wear mechanisms applied to lifeboat slipway...
TRANSCRIPT
Wear Mechanisms applied to Wear Mechanisms applied to
Lifeboat Slipway LaunchesLifeboat Slipway LaunchesB. Thomas*B. Thomas*aa, M. , M. HadfieldHadfieldaa, S. , S. AustenAustenbb
Sustainable Product Engineering Research Centre, Sustainable Product Engineering Research Centre,
Bournemouth University, Bournemouth University, UKUK
aa Bournemouth University, Bournemouth University, bb Royal National Lifeboat InstitutionRoyal National Lifeboat Institution
* Corresponding author. * Corresponding author. [email protected]@bmth.ac.uk
Presentation StructurePresentation Structure
�� Overview of lifeboat slipway launchingOverview of lifeboat slipway launching
�� Friction and Wear problems on lifeboat launch Friction and Wear problems on lifeboat launch slipwaysslipways
�� Experimental MethodologyExperimental Methodology
�� Test rig designTest rig design
�� Tests ScheduleTests Schedule
�� ResultsResults
�� ConclusionsConclusions
�� Recommendations & future workRecommendations & future work
Tamar Class LifeboatTamar Class Lifeboat�� The Tamar slipThe Tamar slip--launched lifeboat is designed as a launched lifeboat is designed as a
replacement to the Tyne class lifeboat. It is significantly replacement to the Tyne class lifeboat. It is significantly larger and heavier than the Tyne and this has meant new larger and heavier than the Tyne and this has meant new slipways and boathouses have had to be built to slipways and boathouses have had to be built to accommodate it.accommodate it.
�� The Tamar currently operates from new boathouses and The Tamar currently operates from new boathouses and slipways at Tenby, Padstow and Cromerslipways at Tenby, Padstow and Cromer
20061982Year Introduced
7
240n. miles
Steel
26 - 27 tonnes
17.6 knots
1.26m
4.48m
14.3m
Tyne Tamar
6Crew
250n. milesRange
FRPConstruction
~ 35 tonnesDisplacement
25 knots Speed
1.35mDraught
5mBeam
16mLength
Slip-launched Lifeboats
Lifeboat Slipway LaunchLifeboat Slipway Launch
Typical Slipway Typical Slipway --
PadstowPadstow
19mm Jute/Phenolic composite panels
Steel rollers
�� Padstow has recently received Padstow has recently received a new boathouse in order to a new boathouse in order to accommodate the new Tamar accommodate the new Tamar class slipclass slip--launched lifeboatlaunched lifeboat
�� The slipway layout is typical of The slipway layout is typical of the next generation boathouses the next generation boathouses and slipways being built for the and slipways being built for the TamarTamar
�� The slipway consists of an The slipway consists of an upper section of steel rollers upper section of steel rollers and a lower section lined with and a lower section lined with lowlow--friction 19mm thick friction 19mm thick Jute/Graphite infused Phenolic Jute/Graphite infused Phenolic resin Composite panelsresin Composite panels
Slipway Lining MaterialsSlipway Lining Materials
�� Weather Treated Weather Treated Wood Wood –– Traditional Traditional c.1850c.1850
�� Nickel/Chromium Nickel/Chromium carbide coated Steel carbide coated Steel –– c.1980c.1980
�� Jute/Graphite Infused Jute/Graphite Infused Phenolic Resin Phenolic Resin Composite Composite –– c.1996 c.1996
Jute/Graphite Infused Phenolic Resin CompositeJute/Graphite Infused Phenolic Resin Composite
- Alignment ropes - Winch cableLifeboat alignment and attachment of winch cable – alignment ropes and winch cable indicated
Lifeboat Slipway RecoveryLifeboat Slipway Recovery
Lifeboat Slipway RecoveryLifeboat Slipway Recovery
- Quarter stop ropes - Winch cableFig. 3.1.2i: Haul Stage – Rope quarter stops and winch cable keel attachment position shown
Problems..Problems..
�� High friction is often present along the slipway panels High friction is often present along the slipway panels ––this is particularly apparent as high winch loading during this is particularly apparent as high winch loading during lifeboat recoverylifeboat recovery
�� Currently marine grease or in some cases other Currently marine grease or in some cases other lubricants, are manually applied to the slipway before lubricants, are manually applied to the slipway before each launch and recoveryeach launch and recovery
�� Due to the exposed nature of the slipway and the Due to the exposed nature of the slipway and the unpredictable intervals between lifeboat launches the unpredictable intervals between lifeboat launches the lubricant grease can be washed away, dry out or lubricant grease can be washed away, dry out or become contaminated with wind blown sand etc. become contaminated with wind blown sand etc. resulting in unpredictable friction coefficientsresulting in unpredictable friction coefficients
�� Severe cracking and wear of composite slipway panels Severe cracking and wear of composite slipway panels has been observed at both Tenby and Padstow requiring has been observed at both Tenby and Padstow requiring regular replacementregular replacement
TE92 Rotary Tribometer TE92 Rotary Tribometer -- SchematicSchematic
TE92 Rotary TribometerTE92 Rotary Tribometer
�� Original geometry is designed Original geometry is designed to measure wear in ball to measure wear in ball bearingsbearings
�� Geometry is modified to a Geometry is modified to a ring/disc arrangement to mirror ring/disc arrangement to mirror the slipway/keel situationthe slipway/keel situation
�� New geometry design features New geometry design features a self levelling pin to ensure a self levelling pin to ensure even contact through strokeeven contact through stroke
�� Tests are designed to Tests are designed to incorporate dwell effects to incorporate dwell effects to simulate launch intervalssimulate launch intervals
Tests ScheduleTests Schedule
801000DryCR4
601000DryCR3
401000DryCR2
201000DryCR1
Contact Pressure (N)
Test Duration (#passes)
LubricantTest ID
Contact Force Tests
Wear Tests
201000Biogrease #1LR6
201000Silicon Microsphere Lub.LR5
201000Marine GreaseLR4
201000FreshwaterLR3
201000SeawaterLR2
201000DryLR1
Contact
Pressure (N)
Test Duration
(#passes)LubricantTest ID
TE92 Jute/Phenolic Composite: Wear Volume vs. Contact Pressure
0
5
10
15
20
25
30
35
40
20 40 60 80
Contact force (N)
We
ar
Vo
lum
e (
mm
3)
TE92 Jute/Phenolic Composite: Wear Coefficient vs. Contact Pressure
1E-12
1E-11
20 40 60 80
Contact force (N)
Wear
Co
eff
icie
nt
TE92 Jute/Phenolic Composite: Wear Volume vs. Lubricant Regime
0
5
10
15
20
25
30
35
40
45
50
Seawater Freshwater Silicon
Microball
Lub.
Marine
Grease
Biogrease Dry
We
ar
vo
lum
e (
mm
3)
TE92 Jute/Phenolic Composite: Wear Coefficient vs. Lubricant Regime
0
1E-12
2E-12
3E-12
4E-12
5E-12
6E-12
7E-12
8E-12
9E-12
Seawater Freshwater Silicon
Microball
Lub.
Marine
Grease
Biogrease Dry
We
ar
Co
eff
icie
nt
Case studiesCase studies
�� Slipways were examined at Selsey, Tenby, Slipways were examined at Selsey, Tenby, SwanageSwanage, Padstow, , Padstow, Bembridge, Sennen Cove and The LizardBembridge, Sennen Cove and The Lizard
�� Jute/Phenolic composite sections at Selsey, Bembridge, Padstow, Jute/Phenolic composite sections at Selsey, Bembridge, Padstow, Tenby and Sennen Cove were all found to have similar wear Tenby and Sennen Cove were all found to have similar wear patternspatterns
BembridgeBembridge SelseySelsey
PadstowPadstow TenbyTenby
Case StudiesCase Studies
Fig #: Wear map for 1mm angled offset – Original panel (top), Chamfer panel (bottom)
1.287E-03 8.579E-04 4.289E-04 1.072E-04
1.072E-03 6.434E-04 2.145E-04 4.289E-05
�� Slipways panels were found to be longitudinally misalignedSlipways panels were found to be longitudinally misaligned
�� Misalignment ranged up to 4mm with an average of 0.88mmMisalignment ranged up to 4mm with an average of 0.88mm
�� FEA simulations were conducted to show the effects of FEA simulations were conducted to show the effects of panel misalignment on panel stress concentrationspanel misalignment on panel stress concentrations
Fig #: Parallel Panel Misalignment Model
Offset Distance
0.E+00
1.E+06
2.E+06
3.E+06
4.E+06
5.E+06
6.E+06
0 1 2 3 4 5
Offset Distance (mm)
Vo
n M
ises M
ax
. S
tress (
N/m
2)
0.E+00
1.E+05
2.E+05
3.E+05
4.E+05
5.E+05
6.E+05
7.E+05
8.E+05
0 1 2 3 4 5
Offset Distance (mm)
Fri
cti
on
Fo
rce
Ma
x.
(N)
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
3.0E-03
0 1 2 3 4 5
Offset Distance (mm)
We
ar
Ma
x.
(mm
/m s
lid
e)
Chart #: Parallel Panel Offset Comparison
FE AnalysisFE Analysis
FEA simulation vs. typical worn and misaligned jute fibre/phenolic resin composite lining section from Tenby slipway
FE AnalysisFE Analysis
84.58Dry
56.30Biogrease
49.88Marine Grease
22.65Silicon Microball Lub.
18.66Freshwater
16.80Seawater
Eq. No of Launches & Recoveriesfor 19mm Wear Scar Depth
Lubricant
Equivalent number of lifeboat launches/recoveries required to generate a 19mm wear scar on a 4mm parallel offset misaligned slipway panel by lubricant used
FE AnalysisFE Analysis
Concluding RemarksConcluding Remarks�� Under ideal conditions the wear coefficients between slipway panUnder ideal conditions the wear coefficients between slipway panels and els and
lifeboat keel are not sufficient to cause failure during the explifeboat keel are not sufficient to cause failure during the expected 2ected 2--year year lifespan of the panel.lifespan of the panel.
�� Real world slipways often exhibit misalignment between slipway pReal world slipways often exhibit misalignment between slipway panels.anels.
�� FEA shows that there a significant stress concentrations and FEA shows that there a significant stress concentrations and correspondingly wear, at these misalignments.correspondingly wear, at these misalignments.
�� This increase in wear due to stress concentrations is sufficientThis increase in wear due to stress concentrations is sufficient to explain to explain the high wear observed at Tenby and Padstow.the high wear observed at Tenby and Padstow.
�� The use of lubricants along the slipway should again have littleThe use of lubricants along the slipway should again have little effect effect under ideal conditions according to the test data. However, withunder ideal conditions according to the test data. However, with panel panel misalignment included the choice of lubricant may become more misalignment included the choice of lubricant may become more significant.significant.
�� Previous work has indicated that lubricants are necessary to meePrevious work has indicated that lubricants are necessary to meet the t the friction specification of the slipway.friction specification of the slipway.
�� It is therefore recommended to review and reIt is therefore recommended to review and re--fit the affected slipways to fit the affected slipways to reduce slipway panel misalignment.reduce slipway panel misalignment.
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