| 1. |
- Berglund, Johan C, 1978, et al.
(författare)
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On discovering relevant scales in surface roughness measurement : an evaluation of a band-pass method
- 2010
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Ingår i: Scanning. - London : John Wiley & Sons. - 0161-0457 .- 1932-8745. ; 32:4, s. 244-249
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Tidskriftsartikel (refereegranskat)abstract
- When characterizing surfaces and searching for correlations to functional properties, such as friction, finding the right scale of roughness for evaluation can improve correlations. However, in traditional roughness parameter analysis, a wide range of scales, or all scales of topography in the surface roughness measurements are evaluated together. In this study a multi-scale method using a series of band-pass filters is employed for finding scales of topography with strong correlations to friction.
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| 2. |
- Berglund, Johan C, 1978, et al.
(författare)
-
Machine Hammer Peening – A Substitute for Polishing of Pressing Die Surfaces?
- 2009
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Ingår i: Proceedings of the International 3'rd Swedish Production Symposium. - 9789163360060 ; :Day 1, s. 184-189
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Konferensbidrag (refereegranskat)abstract
- Machine Hammer Peening (MHP) is a new method for finishing of surfaces. With this method the workpiece surface is hammered with a spherical carbide tool. The main objective of the study was to evaluate whether the MHP method could be used as a plausible substitute for manual polishing in pressing die manufacturing. To do this, sample surfaces were hammered and evaluated. Changes to the surfaces were assessed using surface roughness measurements, hardness measurements and optical images. First of all, the workpiece surface was smoothened. Secondly, the surface hardness was increased significantly. Thirdly, the nodules on the workpiece surface were effected. They appeared to be smaller and not as visible. It is probable that they had been plastically deformed and that some of the graphite in the nodules was replaced by material from the surrounding steel matrix. By replacing the graphite in the larger nodule cavities by surrounding steel material, a die surface is created which would be less prone to galling. In addition, with MHP, the amount of polishing needed to manufacture a die surface can be reduced because of the smoothening effect.
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| 3. |
- Berglund, Johan C, 1978, et al.
(författare)
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Milled die steel surface roughness correlation with steel sheet friction
- 2010
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Ingår i: CIRP Annals - Manufacturing Technology. - Bern : Elsevier BV. - 1726-0604 .- 0007-8506. ; 59:1, s. 577-580
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Konferensbidrag (refereegranskat)abstract
- This work investigates correlations between the surface topography of milled steel dies and friction with steel sheet. Several die surfaces were prepared by milling. Friction was measured in bending under tension testing. Linear regression coefficients (R^2) between the friction and texture characterization parameters were tested. None of the height, spacing, material volume, void or segmentation parameters showed good correlations. Developed area, rms surface gradient, relative area and complexity showed strong correlations (R^2 > 0.7). For area-scale fractal complexity the correlation increases markedly at scales below 200 μm^2, with a maximum R^2 of 0.9 at 50 μm^2.
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| 4. |
- Berglund, Johan C, 1978, et al.
(författare)
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A method development for correlation of surface finish appearance of die surfaces and roughness measurement data
- 2009
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Ingår i: Tribology letters. - Berlin : Springer Berlin/Heidelberg. - 1023-8883 .- 1573-2711. ; 36:2, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- In die and mould manufacturing, the method used for quality control of finished surfaces is usually visual and tactile inspection of the finish, which is not easily quantifiable. In the present study, an evaluation of the connection between surface finish appearance and measured surface roughness was carried out using scale-sensitive fractal analysis to find functional correlations and to determine suitable cut-off limits for functional data filtration. A selection of ball-nose end-mills in combination with two different tool steels (hardness 39 and 47 HRC) were used to manufacture surfaces that were inspected and measured. It was found that the method developed in the present study for evaluating functional correlations and designing filters worked well. It was also found that there is a correlation between the surface roughness parameter Sq and the surface finish appearance and that this correlation is stronger in certain wavelengths on the surface.
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| 5. |
- Berglund, Johan C, 1978, et al.
(författare)
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A Method for Visualization of Surface Texture Anisotropy in Different Scales of Observation
- 2011
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Ingår i: Scanning. - : John Wiley & Sons. - 0161-0457 .- 1932-8745. ; 33:5, s. 325-331
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Tidskriftsartikel (refereegranskat)abstract
- Anisotropy of functional surfaces can in many practical cases significantly influence the surface function. Tribological contacts in sheet forming and engine applications are good examples. This article introduces and exemplifies a method for visualization of anisotropy. In a single graph, surface texture properties related to the anisotropy as a function of scale are plotted. The anisotropy graph can be used to explain anisotropy properties of a studied surface such as texture direction and texture strength at different scales of observation. Examples of milled steel surfaces and a textured steel sheet surface are presented to support the proposed methodology. Different aspects of the studied surfaces could clearly be seen at different scales. Future steps to improve filtering techniques and an introduction of length-scale analysis are discussed.
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| 6. |
- Berglund, Johan C, 1978
(författare)
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Characterisation of Functional Pressing Die Surfaces
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The manufacture of dies and moulds is a critical aspect of many production systems since the manufacturing and try-out of new dies and moulds often is essential in determining the lead-time and quality of a new production system. In the automotive industry, many new car models are introduced each year and for each of these models, a new set of pressing dies has to be designed and manufactured. The manufacturing of pressing dies consists of several different process steps of which machining and manual polishing contribute largely to the time and cost. To be able to improve the manufacturing processes rationally, for example by optimising the machining to reduce or eliminate the subsequent manual work, an appropriate specification of the required surface quality, using a relevant parametric description of the surface, is needed. In pressing dies, the effects of manufacturing processes on functional performance are not fully understood. One of the reasons for this is the lack of effective methods for characterisation. In the work described in this thesis, research is conducted to evaluate and establish such methods.It was found that surface roughness measurement of dies, with the purpose of manufacturing process development, requires 3D data. Replication often needs to be used in these cases since dies usually are too large to bring into a lab measurement equipment. The replication techniques tested in this thesis work adequately. For quality control in production 2D measurements from a handheld instrument are good enough if an appropriate measuring strategy is used and limits for the evaluated parameters are defined.Using a multi-scale approach when analysing roughness data it may be possible to find so called functional bandwidths. With the analysis focused on the functional bandwidth the characterisation is more effective and it is easier to identify roughness parameters which correlate to the functional property or the process parameter of interest. Such a method for functional filtering of roughness data is developed and presented in the thesis.Surface texture anisotropy has been found to be important for the function of a die surface. It has also been observed that texture anisotropy can vary depending on the scale of observation. The method developed in this work to analyse and visualise texture anisotropy as a function of scale can be a helpful tool when evaluating die surfaces, especially when analysing surfaces produced with different manufacturing methods to make sure that the manufactured surface has the required texture properties in the relevant scales.
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| 7. |
- Berglund, Johan C, 1978, et al.
(författare)
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Detailed evaluation of topographical effects of Hirtisation post-processing on electron beam powder bed fusion (PBF-EB) manufactured Ti-6Al-4V component
- 2024
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Ingår i: Precision Engineering. - : Elsevier Inc.. - 0141-6359 .- 1873-2372. ; 85, s. 319-327
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Tidskriftsartikel (refereegranskat)abstract
- Metal additive manufacturing surface topographies are complex and challenging to characterise due to e.g. steep local slopes, re-entrant features, varying reflectivity and features of interest in vastly different scale ranges. Nevertheless, average height parameters such as Ra or Sa are commonly used as sole parameters for characterisation. In this paper, a novel method for selecting relevant parameters for evaluation is proposed and demonstrated using a case study where the smoothing effects after three processing steps of the electro chemical post-process Hirtisation of a metal AM surface are quantified. The method uses a combination of conventional areal texture parameters, multiscale analysis and statistics and can be used to efficiently achieve a detailed and more relevant surface topography characterisation. It was found that the three process steps have different effects on the surface topography regarding the types and sizes of features that were affected. In total, Sdq was reduced by 97 %, S5v was reduced by 81 % and Sa was reduced by 78 %. A surface texture with much lower average roughness, less deep pits and less steep slopes was produced, which is expected to be beneficial for improved fatigue properties.
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| 8. |
- Berglund, Johan C, 1978, et al.
(författare)
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Measuring strategies for smooth tool steel surfaces
- 2008
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Ingår i: Proceedings. - Aachen : Shaker Verlag. - 1610-4773. - 9783832269128 - 3832269126 ; , s. 110-119
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Comparisons between different measuring strategies were made on three types of smooth tool steel surfaces. Three replica materials were tested to study possibilities within replication techniques. An optical interferometer as well as a mechanical stylus was used to evaluate the surfaces. The results showed that the tested replica materials generated good representations of both the form and the surface roughness (Sq > 300 nm). The evaluated surfaces were quite homogeneous, thus, few measurements are needed to get representative results. However, it was found that caution must be taken regarding manually polished surfaces which can be less homogenous and therefore require more measurements to get representative results.
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| 9. |
- Berglund, Johan C, 1978
(författare)
-
Methods for Characterisation of Pressing Die Surfaces
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Design and manufacture of dies and moulds is a critical aspect of many production systems since the manufacturing and try-out of new dies and moulds often is essential in determining the lead-time and quality of a new production system. In the automotive industry, many new car models are introduced each year and for each of these models, a new set of pressing dies has to be designed and manufactured. In manufacturing of pressing dies, the effects of manufacturing processes on functional performance are not fully understood. One of the reasons for this is the lack of effective methods for characterisation. In the work described in this thesis, experimental work is conducted to establish such methods. First, the focus is on methods for obtaining measurement data. Second, the focus is on methods for relating the measurement data to functional performance. In contrast, the technique commonly used today for characterisation is visual and tactile inspection, with the help of reference surfaces, by an experienced operator. In this work, effective 3D measuring strategies were established for pressing die surfaces, including the use a surface replication technique. It was also found that machined surfaces are more homogeneous than manually polished surfaces and therefore require fewer measurements to give representative results. Furthermore, it was established that in production, a 2D profiler can be used for quality control of a finish milled steel surface, in regard to surface roughness, if an appropriate measuring strategy is used and limits for the evaluated parameters first are established for each combination of cutting tools, cutting data, workpiece material etc. In addition, using Rz (average peak-to-valley profile roughness) or Rp (highest peak) is better than using Ra (arithmetical mean deviation) if surface finish appearance is to be assessed. The method employed in this study, using scale-sensitive fractal analysis, for evaluating functional correlations and designing filters was very usable and gave good results. This method can surely be applied to other types of surfaces and functional correlations. Also, there is a correlation between the surface roughness parameter Sq (root-mean-square deviation of the surface) and the surface finish appearance of pressing dies and this correlation is stronger in certain wavelengths on the surface.
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| 10. |
- Berglund, Johan C, 1978, et al.
(författare)
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On finishing of pressing die surfaces using machine hammer peening
- 2011
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Ingår i: The International Journal of Advanced Manufacturing Technology. - Berlin : Springer Berlin/Heidelberg. - 0268-3768 .- 1433-3015. ; 52:1-4, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- Machine hammer peening (MHP) is a new method for finishing of surfaces. With this method, the workpiece surface is hammered with a spherical carbide tool. The main objective of the study was to evaluate whether the MHP method could become a plausible substitute for manual polishing in pressing die manufacturing where nodular cast iron is a common workpiece material. To do this, sample nodular cast iron surfaces were hammered and evaluated. Changes to the surfaces were evaluated using surface roughness measurements, hardness measurements and optical images. First of all, the workpiece surface was smoothened. Secondly, the surface hardness was increased significantly. Thirdly, the nodules on the workpiece surface were affected. They appeared to be smaller and not as visible. This effect would likely create a die surface less prone to galling since the cavities would not be filled with sheet metal to the same extent in a forming operation. In addition, with MHP, the amount of polishing needed to manufacture a die surface can be reduced because of the smoothening effect.
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