Devin Murray
11/3/2013
Homework # 6 – Friction Wear and Lubrication of Materials
1. Watch and study the videos titled “Boundary Lubrication” from IIT (links available at our
class webpage link: References and Links-Useful Tribology Links - scroll down to Videos)
and come prepared to discuss their contents in class next week.
This video discussed the physical and chemical properties of boundary lubrication. In many
lubrication applications, the molecules of the lubricant become attached to the substrate, leading
to a form of corrosion which results in reduced friction and wear. Physical properties of the
lubricant prevail below a certain critical temperature while chemical properties prevail below
(with a temperature distress gap overlapping). Increase in load and speed of a gearbox under
study shows the differences in wear rates based on boundary lubrication. It is apparent that
machinery requires a nominal run in period of relatively high wear before boundary lubrication
becomes effective.
2. Complete the set of In Class Exercises dated 10/28/13. Create summaries of your answers
and post on your webpage.
TBD
3. Starting with your previous essay produce a 1000 word essay providing additional detail
about the term project you have proposed for this class. Your essay must include a clear
description of the problem, the objective of the proposed work, the approach you plan to
use and a well-researched list of references directly related to the problem. It must also
contain actual detailed content on at least some selected sections.
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For my research project this term, I would like to investigate wear in polymers. Specifically, the
project would investigate the wear characteristics of dynamic polymer seals with differing surface
profiles and the various tribological mechanics that affect the functional life of the seal.
In my work experience, I am regularly asked to evaluate new designs and materials to be used in
sealing applications for hydraulic components. The majority of the time, I must differ to the
various vendors and seal manufacturer representatives as the experts in deciding what seal is the
optimal solution for a given system. While there are countless variables involved in selecting a
given seal for an operational condition, a particular interest of mine is in the different seal profiles
that are part of many basic product lines. I would like to take an in depth look into the underlying
mechanics of seal design and study for myself why certain seal designs work well in certain
applications and exactly what aspects of the design relate to increased performance.
For my project, I will select several different seal designs from current industry manufacturers. A
sample is provided in the attached links which show products currently available. Seal material
properties will be compared and a baseline operational condition will be defined. Each seal will
then be modeled mathematically to determine the underlying characteristics of seal wear. While
wear is stated as the overarching goal for this project, friction and lubrication will also have to be
considered if the representation of the selected seals is to be realistic. Of particular interest in my
project will be the study of ‘multi-lobed’ seals which in practice have been shown to outperform
other more standard seal designs. Three seal designs that will be studied are detailed below:
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Devin Murray
11/3/2013
Standard O-Ring:
This seal style is the most universal and is used in both dynamic and static sealing applications.
The main advantage to using a standard o-ring seal in any given application is the wide array of
material choices which are available to meet system requirements.
Quad-Ring Seal:
This seal design is proprietary to the Minnesota Rubber Corporation and is recommended as an
alternative to standard o-rings in difficult dynamic sealing applications. The four lobes of the seal
allow the seal to be used in a wider tolerance range (both temperature and geometric) and provide
two points of contact for sealing.
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Devin Murray
11/3/2013
Quad-O-Dyn Seal:
This seal design is also a proprietary product of the Minnesota Rubber Corporation and is
recommended for the most difficult dynamic sealing applications. This seal has six lobes which
provide another contact point for sealing over the Quad-Ring seals.
Seal analysis will be performed through both hand calculations and FE analysis to approximate
stress distributions and surface forces that will contribute to seal wear. An important aspect of
seal analysis will be the selection of material properties and the mechanical seal gland to sealing
surface geometry. Material properties will control how the seal reacts as it is compressed to create
a seal, and the geometry will control the amount the seal is compressed. The Parker O-Ring
Handbook will be used to select a standard seal ‘squeeze’ to be applied to all evaluated seal
profiles based on recommendations for dynamic seals. Material properties will be selected from
manufacturer data sheets as permitted. As the main goal of the study is to quantify the different
aspects of seal design which contribute to wear, the most important factor is insuring all seals are
evaluated with identical properties and geometries.
Comsol will be used to model the three seal profiles to determine peak stresses and stress
distributions in the material.
References:
http://engineeringmaterials.org/papers/BriscoeSinha_IMechE2002.PDF
http://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf
http://www.mnrubber.com/Design_Guide/6-3.html
http://www.skf.com/binary/12-123222/Hydraulic-seals---12393_1-EN.pdf
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