Rod strings are designed by computing compound stress with the fourth strength energy on the condition of torque and axial force.
应用第四强度理论，求解杆柱在扭矩和轴向力条件下的复合应力，设计抽油杆柱。
2
When the shrinkage of the rod fracture surface much more than that of the cup part fracture surface, its formation by compound extrusion is not applicable.
当杆的断面收缩率比杯形部分断面收缩率大得较多时，不适合直接用复合挤压成形。
3
The new developing carbon fiber compound flexible coiled rod overcome the shortcoming of ordinary steel rod, can meet the need of low permeability oilfield production.