ASTM_E_143_-_13.pdf

Designation:E14313Standard Test Method forShear Modulus at Room Temperature1This standard is issued under the fixed designation E143;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.Scope*1.1 This test method covers the determination of shearmodulus of structural materials.This test method is limited tomaterials in which,and to stresses at which,creep is negligiblecompared to the strain produced immediately upon loading.Elastic properties such as shear modulus,Youngs modulus,and Poissons ratio are not determined routinely and aregenerally not specified in materials specifications.Precisionand bias statements for these test methods are therefore notavailable.1.2 UnitsThe values stated in inch-pound units are to beregarded as standard.The values given in parentheses aremathematical conversions to SI units that are provided forinformation only and are not considered standard.1.3 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical TestingE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsE111 Test Method for Youngs Modulus,Tangent Modulus,and Chord ModulusE1012 Practice for Verification of Testing Frame and Speci-men Alignment Under Tensile and Compressive AxialForce Application3.Terminology3.1 Definitions:Terms common to mechanical testing.3.1.1 angle of twist(torsion test)the angle of relativerotation measured in a plane normal to the torsion specimenslongitudinal axis over the gauge length.3.1.2 shear modulus,G,FL2,nthe ratio of shear stressto corresponding shear strain below the proportional limit,alsocalled torsional modulus and modulus of rigidity.(See Fig.1.)3.1.2.1 DiscussionThe value of shear modulus may de-pend on the direction in which it is measured if the material isnot isotropic.Wood,many plastics and certain metals aremarkedly anisotropic.Deviations from isotropy should besuspected if the shear modulus,G,differs from that determinedby substituting independently measured values of Youngsmodulus,E,and Poissons ratio,in the relationG 5E211!(1)3.1.2.2 DiscussionIn general,it is advisable,in reportingvalues of shear modulus to state the stress range over which itis measured.3.1.3 torque,FL,na moment(of forces)that produces ortends to produce rotation or torsion.3.1.4 torsional stress FL2,nthe shear stress in a body,in a plane normal to the axis or rotation,resulting from theapplication of torque.4.Summary of Test Method4.1 The cylindrical or tubular test specimen is loaded eitherincrementally or continuously by applying an external torqueso as to cause a uniform twist within the gauge length.4.1.1 Changes in torque and the corresponding changes inangle of twist are determined either incrementally or continu-ously.The appropriate slope is then calculated from the shearstress-strain curve,which may be derived under conditions ofeither increasing or decreasing torque(increasing from pre-torque to maximum torque or decreasing from maximumtorque to pretorque).5.Significance and Use5.1 Shear modulus is a material property useful in calculat-ing compliance of structural materials in torsion provided theyfollow Hookes law,that is,the angle of twist is proportional tothe applied torque.Examples of the use of shear modulus arein the design of rotating shafts and helical compression springs.1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.04 onUniaxial Testing.Current edition approved Nov.1,2013.Published May 2014.Originallyapproved in 1959.Last previous edition approved in 2008 as E143 02(2008).DOI:10.1520/E0143-13.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 NOTE1For materials that follow nonlinear elastic stress-strainbehavior,the value of tangent or chord shear modulus is useful forestimating the change in torsional strain to corresponding stress for aspecified stress or stress-range,respectively.Such determinations are,however,outside the scope of this standard.(See for example Ref(1).)35.2 The procedural steps and precision of th