in addition to maximum cutting speeds. Although there were some differences according to cutting conditions, all the kerf widths were narrow, within 2 mm.
Ultra high strength steels provide opportunities for reduced-weight designs since they have higher tensile and fatigue strengths than the conventional mild steel grades. For typical applications such ...as telescopic cranes, tippers, chassis, and agricultural machinery, lower weight leads to lower fuel consumption and better road homologation. Before the start of their service life, steel components must be machined to their final shape as they are supplied in standardized shapes and sizes. Mechanical and thermal cutting strategies invoke various physical phenomena within the cut material affecting the in-use properties. The objective of this study is to quantify the effect of hole-making processes and edge-preparation on fatigue performance of ultra high strength steels. A series of fatigue experiments were conducted on steel grades with yield strengths from 700 to 960 MPa using axially loaded coupon samples with a hole manufactured by punching and laser cutting. Fatigue performance is compared to the detail categories provided by design standards. Additional tests under four-point bending loading were conducted to focus on flat edges machined by laser cutting and milling. Especially at high-cycle and infinite-fatigue lives, tested grades were superior to the typical design curves when the holes were punched with low clearance or laser cut.
This article addresses a critical issue, which has been overlooked, in relation to the design of phase-correcting structures (PCSs) for electromagnetic bandgap (EBG) resonator antennas (ERAs). All ...the previously proposed PCSs for ERAs are made using either several expensive radio frequency (RF) dielectric laminates or thick and heavy dielectric materials, contributing to very high fabrication cost, posing an industrial impediment to the application of ERAs. This article presents a new industrial-friendly generation of PCS, in which dielectrics, known as the main cause of high manufacturing cost, are removed from the PCS configuration, introducing an all-metallic PCS (AMPCS). Unlike existing PCSs, a hybrid topology of fully metallic spatial phase shifters are developed for the AMPCS, resulting in an extremely lower prototyping cost as that of other state-of-the-art substrate-based PCSs. The APMCS was fabricated using laser technology and tested with an ERA to verify its predicted performance. The results show that the phase uniformity of the ERA aperture has been remarkably improved, resulting in 8.4 dB improvement in the peak gain of the antenna and improved sidelobe levels (SLLs). The antenna system including APMCS has a peak gain of 19.42 dB with a 1 dB gain bandwidth of around 6%.
•Simulation of CO2 laser cutting of polycarbonate injected sheets by the DOE approach.•Developing governing equations on thermal fields and boundary conditions.•of the heat source by selecting of an ...appropriate Gaussian distribution.•Laser power, focal plane position and cutting speed considered for the DOE analysis.•Optimizing the laser cutting simulation process.
Laser cutting well-known as a manufacturing process is a rapid, repeatable, and reliable method that is frequently used for cutting various materials such as thermoplastics. Due to their physical and chemical properties such as fatigue resistance, high toughness, and re-melting properties, thermoplastics such as polycarbonate are widely used in automotive parts, electronics, etc. In this study, a numerical simulation of the laser cutting process by a finite element method is developed. The sample simulated in this research is a 3.2 mm thick Polycarbonate sheet that is subjected to the laser cutting process by a low power continuous CO2 laser. The effects of the laser cutting process parameters such as laser power, cutting speed, and laser focal plane position on the top and bottom kerf width, top heat-affected zone, the ratio of upper kerf width to lower kerf width and taper kerf are investigated by statistical techniques of variance analysis. Choosing an appropriate Gaussian distribution is studied as well. The results show that the laser scanning speed has a significant effect on the top kerf width. By choosing a cutting speed of 20 mm/s and a focal length of -3, the taper kerf is minimized. By increasing the laser cutting speed from 4 to 20 mm/s and decreasing the laser power from 50 to 20 W, the heat-affected zone decreases. The developed analysis can predict the depth of kerf in a continuous mode for different values of laser power, speed, and laser focal plane.
•Mathematical models were developed for surface roughness and KW using vibration data.•There is significant correlation between the estimated and experimental results of responses.•Laser power and ...cutting speed have significant effect on surface roughness, KW and MRR.•Size of HAZ was increased when the laser power increased.
Manufacturing industries are increasingly interested in laser beam machining as an efficient material removal process. Accordingly, there is great motivation in the modelling of the machining process to understand the physics behind the machining process in order to improve the machining efficiency. The present study made an attempt to predict surface roughness, kerf width and metal removal rate by utilizing the vibration signals measured during the laser beam machining of AISI 304 stainless steel. As per Taguchi’s L9 design of experiments, nine experiments were conducted at three levels of laser power (2.0, 1.5 and 1.0 kW), laser frequency (10, 8 and 6 kHz), cutting speed (3.0, 2.5 and 2.0 m/min) and nozzle tip distance (1.2, 1 and 0.8 mm) on 6 mm thickness of sheet metal and the vibration of sheet metal was measured using an accelerometer. It was observed that, the sheet vibration along the cutting direction increased the metal removal rate and sheet vibration perpendicular to the cutting direction caused surface roughness. Mathematical models were developed with the vibration data and predicted the surface roughness, kerf width and metal removal rate. The root mean square error of the responses was calculated as 0.615 µm, 5.44 µm and 0.259 m3/min for surface roughness, kerf width and metal removal rate respectively, demonstrating a significant correlation with experimental results. Furthermore, effect of laser power, laser frequency, cutting speed and nozzle tip distance on the surface roughness, kerf width, heat affected zone and metal removal rate was studied. The laser power and cutting speed have significant effect on these responses. Finite element modelling based simulation was carried out and studied effect of molten metal temperature on the heat affected zone. Temperature in the molten pool reached to maximum of 1773 K and the heat affected zone increased, when the laser power increased to 2.0 kW. The root mean square error between the measured and simulated heat affected zone was computed as 4.68 µm, indicating a good correlation between both.
The paper presents the problem of quality assurance of the laser cutting process of wood and wood-like materials and the selection of optimal processing conditions with respect to the required ...evaluation criteria. An experiment conducted to identify processing difficulties and potential causes of defects is described. Samples of three materials: pine wood, hardwood plywood and mixed wood HDF with a thickness of 4 mm were cut with a CO
laser and visually inspected and the width of the slit was measured. It was found that there was a relationship between the laser operating parameters and the obtained slit width. The higher the cutting speed, the narrower the slit. The obtained numerical results allowed to formulate technological guidelines on the selection of laser parameters depending on the material. In turn, based on the visual inspection, defects depending on the material properties were identified. An example of a non-conformity identification manual was developed, which includes illustrations to enable comparative analysis in production. It was found that in the studied process, different criteria can be adopted to qualify a product as compliant or non-compliant. A dilemma may then arise as to which criterion is more important. Therefore, a quality evaluation criteria verification sheet was proposed. Furthermore, due to the fact that the success of the laser cutting process is also dependent on other factors, a list of risks to the process was made.
•This study explores the sharpening mechanism of extremely sharp edges for PCD micro mills.•The transient temperature model of laser cutting PCD is constructed for studying the material removal ...mechanism.•The uniform graphitisation, micro abrasion, and smaller material stress near edge contribute to the extremely sharp edges.•The PCD micro mills with cutting edge radius of rβ = 0.21 μm are fabricated indicating better sharpness compared with rβ = 1–5 μm reported hitherto.
The fabrication of extremely sharp cutting edges for ultra-hard micro mills is crucial for suppressing the severe size effect, restraining burr formation, and improving the surface quality of widely used micro components in micro milling. In this study, a hybrid machining technique, laser-assisted precision grinding, is proposed to improve the grinding efficiency and increase the sharpness of the cutting edges of polycrystalline diamond (PCD) micro end mills. A transient heat model of laser ablation was constructed to investigate the laser-cutting mechanism of PCD with a cobalt binder. Facilitated by suitable heat conduction, cobalt absorbs photon energy to heat itself and transmits thermal energy to the surrounding diamond, resulting in uniform graphitisation and cobalt oxidation on the cut section. Hence, the affected layer on the cut section can be easily ground using a low grinding load. Moreover, the subsequent grinding mechanism of the laser-cut section was demonstrated. The diamond was removed via micro-abrasion without any intercrystalline cracks or grain dislodgement, and the abrasive grain size was optimised to achieve superior ground surface quality. Thus, the uniform graphitization, micro abrasion, and smaller material stress near edge contributed to the extremely sharp edges. Furthermore, PCD micro end mills with a diameter of 400 μm, aspect ratio of 2, and cutting-edge radius of approximately 0.2 μm were fabricated, showing a superior sharpness compared with that of the end mills with an edge radius of 1–5 μm reported hitherto. Subsequently, micro-milling experiments were conducted on oxygen-free high-conductivity copper (OFHC) using the self-fabricated PCD micro end mills. Almost no burrs were observed, and the surface roughness of the machined groove was 19.8 nm, indicating the superior cutting performance of the fabricated PCD micro end mills.
Display omitted
PDF
