ASTM E1544-99(2004)e1
(Practice)Standard Practice for Construction of a Stepped Block and Its Use to Estimate Errors Produced by Speed-of-Sound Measurement Systems for Use on Solids (Withdrawn 2012)
Standard Practice for Construction of a Stepped Block and Its Use to Estimate Errors Produced by Speed-of-Sound Measurement Systems for Use on Solids (Withdrawn 2012)
SIGNIFICANCE AND USE
The use of sound speed values to determine changes in the elastic constants due to applied or residual stress requires that such measurements be of high precision and low bias. For that reason, special evaluation tests to determine a representative precision and bias for the specific technique, method, and equipment setup used are given.
Speed of sound is a measure that depends on the accurate measurements of length of path of travel and transit time or other related parameters such as frequency, etc. Both measurements are subject to certain interpretations and assumptions and are highly dependent on laboratory expertise. This practice provides a means of checking overall technique.
This practice shall be used when it is necessary to assess the systematic and random errors associated with a particular speed of sound measurement in a solid medium. It can be used to check both equipment performance and measurement technique for these errors. It can also be used to study inherent errors in a particular method. It can also be used to assess proposed corrections to sound speed measurements such as the phase corrections of Papadakis (3, 4).
The resultant precision and bias determined by the use of the described block represents a more ideal situation than the same measurement performed in practice, in the field. Thus, the error for the specific field measurement may be larger than indicated by this test. This test represents the best error condition for a given technique and practice.
SCOPE
1.1 This practice provides a means for evaluating both systematic and random errors for ultrasonic speed-of-sound measurement systems which are used for evaluating material characteristics associated with residual stress and which may also be used for nondestructive measurements of the dynamic elastic moduli of materials. Important features and construction details of a reference block crucial to these error evaluations are described. This practice can be used whenever the precision and bias of sound speed values are in question.
1.2 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.
WITHDRAWN RATIONALE
This practice provides a means for evaluating both systematic and random errors for ultrasonic speed-of-sound measurement systems which are used for evaluating material characteristics associated with residual stress and which may also be used for nondestructive measurements of the dynamic elastic moduli of materials. Important features and construction details of a reference block crucial to these error evaluations are described. This practice can be used whenever the precision and bias of sound speed values are in question.
Formerly under the jurisdiction of Committee E28 on Mechanical Testing, this practice was withdrawn in April 2012 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees , which requires that standards shall be updated by the end of the eighth year since the last approval date.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E1544 – 99 (Reapproved 2004)
Standard Practice for
Construction of a Stepped Block and Its Use to Estimate
Errors Produced by Speed-of-Sound Measurement Systems
for Use on Solids
This standard is issued under the fixed designation E1544; 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.
´ NOTE—The correct Figure 2 was reinstated in May 2004.
1. Scope 3.1.2.1 Discussion—There are many different techniques
usedtoavoidterminationerrorsrelatedtoelectronicdelaysand
1.1 This practice provides a means for evaluating both
termination impedance effects and end interference. One com-
systematic and random errors for ultrasonic speed-of-sound
monly accepted procedure is to make the time measurement
measurement systems which are used for evaluating material
between successive echoes instead of using the electrical
characteristics associated with residual stress and which may
driving pulse as the start marker. Reference techniques that use
also be used for nondestructive measurements of the dynamic
two nearly identical sets of experiments, where one is the
elasticmoduliofmaterials.Importantfeaturesandconstruction
reference and the other the unknown and in which the
details of a reference block crucial to these error evaluations
differenceintimeoftravelistheoutputresult,canceloutmany
aredescribed.Thispracticecanbeusedwhenevertheprecision
of the errors mentioned above (1).
and bias of sound speed values are in question.
1.2 This standard does not purport to address all of the
4. Summary of Practice
safety concerns, if any, associated with its use. It is the
4.1 The physical quantity, speed of sound of a particular
responsibility of the user of this standard to establish appro-
solid, is not a fundamental constant because it depends on
priate safety and health practices and determine the applica-
separate measurements of time and distance. It is a computed
bility of regulatory limitations prior to use.
value derived from measured values of distance and of time
2. Referenced Documents and is based on assumptions about the elastic material through
which the sound waves travel. Because this quantity is not a
2.1 ASTM Standards:
fundamental property (dependent upon many other variables
E650 Guide for Mounting Piezoelectric Acoustic Emission
besidestimeanddistance)ofanymaterial,areferencestandard
Sensors
having a specific value of speed of sound is virtually impos-
E494 Practice for Measuring Ultrasonic Velocity in Mate-
sible to construct. Thus, questions of accuracy have to be
rials
addressed in a different way.
3. Terminology 4.2 The measurement of sound speed depends upon many
factors.Considerationsoftheuniformityofboththeelasticand
3.1 Definitions of Terms Specific to This Standard:
thedensitycharacteristicsofthematerial,ofinternalscattering,
3.1.1 path length—length of track along which the sound
of transducer coupling and loading, of temperature uniformity
waves actually propagate.
and value, of external pressure and stress, and of many other
3.1.2 time of flight—the measured time interval between the
physical effects that would alter the overall measurement
launching of a sonic input pulse at the start of a path and the
process must be taken into account. Because the speed of
time of reception of the pulse at the end of the path of travel.
sound is affected by so many physical parameters, the only
available test to evaluate the detrimental influence of these
higher order variables is to examine their combined effects on
ThispracticeisunderthejurisdictionofASTMCommitteeE-28onMechanical
measured speed of sound values as it relates to the definition:
Testing and is the direct responsibility of Subcommittee E28.13 on Residual Stress
Measurement.
V 5 L/t (1)
Current edition approved April 1, 2004. Published MAy 2004. Originally
approved in 1993. Last previous edition approved in 99 as E1544 – 99. DOI: 4.2.1 This defining equation for the sound speed, V, states a
10.1520/E1544-99R04E01.
constantrelationshipbetweenpathlength, L,andtimeofflight,
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
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E1544 – 99 (2004)
t, and is applicable primarily to methods in which the time is condition for the confirmation of system performance to have
measured directly (2). a lack of bias. The described gage block has six path lengths,
4.3 Several different methods of measuring speed of sound although a reference gage block for this purpose need not be
exist. A number of these are itemized in Practice E494. limited to such a geometry. (Another geometry that is easier to
(McSkimin details many ingenious methods in Ref (1)). manufacture is a rectangular parallelepiped with three dis-
Regardless of the method used to calculate the sound speed tinctly different dimensions (2). Polyhedra of parallel opposite
from two measurements, the intent is to determine this con- sides would also be appropriate.)
stant, V, that represents the transport of the elastic potential
4.6 Any gage block used for the purpose of checking the
function and related parameters through the solid body.
processofsoundspeedmeasurementmusthaveuniformelastic
4.4 This definition is based on the assumption that the
and density characteristics throughout the gage block; thus, it
medium that transmits the elastic waves is both homogeneous
must be homogeneous and isotropic. Only then can it be
and isotropic. In such a case, a constant, V, is the applicable
assumed that the speed of sound is uniform and not dependent
property throughout the whole volume and in all directions of
on location and wave direction within the gage block. A
the solid body.To the degree that this assumption holds, (Eq 1)
method for assuring the high uniformity of the block is
and any other analytical description associated with other
detailed.
methods should yield a linear relationship between time of
flight (or other parameters) and path length traversed. (Another
5. Significance and Use
form of this comparison would be for the computed sound
5.1 The use of sound speed values to determine changes in
speed to be a constant for different paths of different lengths.)
the elastic constants due to applied or residual stress requires
Errors from this linear prediction are associated with errors in
that such measurements be of high precision and low bias. For
the measurement of time of flight (or the other parameters) and
that reason, special evaluation tests to determine a representa-
path length. Deviation of the measured values of sound speed
tive precision and bias for the specific technique, method, and
beyond the estimated errors in the time measurement and the
equipment setup used are given.
length measurement are connected with the systematic and
5.2 Speed of sound is a measure that depends on the
random errors associated with all other unwanted variables of
accurate measurements of length of path of travel and transit
non-ideal material, non-ideal measuring technique, and lack of
time or other related parameters such as frequency, etc. Both
control on the many variables of indirect influence. An ex-
measurements are subject to certain interpretations and as-
ample of a second order dependence is a nonlinear relationship
sumptions and are highly dependent on laboratory expertise.
between time and distance due to diffraction effects associated
This practice provides a means of checking overall technique.
with a finite transducer aperture.
5.3 This practice shall be used when it is necessary to assess
4.5 In order to check a particular sound speed measuring
the systematic and random errors associated with a particular
system or particular applied technique, or both, a stepped gage
speed of sound measurement in a solid medium. It can be used
block,similartoFig.1,ofveryuniformmaterialpropertiescan
to check both equipment performance and measurement tech-
be constructed to check the performance of a measurement
nique for these errors. It can also be used to study inherent
system by examining differences from the predicted linear
errors in a particular method. It can also be used to assess
relationship of Eq 1. Demonstrating that the calculated speed
proposed corrections to sound speed measurements such as the
of sound, V, is constant for the different path lengths as
phase corrections of Papadakis (3, 4).
determined in such a gage block experiment is a necessary
5.4 The resultant precision and bias determined by the use
ofthedescribedblockrepresentsamoreidealsituationthanthe
same measurement performed in practice, in the field. Thus,
the error for the specific field measurement may be larger than
indicated by this test. This test represents the best error
condition for a given technique and practice.
6. Procedure
6.1 Speed of Sound Test Block Construction:
6.1.1 Construct a glass block of the general shape and size
of Fig. 1 of optical quality glass having at least a medium
valued stress-optic coefficient (5). A stress-optic coefficient in
the range of 20 to 40 nm/cm/MPa is desirable and the sample
should be well annealed for a low internal stress state. Adhere
to the glass manufacturer’s annealing schedule. The dimen-
sions of such a reference glass block can be chosen to
approximate the dimensions and time of flight simulating the
NOTE 1—Sound speed reference block manufactured of optical quality
situation for which this assurance test is being done.
glassofhighuniformity.Themultiplesoundpropagationpathsaremarked
L1 through L6. NOTE 1—The test block constructed and tested has nominal dimensions
FIG. 1 Sound Speed Reference Block, Optical Glass of L1 = 63.5 mm, L2 = 66.7 mm, L3 = 69.9 mm, L4 = 73 mm, L5 = 88.9
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E1544 – 99 (2004)
mm, and L6 = 101.6 mm. The step or facet on which the transducer is
Carry out a temperature measurement of the gage block for
mounted should, of course, be at least as large as the aperture of the
each ultrasonic measurement and record its value with the
transducer.
ultrasonic times of flight or phase shift. These temperature
measurements should be to a precision of 0.1°C.
6.1.2 Theglassofthisblockshallbefreeofinternalstresses
6.2.3.1 Thermally isolate the block from any external heat-
and variations of optical index throughout its volume. Deter-
ing or cooling gradients such as local heating due to handling.
mine these two important features by examining the glass
Allow a period of 10 min to establish thermal equilibrium after
blank from which the block is to be cut between crossed
any thermal disturbance has occurred.
polarizers before the cutting and polishing processes begin.
6.2.4 Correct each sound speed value for thermal expansion
Also,applythistestintermittentlyduringboththegrindingand
and thermal changes in the elasticity associated with tempera-
polishing processes, and on the completed block. Any signifi-
ture variation occurring between measurements of the different
cant change in optical index or any significant internal stress
path lengths of the set and then plot against the measured path
patterns will show up immediately as a nonuniformity in the
length.
visual optical field. (A good quality optical glass that is well
6.2.5 If poor precision or significant bias is suspected,
annealed and is uniform in temperature during observation will
measure and plot several values for each path length. This
shownoshadowordarkregionswhenviewedbetweencrossed
process will help establish a precision value for this particular
polaroids and the viewing regions will be perfectly uniform.
arrangement and path length. In general, make at least five
Any region of shadow is an indication of optical birefringence
separate measurements of speed of sound for each path length
associated with variations of uniformity of various physical
to ascertain consistency of the process. From this set of
parameters such as density, internal stress, and temperature.)
measurements a standard deviation can be computed and error
Shadowed regions represent positions where the relative retar-
bounds assigned for each length.
dation differs by at least one-fifth of a wavelength of the
6.2.6 The results for all path lengths can then be examined
illumination used. Such a visual indication should be grounds
for the variation of the measured sound speed values from a
for rejection of the material blank.
single constant value. (The average value might be satisfactory
6.1.3 Grind and polish all surfaces to better than 0.5 µm of
for this purpose.)
being flat and each surface shall be cut so as to be parallel to
6.2.7 Such a comparison is shown in Fig. 2. This figure
the opposite surface.
demonstrates the ability to evaluate precision and bias from a
6.1.4 Block thickness between parallel faces and along the
set of measurements. See Appendix X1 for a more thorough
direction of the propagation through this glass block must be
description of this process. The solid line is the average for all
measured to at least the accuracy appropriate to the desired
the data, the dashed lines represent plus or minus one standard
results of the assurance test.
deviation (6 ⁄12000) as computed from the total data set. Each
6.1.5 Thermal expansion for the test block should be known
datamarkerrepresentsonemeasurementofthespeedofsound.
for length correction purposes and, if possible, low thermal
Each data set for a single length has an error 9window9 that is
expansion should be a factor in the choice of the material.
represented by a vertical“ I” bar. This error, “I”, is centered on
Borosilicate crown glass is a good choice because it has a
theaverageforthatlengthsetandindicatesplusandminusone
relatively low thermal expansion.
6.2 Use of This Reference Block to Determine System and
Method Performance for Sound Speed Measurements:
6.2.1 Attach a sending/receiving transducer or transducers
to the various faces of the reference gage block by the means
intended for final use. This might include transducer holders,
delay blocks, coupling materials of different thicknesses, and
acoustic delay lines. Attempt to establish general ultrasonic
conditions of the transducer attachment that closely duplicate
the final conditions of use in pract
...
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