ASTM_E_1315_-_93_2002.pdf

Designation:E 1315 93(Reapproved 2002)Standard Practice forUltrasonic Examination of Steel with Convex CylindricallyCurved Entry Surfaces1This standard is issued under the fixed designation E 1315;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 reapproval.1.Scope1.1 This practice describes the selection of single-elementhard-face ultrasonic search units for which flat-entry-surfacereference blocks can be used for examination of steel withconvex cylindrically curved entry surfaces.1.2 The scope of this practice includes the determination ofsearch unit characteristics and radius of surface curvature ofthe material for which no gain correction is required,or,if alarger search unit is used,the computation of the additionalgain required to allow standardization with a flat referenceblock and examination on a curved surface.1.3 This practice is intended for use during contact exami-nation of convexly curved steel material using round flat face,piezoelectric search units for longitudinal ultrasonic wavegeneration in the frequency range from 1 to 10 MHz.1.4 This standard does not purport to address all of thesafety problems,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:E 1316 Terminology for Nondestructive Examinations23.Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice,see Terminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 critical radius,RcSmallest radius of curvature ofthe material that can be examined without a correction forcurvature.The critical radius is calculated from properties ofthe search unit,couplant and material under examination.Values of Rc for various conditions can be determined from theequations in Annex A1.3.2.2 DiscussionFor contact examination using searchunits with flat wearfaces on convex surfaces,the width,W,refers to the width of the ultrasonic beam generated by thesearch unit.4.Summary of Practice4.1 Three effects are produced by placing a flat faced searchunit on a cylindrically curved convex surface:4.1.1 Cylindrical PlanoA concave lens formed by thecouplant defocuses the ultrasonic beam,reducing amplitude atthe discontinuities.4.1.2 Rays from the search unit strike the curved surface atnon-normal incidence,producing a shear wave as well as alongitudinal wave.The shear wave extracts energy that couldotherwise be used in the longitudinal component.4.1.3 Except at the line of contact between the search unitand the curved surface,a finite varying thickness of couplantexists.This couplant layer transforms the impedance of thematerial undergoing examination,so that the impedance look-ing into the couplant no longer matches the search unitimpedance.The impedance mismatch reduces the energyentering the curved surface.34.2 Of the three effects,the first two are negligible fortypical search units,surface curvatures and properties of thecouplant,search unit wearface and material being examined.The third effect predominates:a couplant layer l/20 in thick-ness can result in an amplitude decrease of 50%in the materialbeing examined.Where the curvature and search unit sizecreate a couplant thickness at diametrically opposite edges ofthe search unit that greatly exceeds l/20,the ultrasound iseffectively not transmitted.The effective transducer width isreduced,the total energy is reduced,and because of thereduced effective width,the beam spread increases.5.Significance and Use5.1 Standardization of ultrasonic equipment for examinationof steel having surfaces with curved surfaces generally requiresinstrument standardization on reference blocks of similar1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.06 onUltrasonic Method.Current edition approved September 15,1993.Published November 1993.Originally published as E 1315 89.Last previous edition E 1315 89.2Annual Book of ASTM Standards,Vol 03.03.3Substantial discussion of the basis of this practice is given in:Birchak,J.R.andSerabian,S.,“Calibration of Ultrasonic Systems for Inspection from CurvedSurfaces,”Materials Evaluation,Vol 36,January 1978,p.39.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.radius of curvature,surface finish,and material properties.Astandardization procedure using flat-entry reference blocks andconventional round search units can result in equipmentamplification errors if corrections are not made for the radius ofcurvature.This procedure restricts the ultrasonic examiner(operator)to conditions in