a study of the factors influencing hose abrasion

© 2013 Eaton. All Rights Reserved.

A Study of the Factors Influencing Hose Abrasion

Aaron D. Clark

Eaton Corp.

2© 2013 Eaton. All Rights Reserved.

Purpose Statement

The purpose of this study is to characterize some of the

factors affecting hose cover abrasion and to draw

comparisons between common abrasion testing methods.


Agenda

• Background of Abrasion

• Mechanism of Elastomer Abrasion

• Influential Factors

• Hose Cover Materials

• Hose Abrasion Testing

• Conclusions

Rules

• Do not name competitor products

• Nothing proprietary presented


Hose Cover Abrasion

• “Abrasion resistance is the ability of a material to resist mechanical action such as

rubbing, scraping, or erosion that tends progressively to remove material from its’

surface.” (Arayapranee, 2012)

• Up to 70% of hose failures are due to cover abrasion.

• “More than 57% of premature hose failures result from abrasion caused by improper

routing” (Plant Engineering; 2017)


Mechanism of Rubber Abrasion –General Overview

Stages of Abrasion

• Abrasion patterns are generally formed during the initial stage

• The “Steady State” segment has consistent frictional behavior and low abrasion rate.

• The final “Catastrophic” phase is characterized as having a high abrasion rate and

significant surface damage.

Ab

rasio

n

Cycles/Time


Mechanism of Rubber Abrasion –General Overview

• Abrasion can be particulate removal through a:

• Fatigue / Fracture mechanism

• Melting at the contact interface

• Chemical degradation

• Fracture and fatigue crack growth

• Rubber abrasion begins with micro-vibration induced by stick-slip oscillation

generating the initial abrasion patterns. The corresponding crack growth

propagation results in eventual material failure.


Mechanism of Rubber Abrasion –Stick/Slip Kinetics

• Stick-slip can be described as surfaces alternating between sticking to each other

and sliding over each other, with a corresponding change in the force of friction

Influential Material Properties

• Elastomer Hardness

• Elastomer COF

• Elastomer Crystallinity

• Material Surface Pattern?

Time

F static

F min

Fo

rce


Mechanism of Rubber Abrasion –Fatigue Crack Growth

• Elastomeric components subjected to fluctuating loads often fail due to nucleation

and the growth of defects or cracks. Driven by shear and tension.

• Measured as a factor of stress intensity.

Influential Material Properties

• Elastomer Physical Properties

• Elastomer Molecular Weight

• Polymer Cross Linking

• Filler Type/Loading


Factors Influencing Abrasion

Factors Influencing Hose Abrasion:

• Material Properties

• Physical properties: Tensile strength,

elongation, hardness and tear strength

• Molecular weight of the polymer

• Cross linking

• Polymer architecture

• Material coefficient of friction

• Formulation constituents (fillers, anti-degradants..etc)

• Design Related

• Adhesion to reinforcement

• Layer thickness

• Surface pattern?

• Environmental / Application

• Environmental – UV; Ozone; humidity, operating

temperature, fluid exposure..etc.

• Sliding Velocity

• Application forces

• Pressure


Materials Studied

NBR/PVC

EPDM

Chloroprene (CR)

Chlorobutyl (CIIR)


Materials Studied

Polyamide (nylon)

Copolyester

Polyurethane (TPU)

Polyester


Rubber Formulations


Hose Abrasion Testing

Granular Abrasion Tests - Associated with movement across a rough surface; common for belting, tires and foot ware. Small cracks and particles are “sanded” off.

• Zwick Rotary Drum• Taber• NBS Abrader (ASTM D1630)

• Akron Abrasion Test

• Gibitre Test (ISO6945/ SAEJ2006)

Fatigue Abrasion Tests – Generally results from routing or contact abrasion failure. The material forms a wave pattern and loses macro pieces (mg weight) of material due to fatigue.

• ISO 6945• ISO/TC 45/SC 1/WG4 * pending


Abrasion Tests – ISO6945• ISO6945 – Determination of abrasion resistance of the outer cover.

• A comparative study for hoses with textile or wire reinforcement and nominally

smooth and parallel covers.

• Response is overall cycles until reinforcement is detected or weight at 2000

cycles

• Effect is a roll formation that progresses until material release.


ISO6945 Abrasion - Appearance

3/4 Life Abrasion Failure

Pre Test ¼ Life

Half Life


Abrasion Results – ISO6945Material Comparison

Test Conditions: 50N load and 1.25 Hz rate. Response is overall cycles to wire exposure


Abrasion Results – ISO6945 Stagesof Abrasion

ISO6945 cycles to failure correlated well with the published “stages of abrasion” chart


Granular Abrasion Tests – Zwick

DIN (Zwick) – Rotary drum (ASTM D5963 or ISO 4649)

• Measures wear behavior under abrasive/frictional service conditions

• A cylindrical rubber test specimen is abraded against an abrasive surface mounted on a

rotating cylindrical drum under a specified load while being traversed across it.

• Typical applications: Tires, conveyor drive belts and shoe soles

IMG_6195.MOV

Measures Granular Abrasion


Granular Abrasion Tests – Zwick

Test Conditions: 7.5N load and 40m of total travel. Response is mm3 of material lost


Granular Abrasion Tests – Taber


Taber – Rotary Platform Dual Head Tester (ASTM F1344; ASTM D1044)

• Measures wear behavior under abrasive/frictional service conditions

• As the turn table platform rotates, two abrasive wheels contact the specimen in varying

directions.

• Typical applications: plastics, coatings, laminates, leather, paper, ceramics, carpeting,

safety glazing..etc).


Granular Abrasion Tests – Taber



Granular Test Comparison

Significant variability exists between granular abrasion tests


Abrasion Results – Total Comparison

In General, high ISO6945 cycles correlate to low Zwick and Taber material loss.


Additional Data

• Product Comparison

• ISO 6945 Test Stand Comparison

• Smooth vs. Wrapped Covers

• Coefficient of Variability

• Rubber Test Variability


Product Comparison


ISO6945 Test Stand Comparison

Significant differences can exist in ISO6945 designs however commercially

produced equipment might produce consistent results.


ISO6945 Test Stand Comparison

Significant differences can exist in ISO6945 designs

15%

1%


Abrasion Results – Cover Pattern

Cover Pattern has minimal effect on abrasion resistance based on this study

14%


Coefficient of Friction

• • The ratio of the force of friction between an object and a surface to the frictional

• force resisting the motion of the object

• • COF values are from published data sets

0 0.5 1 1.5 2 2.5 3 3.5

CR

EPDM

CIIR

NBR/PVC

PA (Nylon)

CoPolyester

TPU

UHMWPE

Coefficient of Friction

Elastomer Coefficient of Friction


Coefficient of Friction vs. Abrasion

COF is not the only factor affecting abrasion resistance


Test Method Consistency

Coefficient of variation (CV), also known as relative standard deviation (RSD), is a

standardized measure to express repeatability and precision.

CV<10% is desirable

CV = (σ / µ) *100


Conclusions

• Material properties such as coefficient of friction can have significant effects on

both granular and fatigue related abrasion however must be considered in

conjunction with other properties and design factors.

• Significant differences in response can be observed between various industry

standard test methods when assessing a cover material.

• Although higher variance exists with the ISO6945 test, it remains an effective

method for assessing fatigue related abrasion resistance.

• Careful consideration regarding hose application must be considered when

selecting an abrasion test or data set.


Future Work

• Assessment of Gibitre abrasion and other test stands

• Draw greater correlation between material factors

and abrasion resistance


Acknowledgements

• Brian Walsh• Chad Borton• Dan Mace• Gina Clark• Recep Muco• Ricky Rizer• Volkan Karayazi• William Lanser


Citations

• Araypranee, W; “Rubber Abrasion Resistance”; Abrasion Resistance of Material; Intech; 2012

• “Nine Reasons why Hydraulic Hoses Fail”; Plant Engineering; 2017

• Yoshihide, F; et al; “Mechanism of rubber abrasion. Part I: Abrasion pattern formation in

natural rubber vulcanizate”; Wear: 1994

• http://www.abrasiontesting.com/abrasion-testing-instruments/taber-rotary-platform-abraser-abrader/

• Muhr, A.H and Roberts, A.D; “Rubber abrasion and wear”; Wear’; 1992

• Grosch, K.A; “Rubber abrasion and tire wear”; Rubber Chemistry and Technology; 2008

• http://www.gibitre.it/Spa/Products/165.html; 2017

a study of the factors influencing hose abrasion

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