V. Fridrici

Influence of Material Nature and Surface Texturing on Wear of Heavy-Duty Diesel Engine Cylinder Liners

The aim of this work is to study the influence of the material (chemical composition and mechanical properties) and the surface texturing on wear of heavy-duty diesel engine cylinder liners. Three kinds of lamellar grey cast iron have been studied: a classical grey cast iron, a surface-quenched grey cast iron, and a micro-alloyed grey cast iron. Honed samples have been tested with different surface roughness parameters. Reciprocating friction tests with the configuration “sphere against a piece of cylinder liner” in lubricated contact have been carried out on a Cameron-Plint test rig. The friction coefficient and the electrical contact resistance were measured during the test. The tribochemical film formation on the wear scars has been studied after different test durations (during and after the running-in stage). The wear volume of the cylinder and the sphere has been determined. Surface heat treatment and phosphorus eutectics can improve the tribochemical film formation and the wear resistance of cylinder liners. Moreover, the surface topography has an important influence; a flat surface with deep valleys shows a better wear resistance than a surface with lots of asperities.

Friction Properties of Medical Metallic Alloys on Soft Tissue–Mimicking Poly(Vinyl Alcohol) Hydrogel Biomodel

In order to investigate the tribological behavior of medical devices in contact with tissue, friction tests for four kinds of medical metallic alloys (316L stainless steel, CoCr, NiTi and TiMoSn) on soft tissue–mimicking poly(vinyl alcohol) hydrogel (PVA-H) biomodel were carried out at low normal load. XPS analysis and wettability tests for them were prepared to understand the difference in friction. According to the surface oxide compositions, these alloys can be divided into two groups: “Fe/Cr-oxide-surface alloys” for 316L and CoCr, and “Ti-oxide-surface alloys” for NiTi and TiMoSn. From the wettability test, Fe/Cr-oxide-surface alloys show lower polar components of surface free energy than Ti-oxide-surface alloys. Fe/Cr-oxide-surface alloys show higher friction coefficients in the elastic friction domain than those of Ti-oxide-surface alloys, while there was no significant difference in the hydrodynamic lubrication. Since elastic friction is governed by the adsorption of hydrogel polymer on counterbody, the surface characteristic of alloys plays an important role in friction. A tentative explanation for this tendency is expressed by linking two different theories describing the adsorption force of hydrogel and wettability of countermaterial.

Degradation of Bioceramics

After roughly 100 years of controlled clinical use, the in vivo and in vitro degradation mechanisms of ceramic materials are still largely unknown. In bioinert ceramics such as alumina and zirconia used in orthopedics, crack propagation mechanisms are well known, but their interactions with other degradation mechanisms (low-temperature degradation, shocks, wear, dissolution, etc.) and the in vivo environment remain to be firmly established. In bioactive ceramics like calcium phosphates and bioactive glasses, dissolution–precipitation processes play a major role on both degradation of the implant and biological efficiency. Even without the ambition to be exhaustive, it is the purpose of this chapter to present the degradation mechanisms of ceramic implants, both inert and bioactive, and the interactions between them and with their environment.

Effect of Surface Topography on Friction and Wear of Cast Iron for Cylinder Liners

This work aims to study and understand the influence of the surface topography on wear of grey cast iron used for heavy duty Diesel engines cylinder liners. A micro-alloyed grey cast iron is tested with different surface topographies: two honed samples with different honing parameters, a polished sample and three model samples with well defined grooves on a polished specimen.

An Energy Approach for Helping the Selection of Solid Lubrication Coatings Under Fretting Conditions

Employing friction reduction coatings is one of the most effective methods to palliate the fretting damage. However, facing numerous available coatings, how to compare them and select the optimum one for a specific application is still a challenging task. In this paper, based on the investigation of the fretting behaviors of several bonded solid lubricant coatings, an energy approach in terms of “initial maximal dissipated energy density” was suggested to compare the tribological response of coatings. According to test results, the lifetime of each coating under different test parameters can be fitted by one master curve. The definition of this master curve for a given coating may be used for the prediction of the coating lifetime only by knowing the initial energy dissipated in the contact. The comparison of different master curves for different coatings can be employed to help the coating selection.Copyright

X-VIEW a high resolution real-time solid state X-ray detection system

The main goal of this paper is the optimization of X-View, a turn-key detection system for high resolution and real-time X-ray non-destructive testing. X-View consists of an microfocus X-ray generator and an acquisition detection system. Two large area detection systems have been developed based on amorphous (a-Si:H) and new CMOS technologies. The first one consists of an X-ray scintillator converter, arrays of amorphous silicon thin film transistors (TFT) and photodiodes (pitch down to 100 μm). The second one, based on CMOS technology, used in high resolution applications, consists of a scintillator and arrays of CMOS photodiodes (pitch of 50 μm). Both are equipped with a fast real-time electronic system for readout and digitization of images and appropriate computer tools for control, real-time image treatment data representation and off-line analysis. Images quality have been improved using a microfocus X-ray generator (focus of 50 μm). Decreasing the spot size of the generator improves the X-ray image quality. The geometric blurring is reduced, and object magnifications are possible. Our study presents the main characteristics of both detection systems (wide dynamic range, lack of blooming, high frame rate), quantitative and qualitative analysis X-ray inspection applications (electronics, various industries, medical, pharmaceutical, etc).

Fretting Wear Behaviour of a Titanium Alloy

When two contacting surfaces are submitted to tangential loading due either to vibrations or to a fatigue loading in one of the contacting component, small amplitude displacements (from one tenth of a micron to hundreds of microns) are induced at the interface. Depending on the materials properties and the normal and tangential loadings, this phenomenon, known as fretting (Waterhouse 1972), can lead to crack nucleation (and possible propagation if one of the component is subjected to a fatigue loading) or to wear by debris formation (Fouvry et al. 1996).