D Designation: D 2990 - 01
`
`~u11 7
`
`INT.RNATIONAL
`
`Standard Test Methods for
`Tensile, Compressive, and Flexural Creep and Creep(cid:173)
`Rupture of Plastics 1
`
`This ~tandard is issued under the fixed designation D 2990; 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 (e) indicates an editorial change since the last revision or reapproval.
`
`This standard has been approved for use by agencies of the Department of Defense.
`
`1. Scope*
`1.1 These test methods cover the determination of tensile
`and compressive creep and creep-rupture of plastics under
`specified environmental conditions (see 3.1.3).
`1.2 While these test methods outline the use of three-point
`loading for measurement of creep in flexure, four-point loading
`(which is used less frequently) can also be used with the
`equipment and principles as outlined in Test Methods D 790.
`1.3 For measurements of creep-rupture, tension is the pre(cid:173)
`ferred stress mode because for some ductile plastics rupture
`does not occur in flexure or compression.
`.
`1.4 Test data obtained by these test methods are relevant and
`appropriate for use in engineering design.
`1.5 The values stated in SI units are to be regarded as the
`standard. The values in parentheses are for information only.
`1.6 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 appro(cid:173)
`priate safety and health practices and determine the applica(cid:173)
`bility of regulatory limitations prior to use. A specific warning
`statement is given in 6.8.2.
`
`NoTE I-This standard and ISO 899 are similar in content, but are not
`equivalent.
`
`2. Referenced Documents
`2.1 ASTM Standards: 2
`D 543 Practices for Evaluating the Resistance of Plastics to
`Chemical Reagents
`D 618 Practice for Conditioning Plastics for Testing
`D 621 Test Methods for Deformation of Plastics Under
`Load3
`
`1 These test methods are under the jurisdiction of ASTM Committee D20 on
`Plastics and are the direct responsibility of Subcommittee D20.1 O on Mechanical
`Properties.
`Current edition approved August 10, 2001. Published October 2001. Originally
`published as D 2990 - 71. Last previous edition D 2990 - 95. These test methods
`and Practice D 2991 replace Practices D 674, which has been discontinued.
`2 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 ASTM website.
`3 Withdrawn.
`
`D 638 Test Method for Tensile Properties of Plastics
`D 695 Test Method for Compressive Properties of Rigid
`Plastics
`.
`D 790 Test Methods for Flexural Properties of Unreinforced
`and Reinforced Plastics and Electrical Insulating Materials
`D 1822 Test Method for Tensile-Impact Energy to Break
`Plastics and Electrical Insulating Materials
`D 2236 Test Method for Dynamic Mechanical Properties of
`Plastics by Means of a Torsional Pendulum3
`D 4000 Classification System for Specifying Plastic Mate(cid:173)
`rials
`D 4968 Guide for Annual Review of Test Methods and
`Specifications for Plastics
`
`3. Terminology
`3.1 Definitions of Terms Specific to This Standard:
`3 .1.1 creep modulus-the ratio of initial applied stress to ·
`creep strain.
`' ·
`3.1.2 creep strain-the total strain, at any given time,
`produced by the applied stress during a creep test.
`3.1.2.1 Discussion-The term creep, as used in this test
`method, reflects current plastics engineering usage. In scientific
`practice, creep is often defined to be the nonelastic portion of
`strain. However, this definition is not applicable to existing
`engineering formulas. Plastics have a wide spectrum of retar(cid:173)
`dation times, and elastic portions of strain cannot be separated
`in practice from nonelastic. Therefore, wherever "strain" is
`mentioned in these test methods, it refers to the sum of elastic
`strain plus the additional strain with time.
`3.1.3 deformation-a change in shape, size or position ofa
`test specimen as a result of compression, deflection, or exten(cid:173)
`sion:
`3.1.4 compression-in a compressive creep test, the de(cid:173)
`crease in length produced in the gage length of a test specimen.
`3.1.5 deflection-in a flexural creep test, the change in
`mid-span position of a test specimen.
`3.1.6 extension-in a tensile creep test, the increase in
`length produced in the gage length of a test specimen.
`3.1.7 slenderness ratio-the ratio of the length of a column
`of uniform cross section to its least radius of gyration; for
`specimens of uniform rectangular cross section, the radius of
`gyration is 0.289 times the sm&ller cross-sectional dimension;
`
`*A Summary of Changes section appears at the end of this standard.
`Copyright @ ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
`
`ClearCorrect Exhibit 1065, Page 1 of 20
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`~ D2990-01
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`·-· -
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`STATIONARY
`FRAME
`
`LOAD ROD -----1-1-W,
`GUIDE TUBE
`SPECIMEN ---H--1
`
`MOBILE FRAME
`
`--WEIGHT
`
`/FIXTURE
`
`---®
`
`© LOCATION OF DIAL INDICATOR WHEN NOT USED. IN ENVIRONMENTAL CHAM.
`© LOCATION OF DIAL INDICATOR WHEN USED IN ENVIRON, ~HAMBER.
`FIG. 1 A Compressive Creep Apparatus lm:ludlng Details When Used In an Environmental Chamber
`
`I j
`I l for specimens of uniform circular cross section, the radius of
`
`gyration is 0.250 times the diameter.
`3.1.8 stress-for tensile or compressive creep, tfie ratio of
`the applied load to the initial cross-sectional area; for flexural
`~ creep, maximum fiber stress is as calculated in accordance with
`ij Test Methods D 790.
`
`i 4. S~ary of Test Methods
`I 4.1 These_ test ~ethods consist of measuring the extension
`I load under specified environmental conditions.
`
`i or compress10n as a function of time and time-to-rupture, or
`! failure of a specimen subject to constant tensile cir compressive
`
`5. Significance and Use
`5. ! Da~ from creep and creep-rupture tests are necessary to
`I predict the creep modulus and strength of materials under
`'··
`long-term loads and to predict dimensional changes that may
`i occur as a result of such loads.
`I 5.2 Data from these test methods can be used: (1) to
`J compare materials, (2) in the design of fabricated parts, (3) to
`! load, and ( 4) under certain conditions, for specification
`, characterize plastics for long-term performance under constant
`j purposes.
`j 5.3 Before proceeding with this test method, reference
`f should be _made to the sp_ecificatio~ ?f ~e ma~erial ~eing tested.
`•j Any specimen preparation, conditiomng, dimens10ns, and/or
`! testing parameters covered in the material specification shall
`I take precedence over those mentioned in this test method
`j except in cases where to do so would conflict with the purpos;
`! for conducting testing. If there are no material specifications,
`i then the default conditions apply.
`j
`l
`
`!
`
`767
`
`6. Apparatus
`6.1 Tensile Creep:
`6.1. l Grips-The grips and gripping technique shall be
`designed to minimize eccentric loading of the specimen.
`Swivel or universal joints shall be used beyond each end of the
`specimen.
`6.1.2 It is recommended that grips permit the final centering
`bf the specimen prior to applying the load. Grips that permit a
`displacement of the specimen within the grips during load
`application are not suitable.
`• 6.2 Compressive Creep:
`6.2.1 Anvils-Parallel anvils shall be used tb apply the load
`to the unconfined-type specimen (see 8.2). One of the anvils of
`the machine shall preferably be self-aligning and shall, in order
`that the load may be applied evenly over the face of the
`specimen, be arranged so that the specimen is accurately
`centered and the resultant of the load is through its center.
`Suitable arrangements are shown in Fig. 1 and Fig. 2 of Test
`Methods D 621.
`6.2.2 Guide Tube____;_A guide tube and fixtures shall be used
`when testing slender specimens (see 8.3) to prevent buckling.
`A suitable arrangement is shown in Fig. 1. The guide tube is a
`3.2-mm (0.125-in.) Schedule 40 stainless steel pipe nipple
`approximately 150 mm (6 in.) long reamed to 6.860 ±
`0.025-mm (0.270 ± 0.001-in.) inside diameter.
`6.3 Flexural Creep:
`6.3.1 Test Rack-A rigid test rack shall be used to provide
`support of the specimen at both ends with a span equal to 16
`( + 4, - 2) times the thickness of the specimen. In order to
`avoid excessive indentation of the specimen, the radius of the
`
`ClearCorrect Exhibit 1065, Page 2 of 20
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`

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`~ D2990-01
`
`FIG. 2 Flexural Creep Test Apparatus
`
`support shall be 3.2 mm (0.125 in). Sufficient space must be
`allowed below the specimen for dead-weight loading at mid(cid:173)
`span.
`6.3.2 Stirrup-A stirrup shall be used which fits over the
`test specimen from which the desired load may be suspended
`to provide flexµral loading at mid~span. In order to prevent
`excessive iriden,tation or failure due, to .stress concentration
`under the st4Tup, ~e radius of the stirrup shall be 3.2 mm
`(0.125 in.). <::;cmnection between stirrup and weight shaU be
`made in a manner to av,oid nonuniform loading caused by
`misalignment or rack not being level.
`6.3.~ A suitable arrangement is shown in Fig. 2.
`6.4 Loading System-The loading system must be so de(cid:173)
`signed that the load applied and maintained on the specimen is
`within ± 1 % of the desin;d load. The loading mechanism. must
`allow reproductively rapid and smooth loading as specified in
`11.3. In c:reep-rupture tests, provision must be made to ensure
`that shock loading, caused by a specimen failure, is not
`transferred to other specimens undergoing testing.
`6.4.1 Loading systems that provide a mechanical advantage
`require careful design to maintain constant load throughout the
`test. For example, lever systems must be designed so that the
`load does not change as the lever arm moves during the test.
`
`'
`
`6.5 Extension, Compression, and Deflection Measurement,:
`6.5.1 The extension or compression of specimen gage
`length under load shall be measured by means of any device
`that will not influence the specimen behavior by mechanical
`(undesirable deformation, notches, etc.), physical (heating of
`specimen, etc.), or chemical effects. Preferably the extension
`shall be measured directly on the specimen, rather than by grip
`separation. Anvil displacement may be used to measure com(cid:173)
`pression. If extension measurements are made by grip separa(cid:173)
`tion, 'suitable correction factors must be determined, so that
`strain within the gage length may be calculated. These correc(cid:173)
`tion factors are dependent on the geometry of the specimen arid
`its drawing behavior, and they must be measured with respect
`to these variables.
`6.5.2 The deflection of the specimen at mid-span shall be
`measured using a dial gage (with loading springs removed,
`with its measuring foot resting on stirrup) or a cathetometer.
`6.5.3 The accuracy of the deformation measuring device
`shall be within ± 1 % of the deformation to be measured.
`6.5.4 Deformation measuring devices shall be calibrated
`against a precision micrometer screw or other suitable standard
`under conditions as nearly identical as possible with those
`encountered in the test. Caution is necessary when using
`
`ClearCorrect Exhibit 1065, Page 3 of 20
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`

`0 D2990-01
`
`FIG. 2 Flexural Creep Test Apparatus
`
`support shall be 3.2 mm (0.125 in). Sufficient space must be
`allowed below the specimen for dead-weight loading at mid(cid:173)
`span.
`6.3.2 Stirrup-A stirrup shall be used which fits over the
`test specimen from which the desired load may be suspended
`to provide flexµral loading at mid-span. In order to prevent
`excessive 1nden_tation or failure due, to .stress concentration
`under the stip-up, the radius of the stirrup shall be 3.2 mm
`(0.125 in.). <;cmnection between stirrup and weight shaH be
`made in a manner to avpid nonuniform loading caused by
`misalignment or rack not beit).g level.
`6.3.~ A suitable arrangement is shown in Fig. 2.
`6.4 Loading System-The loading system must be so de(cid:173)
`signed that the load applied and maintained on the specimen is
`within ± 1 % of the desir~d load. The loading mechanism must
`allow rep_roductively rapid and smooth loading as specified in
`11.3. In c:reep-rupture tests, provision must be made to ensure
`that shock loading, caused by a specimen failure, is not
`transferred to other specimens undergoing testing.
`6.4.1 Loading systems that provide a mechanical advantage
`require careful design to maintain constant load throughout the
`test. For example, lever systems must be designed so that the
`load does not change as the lever arm moves during the test.
`
`6.5 Extension, Compression, and Deflection Measurement,:
`6.5.1 The extension or compression of specimen gage
`length under load spall be measured by means of any device
`that will not influence the specimen behavior by mechanical
`(undesirable deformation, notches, etc.), physical (heating of
`specimen, etc.), or chemical effects. Preferably the extension
`shall be measured directly on the specimen, rather than by grip
`separation. Anvil displacement may be used to measure com(cid:173)
`pression. If extension measurements are made by grip separa(cid:173)
`tion, 'suitable correction factors must be determined, so that
`strain within the gage length may be calculated. These correc(cid:173)
`tion factors are dependent on the geometry of the specimen arid
`its drawing behavior, and they must be measured with respect
`to these variables.
`6.5.2 The deflection of the specimen at mid-span shall be
`measured using a dial gage (with loading springs removed,
`with its measuring foot resting on stirrup) or a cathetometer.
`6.5.3 The accuracy of the deformation measuring device
`shall be within ± 1 % of the deformation to be measured.
`6.5.4 Deformation measuring devices shall be calibrated
`against a precision micrometer screw or other suitable standard
`under conditions as nearly identical as possible with those
`encountered in the test. Caution is necessary when using
`
`ClearCorrect Exhibit 1065, Page 4 of 20
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`~ D2990-01
`all reagents shall conform to the specifications of the Commit(cid:173)
`deformation measuring devices whose calibration is subject to
`(!rifting with time and is dependent on temperature and
`tee on Analytical Reagents of the American Chemical Society,
`where such specifications are available.4 Other grades may be
`humidity.
`6.5.5 Deformation measuring devices shall be firmly at(cid:173)
`used, provided it ·· is first ascertained that the reagent is of
`sufficiently high purity to permit its use without lessening the
`tached to or seated on the specimen so that no slippage occurs.
`accuracy of the determination,
`Electrical resistance gages are suitable only if the material
`7.2 Purity of Water-Unless otherwise indicated, references
`tested will permit perfect adhesion to the specimen and if they
`to water shall be understood to mean distilled water or water of
`~ are consistent with 6. 5 .1.
`i 6.6 Time Measurement-The accuracy of the time measur•
`equal purity.
`I ing device shall be ± 1 % of the time-to-rupture or failure or
`7 .3 Specified Reagents-Should this test method be refer(cid:173)
`j the elapsed time of each creep measurement, or both.
`enced in a material specification, the specific reagent to be used
`I 6.7 Temperature Control and Measurement:
`shall be as stipulated in the specification.
`1 6.7.l The temperature of the test space, especially close to
`7.4 Standard Reagents-A list of standard reagents is also
`I the gage length of the specimen, shall be maintained within ±
`available in Test Method D 543.
`~ 2°C by a suitable automatic device and shall be stated ih
`j reporting the results.
`} Nan:; 2- The thermal contraction and expansion associated with small
`I feroperature changes dunng the test may produce changes in the apparent
`I creep rate, especially near transition temperatures.
`j 6.7.2 Care must be taken to ensure accurate temperature
`l measurements over the gage, length of the specimen throughout
`!·.•· the test. The temperature mea. suring devices shall _be _che·c. ke~
`regularly against temperature standards and shall md1cate the
`.;
`, temperature of the specimen gage area.
`6. 7.3 Temperature measurements shall be made at frequent
`. intervals, or continuously recorded to ensure an accurate
`: determination of thC ave,age test temperature and complianci
` with 6.7.1.
`6.8 Environmental Control and Measurement:
`6.8.l When the test environment is air, the relative humidity
`• shall be controlled to w\thm .± 5 .% during the test unless
`J otherwise specified, or unless the creep . behavior of . the
`l material under testing has been shown to be unaffected by
`i humidity. The controlling and measuring instruments shall be
`i stable for long time intervals; ~d ~curate to withi~ ±. 1 %.
`I (The control of relative hurrud1ty 1s known to be difficult at
`I temperatures much outside the range of 10 to 40°C (50 to
`1 1000F).)
`. .
`.
`.
`! 6.8.2 The composition of the te.st environment shall be
`
`i maintained constant throughout the . test. Warning: Safety
`l precautions should be taken to av01d personal contact, to
`1 eliminate toxic vapors, and to guard i1gainst explosion hazards
`: in accordance with any possible hazardous nature of the
`particular environment being . used.
`6.9 Vibration Control-C.reep tests are quite sensitive to
`shock and vibration. The location of the apparatus, the test
`equipment, and mounting shall be so designated that the
`specimen is isolated from vibration. Multiple-station test
`equipment must be of sufficient rigidity so that no significant
`deflection occurs in the test equipment during creep or creep(cid:173)
`rupture testing. During time-to-rupture or failure, means to
`prevent jarring of other test specimens by the falling load from
`a failed test specimen shall be provided by a suitable net or
`cushion.
`
`7. Reagents
`7.I Purity of Reagents-Reagent grade chemicals shall be
`used in all tests. Unless otherwise indicated, it is intended that
`
`4 "Reagent Chemicals, American Chemical Society Specifications," Am. ,Chemi(cid:173)
`cal Soc., Washington, DC. For suggestions on the testing of reagents not hsted by
`the American Chemical Society, see "Reagent Chemicals and Standards,'' by Joseph
`Rosin, D. Van Nostrand Co,, Inc., New York, NY, and the "United States
`Pharmacopeia."
`
`8. Test Specimens
`8.1 Test specimens for tensile creep measurements shall be
`either Type I or Type II as specified in Test Method D 638. In
`addition to these, specimens specified in Test Method D 1822
`may be used for creep-rupture testing. Tabs may be trimmed to
`fit grips, as long as the gripping requirements in 6.1.1 are met.
`8.2 Specimens for unconfim;d compressive creep tests may
`be suitably prepared in the manner described in Test Method
`D 695, except that the length should be increased so that the
`slenderness ratio lies between _ 11 and 15. The standard test
`specimen shall 1:>e in the fo® ofa right 'cylinderor prism.
`Preferred specimen cross sections are 12.7 by 12.7 mm (0.50
`by 0.50 in.) or Ii7 _ mm (0.50 in.) in diam.eter. Surfaces of tl;le
`test specimens shall be plane anq, parallel.
`_
`8.3 Test specimens for the c9,ipressive creep measure(cid:173)
`ments, using the guide tube specified in 6-~·2, shall be sleqder
`bars o( squar~ cross section with_ s~des II):easµring 4 .. 850 ±
`0.025 mm (0.191± 0.001 in.) and the diagonals 6.860 ± 0.025
`mm (0.270 ± 0.001 in.). The specimen shall be 51 mm (2.0 in.)
`long with the ends machined perpendicular_ to the sides.
`8.4 Test specimens for flexural creep measurements shall be
`rectangular bars conforming to the requirernents of Section 5 of
`Test Methods D 790. Preferred specimen sizes are 635 by 12.7
`by 3.18 mm (2.5 by 0.5by 0.125 in.) or 127 by 12.7 by 6.4 mm
`(5.0 by 0.5 by 0.25 in.). Close tolerances of specimen and span
`dimensions are not critical as long as actual dimensions are
`used in calculating loads.
`8.5 Test specimens may be made by injection or compres(cid:173)
`sion molding or by machining froin sheets or other fabricated
`forms. When the testing objective is to obtain design data, the
`method of sample fabrication shall be the same as that use<i in
`the application.
`8.6 Specimens prepared from sheet shall be cut in the same
`direction. If the material is suspected to be anisotropic, a set of
`specimens shall be cut for testing from each of the two
`principal directions of the sheet.
`8.7 The width and the thickness of the specimens shall be
`measured at room temperature with a suitable micrometer to
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`••1•.
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`I.
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`0 D2990-01
`
`1500
`
`Increasing Time
`
`9
`8
`7
`6
`5
`4
`Tensile Creep Strain (%) At Time t
`FIG. 3 Cartesian Isochronous Stress Strain Curves at Various Times
`
`10
`
`11
`
`12
`
`2
`
`3
`
`square inch) by dividing the load by the average initial
`cross-sectional area. of the reduced section.
`12.1. l For flexural measurements, calculate the maximum
`fiber stress for each specimen in megiipascals (or pounds-force
`per square inch) as follows:
`
`S = 3PU2bd2
`
`whe\:-e:
`.
`S = stress; MPa (psi),
`P = load, N (lbf),
`span; mm (in.),
`L
`b = width, riun (in.), l}Ild
`.d = depth, mm (in.).:'~;
`l22 Fo'r tensile oi- compressive measurements, calculate
`strain by dividing the extension. or· corrtpression at the times
`specified 'in 11.5 by the initial gage length of the conditioned
`specimen; multiply strain by 100 t 6 .obtain percent strain.
`12:2.1 For fl_extrr¥:I: measurements_,, ~~culat~ the maxiriiu~
`strain in the outer fiber at the mid-span as follows: -
`.
`
`. r = 6Dd/L 2
`
`where:
`.
`.
`;_ ,ii ,.J.
`r = maxunum stram, mm/mm (m./m.),
`D = maximum deflection at mid-span; mm (in,),
`d
`- depth, mm (in.), and
`L = span, rtim (in.).
`Multiply strain by 100 to obtain percent strain.
`12.3 When a material shows a, significanI dimensional
`change due to the environment alc:i~e, either ot' the following
`approaches may be used, depending 01i"~e intended use of the
`'·
`'
`results:
`12.3.L Correct each.measurem~nt of deformation under load
`by the algebraic addiµon to it of the average deformation
`m~asured on three nonloaded control specimens at tl}e same
`time and at the sa,ne temperature. Contraction of the control
`specirnens used for tensile measurements s~all be considered
`positive ( + ); expansion shall be considered negative (-),
`Contraction of the control specimens used for compressive
`measurements shall be considered negative (-), • expansion
`positive ( + ). Upward deflection of the control specimens used
`for flexural measurements shall be considered positive ( + );
`
`J If necessary, mount a properly conditioned and measured
`~ control specimen alongside the test specimen in the same
`f manner.
`J 11.2 Attach the deformation measuring devices to the speci(cid:173)
`! men (and control specimen) or, if these are optical devices,
` install ready for measurements. Make the initia)., ?r reference
`I 11 :2.1 If the test environment woul~ be disttrrbed during t!J,e
`measurement for extension or deflection.
`I 11.3 Apply the full load rapid,ly and smoothly to the
`
`l a,ttachment of th,e deformation measuring . devi~~. mount tlie
`~ device prior to mounting the specimen.
`.
`
`specimen, preferably in 1 to 5 s. In no casi:: .shall the loading
`I time exceed 5 s. Start pie timing at the onset, ,of loading.
`I 11.1 lf an environmental age11t is used, apply it. tq tpe entire
`I gage length of the ~pecimen mwiediately after loading,
`I 11.4.1 If the t,nvironmental . agent is volatile, cover the
`I specimen to retard evaporati~n without affecting, tµe applieµ
`! load. Replenish volatile agents periodically.
`•
`•
`I
`: Nott 6--For' liquid environmental agents a cotton swab, film, or other
`device may be wrapped or sealed around the gage length or span of the
`specimen, and the liquid agent applied • to saturate .the .swab. '
`• 11.5 Measure the extension of compression of the specimen
`in accordance with the following approximate time schedule:
`!, 6, 12, and 30 min; 1; 2, ·5, 20, 50, 100, 200, 500; 700, and
`1000 h. For creep tests longer than 1000 h, measure deforma(cid:173)
`tion at least monthly.
`11.5.1 If discontinuities in the creep strain versus time plot ·
`are suspected or encountered, readings should be • taken rnore
`frequently than scheduled above.
`11.6 Measure temperature, relative humidity, and other
`environmental variables arid deformation of control specimen
`in accordance with the same schedule as that for deformation
`of the test specimen.
`11 .7 Upon completion of the test interval without rupture,
`remove the load,rapidly and smoothly.
`
`I.
`
`NoTE 7-If desired, measurements of the recovery can be initiated on
`the same schedule· as used in 11.5 during the load application. Calculate
`recovery strain as described in 12.2.
`
`12. Calculation
`12.1 For tensile or compressive measurements, calculate the
`stresses for each specimen in megapascals ( or pounds-force per
`
`771
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`<4@f 02990-01
`
`CREEP
`MODULUS
`Pl i
`
`4
`L-
`10
`0 .1
`
`- - -- - ' - - - - - - - ,~ - -- -~--,---"in,
`10
`100
`1000
`TIME I houn
`FIG. 4 Logarithmic Creep Modulus Versus Time Curves at Various Stress Levels
`
`downward shall be considered negative (-). Calculate cor(cid:173)
`rected strain using the deformation corrected for dimensional
`change due to the environment. Multiply corrected strain by
`100 to obtain percent corrected strain.
`12.3.2 If, because of the intended use of the results, it is
`desired not to correct the deformation under load for significant
`dimensional change due to the environment alone, then the
`strain calculated in accordance with 12.2 or 12.2.1 shall be
`called uncorrected strain. Calculate the strain change due to the
`environment in accordance with 12.2 or 12.2.1 by using the
`average deformation in the control specimen. Multiply by 100
`to obtain percent strain change due to the environment.
`Contraction of the control specimens used for tensile measure(cid:173)
`ments shall be considered positive ( + ), expansive negative
`(-). Contraction of the conti;ol specimens used for compressive
`measurements shall be considered negative (-), expansion
`positive ( + ). lJpward deflection of the control specimens used
`for flexural measurements shall be considered positive ( + ),
`downward negative (-).
`12.4 Calculate creep modulus in megapascals (or pounds(cid:173)
`force per square inch) by dividing the initial stress by the strain
`at the times specified in 11.5.
`
`Nom 8-For ,purposes of comparing materials, the plot of creep
`modulus versus time not only realistically ranks materials but also
`provides modulus values for use in many design equations (see Fig. 4).
`12.5 At each test temperature, calculate a statistical least
`squares regres_sion equation of log stress versus log time-to(cid:173)
`rupture or failure. From the regression equation calculate the
`stress-to-rupture or faµure in megapascals·(or pounds-force per
`square inch) at 1000 h (see Fig. 5).
`12.6 To calculate the stress to produce 1 % strain at 1000 h,
`plot at each test temperature the 1000°h isochronous stress(cid:173)
`strain curve (see Fig. 3) and interpolate for the stress at 1 %
`strain. The isochronous stress-strain curve at 1000 h is obtained
`from several (a.t least three, and preferably more) creep curves
`at different stresses by plotting stress versus strain calculated
`from deformation measurements at 1000 h.
`12.6.1 Isochronous stress-strain curves may be plotted at
`times other than 1000 h for purposes of analysis or for
`specialized design situations involving relatively short-time
`loads and materials that show pronounced creep at such times.
`
`For long-term loading and in general, however, creep modulus
`curves are more useful.
`
`13. Report
`13.1 Report the following information:
`13.1.1 Description of the material tested, including all
`pertinent information on composition, preparation, manufac(cid:173)
`turer, trade name, code number, date of manufacture, type of
`molding, annealing, etc.,
`13.1.2 Dates of the creep test,
`13.1.3 Dimensions of the test specimen,
`13.1.4 Test method number and revision date, and
`13.1.5 Preconditioning used and description of test condi(cid:173)
`tions, including the relative humidity, temperatures, as well as
`concentration and composition of the environment other than
`air, loads used, type loading, etc.
`13.2 For each test temperature, plot log strain in percent
`-versus log time in hours under load with stress as a parameter
`(see Fig. 6).
`13.2.1 Where deformation measurements of loaded speci(cid:173)
`mens have been corrected from unloaded control specimens,
`plot log corrected strain (in percent) versus log time (in hours)
`under load, and on the same graph also plot the log average
`dimensional change (in percent) due to the environment alone
`versus log time.
`13.2.2 Where sjgnificant changes in deformation due to the
`environment alone have occurred, but because of the intended
`use of the results it is desired not to correct the deformation
`under load, then plot log uncorrected strain, in percent, versus
`log time in hours under load, and on the same graph plot the
`log average strain change (in percent) of the control specimen
`versus log time.
`13.2.3 When a material shows a significant dimensional
`change due to the environment alone, any properties calculated
`from the creep data (such as creep modulus or isochronous
`stress-strain curves) shall be labeled corrected or uncorrected,
`depending on which approach is used.
`
`14. Precision and Bias
`14.1 Attempts to develop a precision and bias statement for
`these test methods have not been successful. For this reason,
`
`772
`
`ClearCorrect Exhibit 1065, Page 7 of 20
`
`

`

`0 D.2990-01
`
`5 r - - - - - - - - - - - - - - - - - - - - - - ,
`
`4
`
`3
`
`Stress
`psi
`[x 103)
`
`STATISTICAL REGRESSION
`(logs "' mlogt + IOQ b)
`
`STRESS TO PRODUCE FAILURE
`AT 1,000H RS
`
`2~ - -- - - -~- - - --
`10
`Time • To • Failure, Hours
`FIG. 5 Logarithmic Time-to-Failure (Stress Rupture) Curve
`
`-
`
`'--- ~ - -- --'
`100
`1000
`
`-
`
`10 r-------.------r------,--.----~
`
`Creep
`Strain,
`%
`
`1.,0
`
`Increasing Stress
`
`I I
`
`j
`
`t
`I
`
`l
`J >
`
`t i I
`I I
`I data on precision and bias cannot be given. Anyone wishing to
`I participate in the development of precision and bias data
`; should contact the Chairman, Subcommittee D20.10 (Section
`l D20.10.24), ASTM, 100 Barr Harbor Drive, West Consho-
`1 l hocken, PA 19428-2959.
`! NOTE 9-Precision data in. the previous edition of these test methods
`I
`i have been judged to be invalid because they were based on round robins
`/ which yielded insufficient data. The available within-laboratory data
`i
`i ;
`I
`'
`
`0.1 ' - - - - - - - - ' - - - --
`0.1
`
`- -L . _ _ _ _ _ ..__ _ _ _ _ __J
`10
`100
`1000
`Time, Hours
`FIG. 6 Logarithmic Creep Stra.ln Versus Tlma Curves at Various Stress Levels
`
`providedtinly two to six total degrees of freedom, artd between-laboratory
`data ..yete biised on only two to four laboratories.
`·'
`,.
`14.2 There are no recognized standards for measuring bias
`in regard to these test methods.
`
`15. Keywords
`
`15.1 creep; creep-rupture; plastics
`
`APPENDIXES
`
`(Nonmandatory Information)
`
`Xl. INTRODUCTION
`
`Xl.1 Since the properties of viscoelastic materials are
`dependent on time-, temperature-, and rate-of-loading, an
`instantaneous test result cannot be expected to show how a
`material will behave when subjected to stress or deformation
`
`for an extended period of time. Therefore, values of modulus
`and strength should be obtained under conditions (stress, time,
`and so forth) that simulate the end-use application, and can be
`used in engineering design.
`
`773
`
`ClearCorrect Exhibit 1065, Page 8 of 20
`
`

`

`0 D2990-01
`
`X2. CREEP CURVE
`
`creep test measures the dimensional changes that
`- o time under a constant static load, while the creep
`measures the time to break under a constant load.
`·- the progressive deformation of a material at constant
`--(srress). A constant load is applied to a specimen in
`==...., loading configurations, (such as, tension, flexure, or
`-
`-nno<sion) at constant temperature and the deformation is
`:::i:::asunxi as a function of time.
`
`'!
`
`Xl.
`Following an initial rapid elongation (E 0 ) upon
`lication of t