| 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)
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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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Jonsson, Per, 1981, et al.
(författare)
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Surface Topography on trimming dies and the influence of wear
- 2010
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Ingår i: Proceedings of the International Deep Drawing Research Group. - 9783851251081 ; , s. 345-354
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Konferensbidrag (refereegranskat)abstract
- In this paper it is investigated how surface topography on trimming dies influences the wear process. Surfaces on both semi-industrial test dies and dies used in production were analyzed with different surface topography analysis methods. The result shows that the wear process is different on the different sides of the trimming edge. The texture direction of the surface is changed due to wear, with the strongest change on the clearance side of the edge. The roughness on sheet side of the edge is reduced due to a hammering effect from the sheet material. The result on the test dies and the production dies correlates well.
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| 7. |
- Rosén, Bengt - Göran, 1962-, et al.
(författare)
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Friction in Sheet Metal Forming : A Comparison Between Milled and Manually Polished Die Surfaces
- 2010
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Ingår i: Proceedings of 4th International Conference on Tribology in Manufacturing Processes. ; , s. 613-622
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Konferensbidrag (refereegranskat)abstract
- The evolvement of product requirements in the automotive industry, e.g. reduced weight, means that the use of advanced high strength steels (HSS, EHSS,UHSS) in automotive applications is continuously increasing. The introduction of high strength steels in production implies increased tool wear and calls for functional tool surfaces that are durable in these severe tribological conditions. In this study the influence of tool surface topography on friction has been investigated. The frictional response was studied in a Bending Under Tension test. The results did show that a low frictional response was generated by low slope of roughness profiles combined with a strong anisotropy applied perpendicularly to the sliding direction. An improved machining strategy has a high potential to significantly reduce the need for manually polished surfaces.
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