Search results

THE SWANSEA Tribology Centre officially came into existence on 1st October, 1968, which was the date when the first members of the staff took office. The formal announcement of the establishment of the Centre had been made in November, 1967, by the Minister of Technology, and was one of the early results of the activities of the Committee on Tribology.

TRIBOLOGY Bronze Medals for 1986 were awarded jointly to Dr Martin Webster, BSc, MSc, PhD, and Dr Paul Newman BSc.PhD, at a recent Tribology Group Meeting in London.

During the operation of Wendelstein 7-X (W7-X), any mechanical disturbance such as stick-slip may cause quenching of superconducting (SC) coils. The friction behavior of MoS₂ lubrication (thin film) for narrow support elements between the SC coils in W7-X is rather important, as there is a design requirement for a coefficient of friction (COF) 0.05 between the sliding surfaces to control the stress contribution (from friction).

The author has carried out intensive calibrations or verifications using verified models considering previous friction tests on various samples which measured the COF in 4.2 K, 77 K and room temperature conditions (at high vacuum) to simulate the actual working condition.

The author has given useful explanations and diagnosis for previous anomalous scattered data. To improve the performance of MoS₂, the author has predicted its better COF (0.002 via tuning of the activation volume), which could be a superlubricating state for MoS₂ thin films considering the long-term operation requirement W7-X.

In this paper, the author has adopted Eyring’s approach to predict the low COF (0.002 via tuning of the activation volume), which could be a superlubricating state for MoS₂ thin films considering the long-term operation requirement W7-X. Finally, some recent progresses about the possible few-layer MoS₂ role in the electromagnetic loads have been provided.

Outlines the history of the specialist lubrication group of the Institution of Mechanical Engineers – which was originally called the Lubrication Group and is now the Tribology Group. Describes how the organization was formed and lists its achievements, special activities and publications. Concludes by looking to the future, stating that the group has developed a dynamic five‐year plan to take it into the next century.

BRIEF news of the Institution of Mechanical Engineers' Tribology Group visit to China as guests of the Chinese Mechanical Engineers Society (CMES), appeared on the “Comment and opinion” page of our September/October issue last year. It was the first since the initial trip in 1979. We asked for a more detailed account and a report of the 3,500 mile journey through the country of a thousand million people, many anxious to know more about the new industrial technologies, now comes from S.J. Crampton, BSc (Eng), FIMechE, FInst Pet, manager, Projects and Research, IMechE, who was a member of the eight‐man party.

The purpose of this paper is to conduct research on the possibility of improving the tribological and utilization properties of lard and rapeseed oil bio-based greases by mixing it with ethanol and selection of thickener and modification with special biological additives.

Rapeseed oil- and lard-based greases with sodium and lithium soap thickeners were mixed with either water or ethanol and modified with a special biological anti-wear additive. Tribological properties of modified lubricants evaluated on a four-ball machine.

Rapeseed oil- and lard-based greases suspended in ethanol and modified with bio-additive have the same wear resistance as the industrial non-biological lubrication grease and much higher wear resistance as bio-based reference grease. The tribological efficiency of the additives is higher in greases of rapeseed oil and less efficient in lard-based greases. Oxidation and wear tests show that investigated bio-based greases have comparatively stable tribological properties also after their aging. Modified greases have sufficient consistence according penetration measurements and high thermal resistance according drop-point temperature measurements. All produced experimental greases pass within the category of the easily degradable materials.

The greases mixed with the ethanol make possible to form more homogeneous and stable grease mixture. Modified bio-based greases have significantly higher wear resistance as bio-based reference grease, their lubrication properties are stable also after the aging and are categorized as easily degradable materials.

In the first part of this article in our last issue P. L. HURRICKS considered the wear resistance of sprayed coatings when subjected to adhesive and abrasive action. In this part he is concerned with the friction of sprayed coatings on bearing and journal surfaces.

PREVIOUS ARTICLES IN THIS SERIES HAVE DESCRIBED THE WORK AT THE THREE CENTRES OF TRIBOLOGY (SWANSEA, JULY '70, LEEDS, SEPTEMBER '70 and RISLEY, APRIL '71) READING IS NOT A TRIBOLOGY CENTRE AS DEFINED IN THE JOST REPORT AND SO EMPHASIS IS MORE ON FUNDAMENTAL RESEARCH AND TEACHING RATHER THAN PROVIDING A SERVICE FOR LOCAL INDUSTRY, BUT LOCAL INDUSTRY DOES, NEVERTHELESS SUPPORT THEIR WORK.

In a high temperature tribometer, stationary carbon has been tested against different rotating ceramics (SiC, Si₃N₄, Al₂O₃, WC‐6Ni, MgO‐ZrO₂, (Ti, Mo)(C, N)) and stainless steel (DIN 1.4876). The rotating discs were grinded, polished and/or lapped. For most material combinations, the wear morphology is known from available literature. A transfer film with a typical wear pattern was found on the rotating disc. The combination of antimony graphite EK3245 against MgO‐ZrO₂ did not form carbonaceous transfer layer. Through advanced variation of the roughness up to R_pk=0.011 μm, the wear rate has been reduced to K_v ≈ 3.5×10⁻⁸ mm³/N m at a stable coefficient of friction in a “millirange” of μ∼0.008 for a sliding distance of 20.000 m.

The purpose of this paper is to evaluate local biodegradable oils with long chain fatty acids namely: castor (Ricinus communis L.), jojoba (Simmondsia chinensis L.), olive (Oleo europaea L.), and sunflower (Helianthus annuus L.) oils for lubrication candidacy as a substitute to petroleum mineral oils.

Evaluation criteria includes antiwear, lubricity, and extreme pressure (load carrying capacity) using the four‐ball configuration, oxidation induction by pressure differential scanning calorimetry, thermal stability by thermo‐gravimetric analyses, and viscometry using relevant American Society of Testing and Materials (ASTM) standards.

The results show that the lubrication films at the interface failed by the decomposition of the metallic soaps formed by the chemical reaction of the constituent fatty acid molecules and the rubbing surfaces. The biodegradable oils show superior lubricant performance compared to the paraffin‐based mineral oil, despite their poor oxidation stability. Oxidation induction and thermo‐gravimetric characteristics of the biodegradable oils are closely related to their polyunsaturated and monounsaturated fatty acid composition.

The paper shows how these biodegradable oils could be used as good substitute for petroleum mineral oils in as‐received state or little antioxidant additives.