ASTM_E_1685_-_13.pdf

Designation:E168513Standard Practice forMeasuring the Change in Length of Fasteners Using theUltrasonic Pulse-Echo Technique1This standard is issued under the fixed designation E1685;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 practice covers a procedure for measuring changesin length of threaded fasteners using conventional ultrasonicpulse-echo bolt-measuring instrumentation which has beenproperly calibrated.1.2 This procedure is normally intended for metal bolting6.3 mm or more in nominal diameter with effective length-to-diameter ratios of 2:1 or greater.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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 practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical TestingE1316 Terminology for Nondestructive ExaminationsE1544 Practice for Construction of a Stepped Block and ItsUse to Estimate Errors Produced by Speed-of-SoundMeasurement Systems for Use on Solids(Withdrawn2012)32.2 ASME Standards:4ASME B46.12009 Surface Texture(Surface Roughness,Waviness,and Lay)3.Terminology3.1 The definitions in this practice are in accordance withTerminology E6 and Section I of Terminology E1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 change in length L,nphysical change in length ofa threaded fastener due to a change in tension within thefastener.3.2.2 effective length L,nthe length of a bolt that isresponsive to stress.3.2.2.1 DiscussionThis quantity lies somewhere betweenthe overall length of the bolt and the grip length.It is usuallyestimated as the grip length plus one half the thickness of thehead and one half the thickness of the nut.3.2.3 longitudinal wave,nthose waves in which the par-ticle motion of the material is in the same direction as the wavepropagation.3.2.4 pulse-echo bolt-measuring instrumentan assemblyof ultrasonic instruments designed specifically to measurechanges in the lengths of bolts.See Appendix X1.3.2.5 reference length L,nthe ultrasonic time of flight inthe test specimen multiplied by a reference propagation veloc-ity.3.2.6 reference propagation velocity,LT-1,nthe veloc-ity of propagation of the ultrasonic wavefront in a calibrationtest block or in the bolts whose changes of length are beingmeasured.3.2.7 time of flight,T,nthe measured time intervalbetween the launching of an ultrasonic pulse at the start of apath of travel and the reception of the pulse at the end of thepath.4.Summary of Practice4.1 This practice describes a procedure for determining thechange in length of a threaded fastener due to a change intension in the fastener.Measurements of the ultrasonic time offlight are made before and after the fastener tension is changed,and a calculation of the change in length is made from thechange in the time of flight.4.1.1 Brief bursts of ultrasound(pulses)are generated byapplying high-voltage electrical signals to an electroacoustic1This practice is under the jurisdiction ofASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.13 on Residual StressMeasurement.Current edition approved Nov.1,2013.Published January 2014.Originallyapproved in 1995.Last previous edition approved in 2006 as E168500(2006).DOI:10.1520/E1685-13.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American Society of Mechanical Engineers(ASME),ASMEInternational Headquarters,Two Park Ave.,New York,NY 10016-5990,http:/www.asme.org.*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 transducer having a resonant frequency in the 5 to 10-MHzrange.The pulses enter the bolt through the transducer/boltinterface,travel to the far end of the bolt,and reflect back(echo)to the transducer.The time of flight required for thesignal to make its round-trip is measured electronically.Bymeasuring the change in the time of flight due to a change intension within the bolt,the equipment can determine thechange in the length of the bolt due to the change in tension.Compensation for the direct effect of stress on the propagationvelocity in the bolt