ASTM_D_6992_-_16.pdf

Designation:D699216Standard Test Method forAccelerated Tensile Creep and Creep-Rupture ofGeosynthetic Materials Based on Time-TemperatureSuperposition Using the Stepped Isothermal Method1This standard is issued under the fixed designation D6992;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers accelerated testing for tensilecreep,and tensile creep-rupture properties using the SteppedIsothermal Method(SIM).1.2 The test method is focused on geosynthetic reinforce-ment materials such as yarns,ribs of geogrids,or narrowgeotextile specimens.1.3 The SIM tests are laterally unconfined tests based ontime-temperature superposition procedures.1.4 Tensile tests are to be completed before SIM tests andthe results are used to determine the stress levels for subse-quent SIM tests defined in terms of the percentage of UltimateTensile Strength(TULT).Additionally,the tensile test can bedesigned to provide estimates of the initial elastic straindistributions appropriate for the SIM results.1.5 Ramp and Hold(R+H)tests may be completed inconjunction with SIM tests.They are designed to provideadditional estimates of the initial elastic and initial rapid creepstrain levels appropriate for the SIM results.1.6 This method can be used to establish the sustained loadcreep and creep-rupture characteristics of a geosynthetic.Results of this method are to be used to augment results of TestMethod D5262 and may not be used as the sole basis fordetermination of long term creep and creep-rupture behavior ofgeosynthetic material.1.7 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.8 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 practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D2990 Test Methods for Tensile,Compressive,and FlexuralCreep and Creep-Rupture of PlasticsD4439 Terminology for GeosyntheticsD4595 Test Method for Tensile Properties of Geotextiles bythe Wide-Width Strip MethodD5262 Test Method for Evaluating the Unconfined TensionCreep and Creep Rupture Behavior of Geosynthetics3.Terminology3.1 For definitions related to geosynthetics see TerminologyD4439.3.2 For definitions related to creep see Test Methods D2990and D5262.3.3 Definitions of Terms Specific to This Standard:3.3.1 creep modulusin SIM analysis,the load divided bythe percent strain at any given point in time.3.3.2 dwell timetime during which conditions(particularload)are held constant between temperature steps.3.3.3 mean test temperaturethe arithmetic average of alltemperature readings of the atmosphere surrounding the testspecimen for a particular temperature step,starting at a timenot later than established temperature ramp time,and finishingat a time just prior to the subsequent temperature reset.3.3.4 offset modulus method or pointingdata analysismethod used to normalize any prestrain in the samples byshifting the origin of a stress versus strain curve to an axisorigin of coordinates;that is,to coordinates(0,0).3.3.5 ramp and hold(R+H)testa creep test of very shortduration;for example,100 to 1000 s.1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-ance Properties.Current edition approved Feb.15,2016.Published February 2016.Originallyapproved in 2003.Last previous edition approved in 2015 as D6992 03(2015).DOI:10.1520/D6992-16.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.3.6 shift factorthe displacement along the log time axisby which a section of the creep or creep modulus curve ismoved to create the master curve at the reference temperature.Shift factors are denoted by the symbol AT when the displace-ments are generally to shorter times(attenuation)or the symbolAT when the displacements are generally to longer times(acceleration).3.3.7 stepped isothermal method(SIM)a method of expo-sure that uses temperature steps and dwell times to acceleratecreep response of a material being tested under load.3.3.8 tensile creeptime-dependent deformation that oc-curs when a specimen is subjected to a constant tensile load.3.3.9 tensile creep-rupturetime dependent rupture thatterminates a creep test at high stress levels.3.3.10