在大型容器 10 0 %射线探伤时 ,对环缝采用偏心内透 (Ｆ Ｒ)分段曝光。首先确定最少曝光次数Ｎ ,即Ｎ =180°/α ,α角是决定曝光次数的关键。其计算方法有以下两种。1　 2α角按一次透照长度对应的圆心角计算如图 1所示 ,Ｏ为圆心 ,Ｐ为射线源 ,η为一次透照最大有效半辐射角 In a large container 10% ray inspection, the use of eccentric annular penetration (F R) segmented exposure. First determine the minimum number of exposures N, that is, N = 180 ° / α, α angle is the key to determine the number of exposure. The calculation method has the following two kinds. 1 2α angle according to a transillumination length corresponding to the central angle calculated as shown in Figure 1, O is the center of the circle, P is the ray source, η is a transillumination maximum effective half-angle of radiation