scholarly journals Numerical Analysis of the Primary Gas Boundary Layer Flow Structure in Laser Fusion Cutting in Context to the Striation Characteristics of Cut Edges

Fluids ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 17
Author(s):  
Madlen Borkmann ◽  
Achim Mahrle
Keyword(s):  
Boundary Layer ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Laser Fusion ◽  
Formation Mechanisms ◽  
Momentum Exchange ◽  
Edge Structure ◽  
Laser Fusion Cutting ◽  
Comparison Of The Results

In cutting metals with solid-state lasers, a characteristic cutting edge structure is generated whose formation mechanisms still elude a consistent explanation. Several studies suggest a major contribution of the pressurized gas flow. Particular emphasis must be devoted to the gas boundary layer and its developing flow characteristics, since they determine the heat and momentum exchange between the cutting gas and the highly heated melt surface and thus the expulsion of the molten material from the kerf. The present study applies a CFD simulation model to analyze the gas flow during laser cutting with appropriate boundary conditions. Specifically, the gas boundary layer development is considered with a high spatial discretization of this zone in combination with a transition turbulence model. The results of the calculation reveal for the first time that the boundary layer is characterized by a quasi-stationary vortex structure composed of nearly horizontal geometry- and shock-induced separation zones and vertical vortices, which contribute to the transition to turbulent flow. Comparison of the results with the striation structure of experimental cut edges reveals a high agreement of the location, orientation, and size of the characteristic vortices with particular features of the striation structure of cut edges.

scholarly journals Laser fusion cutting: evaluation of gas boundary layer flow state, momentum and heat transfer

2021 ◽  
Author(s):  
Madlen Borkmann ◽  
Achim Mahrle ◽  
Eckhard Beyer ◽  
Christoph Leyens
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Laser Fusion ◽  
Flow State ◽  
Momentum And Heat Transfer ◽  
Laser Fusion Cutting ◽  
Layer Flow

Applicability of the boundary-layer approximation to the calculation of a plane turbulent mixing layer

1977 ◽  
Vol 11 (5) ◽  
pp. 683-688 ◽  
Author(s):  
V. I. Rasshchupkin ◽  
A. N. Sekundov
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Turbulent Mixing Layer ◽  
Boundary Layer Approximation

On Laser Fusion Cutting: The Self-Adjusting Cutting Kerf Width

1989 ◽  
Author(s):  
W. Schulz ◽  
D. Becker
Keyword(s):  
The Self ◽  
Kerf Width ◽  
Laser Fusion ◽  
Laser Fusion Cutting

Towards Online-Prediction of Quality Features in Laser Fusion Cutting Using Neural Networks

2020 ◽  
pp. 346-359
Author(s):  
Ulrich Halm ◽  
Dennis Arntz-Schroeder ◽  
Arnold Gillner ◽  
Wolfgang Schulz
Keyword(s):  
Neural Networks ◽  
Laser Fusion ◽  
Online Prediction ◽  
Laser Fusion Cutting ◽  
Quality Features

On the flow near the trailing edge of a flat plate

1968 ◽  
Vol 306 (1486) ◽  
pp. 275-290 ◽  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Governing Equations ◽  
Trailing Edge ◽  
Navier Stokes Equations ◽  
Multiplicative Constant ◽  
Boundary Layer Approximation ◽  
Uniform Shear

It is shown that the boundary layer approximation to the flow of a viscous fluid past a flat plate of length l , generally valid near the plate when the Reynolds number Re is large, fails within a distance O( lRe -3/4 ) of the trailing edge. The appropriate governing equations in this neighbourhood are the full Navier- Stokes equations. On the basis of Imai (1966) these equations are linearized with respect to a uniform shear and are then completely solved by means of a Wiener-Hopf integral equation. The solution so obtained joins smoothly on to that of the boundary layer for a flat plate upstream of the trailing edge and for a wake downstream of the trailing edge. The contribution to the drag coefficient is found to be O ( Re -3/4 ) and the multiplicative constant is explicitly worked out for the linearized equations.

Analysis of process efficiency in laser fusion cutting and some single- and multi-objective optimization aspects

2021 ◽  
pp. 095440892110627
Author(s):  
Miloš Madić ◽  
Mohamed H Gadallah ◽  
Dušan Petković
Keyword(s):  
Laser Power ◽  
Laser Cutting ◽  
Optimization Problem ◽  
Removal Rate ◽  
Cutting Speed ◽  
Process Efficiency ◽  
Laser Fusion ◽  
Cut Quality ◽  
Dross Formation ◽  
Laser Fusion Cutting

For an efficient use of laser cutting technology, it is of great importance to analyze the impact of process parameters on different performance indicators, such as cut quality criteria, productivity criteria, costs as well as environmental performance criteria (energy and resource efficiency). Having this in mind, this study presents the experimental results of CO2 laser fusion cutting of AISI 304 stainless steel using nitrogen, with the aim of developing a semi-empirical mathematical model for the estimation of process efficiency as an important indicator of the achievable energy transfer efficiency in the cutting process. The model was developed by relating the theoretical power needed to melt the volume per unit time and used laser power, where the change of kerf width was modeled using an empirical power model in terms of laser cutting parameters such as laser power, cutting speed, and focus position. The obtained results indicated the dominant effect of the focus position on the change in process efficiency, followed by the cutting speed and laser power. In addition, in order to maximize process efficiency and simultaneously ensure high cut quality without dross formation, a laser cutting optimization problem with constraints was formulated and solved. Also, a multi-objective optimization problem aimed at simultaneous optimization of process efficiency and material removal rate was formulated and solved, where the determined set of Pareto non-dominated solutions was analyzed by using the entropy method and multi-criteria decision analysis method, that is, the Technique for Order of Preference by Similarity to Ideal Solution. The optimization results revealed that in order to enhance process efficiency and material removal rate, while ensuring high cut quality without dross formation, focusing the laser beam deep into the bulk of material is needed with particular trade-offs between laser power and cutting speed levels at high pressure levels of nitrogen.

Investigation on the melt ejection and burr formation during laser fusion cutting of stainless steel

2020 ◽  
Vol 32 (2) ◽  
pp. 022068 ◽  
Author(s):  
S. Stoyanov ◽  
D. Petring ◽  
D. Arntz-Schroeder ◽  
M. Günder ◽  
A. Gillner ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Burr Formation ◽  
Laser Fusion ◽  
Laser Fusion Cutting ◽  
Melt Ejection

scholarly journals Transition from Stable Laser Fusion Cutting Conditions to Incomplete Cutting Analysed with High-speed X-ray Imaging

2020 ◽  
Vol 60 ◽  
pp. 470-480
Author(s):  
Jannik Lind ◽  
Florian Fetzer ◽  
Christian Hagenlocher ◽  
David Blazquez-Sanchez ◽  
Rudolf Weber ◽  
...  
Keyword(s):  
High Speed ◽  
Cutting Conditions ◽  
Laser Fusion ◽  
X Ray ◽  
X Ray Imaging ◽  
Laser Fusion Cutting ◽  
Stable Laser
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