ASTM_C_1678_-_10_2015.pdf

Designation:C167810(Reapproved 2015)Standard Practice forFractographic Analysis of Fracture Mirror Sizes in Ceramicsand Glasses1This standard is issued under the fixed designation C1678;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 pertains to the analysis and interpretationof fracture mirror sizes in brittle materials.Fracture mirrors(Fig.1)are telltale fractographic markings that surround afracture origin in brittle materials.The fracture mirror size maybe used with known fracture mirror constants to estimate thestress in a fractured component.Alternatively,the fracturemirror size may be used in conjunction with known stresses intest specimens to calculate fracture mirror constants.Thepractice is applicable to glasses and polycrystalline ceramiclaboratory test specimens as well as fractured components.Theanalysis and interpretation procedures for glasses and ceramicsare similar,but they are not identical.Different optical micros-copy examination techniques are listed and described,includ-ing observation angles,illumination methods,appropriatemagnification,and measurement protocols.Guidance is givenfor calculating a fracture mirror constant and for interpretingthe fracture mirror size and shape for both circular andnoncircular mirrors including stress gradients,geometricaleffects,and/or residual stresses.The practice provides figuresand micrographs illustrating the different types of featurescommonly observed in and measurement techniques used forthe fracture mirrors of glasses and polycrystalline ceramics.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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:2C1145 Terminology of Advanced CeramicsC1256 Practice for Interpreting Glass Fracture Surface Fea-turesC1322 Practice for Fractography and Characterization ofFracture Origins in Advanced Ceramics3.Terminology3.1 Definitions:(See Fig.1)3.1.1 fracture mirror,nas used in fractography of brittlematerials,a relatively smooth region in the immediate vicinityof and surrounding the fracture originC1145,C13223.1.2 fracture origin,nthe source from which brittlefracture commences.C1145,C13223.1.3 hackle,nas used in fractography of brittle materials,a line or lines on the crack surface running in the local directionof cracking,separating parallel but noncoplanar portions of thecrack surface.C1145,C13223.1.4 mist,nas used in fractography of brittle materials,markings on the surface of an accelerating crack close to itseffective terminal velocity,observable first as a misty appear-ance and with increasing velocity reveals a fibrous texture,elongated in the direction of crack propagation.C1145,C13223.2 Definitions of Terms Specific to This Standard:(See Fig.1)3.2.1 mirror-mist boundary in glasses,nthe peripherywhere one can discern the onset of mist around a glass fracturemirror.This boundary corresponds to Ai,the inner mirrorconstant.3.2.2 mist-hackle boundary in glasses,nthe peripherywhere one can discern the onset of systematic hackle around a1This practice is under the jurisdiction of ASTM Committee C28 on AdvancedCeramics and is the direct responsibility of Subcommittee C28.03 on PhysicalProperties and Non-Destructive Evaluation.Current edition approved July 1,2015.Published September 2015.Originallyapproved in 2007.Last previous edition approved in 2010 as C1678 10.DOI:10.1520/C1678-10R15.2For 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 glass fracture mirror.This boundary corresponds to Ao,theouter mirror constant.3.2.3 mirror-hackle boundary in polycrystalline ceramics,nthe periphery where one can discern the onset of systematicnew hackle and there is an obvious roughness change relativeto that inside a ceramic fracture mirror region.This boundarycorresponds to Ao,the outer mirror constant.Ignore prematurehackle and/or isolated steps from microstructural irregularitiesin the mirror or irregularities at the origin.3.2.4 fracture mirror constant,n(Fl-3/2)an empirical ma-terial constant that relates the fracture stress to the mirrorradius in glasses and ceramics.4.Summary of Practice4.1 This practice provides guidance on