Influence of surface wettability on friction and wear test.

In this work the effect of surface wettability of different materials on friction and wear behaviour with sliding friction of 100% has been studied. The following materials have been chosen: AISI 1050 and AISI 420 steels, pyrex glass, teflon PTFE. and carbon fiber. All have different surface wettability angles u .. Tests with these materials have been carried out with a pin-on-disc tribometer with homogeneous and heterogeneous couplings in dry conditions and with oil and water lubrication. The most important result achieved with the mechanical tests and the SEM examinations is that with couplings of a hydrophillic and a hydrophobic material, water lubrication has a greatly positive effect. Particularly with hydrophobic discs and hydrophillic pins the friction factor and the wear have been lower than those with oil lubrication

A rare complication of small bowel intussusception: report of a case and review of literature.

Volvulus and intussusception are rare conditions in children. We describe an unusual case of intussusception due to a solitary Peutz-Jeghers type hamartomatous polyp complicated by volvulus, which occurred in an 11-year-old girl. A laparotomy allows to successfully treat the pathology. The postoperative course was favourable. We discuss the clinical findings and the values of the preoperative instrumental diagnosis. The literature is reviewed. Identifying a midgut volvulus, as complication of a small bowel intussusception, during the diagnostic phase could help in choosing the most appropriate surgical approach

Dynamics of contact line motion during the wetting of rough surfaces and correlation with topographical surface parameters

Dynamics of contact line motion and wettability is essential in many industrial applications such as liquid coating, lubrication, printing, painting, condensation, etc. However, the wettability of surfaces depends not only on liquid–solid chemical properties but also can be strongly affected by surface roughness. As a practical application of controlled wettability, we can mention the self-cleaning surfaces, protective clothing, microfluidics devices, electro wetting, etc. In this article, we experimentally investigate the spreading of droplets deposited onto rough surfaces. Anisotropic surfaces were prepared by abrasive polishing on the following materials: aluminium alloy AA7064, titanium alloy Ti-6Al-4V, steel AISI 8630, copper alloy UNS C17000, machinable glass ceramic, and poly-methylmethacrylate. Topographical 2D parameters were calculated according to the following standards, defining Geometrical Product Specifications (GPS): ISO 4287, ISO 12085, ISO 13565, ISO 12780, and ISO 12181. The influence of topographical parameters on wettability and spreading phenomenon has been evaluated by statistical covariance analysis. The following parameters have strong influence on fluid spreading on rough surfaces: Rmr is the relative material ratio of the roughness profile, Trc is the microgeometric material ratio, Pmr is the relative material ratio of the raw profile, Kr is the mean slope of the roughness motifs, RONt is the peak to valley roundness deviation, and Psk is the Skewness of the raw profile. The physical meaning of selected parameters is discussed, and Kr (the mean slope of the roughness motifs) is selected as the most important and physically meaningful parameter. It has been found that for all tested materials, fluid spreading shows increasing tendency when mean slope of the roughness motifs (Kr) increases. SCANNING 33: 1–8, 2011. © 2011 Wiley Periodicals, Inc

Wettability versus roughness of engineering surfaces

Wetting of real engineering surfaces occurs in many industrial applications (liquid coating, lubrication, printing, painting, ...). Forced and natural wetting can be beneficial in many cases, providing lubrication and therefore reducing friction and wear. However the wettability of surfaces can be strongly affected by surface roughness. This influence can be very significant for static and dynamic wetting [1]. In this paper authors experimentally investigate the roughness influence on contact angle measurements and propose a simple model combining Wenzel and Cassie-Baxter theories with simple 2D roughness profile analysis. The modelling approach is applied to real homogeneous anisotropic surfaces, manufactured on a wide range of engineering materials including aluminium alloy, iron alloy, copper, ceramic, plastic (poly-methylmethacrylate: PMMA) and titanium alloy

Analysis of the causes of failure in 5Cr-1Mo pipes mounted in a preheating furnace

The oxidation resistance of iron-based alloys depends on the formation of thin protective films consisting of reaction products between the alloys and the ambient atmosphere. The high corrosion resistance of Fe-Cr-Mo alloys has been attributed to the rapid formation of a uniform, highly protective passive film. The pipes hardness and resistance to various forms of corrosion are determined by the composition of the oxide layer that plays an important role in determining the lifetime of the pipes themselves. The thermal stability of the oxide layer is influenced by its composition and thickness as well as by the bond to the underlying metal. Determining factors for the high temperature corrosion are generally: temperature, metallurgy, TAN (chloridric and naphthenic acid), local flow conditions, sulphur compounds