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1、INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXAYHAPOAHAR OPAHM3AklFl il0 CTAHJJAPTMA!M Steels - Manual point counting method for statistically estimating the volume fraction of a constituent with a point grid Aciers - Mkthode ma
2、nuelle Vv is expressed as a percentage. 2 For the values indicated in parentheses, the multipliers of table 3 should be used for the calculation of the confidence interval according to equation (5). Table 3 - Multiplier for calculation of the 95 % confidence interval Number of observed fields n 5 7
3、9 11 13 15 20 25 30 Multiplier 2,57 2.36 2.26 2.20 2.16 2.13 2,09 2,06 2,04 3 -,-,- IS0 9042 : 1999 (E) NOTE - In the case where a structure shows a certain periodicity of the distribution of the constituent being measured, any coincidence of the points of the grid and the structure should be avoide
4、d. This can be achieved with either a circular grid or a square grid that is placed at an angle to the microstructure image. 6.5 Examination and estimation of the fields The volume fraction Vv is given by the equation . . . (4) V,= this is done to eliminate any possibility of operator bias in the fi
5、eld position with respect to the grid. Cl= +2s . . . (5) fi NOTE - When a small number of fields f 30) is used, the multiplier 2 in formula (5) should be replaced by the appropriate value selected from table 3. For each field observed, the number of points included in the constituent Pi is recorded.
6、 The error for the estimation of Vv can be calculated according to the equation Any points falling on the constituent boundary shall be counted as one-half. In the same way, in order to minimize the error, when there is doubt as to whether a point is inside or outside the constituent boundary it sha
7、ll be counted as one-half. % error = fl x 100 6 . . . (6) For each field, the proportion of points included in the consti- tuent P,(i) is calculated according to the equation P,(i) = f-! x loo . . . PT (I) 7 Calculation of the volume fraction VV NOTE - If an improvement of the obtained precision is
8、wanted, addi- tional measurements can be made by increasing the number of fields; to reduce the % error by 50 %, a total of four times the original number of fields should be measured. 8 Test report The test report shall mention at least the following informa- tion : The arithmetic average pp = 1. ”
9、 c P,(i) . . . n i=l (2) b) orientation of the observed surface in the case of anisotropy; c) type of grid used (array, total number of points); The estimated value of the standard deviation about the average is calculated according to the formula d) number of the observed fields by samples and thei
10、r spacing; e) selected magnification; . s.(3) f) value of the volume fraction and, if required, values of the confidence interval and of the calculated error. 4 -,-,- IS0 9042 : 1988 (E) UDC 669.14 : 620.18 Descriptors : steels, tests, microscopic analysis, determination, microstructure. Price based on 4 pages -,-,-