a study of the factors influencing hose abrasion
TRANSCRIPT
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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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