1 mechanical system verification lvdt calibration use nist traceable micrometer eight point...
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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
cell has been fatigued or overstrained
• Acceptance Criteria– Zero reading < 1.5 % of full-scale sensitivity
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Mechanical System VerificationLoad Cell Calibration Certificates
• Check laboratory documentation to determine last NIST traceable calibration
• Acceptance Criteria– NIST traceable calibration within one year
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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
bending and deflections
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Mechanical System Verification Load Cell Calibration Verification
• Procedure– Apply static (ramp) load from
10 - 90% of proving ring capacity @ 10% intervals
– Register load cell/LVDT readings with data acquisition system
– Read dial gauge on proving ring
Figure A.1. 500 lb Static (Ramp) Testing, Load versus Time
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0 50 100 150 200 250 300 350 400
Time, sec
Lo
ad, l
b
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Mechanical System Verification Load Cell Calibration Verification
• Acceptance Criteria– Proving ring versus load cell
value 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
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0 100 200 300 400 500Proving Ring Load, lb
Lo
ad C
ell
Val
ue
, 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 testing– Verify data acquisition
process– Verify data format
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Mechanical System Verification Dynamic 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 Verification Dynamic Response
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Acceptance Criteria Generated haversine close to
ideal Deformation response close to
haversine Deformation within 5% of
standard R-square > 0.99 .002 second or less phase shift
between load and deformation Ymax/Ymin < 1.10 (10%)
Load-deformation characteristics, run #1 - 500 lb dynamic (haversine) test.
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50.00100.00
150.00200.00
250.00
300.00350.00
400.00450.00
500.00
0 0.02 0.04 0.06 0.08 0.1 0.12
Deformation, in
Lo
ad C
ell
Val
ue
, lb
Replicate 1
Upper Limit
Low er Limit
Mechanical System Verification Dynamic Response
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• Dynamic sinusoidal tests– Verify overall system
electronics (phase angle measurements)
– Detect misalignment problems through the use of phase angle measurements
Mechanical System VerificationPhase Angles
Figure A.4. Dynamic Response Check of 500 lb Proving Ring, 1 Hz
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0 0.5 1 1.5 2 2.5
Time, sec
Lo
ad, l
b
• Acceptance Criteria– Phase 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 % of target values– Hold for 10 minutes
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The 3-Phase Startup Process
• Verification of Electronic System
• Verification of Mechanical System
Verification of Laboratory Ability to Conduct P46 Resilient Modulus Test
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Laboratory Proficiency Testing
• Focuses on laboratory ability (personnel/equipment)• Sample preparation• Operator’s ability to conduct a
test• Proper sequence and magnitude
of loading• Proper data format• Analysis of raw data to detect
any discrepancies• Investigation of within and
between laboratory variability
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Laboratory Proficiency Testing
• Acceptance Criteria– Vertical 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 relationship reasonable
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PRESENTATION OBJECTIVES
• What is the Resilient Modulus (Mr) Startup Procedure Product Line
• Why Mr Testing and the Startup Procedure is Important
• Development of the Mr Startup Procedure
• How to Conduct the Mr Startup Procedure
• How to Get Information on the Mr Testing and Startup Product Line
Who Should Use the Mr Testing and Startup Product Line and Why
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Who Should Use the Product?
• Any organization performing resilient modulus testing– State DOT’s– 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 production testing– 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 Problems Electronics
• 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 Problems Software
• 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 Problems Mechanical
• 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 Problems Mechanical (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 benchmark performance 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) Startup Procedure Product Line
• Why Mr Testing and the Startup Procedure is Important
• Development of the Mr Startup Procedure
• How to Conduct the Mr Startup Procedure
• Who Should Use the Mr Startup Procedure and Why
How to Get Information on the Mr Startup Procedure?
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Get and Use Mr Testing and Startup 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)