1、 FORD LABORATORY TEST METHOD BZ 150-01 Date Action Revisi ons 2001 04 30 Revised Editorial no technical change A. Cockman 1999 01 19 Printed copies are uncontrolled Page 1 of 7 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF INTERNAL COMPRESSION STRESSES IN THE EDGE ZONES OF LAMINATE
2、D GLASS WINDSHIELDS Application This method is used to determine qualitatively and quantitatively the internal compression stresses in laminated glass windshields. The qualitative determination of stresses - compression and tension is performed according to the colour change method. The quantitative
3、 determination of stresses is performed according to the compensation method. With the compensator wedge used according to this method, compression stresses are measured in the range of specification requirements for laminated windshields. Apparatus Required Polariscope White light with a maximum in
4、tensity at the wave length of 550 nm; direction of polarisation foil (see Figure). Dimensions of the illumination field approximately 2.0 x 0.9 m. Analyser with Compensator Red I (536 nm) One half of the analyser is covered with Compensator Red I. Field of view 100 mm diameter minimum. Direction of
5、polarisation foil (see Figure). Note: Suitable analyser spectacles with and without Compensator Red I may be used depending on the respective case stated in the Test Procedure. Reflex Camera Commercial. Attachable Analyser Suitable to be fitted on the camera objective mount, consisting of Polarex Fi
6、lter KS-DE (35 % light transmittance) and compensator Red I (536 nm) or equivalent. Supporting of Windshield The windshield supporting device must be such that all edge zones can be placed in a parallel position in front of the illumination field of the polariscope. FORD LABORATORY TEST METHOD BZ 15
7、0-01 Page 2 of 7 Copyright 2001, Ford Global Technologies, Inc. Compensator Wedge For measuring compression stress, made of Plexiglass with face difference of 0.6 ratings linear increasing to the thick end (using white light with a maximum intensity at the wave length 550 nm); the wedge is provided
8、with a compression stress scale calibrated in kN/m2 corresponding with the individual windshield thickness (see evaluation example). Compression Stress Range: 6000 - 16000 kN/m2. Scale Length approximately 10 cm. Source: Unimatic Engineers Limited 122 Granville Rd. London, UK NW2 2LN Checking of Pro
9、per Placement of Plane of Polarisation, Both of the Illumination Field of Polariscope and Analyser. 1. The analyser is placed in front of the illumination field of the polariscope (see Figure). 2. Viewing the illumination field through the left segment of the analyzer (provided with Compensator Red
10、I), the illumination field must appear “red“ when using the prescribed polariscope. 3. Determine the thickness of the windshield in the edge zone in ten positions (three each on horizontal and two each on vertical edges) to the nearest 0.1 mm and compute the average. Conditioning and Test Conditions
11、 All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. The windshield under test shall be place
12、d in the supporting device; the supporting device shall be positioned in such a way that: The edge zone to be tested is placed parallel to the polariscope frame, i.e. under an angle of 45 to the foil direction of the polariscope, and The windshield zone on the edge under test is placed parallel to t
13、he illumination field of the polariscope. The distances between polariscope, windshield and analyser should be kept rather small to obtain optimum illumination effect. FORD LABORATORY TEST METHOD BZ 150-01 Page 3 of 7 Copyright 2001, Ford Global Technologies, Inc. 2. The entire windshield edge is vi
14、ewed through the analyser with Red I as specified (see Figure) and shall be investigated qualitatively for compression stresses all around the windshields. (a) In cases of horizontal edges a colour tone in the blue range (see table) must appear at the outer edge areas. Mark on the windshield edge th
15、e point where the colour tone nearest approaches the Red I tone, this point being the lowest compression stress area. The appearance of a yellow colour tone in these areas indicates tension stresses and shall be marked accordingly. (b) In cases of vertical edges a colour tone in the yellow range (se
16、e Table) must appear at the outer edge areas. Mark on the windshield edge the point where the colour tone nearest approaches the Red I tone, this point being the lowest comparison stress area. The appearance of a blue colour tone in these areas indicates tension stresses and shall be marked accordin
17、gly. 3. The marked compression stress areas are viewed without Red I through the analyser located as specified (see figure) and are quantitatively examined (using the compensator wedge provided for the relevant windshield thickness) for compression stresses and for the width of the compression stres
18、s zones. (a) Determine the maximum width of the compression stress zone. This width is the greatest distance of the O-isochromate (first dark line parallel to the windshield edge) from the edge and is determined to an accuracy of +/- 1 mm. (b) The compression stresses on the marked points will be de
19、termined as follows: Position the compensator wedge vertically to the windshield edge and view through the analyser without compensator Red I. The O-isochromate (dark line) visible in the compensator wedge is displaced by moving the thin end of the wedge in the direction of the windshield centre unt
20、il the O-isochromate appears at the exterior edge zone, i.e. is being placed in compensation position. 4. In this compensation position the compression stress is read from the compensator scale (kN/m2) at the height of the windshield edge. Evaluation Report the area on which any tension stress has b
21、een found. The lowest compression stress value is quoted in kN/m2 (see evaluation example). The maximum width of the compression stress zone is quoted in mm. Note: If necessary, a reference photograph for the documentation of compression, or tension stress zones may be taken using the attachable ana
22、lyser and wedge in measuring position. FORD LABORATORY TEST METHOD BZ 150-01 Page 4 of 7 Copyright 2001, Ford Global Technologies, Inc. Place camera in front of the windshield or of the illumination field respectively at such a distance that the interesting segments of the windshield edges can be re
23、cognised on the focusing screen. Details as to the type of camera, colour film, lens aperture, exposure time and type of attachable analyser shall be added to the photograph. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is respo
24、nsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD BZ 150-01 Page 5 of 7 Copyright 2001, Ford Global Technologies, Inc. TABLE FORD LABORATORY TEST METHOD BZ 150-01 Page 6 of 7 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF INTERNAL COMPRESS
25、ION STRESSES IN THE EDGE ZONES OF LAMINATED GLASS WINDSHIELDS FORD LABORATORY TEST METHOD BZ 150-01 Page 7 of 7 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF INTERNAL COMPRESSION STRESSES IN THE EDGE ZONES OF LAMINATED GLASS WINDSHIELDS EXAMPLE FOR EVALUATION Definition: Glass thic
26、kness = Windshield thickness - Foil thickness Example: Windshield thickness: 6.9 mm (average) Foil thickness: 0.78 mm (-) (See Specification Requirement) Glass thickness: 6.1 mm Glass thickness for which wedge is calibrated: 5.6 mm (See wedge manufacturer instructions) Corrected value kN/m2 = Scale reading kN/m2 x calibrated glass thickness mm (5.6 mm) Glass thickness mm (6.1 mm)
