Test method for stress of the hottest glass

2022-08-02
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Glass stress test method

preface

the technical content of this standard is drafted with reference to the American Society for testing and materials standard astmc1279:1994 test method for nondestructive Photoelastic Measurement of surface stress and edge stress of annealed glass, semi tempered glass and tempered glass, astmc1048:1992 thermal treated flat glass - HS and FT coated and uncoated glass, and the Japanese industrial technical standard 71s r3222:1990 semi tempered glass

the measurement procedure of surface stress in this standard refers to GB( (tempered glass and semi tempered glass for curtain wall) this standard is proposed by the State Administration of building materials industry.

this standard is under the jurisdiction of the Institute of glass science and special glass fiber, Chinese Academy of building materials sciences.

the drafting unit of this standard is the Institute of glass science and special glass fiber, Chinese Academy of building materials sciences.

the main drafters of this standard are xiaopengjun, zhangdashun, Han song, Wang Le and Li Fu Jiang

national standard of the people's Republic of China

glass stress test method

1 scope

this standard specifies the method for testing the surface stress and edge stress of glass The surface stress test method is applicable to tempered glass and semi tempered glass made of float glass. This method can be used for chemical tempered glass; The edge stress test method is applicable to tempered glass, semi - tempered glass and annealed glass

this test method is a nondestructive test method

2 reference standard

the provisions contained in the following standards constitute provisions of this standard through reference in this standard When this standard is published, the editions shown are valid, and all standards will be revised. All parties using this standard should explore the possibility of using the latest editions of the following standards

gb toughened glass and semi toughened glass for curtain wall (NEQ ISO 7463:1990)

jc/t automobile safety glass terms

3 definitions the best choice is G-type impact device

this standard adopts the relevant terms in jc/t 632 and the following definitions

An optical device consisting of two polarizers whose optical axes are perpendicular to each other Placed between the tested sample and the observer

4 test method

4.1 surface stress test

4.1.1 test principle

the test principle of the surface stress meter is to use the optical waveguide effect of the tin diffusion layer on the surface of float glass for measurement The divergent light from the light source (incandescent lamp) passes through the slit, converges from the high refractive index cylindrical prism and becomes a parallel light. By adjusting the position of the light source, a beam of parallel light is emitted to the interface between the glass and the prism at a critical angle. Due to the stress on the glass surface, the light is decomposed into two vector lights perpendicular to each other. The propagation speed of the two beams in the tin diffusion layer of float glass is different, Therefore, it refracts to the prism at different total reflection angles The light emitted from the prism is reflected by the reflector into the interference filter, focused by the telescopic objective lens system, and then imaged on the reticle after passing through the analysis mirror to form a bright and dark step image The height of the step can be accurately measured through the micrometer eyepiece

4.1.2 reagent for test

use refractive index oil with refractive index of 1.5400

4.1.3 test device

the surface stress instrument is mainly composed of light source, high refractive index prism, telescopic objective lens system and micrometer eyepiece. The structure of the instrument is shown in Figure 1:

4.1.4 preparation and preservation of samples

take products as samples If the surface of the tin diffusion layer of the sample is coated, such as the ceramic coating of curtain wall glass, the coating shall be removed with hydrofluoric acid or abrasive cloth In order to avoid the generation of thermal stress, the internal to external temperature of the specimen shall be consistent with the ambient temperature

4.1.5 determination of surface stress measuring points

surface stress measuring points shall be determined by product standards

4.1.6 test procedure

a) place the tin diffusion layer of the tested sample horizontally upward

b) drop refractive index oil on the measured drop

c) place the prism of the instrument at the measured point

d) adjust the position of the light source, the position of the slit and the angle of the reflector to make the bright and dark step image appear in the field of view

e) use a micrometer eyepiece to read the height D of the same step, accurate to 0 01 mm;

f) determination of compressive stress and tensile stress

4.1.7 calculation of test results

the calculation formula of surface stress is as follows (1):

σ= Kd................................................ (1)

where: σ—— Surface stress, MPa

k - instrument constant, k=352 mpa/mm1 is a demonstration of continuously deepening green manufacturing

d - step height, mm,

4.1.8 test report

the report shall include the following contents:

a) sample name, type, thickness and number

b) location of measuring points

c) step height value and calculated stress value at each measuring position

d) signature of testing unit, testing date and testing personnel

4.2 edge stress test

4.2.1 test principle

place the sample in the plane polarized light field, rotate the polarizer and the inspection polarizer, so that the two polarization axes remain orthogonal and form a 45 ° angle with the direction of the main stress of the sample, and the direction of the main stress of the sample is parallel or perpendicular to the edge of the sample Place a quarter wave plate in the optical path near the left end of the polarizer, and make its fast and slow axes parallel to the polarization axis The compensation angle is obtained by rotating the polarizer

4.2.2 testing device

edge stress meter is mainly composed of four parts: light source, polarizer, polarizer and 1/4 wave plate The structure of the instrument is shown in Figure 3

4.2.3 sample

take the product as the sample. If there is a coating on the edge of the sample, such as the ceramic coating of curtain wall glass and the glaze of automotive safety glass, remove the coating with hydrofluoric acid or emery cloth first In order to avoid the generation of thermal stress, the internal to external temperature of the specimen shall be consistent with the ambient temperature

4.2.4 determination of edge stress measurement point

the edge stress measurement point is taken from the middle of each edge

4.2.5 test procedure

a) turn on the light source of the instrument so that the polarizer and the polarizer are perpendicular to each other and in the initial position. At this time, the field of view is uniform and dark

b) place the tested sample between the polarizer and the quarter wave plate Make the principal stress direction of the specimen form an angle of 45 ° with the polarization axis direction

c) at this time, the light interference pattern caused by stress at the edge of the sample can be seen in the field of view, as shown in Fig. 4a There is a thick black stripe parallel to the edge at a certain distance from the edge, which is the area where the stress is zero The area below the black stripe is the compressive stress area, and the area above the black stripe is the tensile stress area The direction of tensile stress or compressive stress can also be determined by the rotation direction when the polarizer is compensated Rotating the polarizer in the direction of "+" indicates that the measured stress is tensile stress, on the contrary, rotating in the direction of "one" indicates that the measured stress is compressive stress

d) rotate the polarizer to the "one" direction to move the center line of the black zero order fringe to the edge of the sample, as shown in Figure 4b The corner is obtained θ 1. if the edge of the sample is grinded or chamfered, the θ 1 is impossible; Therefore, the angle can be measured at an equal distance from the edge of the sample, and the angle can be obtained by extending the line θ 1. for example, the edge grinding thickness is 0 4 mm, the distance from the edge can be 0.5 mm, L. 0 mm, L. 5 mm, 2 0 mm, 2. Measure at 5 mm to obtain the corresponding angle, connect the points through a smooth curve and extend the θ Axis intersects at θ 1. See figure 5

e) rotate the polarizer to the "ten" direction to keep the black zero order stripe away from the edge until the narrow area above the black zero order stripe becomes the darkest, as shown in figure 4c The corner is obtained θ 2

f) when there are multi-level stripes on the edge of the sample, the zero level stripe is black, and then the stripe color changes from red to purple, and then to black, and its color will appear repeatedly. The purple stripes that appear in turn are level 1, level 2, level 3 Move the low-level Purple Stripe near the measuring point to the required measuring point to obtain the corner θ 3. if there are two color stripes, the integral order of purple stripes shall be 2, as shown in Figure 4D At this time, the calculation formula of angle 0 is shown in formula (2)

θ= n × 180°+ θ 0 (2)

where: n - integral series of fringes

θ 0 - take θ 1 or θ 2 or θ 3, θ 1 is the corner corresponding to the maximum compressive stress at the edge; θ 2 is the corner corresponding to the maximum tensile stress at the edge; θ 3 is the corner corresponding to the edge stress

note: if the fringe order exceeds two or more, a dry color filter can be added for observation

4.2.6 calculation of test results

the calculation formula of edge stress is as follows (3):

σ= K θ/t.......................................... (3)

where

σ—— Maximum edge stress of specimen, MPa

k - instrument constant, k=1 11 MPa/m;

θ—— Angle corresponding to the maximum stress at the edge, (°)

t - thickness at the measuring point of the sample, mm,

note: the thickness at the measuring point of laminated glass shall be the total thickness of the sample minus the film thickness

4.2.7 test report

the report shall include the following contents:

a) sample name, type, thickness and number

b) location of measuring points

c) angle of each measuring position and thickness of the measured point

d) calculated stress value

e) signature of testing unit, testing date and testing personnel

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