mechanical system verification

8/11/2019 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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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



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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



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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)

mechanical system verification

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