ASTM G139-05(2022)

Standard Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking Load Method

SIGNIFICANCE AND USE
5.1 The test method was developed for use with high strength aluminum alloys (2XXX and Cu containing 7XXX) that are normally tested in 3.5 weight % NaCl by alternate immersion. However, the concept which uses residual strength as a measure of damage evolution (in this case environmentally assisted cracking) can, in principle, be applied to any alloy and environmental system.  
5.2 This test method has been developed for research studies of alloys and tempers with improved resistance to SCC. The test results permit different material variants to be compared with a high degree of confidence and with much more precision than the results of pass/fail tests. Thus, it is particularly useful for comparing materials with similar levels of resistance to stress-corrosion cracking. The procedure could be modified for use as a quality assurance tool but this has not been a primary purpose during its development.  
5.3 The exposure periods and conditions that are described in this test method apply specifically to high strength aluminum alloys, but the statistical techniques should be valid for other alloy systems with different exposure conditions.  
5.4 Although this particular procedure was primarily intended for testing products in the short-transverse stressing direction, it is useful for other stressing directions, particularly the long-transverse direction in sheet and thin plate products.  
5.5 Determination of the actual serviceability of a material requires stress-corrosion testing performed in the intended service environment, under conditions relating to the end use, including protective measures such as coatings and inhibitors and is outside the scope of this test method.  
5.5.1 There is no good way to compare test environments to actual service because most service environments have large inherent variability with respect to a single structure that may experience many different environments or with respect to two identical structures that serve in different l...
SCOPE
1.1 This test method covers procedures for evaluation of stress corrosion cracking (SCC) resistance by the breaking load test method, a concept which uses residual strength as the measure of damage evolution (in this case environmentally assisted cracking).  
1.2 This test method covers specimen type and replication, test environment, stress levels, exposure periods, final strength determination, and statistical analysis of the raw residual strength data.  
1.3 The test method was developed for use with heat-treatable aluminum alloys, that is, 2XXX alloys and 7XXX with 1.2 to 3.0 % Cu, and test specimens oriented in the short-transverse direction relative to grain structure (1, 2).2 However, the residual strength measurements and the statistics used to analyze the data are not specific to heat-treatable aluminum alloys and can be used for other specimen orientations and different types of materials.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2022
• ICS: 77.150.10 - Aluminium products
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.06 - Environmentally Assisted Cracking

Relations

• Refers: ASTM E8/E8M-24 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM G49-85(2023)e1 - Standard Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens
• Effective Date: 01-Nov-2023
• Refers: ASTM G47-98(2019) - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 15-Jun-2019
• Refers: ASTM E8/E8M-16 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 15-Jul-2016
• Refers: ASTM E8/E8M-15 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Feb-2015
• Refers: ASTM E8/E8M-13 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Jun-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E8/E8M-11 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Dec-2011
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM G47-98(2011) - Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• Effective Date: 01-Sep-2011
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM G49-85(2005) - Standard Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens
• Effective Date: 01-Oct-2005
• Refers: ASTM G64-99(2005) - Standard Classification of Resistance to Stress-Corrosion Cracking of Heat-Treatable Aluminum Alloys
• Effective Date: 01-May-2005
• Refers: ASTM G44-99(2005) - Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5% Sodium Chloride Solution
• Effective Date: 01-May-2005

Overview

ASTM G139-05(2022), titled Standard Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking Load Method, provides a comprehensive procedure to evaluate the resistance of aluminum alloys to stress-corrosion cracking (SCC) through the breaking load method. Developed by ASTM International, this standard focuses on high-strength, heat-treatable aluminum alloys, especially 2XXX and copper-containing 7XXX series, but its methodology is applicable to a broader range of materials and environmental conditions.

Stress-corrosion cracking is a significant failure mode in aluminum alloys, affecting the integrity and longevity of critical components in transportation, aerospace, and structural applications. This standard offers a detailed, statistically robust approach to SCC assessment, enabling reliable comparison between material variants and contributing to enhanced material selection and design.

Key Topics

• Breaking Load Test Method: Utilizes residual strength as a direct indication of SCC damage in metallic specimens after environmental exposure.
• Test Environment: Designed for alternate immersion in 3.5 wt% sodium chloride (NaCl) solutions, simulating aggressive chloride environments commonly encountered in service.
• Specimen Orientation and Type: Primarily targets short-transverse directions of high-strength aluminum alloys, but allows testing in other orientations and for different alloy types.
• Statistical Analysis: Employs advanced techniques such as the Box-Cox transformation to normalize and analyze residual strength data, enhancing precision for comparing material performance.
• Data Reporting: Recommends comprehensive documentation of specimen identification, raw results, and statistical summaries, fostering transparent assessment.

Applications

• Material Development: The breaking load method is especially valuable in R&D settings, where comparisons of SCC resistance among new alloys or tempers with incremental property enhancements are required.
• Quality Assurance: Although not primarily designed as a QA tool, the methodology can be adapted to monitor production consistency or qualify material batches for SCC resistance.
• Product Evaluation: The test can be applied to forms such as sheets, plates, extrusions, forgings, and bars, with flexibility for differential stress directions and environmental exposures.
• Comparative Assessment: By allowing finer distinctions than traditional pass/fail tests, ASTM G139 is effective for distinguishing alloys or treatments with similar SCC resistance profiles.
• Failure Analysis Support: The method provides a basis for correlating laboratory findings with field SCC failure cases and informing protective strategies such as coatings or inhibitors.

Related Standards

• ASTM E8/E8M: Test Methods for Tension Testing of Metallic Materials
• ASTM G44: Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5% Sodium Chloride Solution
• ASTM G47: Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products
• ASTM G49: Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens
• ASTM G64: Classification of Resistance to Stress-Corrosion Cracking of Heat-Treatable Aluminum Alloys
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

These standards collectively support the robust and repeatable application of the breaking load method, ensuring industry-wide compatibility and recognition.

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Keywords: ASTM G139, stress-corrosion cracking, SCC, aluminum alloys, breaking load method, residual strength, 3.5% NaCl, alternate immersion, material testing, quality assurance, statistical analysis, Box-Cox transformation, ASTM standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G139 − 05 (Reapproved 2022)
Standard Test Method for
Determining Stress-Corrosion Cracking Resistance of Heat-
Treatable Aluminum Alloy Products Using Breaking Load
Method
This standard is issued under the fixed designation G139; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers procedures for evaluation of 2.1 ASTM Standards:
stresscorrosioncracking(SCC)resistancebythebreakingload E8/E8MTest Methods for Tension Testing of Metallic Ma-
test method, a concept which uses residual strength as the terials
measure of damage evolution (in this case environmentally E691Practice for Conducting an Interlaboratory Study to
assisted cracking). Determine the Precision of a Test Method
G44PracticeforExposureofMetalsandAlloysbyAlternate
1.2 This test method covers specimen type and replication,
Immersion in Neutral 3.5% Sodium Chloride Solution
test environment, stress levels, exposure periods, final strength
G47Test Method for Determining Susceptibility to Stress-
determination, and statistical analysis of the raw residual
Corrosion Cracking of 2XXX and 7XXX Aluminum
strength data.
Alloy Products
1.3 The test method was developed for use with heat-
G49Practice for Preparation and Use of Direct Tension
treatable aluminum alloys, that is, 2XXX alloys and 7XXX
Stress-Corrosion Test Specimens
with 1.2 to 3.0% Cu, and test specimens oriented in the
G64Classification of Resistance to Stress-Corrosion Crack-
short-transverse direction relative to grain structure (1, 2).
ing of Heat-Treatable Aluminum Alloys
However, the residual strength measurements and the statistics
used to analyze the data are not specific to heat-treatable 3. Terminology
aluminum alloys and can be used for other specimen orienta-
3.1 Definitions of Terms Specific to This Standard:
tions and different types of materials.
3.1.1 censor—a statistical term indicating that the value
1.4 This standard does not purport to address all of the
from an individual observation may fall outside of the range
safety concerns, if any, associated with its use. It is the
that can be measured because of test procedures or conditions.
responsibility of the user of this standard to establish appro-
3.1.2 sample—the nominally uniform, bulk material from
priate safety, health, and environmental practices and deter-
which individual stress-corrosion cracking specimens are ob-
mine the applicability of regulatory limitations prior to use.
tained.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
4.1 This test method describes a procedure for using re-
Development of International Standards, Guides and Recom-
sidual strength after exposure to a corrosive environment to
mendations issued by the World Trade Organization Technical
evaluate stress corrosion cracking susceptibility in heat treat-
Barriers to Trade (TBT) Committee.
able aluminum alloy product forms such as sheet, plate,
extrusions, forgings, and bar. These products generally are
most susceptible to SCC in the long transverse direction of
This test method is under the jurisdiction of ASTM Committee G01 on
Corrosion of Metals and is the direct responsibility of Subcommittee G01.06 on sheet, the short transverse direction of plate, extrusions and
Environmentally Assisted Cracking.
Current edition approved Oct. 1, 2022. Published October 2022. Originally
approvedin2005.Lastpreviouseditionapprovedin2015asG139–05(2015).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/G0139-05R22. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
the standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G139 − 05 (2022)
forgings, and the transverse direction of rod and bar stock. In for preliminary evaluations is often chosen based on a worst
this test, tensile bars or direct tension sheet specimens, pre- case scenario leading to intentional overestimations of corro-
pared according to Practice G49, are exposed to 3.5 weight % sion damage.
aqueous sodium chloride solution (Practice G44), are removed
6. Interferences
before they fail and are tension tested to determine the amount
of corrosion damage that has occurred. The average retained
6.1 The breaking load test factors out pitting corrosion that
strength is then calculated and the Box-Cox Transformation
occurs in environments such as the 3.5% NaCl solution used
can be used for statistical analysis of the results.
in alternate immersion testing per Practice G44. The primary
concerninusingthebreakingloadtestischoiceofappropriate
4.2 The procedure calls for exposure of unstressed speci-
exposure stress. If the exposure stress is too low no damage
mens which are used to factor out the effects of pitting,
will accumulate. On the other hand, if the applied stress is too
intergranular, and general corrosion. These phenomena de-
high many of the specimens will fail before the end of their
grade residual strength but do not require applied stress for
scheduled exposure periods. The statistical procedures in-
their occurrence.
cluded in this test method can accommodate small numbers of
failed specimens but not large numbers.
5. Significance and Use
6.2 The breaking load test is applicable to specimens that
5.1 The test method was developed for use with high
have been exposed in natural and service environments.
strength aluminum alloys (2XXX and Cu containing 7XXX)
However, conditions in these environments may not be con-
that are normally tested in 3.5 weight % NaCl by alternate
stant so consideration must be given to the period and timing
immersion. However, the concept which uses residual strength
ofexposuretoavoidbiasingresults.Forexample,environmen-
asameasureofdamageevolution(inthiscaseenvironmentally
tal conditions that vary seasonally such as temperature,
assistedcracking)can,inprinciple,beappliedtoanyalloyand
moisture, and pollutant concentration may affect the corrosiv-
environmental system.
ity of outdoor exposure stations. Direct material comparisons
5.2 This test method has been developed for research
should be made using identical environmental conditions.
studiesofalloysandtemperswithimprovedresistancetoSCC.
6.3 Some care is required when comparison samples have
The test results permit different material variants to be com-
different original (uncorroded) tensile strength and fracture
pared with a high degree of confidence and with much more
toughness values. Large variations in initial properties can
precision than the results of pass/fail tests. Thus, it is particu-
either reduce or increase the apparent differences in SCC
larly useful for comparing materials with similar levels of
performance of the samples. To avoid bias due to tensile
resistancetostress-corrosioncracking.Theprocedurecouldbe
properties, the statistical procedures incorporated in this test
modified for use as a quality assurance tool but this has not
method are based on percentages of original strength.
been a primary purpose during its development.
However, to examine the effect of fracture toughness, which
5.3 The exposure periods and conditions that are described
affects residual strength, a flaw size calculation must be done
inthistestmethodapplyspecificallytohighstrengthaluminum
using fracture mechanics techniques (3).
alloys, but the statistical techniques should be valid for other
alloy systems with different exposure conditions. 7. Test Specimens
7.1 The breaking load procedure may be conducted using
5.4 Although this particular procedure was primarily in-
any specimen that can be axially stressed in a fixture that will
tended for testing products in the short-transverse stressing
sustain an applied displacement. However, results obtained
direction, it is useful for other stressing directions, particularly
using different specimen geometries or stressing methods can
the long-transverse direction in sheet and thin plate products.
not be directly compared. While the relative susceptibilities of
5.5 Determination of the actual serviceability of a material
the samples will not be changed, the absolute numbers can be
requires stress-corrosion testing performed in the intended
quite different.
service environment, under conditions relating to the end use,
7.2 Wheneverthegeometryofthemetalsamplepermits,the
including protective measures such as coatings and inhibitors
test should be conducted using smooth, round tension speci-
and is outside the scope of this test method.
mens prepared in accordance with Practice G49. In the case of
5.5.1 Thereisnogoodwaytocomparetestenvironmentsto
sheet and other products that may be too thin to yield tensile
actual service because most service environments have large
bars, sheet tensile specimens may be used. The test sensitivity
inherent variability with respect to a single structure that may
increases with the ratio of surface area to volume in the
experience many different environments or with respect to two
specimengagesection;howevertestsmadeusingroundtensile
identical structures that serve in different locations. Unless a
specimens have shown that the same relative rankings can be
sample can be tested in the actual service environment for the
achieved with different size specimens (1).
expected life of the component, no conclusive determination
can be made about the suitability of a particular material for a
8. Exposure Procedure
particular application. Designers must therefore make judg-
ments on the suitability of particular materials for applications 8.1 Stressing Procedure and Exposure Conditions—The
based on knowledge of the material and of the service specimens shall be stressed by axially loading in constant
environment. To avoid service failures, the environment used deflection-type fixtures as in Figure 1 of Practice G49 and
G139 − 05 (2022)
exposed to the 3.5% NaCl alternate immersion test per
Practice G44. The number of specimens for each stress
level/exposure time combination should be a minimum of
three; five or more are preferable.
8.2 Stress Level—The minimum number of stress levels is
two,oneofwhichisacompletesetofspecimensexposedwith
noappliedstress.ForsampleswithunknownSCCresistanceit
is preferable to start with two or three stress levels in addition
to the unstressed specimens. The unstressed specimens allow
the damage caused by general, pitting and intergranular corro-
siontobecalculatedandseparatedfromdamagecausedbythe
appliedstress.Theotherstresslevel(s)mustbechosenforeach
individual sample by considering the expected performance of
the sample.The more SCC resistant the sample, the higher the
stresses should be. The ideal maximum stress would be one
that leads to significant damage by way of cracking but does
notcausemorethanafewspecimenstoactuallybreakintotwo
pieces before the end of the scheduled exposure period (2).
Onestresslevelcanbeusedbutthestatisticalcalculationsonly
evaluate the performance of the sample at that stress level. In
NOTE 1—Some specimens in this set did fail before the end of their
other words, there is no good way to extrapolate and estimate
scheduled exposure periods, but these failed specimens have not been
performance at higher or lower stress levels without actually
included in the averages. The averages represent only specimens that
conducting the test.
survived to be tensile tested. The upturn in the nine-day data at 310 MPa
is caused by not including failed specimens.
8.3 ExposureTime—Thisparametermustbeadjustedforthe
FIG. 1 Plot of Average Residual Strength Values for a
sample to be tested and the size and orientation of the test
Representative Data Set (one laboratory)
specimens.Ingeneral,twotofourtimeperiods(pluszerodays
with no stress) should be used with the maximum time being
approximatelytendaysforshorttransversetestson2XXXand
sample/stress/timecombination)hasbeenshowntoincreaseas
7XXX alloys. In general, long-transverse specimens and more
resistance to SCC decreases. This tendency for variance to
resistant alloy systems (such as 6XXX alloys) should be
increase with decreasing residual strength means that the
exposed for longer periods. Classification G64 gives time
ability of the breaking load test to resolve differences between
periods for these situations which can be used to estimate a
cells can be much greater for the better performing cells than
reasonable maximum exposure time.
the poorer performing cells. Therefore, plots of average re-
sidual strength can be very misleading.
NOTE 1—For material variants with unknown SCC performance in the
test environment, it is advisable to test a limited number of pass/fail
9. Statistical Analysis—Box-Cox Transformation
specimens according to the procedures in Test Method G47. This will
provide guidance for choosing appropriate stress levels and exposure
9.1 Breaking load data can be statistically analyzed by
timesforthesample.Thiscanpreventtheexpenditureoflargeamountsof
following the steps outlined here. There are undoubtedly other
time and money for specimens that do not provide information with
procedures that will work but the Box-Cox transformation has
significant value.
demonstrated its usefulness for situations in which variance is
8.4 Determination of Residual Strength—Upon completion
not constant throughout the data set (4, 5). In the case of stress
ofeachexposureperiod,asetofspecimensshouldberemoved
corrosion cracking data, as residual strength decreases, vari-
from test, rinsed, unstressed, and tension tested in accordance
ance generally increases. The following procedure assumes
with Test Methods E8/E8M. It is recommended that tensile
that a fixed number of specimens have been tested for each
testing be completed on the day the specimens are removed
materialvariant,exposureperiod,andexposurestress.Someof
fromexposure.Ifatimedelaybetweencompletionofexposure
these values will be left-censored, that is, some specimens will
and tensile testing is unavoidable, the specimens must be
fail before they complete their scheduled exposure period. For
thoroughly rinsed with deionized water, stored in a desiccated
such specimens the breaking load value is known to be less
environment, and the delay period should be recorded. The
thanorequaltotheexposurestressbutthisprocedureincludes
breakingstrengthmustbecalculatedandrecordedforeachtest
a statistical method for estimating the values of those data
specimen.
points.
8.5 The residual strength data can be used to show trends
NOTE 2—Appendix X1 contains a sample Box-Cox calculation that
between samples by simply calculating average residual
follows the procedure described in this section of the test method.
strength for each stress/time combination as shown in Fig. 1.
9.2 Transform the original values, X, by means of the
However, statistical procedures must be used to evaluate
preliminary transformation
whether the trends are real or merely data scatter.
8.5.1 During the development of the breaking load test X
X 5 100 (1)
S D
tr
method, the variance of data within individual cells (a single X
O
G139 − 05 (2022)
where X is the average breaking load for no exposure for 9.5.1.1 In this expression n is the number of observations
O
the given material variant. This transformation expresses the per cell; the t-test coefficient, t , depends on the significance
ν
percent retention of original strength for each specimen, and level chosen, and the degrees of freedom, ν, are given by
thereby normalizes the residual strength of different materials.
ν 5 N 2 r 2 c (6)
9.3 The Box-Cox parameters are determined using all data
For 95% significance and ν≈ 100, t ≈2. As ν becomes
ν
that have been generated simultaneously for relatively similar
small, the value of tν increases; this increases the value of the
samples. For example, when testing several samples from one
smallest difference which will be considered significant. For
alloy that have been produced using various fabricating routes
exact values for t , tables of student’s t-distribution must be
ν
or are in different tempers, all data should be considered in
consulted; the correct value will represent a two-tailed t-test.
determining the following parameters. This would also apply
NOTE3—ThetransformedLSDvalue(s)whichhasjustbeencalculated
to alloys from the same system. On the other hand, alloys that
applies to the entire data set over which the Box-Cox Transformation
react differently to the test environment should be considered
parameters were determined.
separately. This would be the case for comparisons of 6XXX
9.5.1.2 When comparing data sets which have been consid-
versus 2XXX alloys, for example.
ered separately, one should first pool the estimated variances
9.3.1 For all data cells with more than one observed value
fromthetwosets.Forexample,ifthedatasetsarecalled1and
(that is, noncensored value), calculate the average, m, and the 2 2
2, with variance estimates s and s and degrees of freedom
1 2
standarddeviation,s.Plotln(s)versusln(m),anddeterminethe
ν and ν respectively, the pooled standard deviation will, in
1 2
slope, α, of the best fit straight line. The parameter λ in the
general, be
Box-Cox transformation:
2 2
ν s 1ν s
λ
1 1 2 2
Y 5CX 21 (2)
tr
s 5Π(7)
p
ν 1ν
1 2
is 1− α.
If both variance estimates are associated with the same
9.3.2 The constant C can be chosen in any way that gives
number of degrees of freedom, the equation becomes
numbers of convenient size. One convenient choice is:
2 2
s 1s
1 2
s 5Π(8)
p
C 5 (3) 2
λ
X ,max
tr
To compare two averages which are not associated with the
where X is the maximum value for X among the
tr,max tr
samenumberofobservations,n,theaboveexpressionforLSD
noncensored values in the data set. This gives numbers in the
is used, with ν= ν + ν and s equal to the above expression
1 2 p
range from 0 to 100, which is the same range as the values of
for the pooled standard deviation.
X .
tr
9.5.1.3 A more elaborate statistical analysis of the data in
this study can be based on the analysis of variance procedure.
9.4 Generate statistically plausible values for the censored
9.5.2 A lower confidence limit for the mean value for any
observations, representing the failed specimens, by uniform
random number generation over the interval (O, Y ), where Y data cell can be calculated from the expression
c c
is the transformation of the censoring value (that is, the
t s
ν p
LCL 5 m 2 , (9)
exposure stress).
B2C
=n
9.5 Analyze the complete, transformed data set using stan-
where m is the average Box-Cox transformed value and
B−C
dard statistical techniques.Asimple way of analyzing a set of
the t value represents a single-tailed t-test and is not the same
ν
data transformed to the Box-Cox metric is to find the averages
as the t value used for th
...