1、BRITISH STANDARD BS 7604-2: 1992 ISO 10345-2: 1992 Method for Determination of stress-optical coefficient of glass Part 2: Bending testBS7604-2:1992 This British Standard, having been prepared under the directionof the Laboratory Apparatus Standards Policy Committee, was published underthe authority
2、 of the Standards Board and comes intoeffect on 15 September 1992 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference LBC/8 Draft for comment 90/53964 DC ISBN 0 580 21160 6 Committees responsible for this British Standard The preparation of this British
3、Standard was entrusted by the Laboratory Apparatus Standards Policy Committee (LBC/-) to Technical Committee LBC/8, upon which the following bodies were represented: British Glass Manufacturers Confederation Society of Glass Technology Amendments issued since publication Amd. No. Date CommentsBS7604
4、-2:1992 BSI 09-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Apparatus 1 5 Test specimens 1 6 Procedure 1 7 Expression of results 3 8 Test report 3 Annex A (informative) Bibliography 4 Figure 1 Principle of stressing equi
5、pment 2 Figure2 Test specimen loading scheme 2 List of references Inside back coverBS7604-2:1992 ii BSI 09-1999 National foreword This British Standard has been prepared under the direction of the Laboratory Apparatus Standards Policy Committee. It is identical with ISO 10345-2:1992 Glass Determinat
6、ion of stress-optical coefficient Part 2: Bending test, published by the International Organization for Standardization (ISO). It has been prepared by Subcommittee 5, Quality of glassware, of Technical Committee48, Laboratory glassware and related apparatus, with the active participation and approva
7、l of the United Kingdom. This British Standard describes a method of test only and should not be used or quoted as a specification defining limits of performance. Reference to this BritishStandard should indicate that the method of test used is in accordance with BS7604-2:1992. A British Standard do
8、es not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an ins
9、ide front cover, pagesi andii, pages1to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7604-2:1992 BSI 09-1999 1 1 Scope This part of ISO
10、 10345 describes the bending test for determining the stress-optical coefficient of isotropic glass. The stress-optical coefficient is a characteristic value of materials and it is necessary for determining the stress from results of measurement of stress birefringence. 2 Definition For the purposes
11、 of this part of ISO 10345, the following definition applies. 2.1 stress-optical coefficient ratio of birefringence effect to applied uniaxial stress on an optical material. ISO 9802 1 where NOTE 1The stress-optical coefficient is a function of the wavelength. It can be either positive or negative.
12、3 Principle Uniaxial loading of the test specimen in the bending test and stress-optical measurement of the optical path difference in the range of the invariable transverse moment at the point of maximum compressive stress and maximum tensile stress (edge of test specimen). 4 Apparatus 4.1 Devices
13、for measuring the test specimen dimensions, suitable for measuring the breadth b and height h of the test specimen to the nearest0,01mm. 4.2 Apparatus, consisting of stressing equipment and polarization measuring equipment The stressing equipment (seeFigure 1) consists essentially of two specimen su
14、pports and two bending edges with loading pieces to be hung on gimbals. The ratio of the support span l Sto the distance of the bending edges l ashould be5:1 (seeFigure 2), for example l S =100mm andl a =20mm. The four edges shall be of a minimum length of 24 mm. The mass of the loading piece to be
15、applied depends on the loading bearing capacity of the test specimen. The polarization measuring equipment shall allow the measurement of the optical path difference with the compensator or by counting the isochromates to5 nm. The light source shall be white light with a corresponding interference f
16、ilter for the wavelength of 589,3 nm. The stressing equipment and the polarization measuring equipment shall be reciprocally adjustable in both the horizontal and vertical directions, so that the measuring point is located in the viewing axis of the polarization measuring equipment. The subtraction
17、position of the compensator of the polarization measuring equipment shall be determined using a glass for which the sign of the stress-optical coefficient is known. 5 Test specimens 5.1 Dimensions of the test specimens Length l: 1,1 l S Breadth b: 20 mm 2 mm Height h: 4mm 0,2 mm The height h and the
18、 breadth b of the test specimen shall not vary by more than 0,01 mm over its lengthl. 5.2 Condition of the test specimens The test specimen shall not have inhomogeneously distributed residual stresses. Homogeneously distributed residual stresses should be lower than1% of the measuring value. The sur
19、faces of the test specimen for light incidence and light exit, with areas of (l h), shall be ground and polished in such a way that the measurement of the optical path difference is not interfered with by surface roughness. The surfaces of the test specimen, with areas of (l b), shall be at least fi
20、ne-ground. 6 Procedure 6.1 Take all measurements at a temperature of25 C 10 C. Any temperatures differing from this value shall be stated in the test report. 6.2 Measure the breadth b and the height h of the test specimen to the nearest 0,01mm. 6.3 Place the test specimen symmetrically to the bendin
21、g edges, in such a way that the parallel faces of the specimen are located in the parallel beam path perpendicular to the beam axis with its main stress direction forming an angle of less than 45 between crossed polarizers. . . . (1) K is the stress-optical coefficient; %s is the optical path differ
22、ence; a is the light path in the test specimen (which is identical with the breadth b of the test specimen); B is the tensile or compressive stress. BS7604-2:1992 2 BSI 09-1999 6.4 Determine the sign of the optical path difference of the glass to be tested from the orientation of the subtraction pos
23、ition of the compensator. 6.5 Determine the optical path difference of the stress birefringence in the central area of the constant bending moment at the point of maximum compressive stress and maximum tensile stress (close to the edge of the test specimen) by means of a compensator or by counting t
24、he isochromates between the neutral axis and the upper surface and lower surface of the test specimen, respectively. Then turn the test specimen through 180 around its longitudinal axis and repeat the measurements. Calculate the arithmetic mean of the optical path difference %s from the four values
25、measured. 6.6 The measurements according to 6.5 should be carried out with at least two different testing forces which should differ by about the factor 1,5. Figure 1 Principle of stressing equipment Figure 2 Test specimen loading schemeBS7604-2:1992 BSI 09-1999 3 7 Expression of results 7.1 For eac
26、h testing force applied, calculate the stress B according to the numerical equation (2): where The bending stress B Edue to the dead-weight of the test specimen is given by the numerical equation(3): where In the case of tensile stress, the value of B is positive, and in the case of compressive stre
27、ss, the value is negative. 7.2 Calculate the stress-optical coefficient K according to the numerical equation (4): where When the measurements have been carried out with more than one testing force, calculate the arithmetic mean of the stress-optical coefficient. 8 Test report The test report shall
28、include the following information: a) reference to this part of ISO 10345; b) type and designation of the glass tested; c) wavelength of the light source, if 589,3 nm was not used; d) testing temperature, if outside the range15 C to 35 C; e) stress-optical coefficient, expressed in 10 6 mm 2 /N to t
29、he nearest 0,0510 6mm 2 /N. . . . (2) B is the tensile stress or compressive stress, in newtons per square millimetre; F is the testing force, in newtons, resulting from Cardanic suspension plus the mass of the load pieces; l S is the support span, in millimetres; l a is the distance between the ben
30、ding edges, in millimetres; b is the breadth of the test specimen, in millimetres; h is the height of the test specimen, in millimetres; B E is the bending stress, in newtons per square millimetre, due to the dead-weight of the test specimen. . . . (3) is the density of the test specimen, in grams p
31、er cubic centimetre; g is the gravitational acceleration (. 9,81m/s 2 ). . . . (4) K is the stress-optical coefficient, expressed in 10 6mm 2 /N; %s is the optical path difference according to6.5, in nanometres, positive or negative according to 6.4; b is the breadth of the test specimen, in millime
32、tres; B is the stress according to the numerical equation (2), in newtons per square millimetre.BS7604-2:1992 4 BSI 09-1999 Annex A (informative) Bibliography 1 ISO9802:, Raw optical glass Vocabulary 1) . 1) To be published.BS7604-2:1992 BSI 09-1999 List of references See national foreword.BS 7604-2
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