Development of Analysis Tools for In Situ TribometryMichel Stephan1,2, Holger Strauss1and Prof. Richard R. Chromik1

Departments of 1Mining and Materials Engineering , and 2Electrical and Computer EngineeringMcGill University , Quebec , Canada

Introduction:What is Tribology ?Tribology is the study of friction, lubrication, and wear of interacting surfaces in relative motion. The standard apparatus used in a tribological experiment is called a tribometer. A tribometer records the friction force when two solid contacts are set in sliding motion.

The Tribological System

[2]

Background:In Situ Tribometer

A sample material is clamped on a stage, which provides reciprocating motion .A video camera looking through the microscope and hemisphere records a video of the test.A piezoelectric sensor, which is housed underneath the sample is used for acquiring lateral forces.A record of the friction coefficient and cycle number is recorded with the

video to allow easy reference between friction data and video frames.The formation and motion of wear debris is revealed by this technique, providing information that can help predict and model wear and the lifetime of protective coatings.

Images from the recorded videos

Newton’s Rings Transfer Film

Debris

Objective:1) Develop a software program that is capable of capturing certain specific images from the

video in order to study and analyze these images .Develop Analysis tools that are accurate and require minimal interaction. For:

2) Measurements of Newton’s Rings to calculate transfer film thickness.3) Measuring the covered area of the transfer film.

Analysis

NEW!

Methods:Newton’s Ring Method to Quantify Transfer Film Thickness

Using Changes in the Covered Area to Determine Wear

Change in transfer film area= Area before turning – Area after turning

Experiment:3 previously studied videos were selected to test the capabilities of the newly developed software tools.

Goals: find possible correlations between friction, wear, and TF behaviour.

TF behaviour

Thickness(Newton’s Rings)

Covered Area (Type of

coverage)

Previous StudyIn situ tribometry was used to examine the role of transfer films for the friction and wear behaviour of hard Ti-Si-C-H coatings (produced by plasma-enhanced chemical vapour deposition) in presence and absence of environmental humidity.

Results:

Conclusion and Future Work:

References:

The analysis tools developed have a significant impact on research using in situ tribology. It allows more data to be analyzed more quickly. New findings on the wear rate can be made from analyzing transfer films.A more rigorous analysis using changes in covered area needs to be undertaken to obtain quantifiable measurements for transfer films that can be compared to ex situ wear measurements.

[1] Stachowiak, and Batchelor, Engineering Tribology, Butterworth Heinemann, Inc., Boston, 2001.[2] Bhushan,Introduction to tribology,John Wiley and Sons, 2002[3] Strauss, Chromik, Hassani, Klemberg-Sapieha, In situ Tribology of NanocompositeTi-Si-C-H Coatings Prepared by PE-CVD, Wear 2011, in press.

Newton’s Ring Method to Quantify Transfer Film Thickness

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200

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1000

0 100 200 300 400

Manually

TFT(

nm

)

Cycle #

Using Changes in the Covered Area to Determine Wear

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[1]

Motivation for Research:Losses resulting from ignorance of tribology

amount in about 4% of the gross national product . Savings from research in tribology are expected

to be in order of 50 times the research costs.The purpose of research in tribology is the minimization and elimination of losses resulting from friction and wear at all levels of technology where rubbing of surfaces is involved. Research in tribology leads to greater efficiency, better performance , fewer breakdowns and significant savings.

[3]

Friction Coefficient:µ=F/N

F

N

[2]

[2]

Sapphire Slider

Specimen

Wear Debris

Wear track with Transfer Film

Developed using:C language ,OpenCV library ,and LabVIEW

Developed using:Macros in ImageJ Microsoft Excel

••

d:= diameter of Newton’s ring in pixels, with i = 2, 3, 4, 5 order of Newton’s ring and n = 1, 2, 3, ..., 2400 number of reciprocating cycle, where n = 0 depicts the time before sliding motion was started

Acknowledgments:This research and project has been supported by grants from SURE program (Faculty of Engineering at McGill university ) , NSERC and FQRNT . I would like to thank Mr. Salim Hassani and Prof. Jolanta Klemberg-Sapieha from ecole polytechnique de montreal for their work in producing and giving us the coatings.I further thank the Faculty of Engineering to their support and services throughout the research.

1

2 3

Area before turning

Area after turning

Wear track

Sideways Debris

Semi automated

Selected test runs:

1: low wear, 0.8at.% Si, ambient air (25–40 %RH)

2: high wear, 0.8 at.% Si, dry air (2 – 3 %RH)

3: high wear, 0.8 at.% Si, dry air (2 – 3 %RH)

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1 2 3Test #

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lum

e o

f w

ear

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ss f

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s (µ

m3)

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Ex Situ In Situ

End patch debris

Is change in transfer film area related to wear?

V

N: Normal ForceF: Friction ForceV: Velocity

Reciprocating Motion

Measurements of Newton's Rings

Video of the experiment

Image grabbing

Measurements of transfer film area

Comparison between manual and semi-automated analysis

TFT(

nm

)

Cycle #

Comparison between In situ and Ex Situ analysis

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Results from semi-automated method gives trends for TFT that are comparable to manual method.

Loss

in T

F ar

ea

* TF

T

(pix

el2*µ

m)

A preliminary analysis of change in covered area * TFT shows trends from test to test that are comparable to ex situ measurements of wear. This is the first time that in situ measurements on transfer films have been used to understand their wear rate.