薄壁管
直径和长度均远大于壁厚的空心、两端开口的圆柱形构件（例如去掉两端的铁皮罐头）。若管的长度相对于其直径变得很小，则成为圆环。
另请参阅圆盘。
Thin-walled tube
A hollow, open-ended, cylindrical member whose diameter and length are much larger than its wall thickness (e.g., a tin can with the ends removed). If the length of the tube becomes small compared to its diameter, then it becomes a ring.
Also see disk.