Mission of Tribology Research, 4th December 2013

Sounds like a good event Geoff. Look forward to reading your review.

This was the first time I attended the Mission of Tribology Research and I found it thoroughly worthwhile. The format was a series of Powerpoint presentations by current PhD students in UK universities. It was a half-day event, professionally organised and hosted by the IMechE at their headquarters in Westminster. Apart from the excellent presentations, the chance to meet a good cross-section of students and academic researchers was a real highlight for me.



I came away with a very positive feeling about the state of tribology research in the UK. If these presentations were a representative sample, UK-based research students are working on a diverse set of problems with real practical benefit and they are well focused and supported by their institutions. I was particularly impressed by the combination of numerical modelling and practical testing and investigation shown by many of the presentations.



From my perspective as a British employee of a British company, I would only hope that the number of British researchers in tribology and the connection to British manufacturing industry can be increased in future. It  appears from this event that most of the know-how and competency uplift from this research will go to benefit organisations overseas. On the other hand, the same observation must confirm that British research centres are prominent and successful at a global level, in order to attract high-quality candidates and research funding globally, which is a positive conclusion.



I would encourage anyone on the fringes of tribological research in the UK, whether considering studying for a PhD or working as an engineer in industry to look out for the 2014 Mission of Tribology Research. If you are an undergraduate or professional person wondering whether to commit to a PhD in this field, the chance to speak with people currently going through that process could be very informative. I hope the event can be additionally marketed with this aim in the future.



I'll give a short, personal summary of what I took as the key learning points from each of the presentations of the 2013 event. This is based entirely on my personal topics of interest and I'm not intending it to be a formal, academic review. If anyone would like to add to or correct what I will say below, please post a reply or email me.



CONTROLLING FRICTION-INDUCED VIBRATION IN COMPLIANT CONTACTS

Oana Dobre, Imperial College London

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  Fully hydrodynamic contact between wiper blade and glass - lubricated by water

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  Test rig using a short length of wiper blade on a CETR UMT2 tribometer ("blade on disc")
  
  
  
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    30k fps camera to observe blade oscillations and air bubbles within the water
  
  
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  Microphone with spectrum analyser to analyse acoustic noise emission

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  Laser doppler vibrometry to quantify the movement of the blades

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  Parametric model of potential influences on blade vibration: including sliding speed, normal contact loading

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  FEA of blade using Abaqus with realistic rubber properties

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  Good correlation of resonant frequencies predicted by FEA with experimental results

TRIBOLOGICAL CHARACTERISATION OF PVD SPUTTERED AL-PTFE NANO-COMPOSITE COATINGS

Miroslaw Kula, Cranfield University

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  Research is applied in journal bearing linings for car engine crankshafts - with particular application on start/stop operation with a high rate of boundary contact events

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  PVD sputtering has been used to create a thin sinter ot Al and PTFE

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  Rotational speed of the table was investigated - strong influence on layer morphology

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  Higher rotational speed was found to produce a more optimal columnar structure, which would provide a stable mu/lifetime characteristic of about 0.15

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  PVD creates a thin layer with surface roughness similar to the substrate, so post-treatment polishing was carried out using ion etching

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  A wear test was carried out (HALT principle) using a TE92 tribometer

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  Patent GB2500487 covers this research

EFFECT OF UNLOADING RATE ON THE ADHESIVE CONTACT BETWEEN HARD AND SOFT MATERIALS

Lizbeth Prieto, Cambridge University

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  Research into bi-mimicry, i.e. understanding the function of certain tribological interfaces in the natural world with the aim of developing analogous engineered solutions

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  Adhesive foot pads are classified as smooth (e.g. stick insect) or fibrillar (e.g. gecko)

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  The van der Waals force is believed to create the adhesive effect. This requires an interface gap of <10nm. Liquid, if available, bridges any voids in the interface

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  Animal feet are formed from Keratin with elastic modulus approx. 2GPa.

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  Foot pad surfaces have an effective E of 12kPa (smooth) and 83kPa (fibrillar) indicating a low-density structure

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  Research has replicated such structures on Si-based rubber using PDMS

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  The Oliver-Pharr method was applied to measure E of the created surfaces

EXPERIMENTAL VALIDATION OF MIXED LUBRICATION MODELS USING ELECTRICAL CONTACT METHOD

Ingram Weeks, Cardiff University

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  Part of the British Gear Association's Project 6 - Micropitting

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  The aim is to predict conditions in gear lubricant films, which cannot be measured

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  Rolling/sliding motion creates 5-10um pits and the released particles can initiate scuffing

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  A test rig using radial disc/disc contact was built.

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  The electrical resistance of the contact interface was measured - this was found to be a function of speed and load. Contact between asperities can be inferred.

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  A numerical simulation of the contact interface has also been created. It shows peak contact stress 2-3x the nominal Hertzian maximum contact stress.

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  The simulation model will be further developed to receive scanned surface profiles instead of parametric descriptions

DEVELOPMENT OF SELF-LUBRICATING NI-P/MOS2 COATINGS BY ELECTRODEPOSITION

Yang He, national Centre for Advanced Tribology, University of Southampton

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  The aim of the research is to develop a replacement for high-Cr coatings

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  A TE-77 reciprocating tribometer was used

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  The weight % composition of the surface layers was measured using EDX

DETECTION OF FAILURES IN TRIBOLOGICAL SYSTEMS

Aaron Cockerill, Cardiff University

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  Macro-level tooth deformation may be critical to some gearbox failures

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  A test rig was constructed to investigate rate of change of torque loss in a pair of helical gears

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  The rig was arranged to circulate power through a secondary spur gear path, so that the input torque could be used as a condition-monitoring parameter

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  Input torque was measured using a contactless magnetic sensor, which was specially developed to enable future tests up to 15krpm

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  A numerical simulation was created using Adams, Patran and Nastran in combination

PFPE LUBRICANT DEGRADATION - A NEW ASSESSMENT METHOD

Michael Buttery, University of Central Lancashire

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  The space environment presents uniquely challenging conditions, including: high vacuum, extreme temperature range, zero gravity, no ambient moisture, radiation and inaccessibility for monitoring or repair

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  PFPE is a lon-chain perfluorinated polymeric lubricant, used in some space applications

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  Lifetime tests were carried out using a novel spiral orbit tribometer (SOT) which is claimed to give 1-2% repeatability

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  Lubricant shearing releases F, which reacts with the boundary material forming FeF3 - this in turn catalyses the lubricant

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  The quantity of lubricant per test was 50 microgrammes, providing about 30 molecular layers of coating thickness. The interface operated predominantly in boundary lubrication.

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  A comprehensive investigation of lubricant degradation was carried out, focusing on temperature and contact stress

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  The research has shown that the lubricant degrades more quickly at higher temperatures and there is an instantaneous degradation at startup, which is particularly significant for intermittently operating equipment

DEVELOPMENT OF A TEST DEVICE TO MEASURE THE TRIBOLOGICAL BEHAVIOUR OF SHOE-SURFACE INTERACTIONS IN TENNIS

Daniel Ura, University of Sheffield

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  The aim is to enable rapid assessment of playing conditions on professional tennis courts

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  Tennis players adopt different playing styles on different surfaces, which are tribologically, hugely different:
  
  
  
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    Clay is a 3-body system
  
  
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  Indoor surfaces are a 2-body system

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  Grass is a 2-body lubricated system

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  Tractive force between the show and the surface has been measured using a bespoke test rig, with slow-motion video to assist the analysis

ULTRASONIC REFLECTION TECHNIQUE FOR MEASURING CONTACT CONDITIONS AT THE TOOL CHIP INTERFACE IN DRY MACHINING

Dlair Ramadan, University of Sheffield

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  The basis of the research is Astakhov's finding that only 30-50% of the machining energy is consumed by chip separation. The balance is consumed by friction. Reducing the friction could substantially reduce the power consumption of machining operations.

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  A piezoelectric transducer was attached to the back of a replaceable cutting tool insert. A thermocouple was embedded next to the transducer for temperature compensation.

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  Ultrasonic impulses, generated by the transducer, would be reflected back from voids in the tool/metal interface but not by asperity contact. The degree of reflection could therefore be used to characterise the rough contact between the tool and the workpiece.

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  A comprehensive parametric investigation was carried out into the factors influencing this contact. These included speed, cutting depth and feed rate.

(THE EFFECT OF SI AND W DOPANTS ON THE MECHANICAL AND TRIBOLOGICAL PROPERTIES OF DIAMOND-LIKE CARBON) - title was changed on the day to reflect the actual presentation

Louise Austin, University of Leeds

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  The aim of the research is to develop coatings for IC engine valvetrain components

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  Balinit C was mentioned as one coating under investigation

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  A comprehensive set of tribological tests was carried out: hardness, scratch test, elastic modulus, TEM, EELS, EDX, white light interferometry

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  A pin on disc tribometer was used to detect ZDDP tribofilms that may form on the coated surfaces

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  Atomic force microscopy demonstrated that the ZDDP film did in fact form - this was unexpected. XPS confirmed P and Zn, confirming that a tribofilm had formed