# The History and Importance of Impact Testing\*

T. A. Siewert,1 M. P. Manahan,2 C. N. McCowan,3 J. M. Holt,4 F. J.
Marsh,5 and E. A. Ruth6

**Reference:** Siewert, T. A., Manahan, M. P., McCowan, C. N., Holt, J.
M., Marsh, F. J. and Ruth, E. A., **\"The History and Importance of
Impact Testing,\"** *Pendulum Impact Testing: A Century of Progress,
ASTM STP 1380*, T. A. Siewert and M. P. Manahan, Sr., Eds., American
Society for Testing and Materials, West Conshohocken, PA, 1999.

**Abstract:** Charpy impact testing is a low-cost and reliable test
method that is commonly required by the construction codes for
fracture-critical structures such as bridges and pressure vessels. Yet,
it took from about 1900 to 1960 for impact-test technology and
procedures to reach levels of accuracy and reproducibility such that the
procedures could be broadly applied as standard test methods. This paper
recounts the early history of the impact test and reports some of the
improvements in the procedures (standard specimen shape, introduction of
a notch, correlation to structural performance in service, and
introduction of shrouds) that led to this broad acceptance.

**Keywords:** absorbed energy, Charpy impact testing, history, impact
testing, pendulum impact

1 Supervisory Metallurgist, Materials Reliability Division, National
Institute of Standards and Technology, Boulder, CO 80303.

2 President, MPM Technologies, Inc., 2161 Sandy Drive, State College, PA
16803.

3 Materials Research Engr., Materials Reliability Division, NIST,
Boulder, CO 80303.

4 Alpha Consultants & Engineers, Pittsburgh, PA.

5 Retired (Bethlehem Steel), San Marcos, CA.

6 Tinius Olsen Test Machine Co., Willow Grove, PA.

\* Contribution of NIST; not subject to copyright. Further details on
the economic impact of Charpy impact testing are included in a previous
version of this report published in *Standardization News*, February
1999.

# The History and Importance of Impact Testing

Without uniformity of test results from day to day and from laboratory
to laboratory, the impact test has little meaning. Over the years,
researchers have learned that the results obtained from an impact test
can depend strongly upon the specimen size and the geometry of the
notch, anvils, and striker. To a lesser degree, impact test results

also depend upon other variables such as impact velocity, energy lost to
the test machine, and friction. The goal of those who have written and
modified ASTM Standard Test Methods for Notched Bar Impact Testing of
Metallic Materials (E 23) has over the years

been to standardize and control the variables associated with impact
testing. This report looks at the history of impact testing, with
emphasis on the key advances in understanding and application of the
impact test, as reflected in the evolution of the test standard.

**Impact Testing: 1824 to 1895**

The earliest publication that we could find on the effects of impact
loading on materials was a theoretical discussion by Tredgold in 1824 on
the ability of cast iron to resist impulsive forces \[*1*\]. In 1849,
the British formed a commission to study the use of iron in the railroad
industry, which began by considering practical approaches to impact
testing \[*2*\]. Apparently, failures of structures in the field were
leading some researchers to speculate that impact loads affected
materials far differently than static loads, so tensile-strength data
(from slowly applied loads) was a poor predictor of performance under
dynamic loads.

In 1857, Rodman devised a drop-weight machine for characterization of
gun steels, and over the subsequent 30-year period, his machine was
widely used to test railroad steels and for qualification of steel
products \[*2*\]. Many of the early experiments with impact tests were
performed on final product forms, such as pipes or axles. Thus they
served as proof tests for a batch of material, or yielded comparative
data for a new product design, or basic reference data on the impact
resistance of different construction materials (such as the comparison
of wrought iron to ductile iron). Instrumentation was poor for the early
impact tests, so the data is often only as break or no-break for a mass
dropped through a certain distance. These early drop weight tests were
conducted using smooth (no notch or crack starter) rectangular bars.
While the test worked well for brittle materials, where crack initiation
is easy, specimens of ductile materials often just bent. LeChatalier
introduced the use of notched specimens while conducting drop-weight
tests in 1892 \[*3*\]. He found that some steels that showed ductile
behavior (bending without fracture) in a smooth rectangular bar, would
exhibit fragile behavior when the test specimen was notched. While the
addition of a notch was a major improvement in the test method, a test
procedure was needed that would provide a continuous, quantitative
measure of the fracture resistance of materials. Also, substantial work
was needed to develop test procedures that produced consistent data, and
to answer the objections of those who doubted the value of impact
testing.

**1895 to 1922**

This period saw the establishment of a number of national and
international standards bodies, which took up the causes of developing
robust test procedures and developing consensus standards for many
technologies, including impact testing. One of these standards bodies
was The American Society for Testing and Materials, established in 1898.
Another was the International Association for Testing Materials,
officially established in 1901, but this association grew out of the
good response to two previous International Congresses that had been
held a number of years before. These two standards bodies seem to have
had a good working relationship, and the President of ASTM, Prof. H. M.
Howe, also served on the Board of IATM during this time \[*4*\].

In 1902, only four years after the founding of ASTM, the ASTM
\"Committee on the Present State of Knowledge Concerning Impact Tests\"
published a bibliography on impact tests and impact testing machines in
the second volume of the Proceedings of ASTM \[*5*\]. This bibliography
listed more than 100 contemporary papers on impact testing published in
the U.S., France, and Germany. Many of these papers contained
information that was also known to the members of IATM. In fact, some of
the papers had been presented and discussed at the IATM Congresses.

Among the references is a report by Russell (published in 1898 and
reprinted in this STP) that shows remarkable insight into the needs of
the design engineers of the time and introduces quantitative measurement
to the test \[*6*\]. He pointed out that none of the machines of the
time, typically of a drop-weight design, had the ability to determine
any data beyond whether the specimen broke or remained intact.
Therefore, he designed and built a pendulum machine which \"would
measure the energy actually absorbed in breaking the test bar\". His
report shows a test machine that is based on the same swinging pendulum
concept as those in common use today and mentions his careful analysis
of the mechanics of the test, including corrections for friction losses
and calculation and comparison of the centers of gravity and percussion.
Since this was before the time of compact, standardized test specimens,
the machine was vary large and massive, and was capable of breaking many
full-size products. Besides showing a prototype of the machines used
today, this report is valuable in that it includes data on over 700
tests of typical construction materials, and emphasizes the effect of
the rate of loading in evaluating materials for different service
conditions. Russell\'s pendulum impact machine finally provided a means
for quantifying the energy absorbed in fracturing a test specimen for a
wide range of materials and conditions. His paper nicely summarizes the
test-machine technology and knowledge for material performance at the
end of the past century, and so served as a benchmark for future
research. To the best of our knowledge, Russell was the first to develop
and demonstrate the advantages of the pendulum design for impact testing
machines.

The members of IATM Commission 22 (On Uniform Methods of Testing
Materials) continued to conduct research that addressed the shortcomings
in the impact testing techniques, until they had developed a knowledge
of most of the important factors in the test procedure. Even though many
of these early machines and reports are simplistic by today's standards,
they provided previously unknown data on the impact behavior of
materials. France seems to have been an early adopter of impact testing
for infrastructure construction standards, and so French researchers
provided much data on the effects of procedure variables and were the
most prolific contributors to the IATM Proceedings between 1901 and
1912. Incidentally, it was a representative from France, G. Charpy, who
became the chair of the impact testing activity after the 1906 IATM
Congress in Brussels, and presided over some very lively discussions on
whether impact testing procedures would ever be sufficiently
reproducible to serve as a standard test method \[*7*\]. Charpy's name
seems to have become associated with the test because of his dynamic
efforts to improve and standardize it, both through his role as Chairman
of the IATM Commission and through his personal research \[*8*\]. He
seems to have had a real skill for recognizing and combining key
advances (both his and those of other researchers) into continually
better machine designs and consensus procedures. For example, Charpy
acknowledges the benefits of Russell\'s pendulum design in his 1901
paper \[*8*\] by stating:

\"Russell described in a paper presented in 1897 at the American Society
of Civil Engineers some \'experiments with a new machine for testing
materials by impact.\' The machine he is using is designed to determine
the work absorbed by the rupture of a bar, for this, the ram used
appears in the form of a pendulum arranged in such a way so that when it
is released from its equilibrium position, it meets the test bar in
passing through the vertical position, breaks it and afterward rises
freely under the influence of the acquired speed. The difference between
the starting height and the finishing height of the pendulum allows
evaluation of the work absorbed by the rupture of the bar.\"

By 1905, Charpy had proposed a machine design that is remarkably similar
to present designs and the literature contains the first references to
\"the Charpy test\" and \"the Charpy method\". He continued to guide
this work until at least 1914 \[*7,9-10*\]. A number of other standard
machine designs and procedures were also under consideration at this
time, and in 1907 the German Association for Testing Materials adopted
one developed by Ehrensberger \[*10*\]. Because the pendulum machine had
not achieved dominance yet, impact machine designers and manufacturers
offered three major types; Drop Weight (Fremont, Hatt-Turner, and
Olsen), Pendulum Impact (Amsler, Charpy, Dow, Izod, Olsen, and Russell),
and Flywheel (Guillery).

This was a period during which the configuration and size of specimens
closely approached what we use today \[*7*\]. Originally, two standard
specimen sizes were most popular. The smaller had a cross section of 10
by 10 mm, a length of about 53 mm (for a distance of 40 mm between the
points of support), a notch 2 to 5 mm deep, and a notch tip radius near
1 mm. The larger and initially more popular of these specimen sizes was
scaled up by a factor of three in all these dimensions. The group
favoring the larger specimen pointed out the advantage of sampling a
larger cross section of the material (for reduced scatter in the data)
and the difficulty of producing the small notch radius on the smaller
specimen. However, the group favoring the smaller specimen eventually
won because a more compact and lower-cost machine could be used, and not
all structures were thick enough to produce the larger specimen. Besides
specimen dimensions that are very similar to what we use today, the
Commission proposed features for a standard impact procedure that
included:

\- limits for the velocity of the striker,

\- rigid mounting to minimize vibration losses,

\- a minimum ratio of anvil mass and rigidity to striker size, and

\- recognition of the artificial increase in energy as ductile specimens
deform around the edges of a wide striker \[*7*\].

One report at the 1912 meeting \[*7*\] included the testimonial from a
steel producer of how the improved impact test procedures had allowed
them to tailor the refining processes to produce less brittle steel. The
report describes a reduction by a factor of 20 in the number of
production parts that were rejected for brittle performance.

**1922 to 1933: The Beginning of ASTM Method E 23**

ASTM Committee E-1 on Methods for Testing sponsored a Symposium in 1922
on Impact Testing of Materials as a part of the 25th Annual Meeting of
the Society, in Atlantic City, New Jersey. The Symposium included a
history of the developments in this area, a review of work done by the
British Engineering Standards Association, several technical
presentations, and the results of a survey sent to 64 U.S. testing
laboratories \[*11*\]. Twenty-three respondents to the survey offered
detailed information on topics such as the types of machines in use, the
specimen dimensions, and procedures. In addition, many responded
positively to a question about their willingness to develop an ASTM
standard for impact testing.

Based on the information in this survey, an ASTM subcommittee began to
prepare a standard test method for pendulum impact testing in 1923. This
effort took until 1933, when ASTM published \"Tentative Methods of
Impact Testing of Metallic Materials,\" ASTM designation E 23-33T. (An
ASTM specification of "Tentative" indicated that it was subject to
annual review and was a work in progress. The tentative designation is
no longer used by ASTM.) (Other countries also developed their own
standards; however, we found it difficult to find their records and to
track their developments.)

ASTM E 23-33T specified that a pendulum-type machine was to be used in
testing and "recognized two methods of holding and striking the
specimen", that is, the Charpy test and the Izod test (where the
specimen is held vertically by a clamp at one end). It did not specify
the geometry of the striking edge (also known at the time as the "tup")
for either test. It stated that "the Charpy type test may be made on
unnotched specimens if indicated by the characteristics of the material
being tested, but the Izod type test is not suitable for other than
notched specimens". Only a V-notch was shown for the Charpy test.
Although the dimensions for both types of specimens were identical with
those currently specified, many tolerances were more restrictive. The
units were shown as English preferred, metric optional. The committee
pointed out many details that influence the test results, but because
they did not have the knowledge and database needed to specify values
and/or tolerances for these details, the document was issued as a
tentative. The original document contains an appendix with general
discussions of applications, the relation to service conditions, and
comparisons between materials. As our understanding of the variables in
Charpy testing has grown, ASTM E 23 has been revised repeatedly to
incorporate the new knowledge.

**1934 to 1940**

The first revision of E 23 was issued in 1934 and it added a dimension
for the radii of the anvil and specifically stated that "these specimens
(both the Charpy and the Izod) are

not considered suitable for tests of cast iron" referencing a report of
ASTM Committee A3 on Cast Iron. The method retained the "tentative"
designation.

The geometry of the Charpy striking tup, specifically the radius of the
tup that contacted the specimen, was not specified in the 1934 revision.
However, the minutes of the 1939 and 1940 meetings for the Impact
Subcommittee of E1 state that this item was discussed and a survey was
made of the geometries used in the United Kingdom and in France. Those
countries had been using radii of 0.57 mm and 2 mm, respectively. For
reasons that were not recorded, the members of the Subcommittee agreed
to a radius of 8 mm at the 1940 meeting and ASTM E 23 was revised and
reissued as E 23-41T. Two other changes that occurred with this revision
were that metric units became the preferred units, and keyhole and U
notches were added for Charpy-test specimens.

**1940 to 1948**

Impact testing seems to have been a useful technique for evaluating
materials, but was not a common requirement in purchase specifications
and construction standards until the recognition of its ability to
detect the ductile-to-brittle transition in steel. Probably the greatest
single impetus toward implementation of impact testing in fabrication
standards and material specifications came as a result of the large
number of ship failures that occurred during World War II. These
problems were so severe that the Secretary of the U.S. Navy convened a
Board of Investigation to determine the causes and to make
recommendations to correct them. The final report of this Board stated
that of 4694 welded-steel merchant ships studied from February 1942 to
March 1946, 970 (over 20%) suffered some fractures that required repairs
\[*12*\]. The magnitudes of the fractures ranged from minor fractures
that could be repaired during the next stop in port, to 8 fractures that
were sufficiently severe to force abandonment of these ships at sea.
Remedies included changes to the design, changes in the fabrication
procedures and retrofits, as well as impact requirements on the
materials of construction. The time pressures of the war effort did not
permit thorough documentation of the effect of these remedies in
technical reports at that time; however, assurance that these remedies
were successful is documented by the record of ship fractures that
showed a consistent reduction in fracture events from over 130 per month
in March 1944 to less than five per month in March 1946, even though the
total number of these ships in the fleet increased from 2600 to 4400
during this same period \[*12*\].

After the war, the National Bureau of Standards released its report on
an investigation of fractured plates removed from some of the ships that
exhibited these structural failures and so provided the documentation of
the importance of impact testing \[*13*\]. The NBS study included
chemical analysis, tensile tests, microscopic examination, Charpy impact
tests, and reduction in thickness at the actual ship fracture plane. A
notable conclusion of the report was that the plates in which the
fracture arrested had consistently higher impact energies and lower
transition temperatures than those in which the fractures originated.
This was particularly important because there was no similar correlation
with chemical composition, static tensile properties (all steels met the
ABS strength requirements), or microstructure. In addition, the report
established 15 ft-lb (often rounded to 20 J for metric requirements) as
a minimum toughness requirement, and recommended that \"some criterion
of notch sensitivity should be included in the specification
requirements for the procurement of steels for use where structural
notches, restraint, low temperatures, or shock loading might be
involved\", leading to a much wider inclusion of Charpy requirements in
structural standards.

**1948 to Present**

By 1948, many users thought that the scatter in the test results between
individual machines could be reduced further, so additional work was
started to more carefully specify the test method and the primary test
parameters. By 1964, when the ASTM E 23 standard was revised to require
indirect verification testing, the primary variables responsible for
scatter in the test were well known. In a 1961 paper, Fahey \[*14*\]
summarized the most significant causes of erroneous impact values as
follows: (1) improper installation of the machine, (2) incorrect
dimensions of the anvil supports and striking edge, (3) excessive
friction in moving parts, (4) looseness of mating parts, (5)
insufficient clearance between the ends of the test specimen and the
side supports, (6) poorly machined test specimens, and (7) improper
cooling and testing techniques. While the machine tolerances and test
techniques in ASTM E 23 addressed these variables, it was becoming
apparent that the only sure method of determining the performance of a
Charpy impact machine was to test it with standardized specimens
(verification specimens).

Much of the work that showed that impact tests did not have inherently
high scatter, and could be used for acceptance testing, was done by
Driscoll at the Watertown Arsenal \[*15*\]. Driscoll's study set the
limits of 1 ft‑lb (1.4 J) and ± 5%, shown in Figures 1 and 2. The data
superimposed on these limits in Figures 1 and 2 are the initial
verification results gathered by Driscoll for industrial impact machines
to evaluate his choice of verification limits. In Figure 1, the
verification results for the first attempt on each machine are shown:
only one machine fell within the ± 1 ft‑lb (1.4 J) limit proposed for
the lower energy range. Results for retests on the same machines after
maintenance are shown in Figure 2. Driscoll's work showed the materials
testing community that not all machines in service could perform well
enough to meet the indirect verification requirements, but that most
impact machines could meet the proposed requirements if the test was
conducted carefully and the machine was in good working condition. With
the adoption of verification testing, it could no longer be convincingly
argued that the impact test had too much inherent scatter to be used as
an acceptance test.

Early results of verification testing showed that 44% of the machines
tested for the first time failed to meet the prescribed limits, and it
was thought that as many as 50% of all the machines in use might fail
\[*16*\]. However, the early testing also showed that the failure rate
for impact machines would drop quickly as *good* machines were repaired,
*bad* machines were retired, and more attention was paid to testing
procedures. It was estimated that approximately 90% of the machines in
use could meet the prescribed limits of ± 1 ft‑lb (1.4 J) or ± 5%.
Recently acquired verification specimen data, shown in Figures 3 through
5, confirm these predictions. Failure rates for verification tests at
low, high, and super‑high energy ranges are currently estimated to be
12, 7, and 10%, respectively \[*17*\].

Overall, the incorporation of verification limits in ASTM E 23 has
greatly improved the performance of impact machines, so that data
collected using ASTM E 23 machines can be compared with confidence. ASTM
E 23 is still the only standard in the world, to our knowledge, that
requires very-low-energy impact specimens (between 15 and 20 J) for
verification, and as shown by the data in Figure 1, results obtained
using machines in need

of maintenance can vary by more than 100% at this energy level. In
effect, the limits imposed by ASTM E 23 have produced a population of
impact machines that are arguably the best impact machines for
acceptance testing in the world.

While ASTM E 23 is used around the world, there are other forums for the
development of global standards. One of these, the International
Organization for Standardization, ISO, allows qualified representatives
from all over the world to come together as equal partners in the
resolution of global standardization problems \[*18*\]. ISO Committee TC
164 handles the topic of Mechanical Testing, and its Subcommittee SC 4
handles toughness testing. While this subcommittee has developed and
maintains ten standards on toughness testing, perhaps the most pertinent
is *ISO Standard R 442:1965 Metallic Materials - Impact Testing -
Verification of Pendulum Impact Machines*. This standard covers the
Charpy test and is presently undergoing balloting for revision. An
important feature of this document is that it recognizes Charpy testing
with both the 2-mm and 8-mm radius striker. There are other regional and
national standards that specify impact testing procedures, such as the
Japanese standard, JIS Z2242, *Method for Impact Test for Metallic
Materials*.![](media/image1.wmf){width="6.0125in"
height="4.883333333333334in"}

**Typical Applications Today**![](media/image2.wmf){width="7.0in"
height="5.777777777777778in"}

*Nuclear*

Since it is impractical to measure the fracture toughness of large
specimens throughout the life of a nuclear power plant, surveillance
programs use Charpy and tensile specimens to track the embrittlement
induced by neutrons. The economic importance of the Charpy impact test
in the nuclear industry can be estimated by noting that most utilities
assess the outage cost and loss of revenue for a nuclear plant to be in
the range of \$300,000 to \$500,000 per day. If Charpy data can be used
to extend the life of a plant one year beyond the initial design life, a
plant owner could realize revenues as large as \$150,000,000. Further,
the cost avoidance from a vessel related fracture is expected to be in
the billion-dollar range. To date, the NRC has shut down one U.S. plant
as a result of Charpy data trends. It is important to note that this
plant\'s pressure vessel was constructed from a one-of-a-kind steel and
is not representative of the U.S. reactor fleet.

![](media/image3.wmf){width="5.667361111111111in"
height="5.500694444444444in"}

![](media/image4.wmf){width="5.704861111111111in" height="5.5375in"}

Nonetheless, with decisions like this based on the Charpy test, the
importance of ASTM E 23 and the restraints it applies cannot be
overemphasized.

*Steel*

The Charpy V-notch (CVN) test specimen and associated test procedure is
an effective cost-saving tool for the steel industry. The specimen is
relatively easy to prepare, many specimens can be prepared at one time,
various specimen orientations can be tested, and relatively low-cost
equipment is used to test the specimen. In many structural steel
applications, the CVN test can be used: (1) as a quality control tool to
compare different heats of the same type of steel, (2) to check
conformance with impact requirements in standards, and (3) to predict
service performance of components. Also, CVN test information can be
correlated with fracture toughness data for a class of steels so that
the results of fracture-mechanics analyses can be compared with the
material toughness.

![](media/image5.wmf){width="5.667361111111111in"
height="5.500694444444444in"}

CVN data have many uses, such as during the design and construction of a
bridge or an offshore oil platform. Before full-scale production of the
steel order can begin, the supplier needs to demonstrate to the buyer
that the steel plate is capable of meeting certain design criteria. The
process begins by making the steel grade and then testing a portion of
the plate to determine if all required criteria are met. Also, steel
mill equipment imposes limitations on plate size; therefore, individual
steel plates need to be welded together in the field to produce lengths
which can reach deep into ocean waters. Small sections of the sample
plate are welded together, and fracture mechanics tests are conducted to
determine the crack tip opening displacement (CTOD) toughness in the
heat affected zone (HAZ) and in areas along the fusion line where the
weld metal meets the base metal. Then, a steel supplier might correlate
the CTOD test results with CVN 50% ductile-brittle transition
temperature (DBTT). By agreement between the customer and supplier, this
correlation can allow the steel supplier to use the Charpy test instead
of the more expensive and time-consuming CTOD testing.

**Continuing Standardization Efforts**

Even after 100 years, the Charpy impact test procedures still have room
for improvement. The ASTM E 23 standard has recently been redrafted to
provide better organization and to include new methods such as in-situ
heating and cooling of the test specimens. Two new related standards are
also under development through ASTM Task Group E 28.07.08, "Miniature
and Instrumented Notched Bar Testing", which was formed a little more
than two years ago. The first standard covers miniature notched bar
impact testing and relies on many of the existing practices related to
test machine requirements and verification as specified in existing
standard E 23. The second standard

is focused on instrumented testing, where strain gages attached to the
striker provide a force-deflection curve of the fracture process for
each specimen. Research is focused on using these data to obtain plane
strain fracture toughness as well as other key test parameters. Upon
acceptance of the standard by ASTM, both the existing E 23 standard and
the new miniature notched bar standards would reference the instrumented
impact standard.

The state of the art in impact testing continues to advance in other
parts of the world also. ISO is balloting a standard (14556) on
instrumented impact testing, there is work in Europe on miniature Charpy
specimens, and ESIS is investigating the use of pre-cracked Charpy
specimens for determining fracture toughness. It can be expected that
harmonization efforts will bring some of this work into E 23 in the
future.

**Conclusion**

The ASTM E 23 standard is a document that continues to improve as our
technical knowledge increases. Several years ago, at the ASTM Symposium
on "The Charpy Impact Test: Factors and Variables" \[*19*\], a bystander
was overheard to say: "I see that there is a Symposium on the Charpy
Test; what can be new there?" Since then, the document has been updated
twice and is currently being revised to reflect new developments and to
make it more "user friendly." Although ASTM E 23 has been a useful
standard for many years, it continues to be a "work in progress," a work
used extensively to help evaluate existing and new materials for
products and structures \-- a test to ensure safety as well as to reduce
the initial and lifetime costs for structures. Knowledge which will help
make the test more accurate and reliable is continually being gained.
New technologies such as miniaturization of the test, instrumenting the
striker to obtain additional data, and developing mechanics models to
enable extraction of plane strain fracture toughness will be areas of
development over the next 100 years. We anticipate that the benefits
from the application of E 23 during the next 100 years will overshadow
the benefits from those in the past 100 years.

**References**

\[1\] Tredgold, T., *Strength of Cast Iron*, 1824, pp. 245-268.

\[2\] White, A.E. and Clark, C.L., *Bibliography of Impact Testing*,
Department of Engineering Research, University of Michigan, 1925.

\[3\] LeChatalier, A., "On the Fragility After Immersion in a Cold
Fluid", *French Testing Commission*, Volume 3, 1892.

\[4\] \"Report on the Work of the Council from the Budapest to the
Brussels Congress - 1901-1906,\" *Proceedings of the International
Association for Testing Materials, Brussels Congress,* 1906.

\[5\] Hatt, W.K. and Marburg, E., \"Bibliography on Impact Tests and
Impact Testing Machines,\" *Proceedings ASTM*, Vol. 2, 1902, p. 283.

\[6\] Russell, S. B. \"Experiments with a New Machine for Testing
Materials by Impact,\" *Transactions ASCE*, Vol. 39, June 1898, p. 237.

\[7\] *Proceedings of the Sixth Congress of the International
Association for Testing Materials*, New York, 1912.

\[8\] Charpy, M.G., \"Note sur l\'Essai des Metaux a la Flexion par Choc
de Barreaux Entailles, *Soc. Ing. Francais*, June 1901, p. 848.

\[9\] \"Impact Testing of Notched Bars,\" *The Engineer*, Vol. 99, March
10, 1905 pp. 249-250.

\[10\] Whittemore, H. L., \"Resume of Impact Testing of Materials, with
Bibliography,\" *Proceedings ASTM*, Vol. 22, Part 2, 1922, p. 7.

\[11\] Warwick, C. L., \"Resume on Notched Bar Tests of Metals,\"
*Proceedings of ASTM*, Vol. 22, Part 2, 1922, p. 78.

\[12\] The Design and Methods of Construction of Welded Steel Merchant
Vessels: Final Report of a (U.S. Navy) Board of Investigation, *Welding
Journal*, Vol. 26, No. 7, July 1947, p. 569.

\[13\] Williams, M. L. and Ellinger, G. A., *Investigation of Fractured
Steel Plates Removed from Welded Ships*, National Bureau of Standards
Report, December 9, 1948.

\[14\] Fahey, N. H., \"Effects of Variables in Charpy Impact Testing,\"
*Materials Research Standards*, Vol. 1, No. 11, Nov., 1961.

\[15\] Driscoll, D. E., \"Reproducibility of Charpy Impact Test,\"
*Impact Testing, ASTM STP 176*, 1955.

\[16\] Fahey, N. H., \"The Charpy Impact Test - Its Accuracy and Factors
Affecting Test Results,\" *Impact Testing of Metals, ASTM STP 466*,
ASTM, 1970.

\[17\] McCowan, C. N., Wang, C. M., and Vigliotti, D. P., \"Summary of
Charpy Impact Verification Data: 1994 - 1996,\" Submitted to the
*Journal of Testing and Evaluation*, 1998.

\[18\] More information is on the ISO World Wide Web site, at
http://www.iso.ch

\[19\] *Charpy Impact Test: Factors and Variables, ASTM STP 1072*, J. M.
Holt, Ed., ASTM, 1990.