ASTM_E_2368_-_10.pdf

Designation:E236810Standard Practice forStrain Controlled Thermomechanical Fatigue Testing1This standard is issued under the fixed designation E2368;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 practice covers the determination of thermome-chanical fatigue(TMF)properties of materials under uniaxiallyloaded strain-controlled conditions.A“thermomechanical”fatigue cycle is here defined as a condition where uniformtemperature and strain fields over the specimen gage sectionare simultaneously varied and independently controlled.Thispractice is intended to address TMF testing performed insupport of such activities as materials research anddevelopment,mechanical design,process and quality control,product performance,and failure analysis.While this practiceis specific to strain-controlled testing,many sections willprovide useful information for force-controlled or stress-controlled TMF testing.1.2 This practice allows for any maximum and minimumvalues of temperature and mechanical strain,and temperature-mechanical strain phasing,with the restriction being that suchparameters remain cyclically constant throughout the durationof the test.No restrictions are placed on environmental factorssuch as pressure,humidity,environmental medium,and others,provided that they are controlled throughout the test,do notcause loss of or change in specimen dimensions in time,andare detailed in the data report.1.3 The use of this practice is limited to specimens and doesnot cover testing of full-scale components,structures,orconsumer products.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE4 Practices for Force Verification of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsE111 Test Method for Youngs Modulus,Tangent Modulus,and Chord ModulusE112 Test Methods for Determining Average Grain SizeE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE337 Test Method for Measuring Humidity with a Psy-chrometer(the Measurement of Wet-and Dry-Bulb Tem-peratures)E467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing SystemE606 Test Method for Strain-Controlled Fatigue TestingE1012 Practice for Verification of Testing Frame and Speci-men Alignment Under Tensile and Compressive AxialForce ApplicationE1823 Terminology Relating to Fatigue and Fracture Testing3.Terminology3.1 The definitions in this practice are in accordance withdefinitions given in Terminology E1823 unless otherwisestated.3.2 Definitions:3.2.1 Additional definitions are as follows:3.2.2 stress,stress is defined herein to be the engineeringstress,which is the ratio of force,P,to specimen original crosssectional area,A:5 P/A(1)The area,A,is that measured in an unloaded condition atroom temperature.See 7.2 for temperature state implications.3.2.3 coeffcient of thermal expansion,the fractionalchange in free expansion strain for a unit change intemperature,as measured on the test specimen.3.2.4 total strain,tthe strain component measured on thetest specimen,and is the sum of the thermal strain and themechanical strain.3.2.5 thermal strain,ththe strain component resultingfrom a change in temperature under free expansion conditions(as measured on the test specimen).th5 T(2)1This practice is under the jurisdiction ofASTM Committee E08 on Fatigue andFracture and is the direct responsibility of Subcommittee E08.05 on CyclicDeformation and Fatigue Crack Formation.Current edition approved May 1,2010.Published June 2010.Originallyapproved in 2004.Last previous edition approved in 2004 as E2368041.DOI:10.1520/E2368-10.2For 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 NOTE1For some materials,may be nonlinear over the temperaturerange of interest.3.2.6 mechanical strain,mthe strain component resultingwhen the free expansion thermal strain(as measured on the testspecimen)is subtracted from the total strain.m5 t2 th(3)3.2.7 elastic strain,elthe strain component resultingwhen the stress is divided by the temperature-dependentYoungs Modulus(in accordance with Test Method E111).el5/ET!(4)3.2.8 inelastic strain,inthe strain component resultingwhen the elastic strain is subtracted from the mechanical strain.in5 m2 el(5)3.2.9 strain ratio,Rthe ratio of minimum mechanicalstrain to the maxim