Tribo-testing Applications in Automotive and Effective

Tribo-testing Applications in Automotive
and Effective Characterization of the
Tribo-tests
Arun K. Sikder (Ph.D., IIT Bombay) – Bruker Nano Surfaces Division,
Bangalore Center of Excellence ([email protected])
Outline
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Introduction to Green Tribology
Review of Tribo-test elements
Review of Tribo-system and Tribo-tests
Automotive Applications
Pre- and Post-tribo test characterization
3D-optical Microscopy Basics
Applications to Tribology
Concluding Remarks
Q&A
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Bruker TMT History and Overview
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Formed as CETR in 1993 manufacturing purpose-built HDD testers
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UMT platform launched in 2000. Over 600 systems sold so far
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Acquired by Bruker, October 2011
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High reliability – 60% of our customer base are returning
customers
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Durability – returning customers expanding capability,
not replacing existing systems.
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Manufacturing and R&D in California, USA
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Largest producer of tribology test equipment
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Staff of Engineers and Application Scientists
provide support capability in US, Europe and Asia
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Now
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Advanced Materials for Tribology
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Scratch Resistant Coating
Self-healing Coatings
Machining
Bearings
Gears
Metal forming
Lubrication and Wear
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Green Tribology
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Save Energy
Reducing use of Lubricant
Bio-based Lubricants
Environment Friendly Coatings
Smart Designing of Machine Parts
Innovative Tribotesting Instrument
Design
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Tribology is All Around Us
• Individual Components
• Assemblies or Products
• Manufacturing Processes
• Construction/Exploration
• Natural Phenomena
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Friction Fundamentals
The COF is Somewhat Complicated
• Surface roughness plays a role
Very Simple Relation:
• Lubricant plays a role
F=N
• Surface chemistry plays a role
• Contact Stress plays a role
N
• Contact geometry plays a role
F
The Coefficient of Friction
 = F/N = “COF”
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• Environment plays a role
• Temperature plays a role
• Sliding speed plays a role
• …
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Tribotesting Fundamentals
When assessing a system’s tribology
need, we must consider:
Friction is NOT a Material
Property
Friction is a “System”
Property
Tribology
Testing Need
to Perform
Define
No such thing as the COF
of “steel”, or the COF of
“rubber”
under the
Your
Like Friction, Wear is a
System Property, NOT a
Materials Property
Conditions
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Right
Tribotest
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Elements of “The Tribosystem”
The Tribo-elements include:
1.
2.
3.
4.
5.
Materials
Contact Geometry
Loading
Motion
Environment
Knowing the application helps us select the triboelements we need to incorporate in the tribo-test.
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Defining the Tribotest
• Always begin with: What is the intended
application?
• Then determine: What are the important
parameters in specific areas of?
1.
2.
3.
4.
5.
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Materials
Contact Geometry
Loading
Motion
Environment
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Example: Brake and Clutch Materials
COF and Wear
• Critical Tribo-Elements:
Materials
Friction Material vs. Cast Iron (or steel)
Contact
Geometry
Flat-on-Flat, or conformal (for drum brake)
Loading
From 2 MPa to 5MPa for cars, up to 7-10 MPa for HDV
Pure sliding, primarily unidirectional.
Motion
Environment
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Max Speed based on 15-20 cm diam rotor @ vehicle
speed 100 kph.
Dry, or wet with water or contaminants. Thermal condition
important.
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Example: Brake and Clutch Materials
Application 2: COF and Wear
• Define the Tribo-Test: For material screening only – Onvehicle test required by regulators.
Materials
Friction Material vs. Cast Iron (or steel)
Contact
Geometry
Flat-on-Flat, probably 3-button test (more stable),
minimum button size ~ 1.5 cm diameter.
Loading
Motion
Environment
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Select between 2 MPa and 5MPa, constant load or:
Varying if running constant torque tests
Pure unidirectional sliding
Multiple “stops” from max speed to zero.
Dry, for screening tests. Multiple stops with Initial Brake
Temperature below 38 ˚C.
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Automotive Applications
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Tribology in Automotive Applications
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Crankshafts & Camshafts
Block on Ring Test
(ASTM G77)
Possible Tests
Representative Data
• Surface Coatings (DLC, etc.)
• Heat treatment effectiveness
• Lubricant comparison
• Base material comparison
Benefits of the UMT
• Measure Vickers hardness in-situ
• Platform can be reconfigured to rotary
or linear test in minutes
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Bruker Confidential
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Door Handles & Lock Mechanisms
Reciprocating Ball on Flat Test
(ASTM G133)
Possible Tests
Representative Data
• Surface Coatings
• Heat treatment effectiveness
• Lubricant comparison
Benefits of the UMT
• Base material comparison
• Measure Vickers hardness in-situ
• Platform can be reconfigured to rotary
or linear test in minutes
• Closed loop control allows constant Fz
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Chains and Timing Belts
Test Method:
Cylinder-on-flat
wear test
Hardness test
Servo
Controlled
Carriage
Mounting
Block
Dual Friction/Load
Force Sensor
Capacitance Sensor
Reference Plate
Wear Test
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Hardness
Indenter Holder
Indenter
Possible Tests:
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Rigid Adaptor
Capacitance Sensor
Specimen
Representative Data
Stationary Table
Benefits of the UMT:
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A single tool can be used for both
hardness and wear testing.
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UMT can also accommodate future
needs for tribology and mechanical
testing
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Engine Valves (stem/roller)
Test Methods:
ASTM E92 & E384 Vickers and Knoop
Hardness
ASTM G133
Reciprocating Ball
on Flat Test
Possible Tests:
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Hardness and modulus of
valve material
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Reciprocating wear test of
valve and cylinder head
interface
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Representative Data
Benefits of the UMT:
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Modular design can help performing
multiple task in a single platform
Bruker Confidential
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Gaskets
ASTM
D412: Tensile properties of elastomers
D2240: Test of Durometer hardness of
rubber
D1415: Test Method for Rubber
Property—International Hardness
Possible Tests
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Deformability
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Creep
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Durometer hardness
Representative Data
Benefits of the UMT:
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Single Platform (hardware and
software) is used for performing
widely different tests
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Mirrors
ASTM
C1624 (05) –Scratch Test
E2546: Instrumented Indentation Test
Possible Tests
Representative Data
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Scratch
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Wear durability
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Nanoindentation
Benefits of the UMT:
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Stiction Test for wettability
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Adhesion testing of coatings
Complete evaluation of functional
properties of mirror
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Wear and scratch testing in one tool
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Paint
ASTM
C1624 (05) –Scratch Test
G171 (03) – Scratch Hardness Test
E2546: Instrumented Indentation Test
Possible Tests:
Representative Data
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Scratch
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Wear durability
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Friction
Benefits of the UMT:
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Indentation test
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Bend test
Comprehensive evaluation of paints
in a single tool
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Switch between scratch and
indentation in minutes
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Piston Pins & Connecting Rods
ASTM
G133: Ball-on-Flat sliding
G77 – Block-on-ring test
Possible Tests
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Wear Test of Pin
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Block-on-ring test for
bearings
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Representative Data
Benefits of the UMT:
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Modular design of UMT can address
challenges of altogether different
types of tests.
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Testing up to 1000C
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Piston Rings & Cylinder Liners
ASTM G181: Friction Tests of Piston
Ring and Cylinder Liner
Loading-unloading profile
Possible Tests:
Friction test of Piston ring and cylinder liner
materials ASTM G181-05.
The test parameters:
• temperature 100 ± 2oC
• loading from 20 N to 200 N with a step
of 20 N with holding time in each load
is 1 min
• unloading from 200N to 20N with 20 N
step and a holding time of 1 s in each
load
• Stroke of 10 mm
• Frequency of 10 Hz
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Representative Data
Benefits of the UMT
• Multi-sensing, modular design makes
UMT a perfect tool for such test
• Computerized servo-control allows for
easy ramping up and down of load in
touch of a button
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Rockers
ASTM
G133:
Ball-on-Flat
G77
Block-on-ring
Possible Tests:
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Wear Test of Pin
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Block-on-ring test for
bearings
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Representative Data
Benefits of the UMT
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Ability to run multiple tests on one
platform
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Precise servo control
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Seat Belts
Tests includes;
ASTM G132 Reciprocating pin-on-flat
wear test
Possible Tests:
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Seat belt fabric wear test
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Buckle wear testing
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Representative Data
Benefits of the UMT
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Change from one test regime to
another in minutes
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Servo Z-axis motion/load control
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Suspension
ASTM G133: Ball-on-Flat sliding
G77 – Block-on-ring test
Possible Tests
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Wear Test of Pin
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Block-on-ring test for
bearings
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Testing elastomer
suspension components
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Representative Data
Benefits of the UMT
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Measure hard materials (spring
steel) and elastomers on one
platform
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Tires
ASTM
D412: Tensile properties
D2240: Durometer hardness
D1415: International Hardness
E2546: Instrumented Indentation
Possible Tests
Representative Data
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Abrasion Test
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Hardness-modulus test
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Creep
Benefits of the UMT
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Friction
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Test from -40C to 350C and above
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Change from ambient to humidity or
in-liquid testing by switching
chambers
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Lubricants
ASTM:
D2266,
D2714,
D4172,
D5706,
D6425
D2509, D2625, D2670,
D2981, D3233, D3704,
D5001, D5183, D5620,
D5707, D6078, D6079,
Possible Tests:
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Stribeck Test
Block-on-ring
Pin-on-disk
Disk-on-disk
Pin-on-vee
4-ball
Twist-compression
Representative Data
Benefits of the UMT:
• Run various tests in one hardwaresoftware platform
• Controlled temperature
• Computer controlled load, speed, etc.
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Why Universal System
• Friction is a system property
• Wear Rate or wear resistance depends on the wear
mode, which is again function of the Tribosystem.
• Need to simulate real scenario as closely as
possible
• Need to have flexibility for designing tribo-test should be able to vary load, motion, environmental
conditions and accept a wide range of
configurations.
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Single Platform for Many Tribosystem
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Environmental Chambers
Full range of heating/cooling chambers to simulate real world conditions.
Humidity chambers also available but not pictured.
1000°C Rotary
Chamber
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1000°C
Reciprocating
Chamber
-25°C
Chamber
-40°C
Chamber
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3D-Optical Microscope
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Typical Interferometer Diagram
CCD
Reference arm
Reference
Mirror
Test arm
Beamsplitter
Sample
Optical Path Difference (OPD)
• Difference in optical path lengths that beams travel
in Reference and Test arms
• The expanded beam
exiting from the light
source is divided by a
Beamsplitter into two
beams
• One beam is reflected
from the Reference
Mirror, and the other
from the Sample
• These two beams are
recombined by the
Beamsplitter to
interfere
• The imaging lens
images the
interferogram onto the
CCD camera
• When OPD=0, the brightest fringes are in focus
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White Light Fringes
In an interferogram obtained with a white light source, such as a white LED, beams of different
wavelengths interfere giving a centroid or maximal intensity point where the optical path difference of
the beams is 0. This is our reference point for the height of an object as we vertically scan a sample.
Fringes for:
blue light
green light
yellow light
red light
Wide bandwidth filter (300nm) - (White Light VSI)
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1
White Light Fringes
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Method simply uses the
maximum fringe contrast
(zero optical path
difference) to record the
height of each pixel as the
turret move vertically
toward the sample. This
gives an image with ~nm
vertical resolution
independent of field of
view. Lateral resolution is
objective dependent.
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Focus 1
Focus 2
Focus 3
Focus 4
4
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Operation of 3D Microscope
Vertical resolution
about 0.1nm
VSI
Uses light of wide
bandwidth i.e. white
light. Fringes are
localized near best
focus
Step Height
Standard
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2D Stylus Method
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Historically, 2D techniques such as stylus are being used for surface texture study.
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For Stylus based techniques, the min feature size is determined by size of stylus tip.
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For critical sub-micron surface roughness applications, this technology lack the critical
data density required to fully characterize the component under investigation
Small Tip
large Tip
Valley can’t reached due to stylus size
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Scan Profile
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System Capability
Nano scale
Demonstration: 0.148nm Roughness
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3D vs. 2D
Not able capture with Single Line
3D Image provides more information on the surface finishing.
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Example of Automotive Applications
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Gear
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Piston and cylinder block wear
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Brake rotor wear
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Cam shaft analyses
• Specialty products
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Development
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Process control
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Gear
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Hypoid Pinion Gear Wear
• Highly convex surfaces
• Currently use contact technique or cut
down parts
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Tooth bow x-section shows range of z-height.
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Clutch Plate Tab Rolloff
• Manufacturing processes for clutch plates grinders, cutters, stamps
• Roll off limits movement of the whole plate- tabs stick to hub
• Friction causes chatter, premature wear,
slippage, overheating
Radius of curvature: 12.50mm & 48.63mm
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Spherical opening on Shaft
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Fuel Line
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Central machining pattern
Pattern height 5 microns, pin height 9 microns
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Black Sample Inspection
Spot 3
4
5
Center
3
2
Center
Position
Surface Roughness
(Sa)
Center
337.2nm
Spot #2
44.3nm
Spot #3
226.4nm
Spot #4
167.9nm
Spot #5
163.2nm
Spot 4
Spot 2
Spot 5
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Plasma spray coating texture
Ra=73.6µm
ContourGT-K1 easily
measures rough low
reflectivity surfaces
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Quantification of Wear Scar Volume
Volume of wear scar
Volume of transferred or
re-deposited matter
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Case Study: Cylinder Block Liner
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Cylinder Liner: Surface Texture at 25mm
area
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Shaft
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Shaft: Radius of Curvature = 8.0mm
(Diameter = 16mm)
Frequency = 1/0.1686 mm
ROC = 8mm
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Shaft: After Form Removal
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Shaft: Waviness and Roughness
Apply Low / High Pass filter to find the waviness and roughness
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Pin and Ball on Disk Wear Studies
• Quantify material
characteristics with
wear studies
• Quantify material
removal in terms of
volume
• Evaluate negative,
positive and missing
volumes
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Vision 64 Analysis Software
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Basic Stats
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SureVision
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Cross Hatch
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Surface Area
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Fresnel Analysis
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Thickness Stats
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Lead Angle
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Trace Analysis
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Lead Angle Single Measurement
Analysis
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User Analysis
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V Parameters
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MTF Analysis
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Volume
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Multiple Region
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XY Averaged PSD
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PSF Encircled Energy Analysis
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Zernike Analysis
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PSF Ensquared Energy Analysis
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Bearing Ratio
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Rz Analysis
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2D Profile
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S Parameters – Functional
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Critical Dimension
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S Parameters – Height
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Histogram
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S Parameters – Hybrid
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Auto Corr
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S Paramaters – Spatial
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APSD
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Step Height
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PSD
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Other Applications
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Example of
Lubrication Testing
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Lab Set-Up
Set-up for 4-ball Test
Set-up for Stribeck Curve
Ball or Cylinder-on-sde
N
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3-D Image of MSBO-B wear
scar at 40kg load using White
Light Interferometer
Bruker Contour GT
White Light Interferometer
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2-D projections of wear scar for diameter
measurement
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Summary
Bruker UMT system
Multipurpose Materials Tester
3D Optical Microscope
Multiple tests on a single
platform - ASTM, DIN and
ISO standards
3/27/2014
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Pin/Ball on Rotating Disc

Linear Wear Test

Ball on Three Balls (4Ball)
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Pin on Vee-Block
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Block on Ring

Disc on Rotating Disc

Plate on Reciprocating
Plate
WLI 3D microscopes
•
are fast, non-contact, easy to
set up
• Have excellent SNR, resolution
and accuracy at all
magnifications
• Measure surface topography
and roughness of varity of
samples:
• 60o + slope
• <0.05% reflectance
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