1、Designation: D 6112 97 (Reapproved 2005)Standard Test Methods forCompressive and Flexural Creep and Creep-Rupture ofPlastic Lumber and Shapes1This standard is issued under the fixed designation D 6112; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of the creepand creep-rupture properties of
3、 plastic lumber and shapes,when loaded in compression or flexure under specified envi-ronmental conditions. Test specimens in the “as-manufactured”form are employed. As such, these are test methods forevaluating the properties of plastic lumber or shapes as aproduct and not material property test me
4、thods.1.2 Plastic lumber and plastic shapes are currently madepredominantly with recycled plastics. However, this testmethod would also be applicable to similar manufacturedplastic products made from virgin resins where the product isnon-homogenous in the cross-section.1.3 The values stated in inchp
5、ound units are to be regardedas standard. The values given in brackets are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health pr
6、actices and determine the applica-bility of regulatory limitations prior to use.NOTE 1There is no similar or equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 543 Practices for Evaluating the Resistance of Plastics toChemical ReagentsD 883 Terminology Relating to PlasticsD 2990 Te
7、st Methods for Tensile, Compressive, and Flex-ural Creep and Creep-Rupture of PlasticsD 4000 Classification System for Specifying Plastic Mate-rialsD 5033 Guide for Development of ASTM Standards Relat-ing to Recycling and Use of Recycled PlasticsD 5947 Test Methods for Physical Dimensions of SolidPl
8、astics SpecimensE4 Practices for Force Verification of Testing Machines3. Terminology3.1 Definitions:3.1.1 compressionin a compressive creep test, the de-crease in length produced in the gage length or the total lengthof a test specimen.3.1.2 creep modulusthe ratio of initial applied stress tocreep
9、strain.3.1.3 creep strainthe total strain, at any given time,produced by the applied stress during a creep test.3.1.3.1 DiscussionThe term creep, as used in this testmethod, reflects current plastics engineering usage. In scientificpractice, creep is often defined to be the nonelastic portion ofstra
10、in. However, this definition is not applicable to existingengineering formulas. Plastics have a wide spectrum of retar-dation times, and elastic portions of strain cannot be separatedin practice from nonelastic. Therefore, wherever “strain” ismentioned in these test methods, it refers to the sum of
11、elasticstrain plus the additional strain with time.3.1.4 deflectionin a flexural creep test, the change inmid-span position of a test specimen.3.1.5 deformationa change in shape, size or position of atest specimen as a result of compression, deflection, or exten-sion:3.1.6 plastic lumber, na manufac
12、tured product composedof more than 50 weight percent resin, and in which the productgenerally is rectangular in cross-section and typically suppliedin board and dimensional lumber sizes, may be filled orunfilled, and may be composed of single or multiple resinblends.3.1.7 plastic shape, na manufactu
13、red product composedof more than 50 weight percent resin, and in which the productgenerally is not rectangular in cross-section, may be filled orunfilled, and may be composed of single or multiple resinblends.1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the
14、 direct responsibility of Subcommittee D20.20 on PlasticProducts (Section D20.20.01).Current edition approved Nov. 1, 2005. Published January 2006. Originallyapproved in 1997. Last previous edition approved in 1997 as D 6112 - 97.2For referenced ASTM standards, visit the ASTM website, www.astm.org,
15、orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.8 resin, na
16、solid or pseudo-solid organic materialoften of high molecular weight, that exhibits a tendency to flowwhen subjected to stress, usually has a softening or meltingrange, and usually fractures conchoidally. (See TerminologyD 883.)3.1.8.1 DiscussionIn a broad sense, the term is used todesignate any pol
17、ymer that is a basic material for plastics.3.1.9 stressfor compressive creep, the ratio of the appliedload to the initial cross-sectional area. For flexural creep,maximum fiber stress is calculated according to Eq 1.3.1.10 Additional definition of terms applying to this testmethod appear in Terminol
18、ogy D 883 and Guide D 5033.4. Summary of Test Method4.1 These test methods consist of measuring the deflectionor compression as a function of time and time-to-rupture, orfailure of a specimen subject to constant flexural or compres-sive load under specified environmental conditions.4.2 The four-poin
19、t loading a outlined in this testing standardshall be used for the flexural creep tests.4.3 Compressive loading as outlined in this testing standardshall be used for the compressive creep tests.4.4 These test methods represent modifications of the com-pressive and flexural creep and creep rupture te
20、st methodsspecified in Test Methods D 2990.5. Significance and Use5.1 Data from creep and creep-rupture tests are necessary topredict the creep modulus and strength of materials underlong-term loads and to predict dimensional changes that mayoccur as a result of such loads.5.2 Data from these test m
21、ethods can be used to characterizeplastic lumber: for comparison purposes, for the design offabricated parts, to determine long-term performance underconstant load, and under certain conditions, for specificationpurposes.5.3 For many products, there may be a specification thatrequires the use of thi
22、s test method, but with some proceduralmodifications that take precedence when adhering to thespecification. Therefore, it is advisable to refer to that productspecification before using this test method. Table 1 in Classi-fication D 4000 lists the ASTM materials standards that cur-rently exist.6. A
23、pparatus6.1 General:6.1.1 Loading System:6.1.1.1 The loading system must be so designed that theload applied and maintained on the specimen is within 61%of the desired load. The loading mechanism must allowreproductively rapid and smooth loading as specified in 11.1.3.In creep-rupture tests, provisi
24、on must be made to ensure thatshock loading, caused by a specimen failure, is not transferredto other specimens undergoing testing. The accuracy of theloading system shall be verified at least once each year inaccordance with Practices E4.6.1.1.2 Loading systems that provide a mechanical advan-tage
25、require careful design to maintain constant load through-out the test. For example, lever systems must be designed sothat the load does not change as the lever arm moves during thetest.6.1.2 Compression and Deflection Measurements:6.1.2.1 The accuracy of the deformation measuring deviceshall be with
26、in 61 % of the deformation to be measured.6.1.2.2 Deformation measuring devices shall be calibratedagainst a precision micrometer screw or other suitable standardunder conditions are nearly identical as possible with thoseencountered in the test. Caution is necessary when usingdeformation measuring
27、devices whose calibration is subject todrifting with time and is dependent on temperature andhumidity.6.1.2.3 Deformation measuring devices shall be firmly at-tached to or seated on the specimen so that no slippage occurs.Electrical resistance gages are suitable only if the materialtested will permi
28、t perfect adhesion to the specimen and if theyare consistent with 6.2.16.1.3 Time MeasurementThe accuracy of the time mea-suring device shall be 61 % of the time-to-rupture or failure orthe elapsed time of each creep measurement, or both.6.1.4 Temperature Control and Measurement:6.1.4.1 The temperat
29、ure of the test space, especially close tothe gage length of the specimen, shall be maintained within62C by a suitable automatic device and shall be stated inreporting the results.NOTE 2The thermal contraction and expansion associated with smalltemperature changes during the test may produce changes
30、 in the apparentcreep rate, especially near transition temperatures.6.1.4.2 Care must be taken to ensure accurate temperaturemeasurements over the gage length of the specimen throughoutthe test. The temperature measuring devices shall be checkedregularly against temperature standards and shall indic
31、ate thetemperature of the specimen gage area.6.1.4.3 Temperature measurements shall be made at fre-quent intervals, or continuously recorded to ensure an accuratedetermination of the average test temperature and compliancewith 6.1.5.6.1.5 Environmental Control and Measurements:6.1.5.1 When the test
32、environment is air, the relative humid-ity shall be controlled to 50 6 5 % during the test unlessotherwise specified, or unless the creep behavior of thematerial under testing has been shown to be unaffected byhumidity. The controlling and measuring instruments shall bestable for long time intervals
33、 and accurate to within 61%.(The control of relative humidity is known to be difficult attemperatures much outside the range from 50 to 104F 10 to40C.)6.1.5.2 If, for any reason, the specified relative humiditycannot be achieved or the test is conducted to determine thesensitivity of the product to
34、high humidity, the actual averagevalue and fluctuation of relative humidity used should bereported.6.1.5.3 The composition of the test environment shall bemaintained constant throughout the test. (WarningSafetyprecautions should be taken to void personal contact, toeliminate toxic vapors, and to gua
35、rd against explosion hazardsD 6112 97 (2005)2in accordance with any possible hazardous nature of theparticular environment being used.)6.1.6 Vibration ControlCreep tests are quite sensitive toshock and vibration. The location of the apparatus, the testequipment, and mounting shall be so designated t
36、hat thespecimen is isolated from vibration. Multiple-station testequipment must be of sufficient rigidity so that no significantdeflection occurs in the test equipment during creep or creep-rupture testing. During time-to-rupture or failure, means toprevent jarring of other test specimens by the fal
37、ling load froma failed test specimen shall be provided by a suitable net orcushion.6.2 Compressive Creep:6.2.1 PlatensParallel platens shall be used to apply theload to the unconfined-type specimen (see 8.2). One of theplatens of the machine shall preferably be self-aligning andshall, in order that
38、the load may be applied evenly over the faceof the specimen, be arranged so that the specimen is accuratelycentered and the resultant of the load is through its center.6.2.2 The compression of specimen gage length under loadshall be measured by means of any device that will notinfluence the specimen
39、 behavior by mechanical (undesirabledeformation, notches, etc.) physical (heating of specimen, etc.),or chemical effects. Alternatively, the compression of thespecimen can be measured using platen displacement with theentire length of the specimen serving as the gage length.6.3 Flexural Creep:6.3.1
40、Test RackA rigid test rack shall be used to providesupport of the test specimen at both ends with a span equal to16 (tolerant +4 and 2) times the depth of the specimen. Inorder to avoid excessive indentation of the specimen, the radiusof the support shall be a minimum of 0.5 in. 12.7 mm and upto 1.5
41、 times the depth of the specimen. Sufficient space must beallowed below the specimen for dead-weight loading.6.3.2 Loading BeamThe loading beam shall be config-ured with loading noses with cylindrical surfaces (see Fig. 1).The radius of noses shall be at least 0.5 in. 12.7 mm or allspecimens. For la
42、rge specimens the radius of the supports maybe up to 1.5 times the specimen depth.6.3.3 A four point loading arrangement shall be used asshown in Fig. 1.6.3.4 For flexural testing the deflection of the specimenshall be measured at the midpoint of the load span at thebottom face of the specimen.7. Re
43、agents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specification are available3. Other grad
44、es may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water or water ofequal purity.7.
45、3 Specified ReagentsShould this test method be refer-enced in a material specification, the specific reagent to be usedshall be as stipulated in the specification.7.4 Standard ReagentsA list of standard reagents is alsoavailable in Test Method D 543.8. Test Specimen8.1 General:8.1.1 Test specimens m
46、ay be made by any of the techniquesnormally employed to produce plastic lumber. When thetesting objective is to obtain design data, the method of samplefabrication shall be the same as that used in the application.8.1.2 In the case of materials whose dimensions are knownto change significantly due t
47、o the specified environment alone(for example, the shrinkage of some thermosetting plastics dueto post-curing at elevated temperatures), provision shall bemade to test unloaded control specimens alongside the testspecimen so that compensation may be made for changes otherthan creep. A minimum of thr
48、ee control specimens shall betested at each test temperature.8.1.3 In creep testing at a single temperature, the minimumnumber of test specimens at each stress shall be two if four ormore levels of stress are used or three if fewer than four levelsare used.8.1.4 In creep-rupture testing, a minimum o
49、f two specimensshall be tested at each of the stress levels specified in 10.2.1 ateach temperature.NOTE 3The scatter of creep-rupture data is considerable, with onehalf to a full decade of variation in time-to-rupture being typical.Therefore, it may be necessary to test more than two specimens at eachstress level to obtain satisfactory results.8.2 Compressive Creep:8.2.1 The standard test specimen shall be in the form of aright prism. With the exception that specimen cross sectionsare the full sections of any manufactured plastic lumber orshape. Surfa
