Johan C Berglund

On discovering relevant scales in surface roughness measurement - an evaluation of a band-pass method

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.

Grit Blasting for Removal of Recast Layer from EDM Process on Inconel 718 Shaft: : An Evaluation of Surface Integrity

The heat generated during EDM melts the work material and thereby allows large amounts to be removed, but an unfavorable surface of a recast layer (RCL) will also be created. This layer has entirely different properties compared to the bulk. Hence, it is of great interest to efficiently remove this layer and to verify that it has been removed. The main objective of this work has been to study the efficiency of grit blasting for removal of RCL on an EDM aero space shaft. Additionally, x-ray fluorescence (XRF) has been evaluated as a nondestructive measurement to determine RCL presence. The results show that the grit-blasting processing parameters have strong influence on the ability to remove RCL and at the same time introduce beneficial compressive stresses even after short exposure time. Longer exposure will remove the RCL from the surface but also increase the risk that a larger amount of the blasting medium will get stuck into the surface. This investigation shows that a short exposure time in combination with a short grit-blasting nozzle distance is the most preferable process setting. It was further found that handheld XRF equipment can be used as a nondestructive measurement in order to evaluate the amount of RCL present on an EDM surface. This was realized by analyzing the residual elements from the EDM wire.

A Method for Visualization of Surface Texture Anisotropy in Different Scales of Observation

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.

Surface Topography on trimming dies and the influence of wear

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.