1、Designation: F 218 05Standard Test Method forMeasuring Optical Retardation and Analyzing Stress inGlass1This standard is issued under the fixed designation F 218; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. 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 test method covers the analysis of stress in glass bymeans of a polarimeter based on the principles developed byJessop a
3、nd Friedel (1, 2).2Stress is evaluated as a function ofoptical retardation, that is expressed as the angle of rotation ofan analyzing polarizer that causes extinction in the glass.1.2 There is no known ISO equivalent to this standard.1.3 This standard does not purport to address all of thesafety con
4、cerns, 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:3C 162 Terminology of Glass and Glass P
5、roductsC 770 Test Method for Measurements of Glass Stress Op-tical CoefficientC 978 Test Method for Photoelastic Determination of Re-sidual Stress in a Transparent Glass Matrix Using aPolarizing Microscope and Optical Compensation Proce-duresC 1426 Practices for Verification and Calibration of Pola-
6、rimeters3. Terminology3.1 For definitions of terms used in this standard, refer toTerminology C 162.4. Significance and Use4.1 The performance of glass products may be affected bypresence of residual stresses due to process, differential ther-mal expansion between fused components, and by inclusions
7、.This test method provides means of quantitative evaluation ofstresses.5. Calibration and Standardization5.1 Whenever calibration of the polarimeter is required byproduct specification, Practices C 1426 for verification andcalibration should be used.6. Polarimeter6.1 The polarimeter shall consist of
8、 an arrangement similarto that shown in Fig. 1. A description of each componentfollows:6.1.1 Source of LightEither a white light or a monochro-matic source such as sodium light (l 589 nm) or a white lightcovered with a narrow-band interferential filter B, (see Fig. 1,)transmitting the desired monoch
9、romatic wavelength.NOTE 1The white light should provide a source of illumination withsolar temperature of at least that of Illuminant A.6.1.2 FilterThe filter should be placed between the lightsource and the polarizer, or between the analyzer and theviewer (see Fig. 1).6.1.3 DiffuserA piece of opal
10、glass or a ground glass ofphotographic quality.6.1.4 PolarizerA polarizing element housed in a rotatablemount capable of being locked in a fixed position shown inFig. 2 and Fig. 4.6.1.5 Immersion CellRectangular glass jar with strain-free, retardation-free viewing sides filled with a liquid havingth
11、e same index of refraction as the glass specimen to bemeasured. It may be surmounted with a suitable device forholding and rotating the specimen, such that it does not stressthe specimen.NOTE 2Suitable index liquids may be purchased or mixed as required.Dibutyl phthalate (refractive index 1.489), an
12、d tricresyl phosphate (index1.555) may be mixed to produce any desired refractive index between thetwo limits, the refractive index being a linear function of the proportion ofone liquid to the other. Other liquids that may be used are:1This test method is under the jurisdiction of ASTM Committee C1
13、4 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Sept. 15, 2005. Published November 2005. Originallyapproved in 1950. Last previous edition approved in 2000 as F 218 95 (2000).2The boldface numbers in p
14、arentheses refer to the reports and papers appearingin the list of references at the end of this test method.3For 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 sta
15、ndards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Liquid Refractive IndexCinnamic aldehyde 1.62Oil of cassia 1.61Monochlorobenzene 1.525Carbon tetrachloride 1.463Dipentene (Eastman) 1.473
16、NOTE 3Cases may arise where the refraction liquid may contaminatethe specimen. When the sample is viewed through faces that areessentially parallel, elimination of the liquid will cause only a minor error.However, when viewing through faces of the sample that are not parallel,the use of liquid of sa
17、me refraction index is essential.6.1.6 Full-Wave (Sensitive Tint) Plate, having a retardationof 565 6 5 nm, which produces, with white light, a violet-redcolor. It should be housed in a rotatable mount capable of beinglocked in a fixed position shown in Fig. 2.6.1.7 Quarter-Wave Plate, having a reta
18、rdation equivalentto one quarter of the wavelength of monochromatic light beingused, or 141 6 5 nm when white light is used. It should behoused in a rotatable mount capable of being locked in a fixedposition shown in Fig. 2.6.1.8 AnalyzerIdentical to the polarizer. It should behoused in a rotatable
19、mount capable of being rotated 360, anda graduated dial indicating the angular rotation a of theanalyzer from its standard position. The polarizer must belockable in position shown in Fig. 2.6.1.9 Telescope, short-focus, having a suitable magnifyingpower over the usable focusing range.7. Setup of Po
20、larimeter7.1 The standard setup of the polarimeter is illustrated inFig. 2. Two reference directions must be identified:7.1.1 Vertical direction (V), (in polarimeters transmitting thelight in horizontal direction) or NS, that is usually a symmetryaxis of an instrument using a vertical light path, an
21、d polarizersare in a horizontal plane.7.1.2 Horizontal (H), or EW (perpendicular to the vertical orNS) (see Fig. 4)7.2 As usually employed, the polarimeter measures retarda-tions in a sample that is placed in the polarimeter and rotateduntil the measured stresses Sxand Syare oriented along V andH (v
22、ertical or a horizontal) direction. This is accomplished bysetting the vibration direction of the polarizer at an angle of 45to the vertical and clockwise to the horizontal (as shown in Fig.2 and Fig. 4). The vibration direction of the analyzer must be“crossed” with respect to that of the polarizer;
23、 that is, the twodirections must be at right angles to each other. In thisrelationship a minimum amount of light will pass through thecombination. To check the 45 angle at which the directions ofthe polarizer and analyzer must be set, use may be made of arectangular-shaped Glan-Thompson or Nicol pri
24、sm. The prismis set so that its vibration direction is 45 to the vertical andhorizontal. The polarizer is then rotated until extinction occursbetween it and the prism. The position of the analyzer is thendetermined in the same way, but by first rotating the Glan-Thompson or Nicol prism through 90; o
25、r, the analyzer may berotated to extinction with respect to the polarizer after the latterhas been set in position with the prism.7.3 When a quarter-wave plate is used, its “slow” raydirection must be set 45 clockwise from the horizontal in anorthwest-southeast direction (see Fig. 2). Adjusted in th
26、isposition, maximum extinction occurs when direction of axes ofall three elements (polarizer, analyzer and quarter-wave plate)are in agreement with Fig. 2.7.4 When the full-wave plate is used with the quarter-waveplate, its “slow” ray direction must be placed in a horizontalposition (see Fig. 2). Ad
27、justed in this position, a violet-redbackground color is seen when the three elements (polarizer,full-wave plate, and analyzer) are placed in series.7.5 Sections 7.3 and 7.4 describe orientations of the quarter-and full-wave plates in the standard positions that have beengenerally adopted. However,
28、the direction of the “ slow” raysmay be rotated 90 without changing the functions of theapparatus. This does, however, cause the analyzer rotations (inthe case of the quarter-wave plate) and the colors (in the caseof the full-wave plate) to have opposite meanings. Tables 1 and2 define these meanings
29、 in whatever is being measured orobserved with the “slow” ray directions in either the standardor the alternate positions.7.6 To assure proper orientation of the directions of the“slow” ray of the quarter-wave and full-wave plates withrespect to the vibration directions of the polarizer and analyzer
30、,use may be made of a U-shaped piece of annealed cane glassas illustrated in Fig. 3. Squeezing the legs together slightly willdevelop a tensile stress on the outside and a compressive stresson the inside. A flat rectangular beam in bending, containing aregion where the direction and sign of stresses
31、 is known canalso be used. Then, if the “slow” ray directions of thequarter-wave and full-wave plates are oriented in the standardposition, the stress conditions of Columns 1 through 4 of Table1 will be noted in the vertical and horizontal sides of theU-tube. If the opposite meaning of the color def
32、inition ispreferred, it will be necessary to rotate the “slow” ray direc-tions of the Full-Wave Plate 90 to the alternate positions. Theorientation of the full wave plate can be verified, comparing theobserved colors to the expected colors shown in the Table 2.The orientation of the quarter wave pla
33、te can be verified,checking that a clockwise rotation of the analyzer will decreasethe light intensity, whenever a black (zero-order) line is verynear the point of interest.7.7 If a major stress component lies in any direction otherthan vertical or horizontal, its measurement requires that either:AL
34、ight source (white, sodium vapor, or mercury vapor arc)BFilter (used only with mercury arc light) (used with white light)CDiffuserDPolarizerEImmersion cellFFull-wave plate (used only with white light)GQuarter-wave plateHAnalyzerITelescopeFIG. 1 PolarimeterF2180527.7.1 The entire optical system be ro
35、tated so that thevibration directions of the polarizer and analyzer are set at 45to the stress direction, or7.7.2 That the part containing the stress direction be rotatedto suit assure the orientation shown in Fig. 4.8. Procedure8.1 Before proceeding with measurements, evaluate thestress field by ob
36、serving the sample with and without the FullWave Plate (tint plate) in place. The colors observed when thetint plate is introduced provide an initial evaluation of theretardation.8.2 Identify directions and sign of stresses:8.2.1 Remove the tint-plate from the path of light. Rotatethe sample in its
37、plane. Observe the point of interest (POI)becoming dark (minimum transmitted light intensity) when-ever the direction of stress Sxor Syis parallel to the polarizer.From the position of extinction, rotate the sample 45, placingone of principal stresses, Sx, in vertical orientation, at 45 to thepolari
38、zation axes. In this position, maximum brightness isobserved. (See Fig. 4.)8.2.2 For a region near the POI exhibiting small retardation( 0). If the colors observed areblueblue green, the stress Sxis compressive (or Sx-Sy150 nm),use the analyzer rotation to identify the sign of Sx,orSx Sy.With the Ti
39、nt-Plate removed, rotate the Analyzer clockwise,and observe the sequence of changing colors.8.3.1 The sequence Yellow-BlueGray-Brown-Yellow-BlueGray, or for larger retardation (approximately 300 nm)Yellow-Blue-Red-Orange-Yellow-LightYellow-Blue, indicatestensile stress (Sx0orSx Sy 0).8.3.2 The rever
40、se sequence Yellow-Brown- BlueGray-Yellow, or for larger retardation (approximately300 nm)Yellow-Orange-Red-Blue-Yellow-Orange-Red, indicates com-pressive stress (Sx0).8.4 Measure the retardation:8.4.1 To measure the retardation at any given point, removethe tint plate, place the monochromatic filte
41、r in the field ofview, and rotate the analyzer with respect to its initial positionuntil maximum extinction (darkness) occurs at the POI. TheThe direction of vibration of the polarizer and analyzer may be oriented 90 from indicated positions.FIG. 2 Orientation of Polarimeter in Standard PositionNOTE
42、 1When the legs are squeezed together, Sides A and C becometensile and Sides B and D become compressive.NOTE 2MaterialCane glass of approximately 7 mm diameter,annealed after forming.NOTE 3When viewed in the polarimeter, immerse in a liquid havingthe same refractive index as the glass.FIG. 3 Referen
43、ce SpecimenF218053angle a through which the analyzer must be rotated to the leftor the right is a measure of the retardation at the point.8.4.1.1 In white light, the color of the fringe moving towardthe POI will keep changing. To eliminate possible errors and toincrease the contrast, the monochromat
44、ic filter, B, must beinserted for this operation, or the monochromatic lamp must beused.8.4.2 The rotation of the Analyzer must be clockwise. If thestress is tensile (Sxor Sx Sy0), the measured angle a isindicated directly on the dial, in degrees. When a fractionalgraduation of the dial is used, the
45、 fraction f = a/180 is indicatedon the dial.8.4.3 If the stress is compressive (SxorSx Sy0. In uniaxial stress, Sxis tension or Syis compression.Yellow 60Pale yellowA73 If the slow ray of the full wave plate is in vertical position:Yellow white 85WhiteA97 Sx Syis 0. In uniaxial stress, Sxis compress
46、ion or Syis tension.Gray white 110Iron gray 172Black 180AMore distinctive color of pair.F218055where:C = the stress-optical coefficient of the measured glasssample typically obtained by calibration.NOTE 4 In SI system Stresses are expressed in Mpa (megapascals), Cin Brewsters, 10-12(1 / Pa), thickne
47、ss is in mm and the retardation in nm.Using conventional in-lbs system, the stresses are expressed in psi,thickness in inches and the material constant C converted into nm/ inpsi.10. Keywords10.1 glass; optical retardation; polarimeter; stressAPPENDIXES(Nonmandatory Information)X1. POLARIZED LIGHT F
48、UNDAMENTALSX1.1 Light propagates in a vacuum or in air at a speed (C)of 331010cm/s. In glass and other transparent materials, thespeed of light (V) is lower, and the ratio C/V is called the indexof refraction, n. In an isotropic body this index is constantregardless of the direction of propagation o
49、r plane of vibration.However, in crystals, the index depends upon the orientation ofvibration with respect to its axis. Most materials (glass,plastics), are isotropic when unstressed but become anisotropicwhen stressed. The change in index of refraction is a functionof the stresses. Brewsters Law established that the relativechange in index of refraction is proportional to the difference ofprincipal stresses:nx ny! 5 CSx Sy! (X1.1)X1.1.1 The constant C is the “stress-optic” material con-stant, typically established by calibration. Typica
