On surface structure characterization and application on additive manufacturing
Doktorsavhandling, 2020

Countless industrial applications over the past decades have indicated the increased need to relate surface texture to surface function. The fast-growing industry of additive manufacturing admits the surface roughness as one of the main challenges. It makes the need for quantitative and qualitative control of surfaces and an understanding of surface measurements and analysis more important than ever. Surface metrology covers the questions related to surface measurements, its analysis, representation, and interpretation. Despite the long experience of surface measurements, there are still a lot of open questions.

The aim of this thesis was to investigate the interaction between surfaces and the optical metrology of surfaces’ topographical properties’.  More precisely this thesis includes an examination of tools and methods for quantitativeand qualitative characterization of surfaces measured by optical instruments in particular coherence scanning interferometry. Further, those methods and analysis were used on additively manufactured surfaces.

The contribution of this thesis lies in the intersection of the fields of characterization, manufacturing and function.

First of all, the use of power spectral density (PSD) analysis in this thesis proved it to be a powerful analysis tool for identification of differences and equalities between instruments measuring similar topographies. Besides PSD analysis together with surface roughness parameters were used for comparison of surface topography and its characterization.

Secondly, texture analysis of the surfaces used in dental industries, piston rings and selective laser melting surfaces showed that thus the effectiveness of surface parameters representing surface topography depends on the specific measurement range.

Finally, research was focused on the characterization of additively manufactured surfaces. The surfaces produced by fused deposition modelling (FDM) and by selective laser melting (SLM) manufacturing processes were studied. An areal model with the aim to produce a visual representation of FDM surfaces was built based on the ellipse geometry. The model was validated by comparison with the areal measurement using surface parameters and PSD analysis. Analysis of surface topography produced by SLM techniques was used to compare heat transfer and flow rate of cooling channels with different roughness.

This thesis, through the use of a combination of analysis tools thus sheds new insights into the field of additive manufacturing, the virtual representation of surfaces and connection between surface functional performance and choice of characterization linked both to measurement techniques and evaluation methods.

surface texture parameters.

fused deposition modelling

power spectral density

coherence scanning interferometer

selective laser melting

Surface characterization

Borås, Brinellgatan 4, hus 1, konferensrum da Vinci
Opponent: Professor Mohamed El-Mansori, Ecole Nationale Supérieure d'Arts et Métiers (ENSAM) ParisTech, France

Författare

Olena Flys

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Olena Flys, Vijeth Reddy, Amogh Vedantha Krishna, B-G Rosen "Investigations on modelling and visualization of surfaces produced by Fused Deposition Modeling"

“Nobody will deny that there is at least some roughness everywhere,” said mathematician Benoit Mandelbrot. A phrase you cannot disagree with, as we are coming across surface roughness every day in our life. When we speak about “a rough ground”, “a rough fabric”, “polished surface” we mean features of different scale and understand which surface we describe. But what causes roughness? Roughness is the natural state of the surface or it is a measure of its disorder. Why is roughness important and why need we describe it? Nowadays it is proven by scientists and engineering society that the surface roughness is important to the function of any kind of industrial products ranging from optics to highways. That is why it is highly important to understand the nature of surfaces used for different applications to find a connection between surface appearance and its function. The improvements in surface topography lead to avoiding waste parts and optimize the number of iterations needed during manufacturing, leading to a reduced environmental impact. In order to describe the surface structure, the appropriate measurement instrument needs to be chosen and later suitable analysis needs to be applied to measured data.

The need for a fast non-destructive technique for measuring surface roughness has recently accelerated the decade long development of optical methods. The coherence scanning interferometry has an important place in noncontact strategies for product development and quality control by providing an areal measurement of surface, which in turn can be linked to surface functional behaviour of produced parts. In surface metrology, coherence scanning interferometry plays an important role in the transition from tactile to non-contact methods. The reliable characterization of surfaces measurement is of the same importance as achieving valid measurement. Among qualitative and quantitative methods we would like to highlight power spectral density analysis and areal surface parameters. The power spectral density as qualitative analysis reveals periodic surface features that appears randomly in the surface and provides a graphic representation of how such features are distributed. The main advantages of power spectral density are that it contains statistical information independent of measurement resolution and size. The main problem for the surface-related research is to identify parameters that correlate to the surface properties, surface formation mechanism, surface function and surface geometry in a fundamental way. Therefore the areal surface parameters values and visual representation of the surface are widely used as quantitative characterization of surfaces.

The constant search of manufacturing industries for techniques to lower cost, minimize energy consumption and increase capacity led to the development of additive manufacturing.  The additive manufacturing is fundamentally different from traditional forming- or subtractive manufacturing. Additive manufacturing is a process that adds successive layers of material to create an object. The 3D file/model is the starting point for additive manufacturing. In the next step, this model is divided into the layers and software is creating the supporting structures to enable the progressive manufacture of each one of layers that forms the modelled geometry. The surface topography of additive manufactured objects inherits the traces of the manufacturing process and is listed as one of the drawbacks of this technology. The additively manufactured surfaces are quite different from traditionally produced, and lots of research need to be done in order to find characterization parameters linked to the quality and functionality of manufactured parts. The 3D based simulation model has been developed to enable prediction of the topography of the produced object.

This thesis through the number of comparisons performed with different measurement techniques on surfaces used for various application and combining different analysis shows the connection between surface function and its characterization. The model-based visual representation of additive manufactured surface opens the opportunity for investigation of surface properties in the virtual environment. A technical abstract of this thesis can be found on page Ⅰ.

Ämneskategorier

Tribologi

Bearbetnings-, yt- och fogningsteknik

Annan kemi

Styrkeområden

Produktion

ISBN

978-91-7905-303-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4770

Utgivare

Chalmers tekniska högskola

Borås, Brinellgatan 4, hus 1, konferensrum da Vinci

Online

Opponent: Professor Mohamed El-Mansori, Ecole Nationale Supérieure d'Arts et Métiers (ENSAM) ParisTech, France

Mer information

Senast uppdaterat

2020-05-06