重量= 截面积*长度* 8.96/1000 = (3.14 * (外径/2)^2 - 3.14 *((外径-2*壁厚)/2)^2)*长度* 0.0089 = (((外径/2)^2-((外径-2*壁厚)/2)^2)*长度* 0.00896*3.14 = 【外径/2+(外径-2*壁厚)/2】*【外径/2-(外径-2*壁厚)/2】 * 0.028*长度 =(外径-壁厚)*壁厚*0.028*长度内孔尺寸是:外径-2*壁厚