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84年物理分册第二期上刊登的一篇题为对YB27-77晶粒度弦测法计算方法的探讨文章中把等轴晶粒近似作为球体来处理,论证了平均弦长l与平均面积S的计算公式,并指出部标“YB27-77”给出的晶粒平均直径D和每立方毫米中平均晶粒数N的数据误差很大,这些都是正确的。但是在计算晶粒平均直径D和平均晶粒数N时,尚有不妥之处。该文把晶粒平均直径d与晶粒大圆面上的平均弦长L混为一谈,这是错误的,实际上两者是两个不同的概念,它们也不相等。下面分别求d、L以进行比较。作一个直径为D的球(图1)用n个平行平面去截球,截得n个圆,由于这些圆在球上任何部位的几率都相等,所以可视为n个平行的圆均匀地分布在球上。当n足够大时,每相邻两平行平面间的几何形状
84 physical volume published in the second issue of a titled on the YB27-77 crystal grain size method of measuring the article in the paper, the equiaxed grain approximation as a sphere to deal with demonstrated that the average chord l and the average area S calculation formula, and pointed out that the standard “YB27-77” gives the average grain diameter D per cubic millimeter and the average number of grains N error is large, these are correct. However, when calculating the average grain diameter D and the average number of grains N, there are still some problems. In this paper, it is wrong to confuse the average grain diameter d with the average chord length L on the major surface of the grain. In fact, they are two different concepts and they are not equal. Find the following d, L for comparison. Make a ball of diameter D (Fig. 1). Use n parallel planes to cut the ball and cut n circles. Since these circles have the same probability in any part of the ball, they can be considered as n parallel circles evenly Spread on the ball. When n is large enough, the geometry of each adjacent two parallel planes