Embed Size (px)
Citation preview
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
• 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
3/27/2014 2
• Formed as CETR in 1993 manufacturing purpose-built HDD testers
• UMT platform launched in 2000. Over 600 systems sold so far
• Acquired by Bruker, October 2011
• High reliability – 60% of our customer base are returning
customers
• Durability – returning customers expanding capability,
not replacing existing systems.
• Manufacturing and R&D in California, USA
• Largest producer of tribology test equipment
• Staff of Engineers and Application Scientists
provide support capability in US, Europe and Asia
Bruker TMT History and Overview
3/27/2014 3
Now
• Scratch Resistant Coating • Self-healing Coatings • Machining • Bearings • Gears • Metal forming • Lubrication and Wear
Advanced Materials for Tribology
4 3/27/2014
• Save Energy • Reducing use of Lubricant • Bio-based Lubricants • Environment Friendly Coatings • Smart Designing of Machine Parts • Innovative Tribotesting Instrument Design
Green Tribology
5 3/27/2014
Tribology is All Around Us
• Individual Components
• Assemblies or Products
• Manufacturing Processes
• Construction/Exploration
• Natural Phenomena
6 3/27/2014
Friction Fundamentals
7
Very Simple Relation:
F=N
N
F
= F/N = “COF”
The Coefficient of Friction
• Surface roughness plays a role
• Lubricant plays a role
• Surface chemistry plays a role
• Contact Stress plays a role
• Contact geometry plays a role
• Environment plays a role
• Temperature plays a role
• Sliding speed plays a role
• …
The COF is Somewhat Complicated
3/27/2014
Tribotesting Fundamentals
When assessing a system’s tribology
need, we must consider:
8
Friction is NOT a Material Property
Friction is a “System” Property
No such thing as the COF of “steel”, or the COF of
“rubber”
Like Friction, Wear is a System Property, NOT a
Materials Property
Tribology
Testing Need
to Perform
under the
Right
Conditions
Define
Your
Tribotest
3/27/2014
Elements of “The Tribosystem”
The Tribo-elements include:
1. Materials
2. Contact Geometry
3. Loading
4. Motion
5. Environment
Knowing the application helps us select the tribo-elements we need to incorporate in the tribo-test. 9 3/27/2014
Defining the Tribotest
• Always begin with: What is the intended
application?
• Then determine: What are the important
parameters in specific areas of?
1. Materials
2. Contact Geometry
3. Loading
4. Motion
5. Environment
3/27/2014 10
Example: Brake and Clutch Materials
COF and Wear
• Critical Tribo-Elements:
3/27/2014 11
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
Motion Pure sliding, primarily unidirectional.
Max Speed based on 15-20 cm diam rotor @ vehicle
speed 100 kph.
Environment Dry, or wet with water or contaminants. Thermal condition
important.
• Define the Tribo-Test: For material screening only – On-
vehicle test required by regulators.
3/27/2014 12
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 Select between 2 MPa and 5MPa, constant load or:
Varying if running constant torque tests
Motion Pure unidirectional sliding
Multiple “stops” from max speed to zero.
Environment Dry, for screening tests. Multiple stops with Initial Brake
Temperature below 38 ˚C.
Example: Brake and Clutch Materials
Application 2: COF and Wear
Automotive Applications
3/27/2014 13
3/27/2014 14
Tribology in Automotive Applications
Crankshafts & Camshafts
Block on Ring Test
(ASTM G77)
Benefits of the UMT
• Measure Vickers hardness in-situ
• Platform can be reconfigured to rotary or linear test in minutes
3/27/2014 15 Bruker Confidential
Possible Tests
• Surface Coatings (DLC, etc.)
• Heat treatment effectiveness
• Lubricant comparison
• Base material comparison
Representative Data
Door Handles & Lock Mechanisms
Reciprocating Ball on Flat Test (ASTM G133)
Benefits of the UMT
• Measure Vickers hardness in-situ
• Platform can be reconfigured to rotary or linear test in minutes
• Closed loop control allows constant Fz
3/27/2014 16
Possible Tests
• Surface Coatings
• Heat treatment effectiveness
• Lubricant comparison
• Base material comparison
Representative Data
Chains and Timing Belts
Test Method:
Cylinder-on-flat wear test
Hardness test
Benefits of the UMT:
• A single tool can be used for both hardness and wear testing.
• UMT can also accommodate future needs for tribology and mechanical testing
3/27/2014 17
Possible Tests:
• Wear Test
• Hardness
Representative Data
Servo
Controlled
Carriage
Mounting
Block
Dual Friction/Load
Force Sensor
Capacitance Sensor
Reference Plate
Capacitance Sensor
Stationary Table
Rigid Adaptor
Indenter Holder
Indenter
Specimen
Engine Valves (stem/roller)
Test Methods:
ASTM E92 & E384 Vickers and Knoop Hardness
ASTM G133 Reciprocating Ball on Flat Test
Benefits of the UMT:
• Modular design can help performing multiple task in a single platform
3/27/2014 18 Bruker Confidential
Possible Tests:
• Hardness and modulus of valve material
• Reciprocating wear test of valve and cylinder head interface
Representative Data
Gaskets
ASTM
D412: Tensile properties of elastomers
D2240: Test of Durometer hardness of rubber
D1415: Test Method for Rubber Property—International Hardness
Benefits of the UMT:
• Single Platform (hardware and software) is used for performing widely different tests
3/27/2014 19
Possible Tests
• Deformability
• Creep
• Durometer hardness
Representative Data
Mirrors
ASTM
C1624 (05) –Scratch Test
E2546: Instrumented Indentation Test
Benefits of the UMT:
• Complete evaluation of functional properties of mirror
• Wear and scratch testing in one tool
3/27/2014 20
Possible Tests
• Scratch
• Wear durability
• Nanoindentation
• Stiction Test for wettability
• Adhesion testing of coatings
Representative Data
Paint
ASTM
C1624 (05) –Scratch Test
G171 (03) – Scratch Hardness Test
E2546: Instrumented Indentation Test
Benefits of the UMT:
• Comprehensive evaluation of paints in a single tool
• Switch between scratch and indentation in minutes
3/27/2014 21
Possible Tests:
• Scratch
• Wear durability
• Friction
• Indentation test
• Bend test
Representative Data
Piston Pins & Connecting Rods
ASTM
G133: Ball-on-Flat sliding
G77 – Block-on-ring test
Benefits of the UMT:
• Modular design of UMT can address challenges of altogether different types of tests.
• Testing up to 1000C
3/27/2014 22
Possible Tests
• Wear Test of Pin
• Block-on-ring test for bearings
Representative Data
Piston Rings & Cylinder Liners
ASTM G181: Friction Tests of Piston
Ring and Cylinder Liner
Loading-unloading profile
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
3/27/2014 23
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
Representative Data
Rockers
ASTM
G133: Ball-on-Flat G77 Block-on-ring
Benefits of the UMT
• Ability to run multiple tests on one platform
• Precise servo control
3/27/2014 24
Possible Tests:
• Wear Test of Pin
• Block-on-ring test for bearings
Representative Data
Seat Belts
Tests includes;
ASTM G132 Reciprocating pin-on-flat wear test
Benefits of the UMT
• Change from one test regime to another in minutes
• Servo Z-axis motion/load control
3/27/2014 25
Possible Tests:
• Seat belt fabric wear test
• Buckle wear testing
Representative Data
Suspension
ASTM G133: Ball-on-Flat sliding
G77 – Block-on-ring test
Benefits of the UMT
• Measure hard materials (spring steel) and elastomers on one platform
3/27/2014 26
Possible Tests
• Wear Test of Pin
• Block-on-ring test for bearings
• Testing elastomer suspension components
Representative Data
Tires
ASTM
D412: Tensile properties
D2240: Durometer hardness
D1415: International Hardness
E2546: Instrumented Indentation
Benefits of the UMT
• Test from -40C to 350C and above
• Change from ambient to humidity or in-liquid testing by switching chambers
3/27/2014 27
Possible Tests
• Abrasion Test
• Hardness-modulus test
• Creep
• Friction
Representative Data
Lubricants
ASTM:
D2266, D2509, D2625, D2670, D2714, D2981, D3233, D3704, D4172, D5001, D5183, D5620, D5706, D5707, D6078, D6079, D6425
Benefits of the UMT:
• Run various tests in one hardware-software platform
• Controlled temperature
• Computer controlled load, speed, etc.
3/27/2014 28
Possible Tests:
• Stribeck Test • Block-on-ring • Pin-on-disk • Disk-on-disk • Pin-on-vee • 4-ball • Twist-compression
Representative Data
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.
20/02/2014 29
Single Platform for Many Tribosystem
20/02/2014 30
Environmental Chambers
3/27/2014 31
1000°C Rotary
Chamber
1000°C
Reciprocating
Chamber
-25°C
Chamber
-40°C
Chamber
Full range of heating/cooling chambers to simulate real world conditions.
Humidity chambers also available but not pictured.
3D-Optical Microscope
3/27/2014 32
Typical Interferometer Diagram
• 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
CCD
Sample
Reference
Mirror
Beamsplitter
Test arm
Reference arm
Optical Path Difference (OPD) • Difference in optical path lengths that beams travel
in Reference and Test arms
• When OPD=0, the brightest fringes are in focus 3/27/2014 33
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.
blue light green light yellow light red light
Fringes for:
Wide bandwidth filter (300nm) - (White Light VSI)
3/27/2014 34
Focus 1
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. Focus 2
Focus 3 Focus 4
1
4
3
2
White Light Fringes
3/27/2014 35
VSI
Operation of 3D Microscope
Step Height Standard
Vertical resolution about 0.1nm
Uses light of wide bandwidth i.e. white
light. Fringes are localized near best
focus
3/27/2014 36
2D Stylus Method
• Historically, 2D techniques such as stylus are being used for surface texture study.
• For Stylus based techniques, the min feature size is determined by size of stylus tip.
• For critical sub-micron surface roughness applications, this technology lack the critical data density required to fully characterize the component under investigation
Scan Profile
large Tip Small Tip
Valley can’t reached due to stylus size
3/27/2014 39
System Capability Nano scale Demonstration: 0.148nm Roughness
3/27/2014 41
3D vs. 2D
3D Image provides more information on the surface finishing.
Not able capture with Single Line
3/27/2014 42
Example of Automotive Applications
• Gear
• Piston and cylinder block wear
• Brake rotor wear
• Cam shaft analyses
• Specialty products
• Development
• Process control
3/27/2014 43
Gear
3/27/2014 44
Hypoid Pinion Gear Wear
• Highly convex surfaces
• Currently use contact technique or cut down parts
Tooth bow x-section shows range of z-height. 3/27/2014 45
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
3/27/2014 46
47
Spherical opening on Shaft
3/27/2014
Fuel Line
3/27/2014 48
Central machining pattern
Pattern height 5 microns, pin height 9 microns
3/27/2014 49
Black Sample Inspection
Center
2
3
4
5
Position Surface Roughness (Sa)
Center 337.2nm
Spot #2 44.3nm
Spot #3 226.4nm
Spot #4 167.9nm
Spot #5 163.2nm
Center
Spot 2
Spot 3
Spot 4
Spot 5
3/27/2014 50
Plasma spray coating texture
ContourGT-K1 easily
measures rough low
reflectivity surfaces
Ra=73.6µm
3/27/2014 51
Quantification of Wear Scar Volume
Volume of transferred or re-deposited matter
Volume of wear scar
3/27/2014 52
Case Study: Cylinder Block Liner
3/27/2014 53
Cylinder Liner: Surface Texture at 25mm area
3/27/2014 54
Shaft
3/27/2014 55
Shaft: Radius of Curvature = 8.0mm (Diameter = 16mm)
Frequency = 1/0.1686 mm
ROC = 8mm
3/27/2014 56
Shaft: After Form Removal
3/27/2014 57
Shaft: Waviness and Roughness
Apply Low / High Pass filter to find the waviness and roughness 3/27/2014 58
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
3/27/2014 59
Vision 64 Analysis Software
• Basic Stats
• Cross Hatch
• Fresnel Analysis
• Lead Angle
• Lead Angle Single Measurement Analysis
• MTF Analysis
• Multiple Region
• PSF Encircled Energy Analysis
• PSF Ensquared Energy Analysis
• Rz Analysis
• S Parameters – Functional
• S Parameters – Height
• S Parameters – Hybrid
• S Paramaters – Spatial
• Step Height
3/27/2014 60
• SureVision
• Surface Area
• Thickness Stats
• Trace Analysis
• User Analysis
• V Parameters
• Volume
• XY Averaged PSD
• Zernike Analysis
• Bearing Ratio
• 2D Profile
• Critical Dimension
• Histogram
• Auto Corr
• APSD
• PSD
Other Applications
3/27/2014 61
Example of
Lubrication Testing
3/27/2014 62
Lab Set-Up
3/27/2014 63
Set-up for 4-ball Test
N
Set-up for Stribeck Curve
Ball or Cylinder-on-sde
3-D Image of MSBO-B wear scar at 40kg load using White Light Interferometer
Bruker Contour GT
White Light Interferometer
3/27/2014 64
2-D projections of wear scar for diameter measurement
3/27/2014 65
Bruker UMT system Multipurpose Materials Tester
Multiple tests on a single platform - ASTM, DIN and ISO standards
Pin/Ball on Rotating Disc
Linear Wear Test
Ball on Three Balls (4-Ball)
Pin on Vee-Block
Block on Ring
Disc on Rotating Disc
Plate on Reciprocating Plate
3/27/2014 66
Summary
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
3D Optical Microscope
www.bruker.com
© Copyright Bruker Corporation. All rights reserved.
For further information please contact
