ISO 4469-1981 Wood Determination of radial and tangential shrinkage《木材 径向和强向收缩率的测定》.pdf

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1、4467-83 4853703 0033977 7 I temperature 20 + 2 OC) so that no checks distor- ting their dimensions and shape occur. Check the changes in dimensions of two or three control test pieces by repeated measurements, as specified in 6.2, every 6 h after stabilization of the conditioning environment. Stop t

2、he conditioning when the difference between two successive measurements does not exceed 0,02 mm. The conditioning of test pieces may be stop- ped by using the method of successive weighing in accordance with IS0 3130. 1) If necessary, shrinkage may also be determined at relative humidities between 3

3、0 and 90 %. Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 4469-1981 (E) 4469-83 4853703 0033780 6.4 every test piece, as specified in 6.2. Measure the cross-section

4、al dimensions, Ir and It, of 6.5 Dry the test pieces to constant dimensions at a temperature of 103 f 2 OC in the oven (4.2) so that no checks distorting their dimensions and shape occur. Check the changes in dimensions of two or three control test pieces by repeated measurements, as specified in 6.

5、2, every 2 h after 6 h from the beginning of drying. Stop the drying when the dif- ference between two successive measurements does not ex- ceed 0,02 mm. The drying of test pieces may be stopped by us- ing the method of successive weighing in accordance with IS0 3130. 6.6 period shall be disregarded

6、. Test pieces in which checks occurred during the test 6.7 vessel containing the desiccant (4.4). Cool the test pieces to room temperature in the air-tight 6.8 of each test piece, as specified in 6.2. Measure the cross-sectional dimensions, Ir min and I, min, 7 Expression of results 7.1 tage, by the

7、 formulae Calculate the total linear shrinkage, max, as a percen- a) for the radial direction x loo Ir max - 4 min Ir max r max = b) for the tangential direction : x loo It max - 4 min 4 max i max = where Ir and It are the dimensions, in millimetres, of the test piece at a moisture content above the

8、 saturation point, measured in the radial and tangential directions respect- ively; 1, and I, min are the dimensions, in millimetres, of the test piece after drying, measured in the radial and tangential directions respectively. Express the results to the nearest 0,l %. 7.2 Calculate the linear shri

9、nkage, D, when the moisture content changes to equilibrium with the normal environment, (relative humidity 65 f 5 %; temperature 20 f 2 OC), as a percentage, by the formulae a) for the radial direction : x 100 Ir max- Ir Ir max r, = b) for the tangential direction : x 100 4 max- 4 4 max BI, = where

10、I, and 1, are the dimensions, in millimetres, of the test piece at a moisture content in equilibrium with the normal envi- ronment, measured in the radial and tangential directions respectively; I, max and It max have the same meanings as in 7.1. Express the results to the nearest 0,l %. 8 Test repo

11、rt The test report shall include the following particulars : reference to this International Standard information required by IS0 3129 (sub-clause 6.4); a) b) c) type and volume of material tested (stand and nun-.-?r of selected trees; lot of sawn timber and number of selected boards, etc.); d) grai

12、n; dimensions of the test piece and the direction of the e) number of test pieces tested; f) moisture content in equilibrium with the normal en- vironment (relative humidity 65 f 5 %; temperature 20 f 2 OC); g) the test results, calculated as specified in clause 7, and their statistical values (toge

13、ther with the relative humidity and temperature if shrinkage was determined under condi- tions different from those specified in 6.3); h) date of testing; j) name of the organization responsible for testing. Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-