ASTM E1685-00(2006)
(Practice)Standard Practice for Measuring the Change in Length of Fasteners Using the Ultrasonic Pulse-Echo Technique
Standard Practice for Measuring the Change in Length of Fasteners Using the Ultrasonic Pulse-Echo Technique
SIGNIFICANCE AND USE
The techniques described provide for the indirect measurement of change in length of a fastener. Such measurements are made from one end of the specimen without requiring access to the rear surface.
The equipment is field portable and should be used in the manner prescribed by the manufacturer. Common uses include monitoring changes in length of fasteners and as a tool for industrial quality control. Current applications include fasteners used in turbines, petrochemical pressure vessels, aircraft, automotive manufacturing, general bolting within the nuclear industry, structural steel connections, laboratory testing, and so forth.
SCOPE
1.1 This practice covers a procedure for measuring changes in length of threaded fasteners using conventional ultrasonic pulse-echo bolt-measuring instrumentation which has been properly calibrated.
1.2 This procedure is normally intended for metal bolting 0.25 in. (6.4 mm) or more in nominal diameter with effective length-to-diameter ratios of 2:1 or greater.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E1685 − 00(Reapproved 2006)
Standard Practice for
Measuring the Change in Length of Fasteners Using the
Ultrasonic Pulse-Echo Technique
This standard is issued under the fixed designation E1685; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.2 effective length—the length of a bolt that is responsive
to stress.
1.1 This practice covers a procedure for measuring changes
3.2.2.1 Discussion—This quantity lies somewhere between
in length of threaded fasteners using conventional ultrasonic
the overall length of the bolt and the grip length. It is usually
pulse-echo bolt-measuring instrumentation which has been
estimated as the grip length plus one half the thickness of the
properly calibrated.
head and one half the thickness of the nut.
1.2 This procedure is normally intended for metal bolting
3.2.3 longitudinal wave—those waves in which the particle
0.25 in. (6.4 mm) or more in nominal diameter with effective
motion of the material is in the same direction as the wave
length-to-diameter ratios of 2:1 or greater.
propagation.
1.3 This standard does not purport to address all of the
3.2.4 pulse-echo bolt-measuring equipment—an assembly
safety concerns, if any, associated with its use. It is the
of ultrasonic instruments designed specifically to measure
responsibility of the user of this standard to establish appro-
changes in the lengths of bolts. See Appendix X1.
priate safety and health practices and determine the applica-
3.2.5 reference length—the ultrasonic time of flight in the
bility of regulatory limitations prior to use.
test specimen multiplied by a reference propagation velocity.
2. Referenced Documents
3.2.6 reference propagation velocity—the velocity of propa-
gation of the ultrasonic wavefront in a calibration test block or
2.1 ASTM Standards:
in the bolts whose changes of length are being measured.
E6 Terminology Relating to Methods of Mechanical Testing
E1316 Terminology for Nondestructive Examinations
3.2.7 time of flight—the measured time interval between the
E1544 Practice for Construction of a Stepped Block and Its
launching of an ultrasonic pulse at the start of a path of travel
Use to Estimate Errors Produced by Speed-of-Sound
and the reception of the pulse at the end of the path.
Measurement Systems for Use on Solids (Withdrawn
2012)
4. Summary of Practice
4.1 This practice describes a procedure for determining the
3. Terminology
change in length of a threaded fastener due to a change in
3.1 The definitions in this practice are in accordance with
tension in the fastener. Measurements of the ultrasonic time of
Terminology E6 and Section I of Terminology E1316.
flightaremadebeforeandafterthefastenertensionischanged,
and a calculation of the change in length is made from the
3.2 Definitions of Terms Specific to This Standard:
change in the time of flight.
3.2.1 change in length—physical change in length of a
4.1.1 Brief bursts of ultrasound (pulses) are generated by
threadedfastenerduetoachangeintensionwithinthefastener.
applying high-voltage electrical signals to an electroacoustic
transducer having a resonant frequency in the 5 to 10-MHz
range. The pulses enter the bolt through the transducer/bolt
This practice is under the jurisdiction ofASTM Committee E28 on Mechanical
interface, travel to the far end of the bolt, and reflect back
Testing and is the direct responsibility of Subcommittee E28.13 on Residual Stress
Measurement.
(echo) to the transducer. The time of flight required for the
Current edition approved Dec. 1, 2006. Published January 2007. Originally
signal to make its round-trip is measured electronically. By
approved in 1995. Last previous edition approved in 2000 as E1685–00. DOI:
measuring the change in the time of flight due to a change in
10.1520/E1685-00R06.
tension within the bolt, the equipment can determine the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
change in the length of the bolt due to the change in tension.
Standards volume information, refer to the standard’s Document Summary page on
Compensation for the direct effect of stress on the propagation
the ASTM website.
velocity in the bolt is automatically done by a computer or
The last approved version of this historical standard is referenced on
www.astm.org. microprocessor within the equipment.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1685 − 00 (2006)
4.2 This procedure is used on fasteners as they are tightened allelism is recommended.Acceptable standards include a glass
within their elastic limits; or on previously tightened fasteners block, two metal bars of unequal length, and single bars of
as they are loosened. The latter can have been tightened past known acoustic velocity. The path length of the standard must
yield. be determined by a technique of higher accuracy. See Practice
E1544. Calibration of standards should be traceable to NIST.
5. Significance and Use
5.1 The techniques described provide for the indirect mea- 7. Procedure
surement of change in length of a fastener. Such measurements
7.1 Theperformanceofthepulse-echoinstrumentshouldbe
are made from one end of the specimen without requiring
verified or adjusted to a reference standard in accordance with
access to the rear surface.
the manufacturer’s specifications. See Annex A2.
5.2 The equipment is field portable and should be used in
7.1.1 In noncritical applications, where uncertainties
the manner prescribed by the manufacturer. Common uses
smallerthan 615 %ofthechangeinlengtharenotrequired,an
include monitoring changes in length of fasteners and as a tool
instrument calibrated on one bolt of a given material can be
for industrial quality control. Current applications include
used on other bolts of the same material but having different
fasteners used in turbines, petrochemical pressure vessels,
shapes.
aircraft, automotive manufacturing, general bolting within the
7.1.2 At the other extreme, if the instrument is to be used on
nuclear industry, structural steel connections, laboratory
bolts in critical, safety-related applications or where uncertain-
testing, and so forth.
ties of 61 to 3 % are required, or both, consideration should be
given to recalibration on a statistically significant sample of
6. Apparatus
each new lot of bolts.
6.1 Pulse-Echo Instrument—For ultrasonic measurementsof
7.2 Fastener Preparation—For reliable ultrasonic measure-
thechangeinlengthofbolts,anylongitudinal-wavepulse-echo
ments the fastener must have suitable finish and geometry
ultrasonic instrument capable of reporting calculated changes
requirements. One end must be accessible for transducer
in length is acceptable provided that its accuracy and precision
placement. This end must, for at least the diameter of the
satisfy the requirements set forth in Annex A1. The major
transducer, be flat and perpendicular to the axis of the bolt. A
components of suitable instruments are as follows:
machined surface with a finish of 125 RMS or better is
6.1.1 Pulser/transmitter, a means of generating electrical
recommended, exclusive of indented grade markings. Raised
pulses to excite an acoustic transducer.
grade markings must be removed. (See Note 1.) If the end is
6.1.2 Receiver/detector, a means of amplifying and detect-
recessed it must have a flat spot face. The reflector end of the
ing the returning back-wall echo.
fastener must have a flat surface parallel to the other end. The
6.1.3 Time-base Controller, a means of measuring changes
amount of axial runout on the end is dependent on fastener size
in ultrasonic time of flight.
and the accuracy requirement. An area as small as ⁄8 in. (3
6.1.4 Acoustic Transducer, a means of sending and receiv-
mm) in diameter may be sufficient. The ends of bolts with
ing ultrasonic waves. Experience has shown that transducers
through center holes may be prepared adjacent to the holes,
with resonances in the 5 to 10-MHz frequency range are
with the transducer locations marked.
usually satisfactory. In general, select an acoustic transducer
having an element of the largest diameter available while not
NOTE 1—Grade markings should not be moved indiscriminately.
exceeding the minimum body diameter of the bolt.
Documentation of grade marking removals should be created and main-
tained.
6.2 Other Apparatus:
7.3 Measure average fastener temperature within 1°C, in
6.2.1 Couplant—For longitudinal pulse-echo
measurements, a liquid is required to couple ultrasound be- accordance with instructions in the instrument operating
tween the transducer and the fastener. Of the couplants manual.
commonly used, where applicable a 50/50 glycerine/water mix
7.4 Transducer Placement:
often provides optimal results. Light oil or standard commer-
7.4.1 Apply a suitable acoustic couplant to allow adequate
cially available ultrasonic couplants are also satisfactory.
sound transmission. Glycerine or some other high-viscosity
6.2.2 Oscilloscope—For optimal adjustment of the
couplant is recommended if the fastener has indented grade
apparatus, the use of an oscilloscope is necessary. The oscil-
markings or if its surface has a few pits.
loscope must have two input channels, two traces,
...
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