Rolling contact mechanics

Johnson, K. L. (1985). Contact Mechanics. Cambridge University Press, Cambridge. Kalker, J. J. (1990). Three dimensional elastic bodies in rolling contact. Kluwer Academic Publishers, Dordrecht. 

Black Tea. The freshly harvested leaves are spread out on mats and allowed to dry slowly and wither, after which they are mechanically rolled and broken to liberate the oxidase enzymes present in the cell sap and ensure their close contact with precursors. The rolled leaves are then fermented for several hours, usually in baskets or spread out under damp cloths. During this stage the colorless tea tannins are partially oxidized, changing to a reddish brown color, and some essential oil is formed. This primary oxidation gives to the leaves a very agreeable odor and color and determines the flavor quality, strength, body, and color of tea made from them. The process is stopped by firing at about 85°C. This induces a secondary oxidation, a reduction in moisture content to about 5% and the full development of the characteristic tea odor and color. The whole process demands skill and experience to achieve a consistent quality. 

It is now well-known that surface properties of solids are able to activate their bulk properties, and, as a consequence, strongly influence the mechanical belmvior of the interface area of solids in contact. Our aim is to illustrate this matter through three examples the no-rebound of balls on the smooth surface of a soft elastomer, the spontaneous peeling due to the intervention of internal stresses and the adhesive contact and rolling of a rigid cylinder under a smooth-surfaced sheet of rubber. 

Sjo96] Sjo A. (1996) Numerical Aspects in Contact Mechanics and Rolling Bearing Simulation. Licensiate Thesis at the Dept, of Computer Science, Univ. Lund (Sweden). 

Krause H., Poll G. - The Influence of Real Materials and System Properties on the Traction/Creep Relationships in Rolling Contact. Proceedings of 1 International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Kalousek et al. Editors, UW press, 1983, pp. 353-371. 

The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

Skiving is a variant in which the base metal surface oxides are mechanically removed foUowed immediately by pressure rolling of a precious metal or alloy strip. This is commonly used for inlays for electrical contacts and for jewelry fabrication. The common inlay materials include gold, silver, copper, brass, and solder. No heat is needed, and the coating is appHed only to designated areas so there is Htde waste (3,50). 

Fully Adhered. The substrate, ie, insulation, cover board, etc, that the single-ply membrane is to be attached to is either fuUy adhered or mechanically fastened to the deck. However, there are also appHcations where the membrane is adhered directly to the deck. The membrane is then adhered to the substrate. The typical method for adhering the membrane to the substrate is by applying a contact adhesive to the membrane and substrate, rolling the membrane into place, and brooming once the adhesive is ready. There are one-sided appHcations where the membrane is roUed directly into the adhesive that has been appHed to the substrate only. The membrane used in this appHcation method may be fleece-backed. FuUy adhered systems can be installed on any slope. The fuUy adhered appHcation offers a smooth surface that is easy to maintain and inspect, as weU as exceUent wind resistance on account of positive attachment. 

The motor carries and supports any axial thrust by the pump (hydraulic or mechanical). The motor on these pumps can be fitting with precision rolling element bearings, either angular contact, spherical rollers, or pillow blocks inclined depending on the thrust load and velocit of the shaft. 

In 1996, Liu et al. [129] analyzed the wear mechanism based on the rolling kinematics of abrasive particles between the pad and wafer. They summarized that the kinetics of polishing are (1) material removal rate is dependent on the real contact area between the slurry particle and the wafer surface. The real contact area is related to the applied pressure, the curvature, and Young s modulus of the slurry... 

---