Modeling and Characterization of Laser Drilling of Small Holes on Metal Sheets

2004 ◽  
Author(s):  
Wei Han ◽  
Ryszard J. Pryputniewicz
Keyword(s):  
Laser Beam ◽  
Manufacturing Industry ◽  
Pulse Length ◽  
Experimental Studies ◽  
Laser Drilling ◽  
Melting Front ◽  
Laser Parameters ◽  
Metal Sheets ◽  
Small Holes ◽  
Melt Ejection

Laser drilling is increasingly being used in fabrication of small components in various materials with applications in aerospace, automotive, electronics and medical industries, and it offers a unique combination of benefits for the contemporary manufacturing industry as a rapid, precise, clean, flexible, and efficient process. Laser drilling involves a stationary laser beam which uses its high power density to melt or vaporize material from the workpiece, and the process is governed by an energy balance between the irradiating energy from the laser beam, the conduction heat into the workpiece, the energy losses to the environment, and the energy required for phase change in the workpiece. There are three major mechanisms of removal of material from the beam interaction zone and consequent propagation of the melt front into the metal bulk. They are (1) melt ejection due to interaction between the melt and an assisting gas, (2) melt ejection by the vaporization-induced recoil force, and (3) melt evaporation. The results of laser drilling processes, such as the profile of the heat affected zone (HAZ) and the geometry of the holes, strongly depend on settings of the laser parameters such as peak power, pulse length, pulse repetition rate, number of pulses, focal condition, etc. In addition, the processing results are strongly influenced by geometrical and material properties of the workpiece. This paper presents theoretical and experimental studies of laser drilling of micrometer size holes on metal sheets using a pulsed Nd:YAG laser. A model of the temperature distribution and the motion of the melting front for laser drilling is presented and compared with experimental data. Effects of laser parameters on the resultant geometry of the hole are investigated and summarized, and an optimum procedure for laser drilling of small holes on metal sheets is outlined.

scholarly journals Generalized Thermoelastic Functionally Graded on a Thin Slim Strip Non-Gaussian Laser Beam

Symmetry ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1094 ◽  
Author(s):  
Sayed M. Abo-Dahab ◽  
Ahmed E. Abouelregal ◽  
Marin Marin
Keyword(s):  
Laser Beam ◽  
Pulse Length ◽  
Generalized Thermoelasticity ◽  
Functionally Graded ◽  
Strong Impact ◽  
Problem Solution ◽  
Gaussian Laser Beam ◽  
Laser Parameters ◽  
Non Gaussian ◽  
The Impact

The present study utilizes the generalized thermoelasticity theory, with one thermal relaxation time (TR), to examine the thermoelastic problem of a functionally graded thin slim strip (TSS). The authors heated the plane surface bounding using a non-Gaussian laser beam with a pulse length of 2 ps. The material characteristics varied continually based on exponential functions. Moreover, the equations governing the generalized thermoelasticity for a functionally graded material (FGM) are recognized. The problem’s ideal solution was primarily obtained in the Laplace transform (LT) space. The LTs were converted numerically because of the considerable importance of the response in the transient state. For a hypothetical substance, the numerical procedures calculating the displacement, stress, temperature and strain were given. The analogous problem solution to an isotropic homogeneous material was provided by defining the parameter of non-homogeneity adequately. The obtained results were displayed using graphs to illustrate the extent to which non-homogeneity affected displacement, stress, temperature and strain. A comparison was been made between the present study and those previously obtained by others, when the new parameters vanish to show the impact of the non-homogeneity, TSS and laser parameters on the phenomenon. The results obtained indicate a significant strong impact of FGM, TSS and laser parameters.

scholarly journals Femtosecond Laser Drilling of Cylindrical Holes for Carbon Fiber-Reinforced Polymer (CFRP) Composites

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2953
Author(s):  
Hao Jiang ◽  
Caiwen Ma ◽  
Ming Li ◽  
Zhiliang Cao
Keyword(s):  
Carbon Fiber ◽  
Femtosecond Laser ◽  
Picosecond Laser ◽  
Laser Drilling ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Laser Parameters ◽  
Reinforced Polymer ◽  
Cfrp Composites ◽  
Cylindrical Holes

Ultrafast laser drilling has been proven to effectively reduce the heat-affected zone (HAZ) of carbon fiber-reinforced polymer (CFRP) composites. However, previous research mainly focused on the effects of picosecond laser parameters on CFRP drilling. Compared with a picosecond laser, a femtosecond laser can achieve higher quality CFRP drilling due to its smaller pulse width, but there are few studies on the effects of femtosecond laser parameters on CFRP drilling. Moreover, the cross-sectional taper of CFRP produced by laser drilling is very large. This paper introduces the use of the femtosecond laser to drill cylindrical holes in CFRP. The effect of laser power, rotational speed of the laser, and number of spiral passes on HAZ and ablation depth in circular laser drilling and spiral laser drilling mode was studied, respectively. It also analyzed the forming process of the drilling depth in the spiral drilling mode and studied the influence of laser energy and drilling feed depth on the holes’ diameters and the taper. The experimental results show that the cylindrical hole of CFRP with a depth-to-diameter ratio of about 3:1 (taper < 0.32∘, HAZ < 10 m) was obtained by using femtosecond laser and a spiral drilling apparatus.

Abstract 60: Inducible Arrythmogenicity of Direct Current Electroporation Ablation: Insight from a Series of Acute Canine Studies

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Alan Sugrue ◽  
Chance Witt ◽  
Christopher V DeSimone ◽  
Deepak Padnanabhan ◽  
Ammar Killu ◽  
...  
Keyword(s):  
Direct Current ◽  
Superior Vena ◽  
Pulmonary Veins ◽  
Pulse Length ◽  
Experimental Studies ◽  
Tissue Destruction ◽  
Ecg Gating ◽  
Actual Mechanism ◽  
Membrane Poration ◽  
Current Energy

Background: The use of direct current electroporation has the potential for significant utility because of its non-thermal approach to tissue destruction. However, the fear of inducibility of cardiac arrhythmias (particular ventricular fibrillation) when using electroporation remains of concern due to membrane poration and ion flux during periods of vulnerability occurring in ventricular repolarization. Objectives: Critically examine the incidence of arrhythmias in a series of acute canine studies to retrospectively determine cause and safe electoporative dosing margins. Methods: We performed electroporation ablation in 6 acute canine studies. These were experimental studies performed at sites critical in arrhytmogenesis. Sites included the pulmonary veins, left atrial appendage, superior vena cavae, right atrium and ventricle. Electroporation was delivered using an ECG gating algorithm so that QRS complexes are tagged and direct current energy is not delivered during the vulnerable portion of the T wave. Results: In 6 acute canine experiments, we delivered a total of 62 electroporation applications for ablation purposes. The average electroporation dosage delivered involved an average of 1427 Volts (range 750-3000 V), Pulse length of 100 ms, and number of pulses of 20.2 (range 10-100). AF was induced in 27.4% of electroporiatve applications. Atrial flutter/tachycardia occurred in 8.1%. VF occurred in only one application at a location of the left superior pulmonary vein. Conclusion: These data suggest that induction of VF is relatively uncommon with ECG gating and highlight its importance when using this modality. However, the induction of AF occurs with higher frequency. The actual mechanism as to why this occurs requires further systematic study.

scholarly journals INCREASING THE EFFICIENCY OF SURFACE STRENGTHENING OF METAL PRODUCTS BY COMBINED THERMODEFORMATION PROCESSING

2020 ◽  
pp. 103-110
Author(s):  
Oleksandr Danyleiko ◽  
Vitaliy Dzhemelinskyi ◽  
Dmytro Lesyk ◽  
Artemii Bernatskyi
Keyword(s):  
Surface Layer ◽  
Laser Beam ◽  
Surface Hardening ◽  
Thermal Deformation ◽  
Experimental Studies ◽  
Numerical Control ◽  
Surface Plastic ◽  
Beam Diameter ◽  
Metal Products ◽  
Deformation Surface

The article discusses the prospects of using combined thermal deformation surface processing to improve the performance properties of metal products. There is a new method of thermal deformation surface hardening (shot peening (SP) followed by laser heat treatment (LHT)) for tools and crown housings operating under difficult conditions proposed. For carrying out experimental studies, flat samples of 30KhGSA steel and steel 45 were selected. Preliminary hardening and finishing with static or dynamic methods of surface plastic deformation were carried out on a modernized installation based on a DYNAMITE 2800 numerical control machine, and SP was implemented on industrial equipment. Laser surface hardening of the samples was carried out in single passes with a sample moving speed of 300...500 mm/min with a laser beam diameter of 7.3 mm and a laser power of 1 kW using the ROFIN-SINAR DY 044 technological unit. The optimal regimes of surface hardening are determined under the deformation action of a gas-dynamic flow with solid particles and thermal action by a laser beam to obtain maximum values ​​of hardening depth and hardness. In particular, with SP, the gas-feed stream feed pressure is 0.5 MPa, the processing time is 1 min, regardless of the type of material. The optimal laser beam power is 1 kW at a sample travel speed of 300 mm/min. There are the results of experimental studies of the change in the hardening depth as a function of time and pressure after SP, the speed of movement of the treated sample from carbon steel 45 and medium alloyed steel 30KhGSA after LHT and combined SP+LHT, and also the distribution of microhardness over the depth of the hardened layer presented. It is revealed that the combined SP+LHT of 30 KhGSA steel at optimal modes forms 1.5 times (1.3 mm) greater depth of the strengthened surface layer in comparison with LHT, while providing the surface layer hardness of ~5400 MPa.

A Study on the Influence of Laser Parameters on Laser-Assisted Machining of AISI H-13 Steel

2019 ◽  
Vol 827 ◽  
pp. 92-97 ◽  
Author(s):  
Evaggelos Kaselouris ◽  
A. Baroutsos ◽  
T. Papadoulis ◽  
Nektarios A. Papadogiannis ◽  
Michael Tatarakis ◽  
...  
Keyword(s):  
Laser Beam ◽  
Cutting Forces ◽  
Local Heating ◽  
Orthogonal Cutting ◽  
Material Model ◽  
Beam Diameter ◽  
Laser Parameters ◽  
Laser Assisted Machining ◽  
Von Mises ◽  
Cutting Processes

The machinability of a steel workpiece through conventional and Laser-Assisted Machining (LAM) is studied by the help of the Finite Element Method (FEM). In LAM, the laser beam is applied as a heat source to ensure sufficient local heating of the workpiece at a certain distance from the cutting tool and the machinability of materials is increased since the values of the cutting forces are decreased. A thermostructural FEM model is developed to simulate the conventional and the LAM orthogonal cutting of AISI H-13 steel. The Johnson-Cook material model that takes into account the effect of plastic strain, strain rate and temperature, along with a fracture model, is used in the simulations. For varying feed rate, parametric simulations are carried out, for different test cases of the laser beam diameter and the laser heat flux. Key engineering parameters, like cutting forces, temperature distributions, Von Mises stresses and plastic strains, are compared for both cutting processes. This comparison leads to important notifications on the influence of the cutting and laser parameters to LAM. The obtained results indicate that LAM may improve the machinability of AISI H-13 steel by reducing the cutting forces to a maximum percentage of ~15%.

Quantifying Powder Losses and Analyzing Powder Conditions in order to Determine Material Efficiency in Laser Beam Melting

2016 ◽  
Vol 856 ◽  
pp. 231-237 ◽  
Author(s):  
Max Lutter-Günther ◽  
Alexander Hofmann ◽  
Christoph Hauck ◽  
Christian Seidel ◽  
Gunther Reinhart
Keyword(s):  
Laser Beam ◽  
Experimental Studies ◽  
Manufacturing Processes ◽  
Ecological Evaluation ◽  
Powder Bed ◽  
Material Efficiency ◽  
Laser Beam Melting ◽  
Measurement Results ◽  
Subtractive Manufacturing ◽  
End Use

Laser Beam Melting (LBM) is an additive manufacturing process, which is increasingly applied for the production of end use parts. One advantage of this powder bed fusion technology lies in the high material efficiency in comparison with subtractive manufacturing processes (i. e. milling, lathing). However, only few experimental studies have been conducted on the material efficiency of LBM. For the accurate evaluation of the LBM material efficiency, empirical values for powder losses are required. Furthermore, a lack of terminology for waste types and powder conditions in the context of LBM impedes communication and research on the topic. The presented paper aims to increase the understanding of material efficiency and powder conditions in Laser Beam Melting. A quantitative analysis of waste types is presented for different LBM application scenarios. This sets a basis for the ecological evaluation and comparison with conventional manufacturing processes. In order to achieve the aim, a terminology is introduced for waste types and powder conditions in the context of powder bed-based additive processes. Therefore, considerations regarding powder quality are taken into account. For the quantification of powder losses, the experimental setup and measurement results are described. Furthermore, loss types and their significance are analyzed and discussed.

Experimental studies of surface relief gratings on polymer Films

1995 ◽  
Vol 413 ◽  
Author(s):  
X. L. Jiang ◽  
D. Y. Kim ◽  
L. Li ◽  
V. Shivshankar ◽  
J. Kumar ◽  
...  
Keyword(s):  
Laser Beam ◽  
Polymer Films ◽  
Surface Relief ◽  
Experimental Studies ◽  
Laser Beams ◽  
Recording Conditions ◽  
Surface Modulation ◽  
High Diffraction Efficiency ◽  
Surface Relief Gratings ◽  
High Diffraction

ABSTRACTWe report our investigation on the recording of surface relief gratings on azobenzene containing polymer films by laser beams with different polarizations. Experimental evidence shows that it is necessary to have spatial variations of both magnitude and direction of net electric field in the films to record surface relief gratings. Large surface modulation (> 3500 Å) and high diffraction efficiency (about 30%) were obtained under optimized recording conditions. In addition, polarization dependent erasure of the gratings by a single laser beam has been studied.

Theoretical and Experimental Investigation of Laser Drilling in a Partially Transparent Medium

1992 ◽  
Vol 114 (1) ◽  
pp. 71-80 ◽  
Author(s):  
T. Nowak ◽  
R. J. Pryputniewicz
Keyword(s):  
Laser Beam ◽  
Three Dimensional ◽  
Laser Drilling ◽  
Drilling Process ◽  
Transparent Medium ◽  
Finite Sample ◽  
Cross Sectional ◽  
Quantitative Correlation ◽  
Study Results ◽  
Successful Prediction

An investigation of pulsed, laser drilling in a partially transparent medium was conducted. The study included both theoretical and experimental analyses. The theoretical analysis included development of a computer simulation to model the laser drilling process—a three-dimensional finite difference solution with temperature-dependent thermal properties, finite sample geometry, and experimentally determined laser beam characteristics. Both qualitative and quantitative correlation of the theoretical and experimental results was good with successful prediction of hole shapes and minimum error in the theoretically predicted cross-sectional areas of the laser-drilled holes ranging approximately ± three percent over the range of energies per laser pulse considered in this study. Results of calculations and experiments demonstrated the importance of the shape and irradiance distribution of the incident laser beam on the quality of laser-drilled holes in Al2O3 samples.

Numerical simulations of preliminary state of stress in bundles of metal sheets on the guillotine

2017 ◽  
Vol 85 (1) ◽  
pp. 14-23 ◽  
Author(s):  
J. Kaczmarczyk
Keyword(s):  
Numerical Simulations ◽  
Experimental Studies ◽  
Cutting Parameters ◽  
Cutting Process ◽  
Main Task ◽  
Force Loading ◽  
State Of Stress ◽  
Metal Sheets ◽  
Optimum Cutting ◽  
Selection Of

Purpose: The work is aimed at determination of the influence of selected technological parameters on the preliminary state of stress in bundles of metal sheets being compressed by the pressure beam and submitted to the cutting process on a guillotine. Design/methodology/approach: The numerical simulations concerning the preliminary state of stress in the bundle of sheets were conducted by means of the finite element method and the computer system MSC.Patran with the computational module MSC.Marc. The experimental studies concerning the influence of a force loading the pressure beam on the quality of metal sheets were carried out using scanning electron microscopy. Findings: Possibilities of finding the optimum cutting parameters to maximise the values of preliminary state of stress in the bundle of metal sheets subjected to cutting. Higher values of stresses in the bundle coming from loading the pressure beam on the one hand decrease the maximum values of cutting force and thereby facilitate the performance of the cutting process, however on the other hand too high values of stresses might damage the surface of the top sheet in a bundle. Research limitations/implications: The main task of the presented research concerns the reduction of the maximum force generated on a knife during the cutting process. It is possible by increasing the values of preliminary state of stress realized in practice by applying higher values of a force loading the pressure beam. The force should not be too high in order to avoid damaging of the top sheet in the bundle loading by the pressure beam. Practical implications: The appropriate selection of the cutting parameters on account of preliminary state of stress in the bundle of sheets is essential in terms of industrial economy. It enables reducing the amount of waste caused by defects in bundles of sheets and decreases wear of the cutting tool. The research has been conducted in order to reduce the number of randomly occurring defects during cutting of metal sheets on a guillotine. Originality/value: The results acquired from the research facilitate selection of the best parameter settings required for conducting the optimum cutting process on a guillotine. The optimum set of cutting parameters leads to the reduction of defects’ number occurring during the process.

Rapid Tooling by Laminated Object Manufacturing of Metal Foil

2005 ◽  
Vol 6-8 ◽  
pp. 303-312 ◽  
Author(s):  
M. Prechtl ◽  
Andrea Otto ◽  
Manfred Geiger
Keyword(s):  
Laser Beam ◽  
Rapid Tooling ◽  
Diffusion Welding ◽  
Metal Foil ◽  
Powder Bed ◽  
Laminated Object Manufacturing ◽  
Green Part ◽  
Metal Sheets ◽  
Cutting Velocity ◽  
The Stability

The technology of Laminated Object Manufacturing (LOM) is not very new. For hundreds of years wooden parts are built by stacking layers together. Nowadays also paper, plastic, ceramic composite and metal sheets are treated in layers. For the manufacture of prototypes and especially technical tools, e. g. moulds for gravity casting, die casting or injection molding, out of metallic foil however the low self stiffness of this material is a great challenge. In this case it is useful to produce the parts in a two step process. The first subprocess is the stacking of the layers, which can be realised by laser beam spot welding to determine the position of the layer in combination with generating the defined contour by a laser beam cutting process. This procedure is done in a fully automated machine where the CAD-file of the desired part and the building parameters like the laser parameters and the cutting velocity are needed as input. However the stability of the produced green part is insufficient for most kind of application. Hence, a second sub-process to enhance the mechanical properties of the part is necessary. This can for example be realised by high temperature soldering or by diffusion welding in a furnace with inert gas or vacuum. During these kinds of joining processes the green part is homogeneously pressed with the help of a powder bed and at the same time it is tempered for a defined term. In this paper the principle of sheet metal LOM is described as well as the process chain of Laminated Object Manufacturing of metal foil. For each sub-process of metal foil LOM the results of the experimental work for qualifying and optimizing the sub-process are shown. Finally some examples of possible applications especially in the field of Rapid Tooling and Rapid Manufacturing are discussed.

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