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ROTATIVE OR LINEAR WEAR & COF?
A COMPREHENSIVE
STUDY USING THE
NANOVEA TRIBOMETER
Prepared by
Xavier Herrera-Keehn and Jocelyn Esparza
Today's standard for tomorrow's materials. © JULY 2019 NANOVEA
NANOVEA
www.nanovea.com
A Better Measure
info@nanovea.com
info@nanovea.com
euro@nanovea.com
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www.nanovea.com
949-461-929
(949)-461-9292
Introduction
Wear is the process of removal and deformation of material on a surface as a result of mechanical action of
the opposite surface1. It is influenced by a variety of factors, including unidirectional sliding, rolling, speed,
temperature, and many others. The study of wear, tribology, spans many disciplines, from physics and
chemistry to mechanical engineering and material science. The complex nature of wear requires isolated
studies towards specific wear mechanisms or processes, such as adhesive wear, abrasive wear, surface
fatigue, fretting wear and erosive wear2. However, “Industrial Wear” commonly involves multiple wear
mechanisms occurring in synergy.
Linear reciprocating and Rotative (Pin on Disk) wear tests are two widely used ASTM compliant setups34
for measuring sliding wear behaviors of materials. Since the wear rate value of any wear test method are
often used to predict the relative ranking of material combinations, it is extremely important to confirm
the repeatability of the wear rate measured using different test setups. This enables users to carefully
consider the wear rate value reported in literature, which is critical in understanding the tribological
characteristics of materials.
Measurement Objectives
Equipment Featured
NANOVEA T50
Versatile Wear & Friction Tester
Multi-Module System
Speed Control from 0.01-5000 RPM
Robust with Open Platform
Wide Rang of Environmental Conditions
Learn More about the T50
Measurement Objectives
In this study, the wear rate of an aluminum sample is measured in a controlled and monitored manner
using the linear reciprocating and rotative wear test setups of the Nanovea Tribometer for comparison.
The versatility of the Nanovea Tribometer is showcased when measuring the wear rate of a single sample
using different setups.
Sample tested on T50 (Rotative and Linear)
Tribology Results
Measurement Parameters
The wear behavior, e.g. coefficient of friction (COF) and wear resistance of the aluminum sample was
evaluated using the Nanovea Tribometers linear reciprocating and rotative modules for comparison. An
SS440 ball tip, 6mm in diameter, was applied against the tested sample. The COF was monitored in situ.
Finally, the volume loss of each test was measured using the Nanovea HS2000 Line Sensor to determine
the respective wear rate of the two tests conducted.
Instrument T50
Normal Force (N) 10
Rotative Speed (RPM) 60
Linear Speed 1 Hz for reciprocating wear
Number of Strokes 1200
Duration of Test (minutes) 20
Distance Traveled (m) 12
Table 1:Test parameters for COF and wear measurements
Sample Tested
Sample of aluminum
Tribology Results
Results & Discussion
It is important to note that for the linear testing, a stroke will be defined as the travel in one direction. This
attempts to minimize the difference in speed at which the sample is traveling when comparing the rotative
and linear results. The COF per test was recorded in situ and is shown in Figure 1. The two testing methods
produced distinct values for their average COF, 0.575 for linear and 0.407 for rotative. This discrepancy can be
attributed to a multitude of factors, one of them being a greater wear rate which increases the ball bearings’
contact area. This can also create more debris, that may enter the wear track, influencing the surface which
the ball bearing is reciprocating on.
(a)
(b)
Figure 1: Coefficient of friction during (a) linear reciprocating and (b) rotative wear tests
Tribology Results
Results & Discussion
The subsequent wear tracks were evaluated using the Nanovea HS2000 Line Sensor, allowing us to compare
their respective wear rates and track depths shown in Figures 2, 3, and 5. It is interesting to note the stark
difference in wear rates when comparing the linear versus the rotative results. The wear rate for the linear test
was 998.88 x 10-5 mm3/Nm and 100.67 x 10-5 mm3/Nm for the rotative test. Both samples underwent similar
testing parameters but the linear test achieved a wear rate of 10 times the rotative. This disparity can also be
seen in the wear tracks for each sample. Figures 3 depicts a much more significant wear track when com-
pared to Figure 2. This is to be expected given their wear rates.
Figure 2: Rotative wear track profile
Figure 3: Linear wear track profile
Tribology Results
Results & Discussion
Figure 4: 3D profile of rotative and linear test respectively
Tribology Results
Results & Discussion
Figure 5: Wear Rate for Linear vs. Rotative
The substantially different wear resistance measured in two commonly used wear test setups shows the impor-
tance of comparing wear resistance of the materials using identical experimental setup and test conditions. It
illustrates that wear can change drastically when small changes in testing conditions are introduced into the
tribometer system. The versatility of the Nanovea Tribometer allows the user to measure both rotative and linear
reciprocating wear on one single system under various environmental conditions, including high temperature,
lubrication, tribo-corrosion etc. and test parameters. Making it an ideal tool for research/testing labs dealing
with a variety of materials applied in different tribological conditions.
NANOVEA
www.nanovea.com
A Better Measure
info@nanovea.com
euroinfo@nanovea.com
info@nanovea.com
euro@nanovea.com
A Better Measure mexinfo@nanovea.com
www.nanovea.com
949-461-929
+1(949)-461-9292
(949) 461-9292
Conclusion
Based on the comprehensive tribological analysis in this study, we show that the aluminum sample exhibits
significantly different wear rates measured under linear reciprocating and rotative pin on disk setups. This
demonstrates the importance of caution in comparing the wear rate measured using different test setups,
even though many of the parameters were similar in this study.
Nanovea Tribometer offers precise and repeatable wear and friction testing using ISO and ASTM compliant
rotative and linear modules. It also provides optional high temperature wear, lubrication, and tribo-corro-
sion modules available in one pre-integrated system. Such versatility allows users to better simulate the real
application environment and improve fundamental understanding of the wear mechanism and tribological
characteristics of various materials.
Optionally, a 3D non-contact profilometer is available to acquire high resolution 3D images of a samples’
wear track, in addition to other surface measurements such as roughness.
Check out our full application notes library!
References
1 Rabinowicz, E. (1995). Friction and Wear of Materials. New York, John Wiley and Sons
2 Jones, M., H and D. Scott, Eds. (1983). Industrial Tribology: the practical aspects of friction, lubrication, and wear. New York,
Elsevier Scientific Publishing Company.
3 ASTM G133-05(2010). Standard Test Method for Linearly Reciprocating Ball-on-Flat Sliding Wear.
4 ASTM G99-05(2010). Standard Test Method for Wear Testing with a Pin-on-Disk Apparatus.
