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金虫 (小有名气)

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虫号: 460026
注册: 2007-11-15
专业: 金属材料的合金相、相变及

[交流] 比利时根特大学 ME CSC 博士职位招生

代发，项目详情请见下面的简介。希望力学/机械/材料背景，有限元经验优先。距离CSC截至时间不多了，有意者请联系  joachim.antonissen@arcelormittal.com

Proposal of PHD
(Sliding) Contact of rough surfaces
Summary

An accurate prediction of the surface topography (roughness) evolution of metallic surfaces under conditions of normal and shear loading is important for various industrial applications such as deep drawing and roughness transfer during rolling; it also determines the leakage resistance of threaded connections used in oil & gas transport.  At the level of the surface, leakage can be described as a flow passing through the peaks and valleys between the surface of the male and female parts of the connection.  Models of leakage already have been presented for self-affine surfaces, like for example rubber on steel.  Pipeline connections however are normally produced by turning.  Such surfaces cannot be described adequately anymore by the previously mentioned theories. Leakage can occur by flow in the valleys having a spiral form or by the presence of short paths between two parallel grooves.

Increasing the contact pressure, the peaks of the surfaces will be flattened, and the conservation of the volume should push some material of the peaks to the valleys of the surface, decreasing the valleys depth. Consequently, the leakage rate should be decreased and sealing will be improved. In the contact evolution with the normal pressure, the sliding contribution (shear) is generally neglected, and only normal pressure is considered.  Moreover it is assumed that this rise of the non-contacting surface is uniform. The validity of these assumptions is debatable, yet it is to this date widely applied. There is however an upper bound to the contact pressure, which is determined by the deterioration of the surface, generally called here “galling”. Most of the literature concerning this topic comes from the field of stamping, where a smooth hard surface is in contact with a rough soft material.

Research in the modelling of contact mechanics of rough surfaces has progressed substantially in recent years. However most of the published papers only deal with a sub-set of conditions and/or aspects that are simulated.  The aim of the proposed research is to set up a comprehensive model that includes the most important aspects and specifically deals with layered material and thermal effects.  A generic approach is aimed for to study “layers” very broadly.  Amongst others the difference in mechanical properties of the top layer of “nominally” bulk material has to be looked at, as well as thin metallic (e.g. Zn, Al, … ) as non-metallic coatings (plastics and even hard ceramic coatings).  In the case of sliding contact the interactions between thermal and mechanical effects will have to be considered as well: the friction heating causes thermal softening and/or micro-weldments, which in turn affect the asperity (de-)formation, etc... Multi-scale and multi-physics modelling will need to be applied, if one is looking for real applications, such as the prediction of friction, wear, rolling roughness transfer, thermal contact resistance.

This PhD research is supported by the research Centre OCAS in Flanders, Belgium, a joint initiative of the ArcelorMittal Group and the Flanders Government. www.ocas.be

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