Mechanical System Verification
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Transcript of Mechanical System Verification
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Mechanical System VerificationLVDT Calibration
Use NIST traceable
micrometer
Eight point calibration
Acceptance Criteria Near zero intercept R-squared > 0.99
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Mechanical System VerificationLoad Cell Zero
Use strain indicator
Measure load cell zero reading
Used to determine if load cellhas been fatigued oroverstrained
Acceptance CriteriaZero reading < 1.5 %
of full-scale sensitivity
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Mechanical System VerificationLoad Cell Calibration Verification
Requires NIST traceable
proving rings
Utilizes static loading Verifies load cell calibration
Measures unwanted friction
Measures unwanted bendingand deflections
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Mechanical System VerificationLoad Cell Calibration Verification
Acceptance Criteria
Proving ring versus load cellvalue within 5% of each other
Proving ring dial gauge versus
LVDT reading within 5% of
each other
Load cell reading versus proving ring load values, run #1
0
100
200
300
400
500
0 100 200 300 400 500
Proving Ring Load, lb
LoadCellValue,
lb Replicate 1
Upper Load Limit
Lower Load Limit
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Mechanical System VerificationDynamic Response
Verify overall equipment ability
to conduct Resilient Modulus
testingVerify data acquisition process
Verify data format
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Mechanical System VerificationDynamic Response
Procedure
Remove dial gauge from proving ring
Use external LVDTs or internally
mounted LVDT for displacement
measurements
Apply haversine shaped load pulse
(.1 seconds on, .9 seconds off)
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Procedure (continued)Apply dynamic load from 10 -
90% of proving ring capacity @
10% intervals
Read deformation using data
acquisition system
Mechanical System VerificationDynamic Response
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Acceptance Criteria Generated haversine close to ideal
Deformation response close tohaversine
Deformation within 5% ofstandard
R-square > 0.99
.002 second or less phase shiftbetween load and deformation
Ymax/Ymin < 1.10 (10%)
Load-deformation characteristics, run #1 - 500 lb dynamic (haversine) test.
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
400.00
450.00
500.00
0 0.02 0.04 0.06 0.08 0.1 0.12
Deformation, in
Load
CellValue,
lb
Replicate 1
Upper Limit
Lower Limit
Mechanical System VerificationDynamic Response
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Dynamic sinusoidal tests
Verify overall system electronics
(phase angle measurements)
Detect misalignment problemsthrough the use of phase angle
measurements
Mechanical System VerificationPhase Angles
Figure A.4. Dynamic Response Check of 500 lb Proving Ring, 1 Hz
0
50
100
150
200
250
300
350
400
450
500
0 0.5 1 1.5 2 2.5
Time, sec
Load,
lb
Acceptance CriteriaPhase angle < 2.8 degrees
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Procedure Use autonomous pressure reading
device to verify pressure
Mechanical System VerificationTriaxial Pressure Chamber
Acceptance Criteria
Gauge readings 2.5 % oftarget values
Hold for 10 minutes
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Laboratory Proficiency Testing
Acceptance CriteriaVertical deformations within 30%
Approval by Representative based
on visual observations Conformance to all aspects of the
protocol
Haversine wave form close to
ideal Deformation response reasonable
Resilient Modulus relationshipreasonable
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PRESENTATION OBJECTIVES
What is the Resilient Modulus (Mr) StartupProcedure Product Line
Why Mr Testing and the Startup Procedure is
Important Development of the MrStartup Procedure
How to Conduct the MrStartup Procedure
How to Get Information on the MrTestingand Startup Product Line
Who Should Use the MrTesting and
Startup Product Line and Why
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Who Should Use the Product?
Any organization performingresilient modulus testing State DOTs
Universities
Consultant laboratories
Can be used for other tests as
well Complex modulus Creep compliance
Indirect tensile testing, etc.
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When Should Product Be Used?
General Prior to starting a testing program
Every year during productiontesting
After a period of system inactivity
Other recommendations
Verify the operation of older
machines for new applications When equipment is replaced
When equipment is moved
Whenever a suspected overload or
malfunction occurs
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Uncover and Avoid ProblemsElectronics
Over-ranged load cell
Inadequate filters
Amplitude roll off: 2 Hz - 50 Hz
Unmatched filters
Excessive time delay (phase
angle) between channels
Filters on and off
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Uncover And Avoid ProblemsSoftware
Software not controlling the load
adequately
Inadequate sampling rate
Raw data with no units Automatic gain control, error range
too big
Lack of gain control adjustment
during testing
Improper raw data format -
command values were saved rather
than the feedback values
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Uncover And Avoid ProblemsMechanical
System not fast enough to apply proper
haversine loads - complete upgrade of signal
conditioning and control
Oversize servo-value Friction in servo-value piston
Friction in triaxial cell seals
Misalignment caused by improperly designed
triaxial cell fixture
Excessive deformation, up to 76% of total
deformation due to bending of triaxial cell
base plate
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Uncover And Avoid ProblemsMechanical (continued)
Excessive deformation due to
unrestrained triaxial cell
Slippage of LVDT holders
Lack of control of pressure
transducer
Malfunction of air pressure regulator
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Benefits of Use
Provides guidelines for
standardization of test process
Provides a benchmarkperformance standard for
equipment
Minimizes equipment and
operator variability Promotes greater confidence in
resilient modulus testing and
resulting pavement design
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Current Status of Product
P46 test procedure established Videos produced and
distributed
Startup procedure published Startup procedures completed FHWA
Kansas
North Carolina Minnesota
University of Rhode Island
Consultant laboratories
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PRESENTATION OBJECTIVES
What is the Resilient Modulus (Mr) StartupProcedure Product Line
Why Mr Testing and the Startup Procedure is
Important Development of the MrStartup Procedure
How to Conduct the MrStartup Procedure
Who Should Use the MrStartup Procedure
and Why
How to Get Information on the Mr StartupProcedure?
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Get and Use Mr Testing andStartup Procedure Product Line
Download procedure manuals from
LTPP homepage at
www.tfhrc.gov
Order procedure manuals/videos: Through LTPP homepage
Through LTPP customer service
(Tel Number: 865-481-2967)