Investigation of the tribological performance of ionic liquids in non-conformal EHL contacts under electric field activation

Real-time external alteration of the internal properties of lubricants is highly desirable in all mechanical systems. However, fabricating a suitable and effective smart lubricant is a long-lasting experimental process. In this study, the film thickness and frictional response of ionic liquid-lubricated non-conformal contacts to an electric field excitation under elastohydrodynamic conditions were examined. Film thickness was evaluated using a "ball-on-disc" optical tribometer with an electric circuit. Friction tests were carried on a mini traction machine (MTM) tribometer with a "ball-on-disc" rotation module and an electric circuit for contact area excitation. The results demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation at the evaluated film thicknesses. The results of evaluated film thicknesses demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation. Therefore, the ionic liquids could be a new basis for the smart lubrication of mechanical components. Moreover, the proposed experimental approach can be used to identify electrosensitive fluids

EXPERIMENTAL STUDY OF ARTIFICIAL FEATURES ATTENUATION IN ROLLING/SLIDING CONCENTRATED CONTACTS

ABSTRACT A surface roughness attenuation approach based on the Fourier decomposition of surface roughness into harmonic components may allow predictions of the behavior of real rough surfaces within concentrated contacts. Recently the simplified model for rolling/sliding conditions was suggested. A high pressure ball on disk tribometer was complemented by hi-speed digital camera with the aim to observe a progress of roughness feature pass through the contact. The experiments with artificial features were carried out under rolling/sliding conditions, evaluated by thin film colorimetric interferometry and compared with theory. Detail understanding of real roughness behavior inside contact under rolling/sliding conditions can have extensive impact on practical design of machine components

Towards near-permanent CoCrMo prosthesis surface by combining micro-texturing and low temperature plasma carburising

This article will argue that the legal academy has much to learn by recording, transcribing and systematically studying student-client and attorney-client consultations. Clinical faculty can utilize conversation analysis and other social science techniques to do this. Social scientists and medical providers have studied doctor-patient conversations in this way over many years. Through this systematic study researchers have reached conclusions about effective doctor-patient consultations that form the basis for teaching these skills in medical school. This article will highlight some of these studies and their findings. Some have contended that attorney-client conversations simply cannot be recorded and studied in the same way as doctor-patient consultations due to attorney-client privilege. This article will lay out how a law clinic could obtain client informed consent to this procedure, protect client confidentiality and privilege, and gain the necessary approval of the Institutional Review Board. Finally, this article will suggest topics about client consultations that could merit study in the law clinic

The impact of surface and geometry on coefficient of friction of artificial hip joints

Coefficient of friction (COF) tests were conducted on 28-mm and 36-mm-diameter hip joint prostheses for four different material combinations, with or without the presence of Ultra High Molecular Weight Polyethylene (UHMWPE) particles using a novel pendulum hip simulator. The effects of three micro dimpled arrays on femoral head against a polyethylene and a metallic cup were also investigated. Clearance played a vital role in the COF of ceramic on polyethylene and ceramic on ceramic artificial hip joints. Micro dimpled metallic femoral heads yielded higher COF against a polyethylene cup; however, with metal on metal prostheses the dimpled arrays significantly reduced the COF. In situ images revealed evidence that the dimple arrays enhanced film formation, which was the main mechanism that contributed to reduced friction

Artificial Surface Roughness Deformation in the Starved EHL Contacts

Starved elastohydrodynamically lubricated contact is described as deviation from fully flooded contact due to insufficient lubricant supply. This insufficiency causes thinner lubricant film compared to fully flooded regime. Thinner lubricant film means that rolling surfaces are closer together. Each surface has its own roughness, which is created by machining of the surface and is composed by many individual asperities. These asperities are elastically deformed while passing through the contact area of the EHL contact as well as whole contact surface. It is important to know the magnitude of the deformation. Especially in the starved contact where is increased risk of surface wear due to mutual contact of asperities on the opposite surfaces. This paper presents experimental work on the topic of the surface roughness deformation, which is passing by contact. Analytical method called amplitude attenuation theory was used to predict deformation of the artificial asperity (ridge) under starved conditions. Deformations provided by predictions were compared with the experiments and from both method is clear that roughness deformation is increasing with the progressing starvation - thinning the lubricant film. Magnitude of the deformation however depends on the asperity profile