Standard Test Methods for Tensile, Compressive, …

1 Designation: D 2990 01 Standard Test Methods forTensile, compressive , and flexural creep and creep -Rupture of Plastics1 This Standard is issued under the fixed designation D 2990; the number immediately following the designation indicates the year oforiginal adoption or, in the 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 Standard has been approved for use by agencies of the Department of Scope * These test Methods cover the determination of tensileand compressive creep and creep -rupture of plastics underspecified environmental conditions (see ).

2 While these test Methods outline the use of three-pointloading for measurement of creep in flexure, four-point loading(which is used less frequently) can also be used with theequipment and principles as outlined in Test Methods D For measurements of creep -rupture, tension is the pre-ferred stress mode because for some ductile plastics rupturedoes not occur in flexure or Test data obtained by these test Methods are relevant andappropriate for use in engineering The values stated in SI units are to be regarded as thestandard.

3 The values in parentheses are for information 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 practices and determine the applica-bility of regulatory limitations prior to specific warningstatement is given in This Standard and ISO 899 are similar in content, but are Referenced Standards:D 543 Practices for Evaluating the Resistance of Plastics toChemical Reagents2D 618 Practice for Conditioning Plastics for Testing2D 621 Test Methods for Deformation of Plastics UnderLoad3D 638 Test Method for tensile Properties of Plastics2D 695 Test Method for compressive Properties of RigidPlastics2D 790 Test Methods for flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating Materi-als2D 1822 Test Method for tensile -Impact Energy to

4 BreakPlastics and Electrical Insulating Materials2D 2236 Test Method for Dynamic Mechanical Properties ofPlastics by Means of a Torsional Pendulum4D 4000 Classification System for Specifying Plastic Mate-rials5D 4968 Guide for Annual Review of Test Methods andSpecifications for Plastics63. of Terms Specific to This modulus the ratio of initial applied stress tocreep strain the total strain, at any given time,produced by the applied stress during a creep The term creep , as used in this testmethod, reflects current plastics engineering usage.

5 In scientificpractice, creep is often defined to be the nonelastic portion ofstrain. 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 elasticstrain plus the additional strain with a change in shape, size or position of atest specimen as a result of compression, deflection, or exten- in a compressive creep test, the de-crease in length produced in the gage length of a test in a flexural creep test, the change inmid-span position of a test in a tensile creep test.

6 The increase inlength produced in the gage length of a test ratio the ratio of the length of a columnof uniform cross section to its least radius of gyration; for1 These test Methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee on edition approved August 10, 2001. Published October 2001. Originallypublished as D 2990 71. Last previous edition D 2990 95. These test methodsand Practice D 2991 replace Practices D 674, which has been Book of ASTM Standards, Vol.

7 See1994 Annual Book of ASTM Standards, Vol , see1984 Annual Book of ASTM Standards, Vol Book of ASTM Standards, Vol Book of ASTM Standards, Vol *A Summary of Changes section appears at the end of this ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United of uniform rectangular cross section, the radius ofgyration is times the smaller cross-sectional dimension;for specimens of uniform circular cross section, the radius ofgyration is times the for tensile or compressive creep , the ratio ofthe applied load to the initial cross-sectional area.

8 For flexuralcreep, maximum fiber stress is as calculated in accordance withTest Methods D Summary of Test These test Methods consist of measuring the extensionor compression as a function of time and time-to-rupture, orfailure of a specimen subject to constant tensile or compressiveload under specified environmental Significance and 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 Data from these test Methods can be used.

9 (1)tocompare materials, (2) in the design of fabricated parts, (3)tocharacterize plastics for long-term performance under constantload, and (4) under certain conditions, for Before proceeding with this test method, referenceshould be made to the specification of the material being specimen preparation, conditioning, dimensions, and/ortesting parameters covered in the material specification shalltake precedence over those mentioned in this test method,except in cases where to do so would conflict with the purposefor conducting testing.

10 If there are no material specifications,then the default conditions The grips and gripping technique shall bedesigned to minimize eccentric loading of the or universal joints shall be used beyond each end of It is recommended that grips permit the final centeringof the specimen prior to applying the load. Grips that permit adisplacement of the specimen within the grips during loadapplication are not Parallel anvils shall be used to apply the loadto the unconfined-type specimen (see ).