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16 问:当采用有效焦点尺寸2mm 的 X 光机,检查母材厚度为20mm 厚的对接焊缝时,在 GB3323—87标准的诺模图上查得:A 级照相,焦点至工件表面的最小距离 L_1为110mm;B 级照相,焦点至工件表面的最小距离 L′_1为220mm。求该两种照相底片在最小距离条件下照相时的几何不清晰度 U_g。
16 Q: When using the X-ray machine with the effective focal spot size of 2mm, check the butt weld with a base metal thickness of 20mm thick and check it on the nomogram of the GB3323-87 standard: Class A photograph with the smallest focal point to the workpiece surface Distance L_1 is 110mm; B class photography, the focal point to the surface of the minimum distance L’_1 is 220mm. Find the two kinds of photographic film at minimum distance under the conditions of the geometric unsharpness U_g.