Characterisation of the flattening behaviour of modelled asperities
Characterisation of the flattening behaviour of modelled asperities
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DOI：
10.1016/j.wear.2008.04.063
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发表时间：
2009-03
期刊：
影响因子：
5
通讯作者：
S. Weidel;U. Engel
中科院分区：
文献类型：
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作者：
S. Weidel;U. Engel
在金属成形工艺中，工具和工件之间的摩擦学条件对于工艺质量和工艺可行性至关重要。这对于微成形应用更是如此，其中工件的至少两个尺寸在亚毫米范围内，这是由于当工艺尺寸按比例缩小时增加的摩擦。这种效果可以解释的模型的开放和封闭的润滑剂口袋表征工件表面和不变性的地形缩放。由于接触工具的工件微凸体的数量急剧减少，单个微凸体的平坦化行为对于更详细地表征微成形过程中的摩擦学具有重要意义。特别是，出现在平坦凸体顶部的地形，所谓的纳米地形及其对摩擦条件的影响，必须加以考虑。利用高分辨率的实验装置对基底面积为120μm×120μm、高度为32μm的金字塔形模型表面粗糙体进行了平整化处理，实现了对接触面积的原位观察。在过程中的测量是由共焦显微镜和扫描探针显微镜的地形分析后处理的补充。本文将表明，在一定的几何条件下，可以出现在平坦的凸体顶部的纳米形貌，它对工具/工件界面的摩擦条件有影响。关于表面形貌演变的详细知识特别与微成形有关，但也有助于更好地理解一般的摩擦学现象。
In metal-forming processes tribological conditions between tool and workpiece are of greatest importance for process quality and process feasibility. This is even truer for microforming applications, where at least two dimensions of the workpiece are in the sub-millimetre range, due to increasing friction when process dimensions are scaled down. This effect can be explained by the model of open and closed lubricant pockets characterising the workpiece surface and the invariance of topography to scaling. As the number of workpiece asperities contacting the tool is drastically reduced the flattening behaviour of single asperities is of major interest for characterising tribology in microforming processes in more detail. Especially, a topography emerging on top of flattened asperites, the so-called nanotopography and its impact on the friction conditions has to be considered. Modelled asperities represented by pyramids with a base area of 120μm×120μm and a height of 32μm are flattened with a high-resolution experimental setup which enables in situ observation of the contact area. In-process measurement is complemented by post-process analysing the topography by confocal microscopy and scanning probe microscopy. This paper will show that a nanotopography on top of flattened asperities can emerge under certain geometrical conditions and that it has an impact on the friction conditions in the tool/workpiece interface. The detailed knowledge about the evolution of surface topography is relevant in particular to microforming but also for an improved understanding of tribological phenomena in general.