1、Designation:D797115Standard Guide forMeasuring Roundness of Glass Spheres Using a FlowingStream Digital Image Analyzer1This standard is issued under the fixed designation D7971;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year
2、 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 guide covers the determination of the roundness ofglass spheres used in pavement marking systems using aflowing st
3、ream digital analyzer.Typical gradations for pave-ment marking systems are defined in ranges from Type 0through 5 in AASHTO M247.1.2 This guide provides for the presentation of roundnessdata in a variety of formats to the requirement of the agencypavement marking material specification.For most spec
4、ifica-tions the standard format is to present the roundness data asPercent True Spheres relative to a series of standard ASTMsieve sizes.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 ad
5、dress 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:2B215 Practices f
6、or Sampling Metal Powders2.2 AASHTO Standard:3AASHTO M247 Standard Glass Beads Used in TrafficMarkings2.3 ISO Standards:ISO 92766 Representation of results of particle size analy-sis Part 6:Descriptive and quantitative representationof particle shape and morphologyISO 133221 Particle size analysis I
7、mage analysis meth-ods Part 1:Static image analysis methods3.Terminology3.1 Flowing Stream Digital Analyzer:3.1.1 A computer controlled particle analyzer employing ahigh resolution digital imaging device and computer imageprocessing software to do photo optical single particle countingand particle s
8、ize analysis.3.2 Roundness of Glass Beads:3.2.1 Roundness,in the context of this guide,refers to thepercentage of true spheres in a sample as a ratio of the totalnumber of particles measured.3.2.2 Methods:3.2.2.1 These are specific observations and calculations ofthe streaming particles that combine
9、 to form a protocol formeasuring the percentage of true spheres within the sample.3.3 Aspect Ratio:3.3.1 Aspect ratio,often referred to as b/l or w/l,is one ofthe several methods of determining roundness and is illustratedin Fig.1.3.3.2 Aspect ratio will be the recommended method for themajority of
10、roundness measurements,especially when thereexists a reasonable expectation that all of the particles beingmeasured have rounded surfaces and mostly resemble theshape of a sphere.3.4 Sphericity(also referred to as circularity):3.4.1 Sphericity is one of a number of methods of determin-ing roundness
11、and is illustrated in Fig.2.3.4.2 SPHT-value or sphericity is calculated from the mea-surements of1.the area*A*of the particle projection(particle image),2.multiplied by four Pi(4)and3.divided by the perimeter P of the particle projectionsquared(P2).3.4.3 SPHT result values are between 0 and 1(inclu
12、ding 1)and following ISO 92766.NOTE1A high percentage of the volume of glass beads are producedfrom crushed and sized recycled glass.The most common method ofproduction involves passing the particles in a reverse free fall through agas-rich,highly luminous,natural gas flame wherein they reach their1
13、This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.44 on Traffic Coatings.Current edition approved April 1,2015.Published April 2015.DOI:10.1520/D7971-15.2For referenced ASTM standards
14、,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.3Available from American Association of State Highway and TransportationOfficials(AASHTO),444 N.
15、Capitol St.,NW,Suite 249,Washington,DC 20001,http:/www.transportation.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 melting point.Due to natures insistence that all liquids exhibit tension attheir surface,the particles are then forc
16、ed to reconfigure into a shapewhich maintains the smallest ratio of surface area to volume.This shapeis a sphere.One of the main quality control concerns of this productionmethod is ensuring that all the particles pass through the flame andbecome spheres.If not,the particles will remain in the state in which theyare introduced and will consist of irregular shapes with sharp edges.Alarge variance between sphericity and aspect ratio could reveal thatsphericity is the better method in this particul
