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A Study of the Factors Influencing Hose Abrasion

Aaron D. Clark

Eaton Corp.

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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.

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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

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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)

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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

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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.

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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

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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

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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

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Materials Studied

NBR/PVC

EPDM

Chloroprene (CR)

Chlorobutyl (CIIR)

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Materials Studied

Polyamide (nylon)

Copolyester

Polyurethane (TPU)

Polyester

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Rubber Formulations

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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

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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.

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ISO6945 Abrasion - Appearance

3/4 Life Abrasion Failure

Pre Test ¼ Life

Half Life

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Abrasion Results – ISO6945Material Comparison

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

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Abrasion Results – ISO6945 Stagesof Abrasion

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

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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

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Granular Abrasion Tests – Zwick

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

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Granular Abrasion Tests – Taber

Measures Granular Abrasion

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).

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Granular Abrasion Tests – Taber

Measures Granular Abrasion

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Granular Test Comparison

Significant variability exists between granular abrasion tests

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Abrasion Results – Total Comparison

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

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Additional Data

• Product Comparison

• ISO 6945 Test Stand Comparison

• Smooth vs. Wrapped Covers

• Coefficient of Variability

• Rubber Test Variability

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Product Comparison

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ISO6945 Test Stand Comparison

Significant differences can exist in ISO6945 designs however commercially

produced equipment might produce consistent results.

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ISO6945 Test Stand Comparison

Significant differences can exist in ISO6945 designs

15%

1%

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Abrasion Results – Cover Pattern

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

14%

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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

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Coefficient of Friction vs. Abrasion

COF is not the only factor affecting abrasion resistance

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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

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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.

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Future Work

• Assessment of Gibitre abrasion and other test stands

• Draw greater correlation between material factors

and abrasion resistance

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Acknowledgements

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

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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

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