scholarly journals Macroscopic Effects of Surface Roughness in Confined Air Flow

2004 ◽  
Vol 126 (2) ◽  
pp. 216-222
Author(s):  
M’hamed Boutaous ◽  
Patrick Bourgin
Keyword(s):  
Surface Roughness ◽  
Air Flow ◽  
Threshold Value ◽  
Real Surface ◽  
Plastic Films ◽  
Wound Rolls ◽  
Theoretical Predictions ◽  
Flow Through ◽  
Thin Plastic

The general framework deals with the winding of thin plastic films, in order to obtain good-quality rolls. This issue is tightly connected to the thickness of the residual air layer entrapped between the film layers. It is then of importance to optimize the surface topography of the films so that to improve the quality of the wound rolls. In a previous work, we proposed a simple model for the flow of an air layer squeezed between a solid smooth substrate and a plastic film sample: it was shown experimentally that the macroscopic characteristics of the flow are connected to the film roughness, but how? In order to answer this question, we assimilated the confined air flow to a flow through a periodic array of cylinders and a mathematical model based on homogenization techniques was developed. In the present paper, we search for pertinent parameters which describe the real surface roughness of plastic films. The experiments were carried out by using a 3-D roughness measurement device and the first observation is that the roughness distribution is not uniform. We made a sampling expressed by the percentage of peaks exceeding some given height threshold. The corresponding experimental parameters are used to define the network of cylinders. For each type of film, the threshold value is the only adjustable parameter and the following results are obtained: It is possible to adjust this parameter so that to obtain a very good agreement between the experimental data and the theoretical predictions. In addition, the smoother the film, the more important the highest peaks are in terms of air leakage.

scholarly journals Macroscopic Effects of Surface Roughness in Confined Air-Flow

2002 ◽  
Author(s):  
M’hamed Boutaous ◽  
Patrick Bourgin
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Surface Roughness ◽  
Spatial Distribution ◽  
Surface Topography ◽  
Air Flow ◽  
Threshold Value ◽  
Squeeze Flow ◽  
Real Surface ◽  
Plastic Films

The general framework deals with the winding of thin plastic films. It is well known by the man-of-the art that the “windability” of plastic films is mainly governed by their surface topography. One key issue is then to optimize their surface topography so that to improve the quality of the wound roll. In a previous work, we proposed a simple model which considers the flow of an air layer squeezed between a solid smooth substrate and a plastic film sample : it was shown experimentally that the macroscopic characteristics of the flow are connected to the film roughness, but how? To answer this question, we assimilate the confined air flow to a flow through a periodic array of cylinders. A mathematical model based on homogenization techniques was proposed, where the heights of the cylinders, their diameter and their spatial distribution are the governing parameters. In the present paper, we propose pertinent parameters which describes the real surface roughness of plastic films fairly well. The measurements were carried out by using a 3D roughness measurement device. The first observation is that the films roughness distribution is not uniform, but forms “packages” (agglomerates) giving place to large packs of roughness. We made a sampling at different levels expressed by the percentage of peaks exceeding some given height. The heights of the peaks over a threshold value are averaged and the corresponding averaged value will be regarded as the initial gap in the squeeze flow model. Now, the networks of cylinders is built as follows : • The cylinder diameters is the averaged width of the large peaks, • The distance between the cylinder axes is the mean value of the spatial distribution of the peaks. Thus, for each type of film, the threshold value will be the only adjustable parameter. Introducing these parameters into the mathematical model which predicts the evolution of the squeezed air layer and comparing to the experimental data, the following results are obtained: (1) It is possible to adjust one single parameter so that to obtain a very good agreement between the experimental data and the theoretical results. (2) The smoother the film, the more important the highest peaks are in terms of air leakage.

scholarly journals Comparison of Surface Roughness When Turning and Milling

2021 ◽  
Author(s):  
Abdulwahab Mgherony ◽  
Balázs Mikó ◽  
Gabriella Farkas
Keyword(s):  
Surface Roughness ◽  
Geometric Model ◽  
Cutting Parameters ◽  
Machining Process ◽  
Depth Of Cut ◽  
Real Surface ◽  
Machined Surface ◽  
Longitudinal Turning ◽  
Machining Process Planning

The quality of a machined surface can be described by macro and micro parameters, like the size error, the form and position error or the surface roughness. The task of machining process planning is to find the best machining method and parameters, which ensure the required quality. In this article, the surface roughness in the case of turning and milling technologies is analysed. The effect of the cutting parameters (feed at turning and depth of cut at milling) and the tool parameter (corner radius) are investigated. The results are compared with the theoretical geometric model of surface roughness. In longitudinal turning as well as in constant Z-level milling, the geometric model of surface roughness is similar. The article presents whether the real surface roughness is similar too.

Periodic Homogeneization Techniques As a Way to Account for Surface Roughness in a Confined Air Flow

2001 ◽  
Author(s):  
Patrick Bourgin ◽  
M’hamed Boutaous ◽  
Pierre Woehl
Keyword(s):  
Surface Roughness ◽  
Internal Stress ◽  
High Speed ◽  
Average Distance ◽  
Air Flow ◽  
Film Surface ◽  
Roughness Coefficient ◽  
Spatial Period ◽  
Plastic Films ◽  
Order Of Magnitude

Abstract The motivation of the study is concerned with high speed winding of plastic films (i.e. PET). During this process, some air is entrapped between the first wrap and the roll being wound. It is well known that the residual air layer between the plastic layers has a strong influence on the internal stress state within the roll. The surface roughness of the film plays an important role on these aerodynamic effects and consequently on the internal stress. Nevertheless, the mechanisms involved are not clarified yet. As a first step, an experimental study was conducted with the aim of characterizing the global flow kinetics of an air layer squeezed between a plastic film sample and a smooth substrate. In so doing, a new parameter was defined: some sort of a “dynamic roughness coefficient”. Nevertheless, the correlation between this parameter and those which describe the topography of a film surface (static) needed to be established. Using the tools of 3D roughness measurements, it was observed that the heights of the peaks and the mean distances between them are of the same order of magnitude as the average distance between the opposite surfaces. We therefore assimilated the surface topography to a periodic array of cylinders of known dimensions, their spatial period and their height being of the same order as the interlayer distance. In such conditions, the air flow squeezed in the space confined between the two surfaces is studied by using an approach based on periodic homogeneization techniques. The first tendencies indicate that a good qualitative agreement exists between the global experimental data and the theoretical results.

Improving of quality of gate assembly contact surfaces of high-pressure fi ttings by diamond burnishing

2020 ◽  
pp. 99-104
Author(s):  
S.A. Zaydes ◽  
A.N. Mashukov ◽  
T.Ya. Druzhinina
Keyword(s):  
Surface Roughness ◽  
High Pressure ◽  
Main Part ◽  
Conical Surface ◽  
The Real ◽  
Metal Seal ◽  
Diamond Burnishing ◽  
Air Tightness ◽  
Contact Surfaces

The contact belt of the gate assembly is the main part of high pressure fittings. The serviceability of the fittings assembly as whole depends on the air-tightness and quality of the mating surfaces. The technology of diamond burnishing allows to increase the interface of the nodes by red ucing the surface roughness of the metal-to-metal seal. The real experience for improving of the fittings contact belt due to the use of diamond burnishing of the nozzles seats and the conical surface of the rods.

scholarly journals Smoothing additive manufactured parts using ns-pulsed laser radiation

2021 ◽  
Author(s):  
Florian Kuisat ◽  
Fernando Lasagni ◽  
Andrés Fabián Lasagni
Keyword(s):  
Surface Roughness ◽  
Mechanical Performance ◽  
State Of The Art ◽  
Pulsed Laser ◽  
Industrial Applications ◽  
Laser Source ◽  
Pulsed Laser Radiation ◽  
Current State ◽  
The Impact

AbstractIt is well known that the surface topography of a part can affect its mechanical performance, which is typical in additive manufacturing. In this context, we report about the surface modification of additive manufactured components made of Titanium 64 (Ti64) and Scalmalloy®, using a pulsed laser, with the aim of reducing their surface roughness. In our experiments, a nanosecond-pulsed infrared laser source with variable pulse durations between 8 and 200 ns was applied. The impact of varying a large number of parameters on the surface quality of the smoothed areas was investigated. The results demonstrated a reduction of surface roughness Sa by more than 80% for Titanium 64 and by 65% for Scalmalloy® samples. This allows to extend the applicability of additive manufactured components beyond the current state of the art and break new ground for the application in various industrial applications such as in aerospace.

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